Digestible Tryptophan Requirements of Starting, Growing, and Finishing Pigs' K. G. Burgoon, D. A. Knabe2, and E. J. Gregg Department of Animal Science, Texas A&M University, College Station 77843
ken-line regression analyses determined the total dietary Trp requirements needed to optimize performance to be .19, .13, and .09% (as-fed basis) for starting, growing, and finishing pigs, respectively. These concentrations equated to Trp intakes of .96, 2.18, and 2.88 g/d. A digestion trial using growing pigs (29 kg initially) determined the apparent ileal digestibility of Trp in the basal starting and growing diets to be 72 and 709'0, respectively; a similar trial with finishing pigs (55 kg initially) found 59% Trp digestibility for the basal finishing diet. Mean digestibility of L-Trp was 97%. Based on these values and the total Trp requirements given above, the digestible Trp requirements are .15, .lo, and .O6% for starting, growing, and finishing pigs, respectively.
Key Words: Pigs, Tryptophan, Requirements, Amino Acids, Digestibility
J. Anim. Sci. 1992. 70:2493-2500
Introduction Lysine (Lys) and tryptophan (Trp) are generally considered the first- and second-limiting amino acids in most corn-based pig diets. A large amount of research has been conducted to estimate the total dietary Lys and Trp requirements. Only recently was the digestible Lys requirement reported for starting and growing pigs (Martinez and Knabe, 1990). Estimates of the total dietary Trp requirements have been reviewed by the ARC (19811, SCA (19871, and NRC (1988). Results of experiments cited in these publications vary considerably for pigs within a given weight range. A number of factors may affect these results, including genotype, dietary energy and protein content,
'Publication T. A. 30219, Texas Agric. Exp. Sta. Appreciation is expressed to Heartland Lysine, for providing the crystalline amino acids used in this research. 2To whom correspondence should be addressed. Received September 18, 1991. Accepted March 18, 1992.
initial and final pig weights, feed intake, and variation in digestibility or availability of amino acids among feedstuffs. The apparent digestibilities of amino acids vary among feedstuffs used in pig diets (Sauer and Ozimek, 1986; Knabe et al., 1989). The ARC (19811, SCA (19871, and NRC (19881 acknowledge a need to formulate diets based on a digestible basis. Formulating diets on a digestible amino acid basis would improve feedstuff use and more accurately meet the requirements of swine (Tanksley and Knabe, 1984). The objective of this study was to determine the digestible Trp requirement of starting, growing, and finishing pigs.
Experimental Procedures Representative samples of the corn, soybean meal, menhaden fish meal, and corn gluten meal used in these studies were ground through a 1-mm screen and then analyzed for CP content IAOAC, 19841, amino acid content (Knabe et al., 19891, and Trp content (LaRue, 1985). Diets were
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ABSTRACT: Seven hundred eight crossbred pigs were used in growth and digestion trials to determine the digestible tryptophan ITrp) requirement of starting (6 to 16 kgl, growing (22 to 50 kg), and finishing (55 to 97 kg) pigs. Each growth trial evaluated a corn-fish meal-corn gluten meal basal diet, the basal diet with five incremental additions of L-Trp, and a control corn-soybean meal diet. The tryptophan content of the six incremental diets ranged from .13 to .255% for starting pigs, .08 to .18% for growing pigs, and .063 to .163% for finishing pigs. Lysine contents of basal diets were 1.38, .90, and .72% for starting, growing, and finishing diets, respectively. In all trials, ADG, ADFI, and gain/feed increased (P < .001) linearly and quadratically as dietary Trp increased. Bro-
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BURGOON ET AL.
Table 1. Chemical analyses of feedstuffsa Soybean meal
Corn Item
DM,% CP,Yo
-
Corn gluten meal
12
3
12
3
1.2,3
1.2
3
89.2 10.5
90.0 7.2
91.5 44.5
91.7 43.8
93.9 62.1
89.1 59.8
93.5 62.3
.51 .31 .40 .43 .28 .26 .26 .57 .40 .06 .53
.40 .22 .28 .95 .25 .38 .29 .05 .39
3.37 1.21 2.07 3.41 2.88 .66 .73 2.25 1.68 .54 2.18
3.44 1.23 2.23 3.66 2.94
2.37 1.88 .54 2.31
3.71 1.66 2.74 4.71 4.94 1.84
BO 2.62 2.69 .54 3.22
1.92 1.09 2.55 9.95 1.14 1.42 1.19 3.86 1.98 .22 2.80
2.01 1.20 2.73 10.60 1.20
4.20 2.14 .25 3.00
*Values are expressed on an as-fed basis. bAnalyses of methionine and cystine were conducted by Heartland Lysine, Eddyville, IA.
formulated using the analyzed CP and amino acid contents (Table 1). A total of seven dietary treatments were used in each growth trial. The basal diets were formulated to provide 22, 15.5, and 12% protein for starting, growing, and finishing pigs, respectively (Table 2). Calculated tryptophan contents of the corresponding basal diet were .13, .08, and .063%, respectively. Additions of crystalline lysine were made to basal diets to provide 120% of the lysine requirements (NRC, 1988). Crystalline threonine was added to provide an estimated dietary digestible threonine content equal to 70% of the estimated digestible lysine content. Digestible amino acid contents were calculated using apparent digestibilities reported by Lin et al. (1987) for corn and digestibilities reported by Knabe et al. (1989) for other feedstuffs. Dietary contents of remaining amino acids were a t least 120, 120, and 114% of the NRC (1988) requirements for 5- to 10-kg, 20- to 50-kg, and 50- to 110-kg pigs, respectively. Crystalline tryptophan (L-Trp)was added a t five incremental amounts to the basal diet in each trial to produce a titration effect. A glutamic acid/ glycine mixture (1.96:l) was substituted at the expense of cornstarch and L-Trp to ensure that experimental diets were isonitrogenous. Conventional corn-soybean meal diets (22, 17, and 13% CP, and 1.20, .80, and .65% lysine for starting, growing, and finishing pigs, respectively) were included in each trial to serve as a control. Experiment 1 consisted of two 28-d trials using 336 crossbred (Yorkshire-Landrace sows x DurocHampshire boars) pigs. The average initial weight was 6.2 kg. Trials started on the day of weaning when pigs were approximately 28 d of age. Each trial was arranged in a randomized complete
block design; blocks consisted of initial weight and pen location within the nursery. Littermates were balanced across treatments as much as possible without regard to sex. Pigs were housed six per pen (1.5-m x 1.5-m,with woven-wire flooring) in an enclosed nursery. Ambient temperature in the nursery was maintained at 29OC for the initial 7 d, and then gradually lowered to 24OC by d 21. Pigs were allowed a d libitum access to feed and water. Experiment 2 used 196 crossbred pigs (same genotype as Exp. 1) in two 35-d trials. Average initial pig weight was 21.9 kg. Each trial was arranged in a randomized complete block, with 14 replicates blocked according to initial weight and sex. Littermates were distributed as in Exp. 1. Pigs were housed two per pen (1.22-m x 4.9-m, with a solid concrete floor) in a n open-sided growing finishing building. Each pen was equipped with a fogger activated by a thermostat when the air temperature was > 29°C. The trials were conducted between April 7, 1989 and June 19, 1989; mean daily minimum and maximum temperatures were 19.1 and 30.1°C, respectively. Pigs were allowed a d libitum access to feed and water. Experiment 3 was identical in experimental design to Exp. 2 but only 12 replicates were used (168 total pigs) and the trials lasted 42 d. Average initial pig weight was 55.4 kg. The trials were conducted between November 17, 1989 and February 16, 1990; mean daily minimum and maximum temperatures were 5.3 and 11.8”C, respectively. Bedding was provided when temperatures were < 0°C. Experiment 4 was a digestion trial arranged in a 4 x 4 Latin square design. Diets consisted of the basal diets from Exp. 1 and 2 and the same diets with .10 or . O 8 % Trp added, respectively. Composi-
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Amino acids, TO Arginine Histidine Isoleucine Leucine Lysine Methionineb Cystine” Phenylalanine Threonine Tryptophan Valine
Fish meal
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DIGESTIBLE TRYPTOPHAN REQUIREMENTS OF PIGS
period, and feed intake was adjusted before the first meal of subsequent periods. Water was mixed with feed a t a 1:l feed:water ratio to form a moist mash. Pigs were allowed ad libitum access to water in stainless steel feeders after consumption of each meal. Experimental periods consisted of 5 d of diet adjustment, 2 d of feces collection, and 3 d of ileal digesta collection. Feces were collected at 12-hintervals; ileal digesta were collected between 0700 and 1800. Ileal digesta samples were collected, stored, and prepared using procedures described by Knabe et al. (1989). Ileal and diet samples were analyzed for protein and amino acid content as described for
Table 2. Percentage of composition and analyses of positive control and basal diets used in the growth trialsa Starting Item Corn Soybean meal Corn gluten meal Fish meal Dicalcium phosphate Limestone Vitamin premix” Trace mineral premixC Antibacterial mixd Salt 1.96:1 Glu:Glye L-LYs HCl, 98% L-Thr Calculated content, YO CP, Yo Lysine Tryptophan Threonine Isoleucine Calcium Phosphorus Analyzed content, % CP, 010 Lysine Tryptophan Threonine Isoleucine, DE, kcal/d
Growing
Finishing
Control
Basal
Control
Basal
Control
Basal
59.84 35.65 -
77.27 20.00
87.37
82.17 15.40
89.07
-
72.23 4.00 11.34 8.00 1.a5 .44 .50 .15 1 .oo .25 .14 .67 .23
22.15 1.20 .23 .84 .98 .85 .70
22.02 1.38 .13 1.03 .88 .85 .70
17.01
22.4 1.24 ,233 .94 1.03
22.41 1.39 .13gf 1 .OB .91 3.59
17.0 .81 ,156 .67 .74
-
1.61 1.00 .50 .15 1 .oo .25 -
-
-
1.12 .86 .25 .15 .10 .25
-
.EO
.15 .65 .72 .65 .55
-
-
6.80 2.50 1.12 .64 .25 .15 .10 .25 .ll .57 .14
-
-
.90
.88 .25 .15
-
.25
-
-
-
-
6.00 2.00 .90 .72 .25 .15 .25 .ll .42 .13
15.52 .90 .08 .70 .59 .65 .55
12.65 .65 .12 .51 .57 .60 .50
11.98 .72 .06 .54 .46
15.64 .92 ,0928 .09 .59 3.75
13.06
12.20 .73 .064h .56 .46 3.60
.66
.ll .52 .50 -
BO .50
‘Values are expressed on a n as-fed basis. bAdding .50% of the premix contributed the following per kilogram of diet: vitamin A,7,715IU; vitamin DB,770 IU; vitamin E,44 IU; menadione sodium bisulfate complex, 9 mg; riboflavin, 7.7 mg; d-calcium pantothenate, 33 mg; niacin, 33 mg; choline, 287 mg; vitamin BIZ,44 pg;and d-biotin 220
M.
‘Contributed the following per kilogram of diet: Cu, 10 mg; Fe, 100 mg;I, .3mg; Mn, 20 mg; Zn, 100 mg; Se, .3 mg. dContributed 25 mg of carbadox or 110 mg of chlortetracycline/kg of starter and grower diets,
respectively. eWeighted ratio provided equal N from Glu and Gly. ‘Analyzed total tryptophan contents of the six experimental starting diets were ,139,,160,,177, ,202,,213,and .235%. BAnalyzed total tryptophan contents of the six experimental growing diets were .092,,106,,125, .142 152, and .172%. ~ k a l y z e dtotal tryptophan contents of the six experimental finishing diets were ,064,,078,,093, ,107,.119,and .141%. ’Based on results of Exp. 4 and 5.
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tion of diets was identical to diets used in Exp. 1 and 2 except that .25% chromic oxide was substituted for corn. Four barrows, initially weighing 29 kg, were fitted with a simple T-cannula approximately 10 cm anterior to the ileo-cecal junction. Halothane gas was used to induce and maintain a surgical plane of anesthesia. Pigs were placed in 1-m x 2-m stainless steel metabolism cages immediately after surgery, and the trial was initiated after a 14-d postoperative recovery period. Ambient temperature was maintained a t 21 & 1°C. Pigs were fed approximately 3.8% BW/d in two equal meals at 0700 and 1800. Body weight of pigs was measured at the end of each experimental
BURGOON ET AL.
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Table 3. Effect of dietary tryptophan level on performance of starting pigsa Control diet Trp, YO
Dietary Trp,% Item
,130
,155
ADG, kgCd ADFI, kgCd Gain/feedcd Trp intake, g/d
.17
.25 .39 .64
.so .57 .40
.61
Percentage of tryptophan determined to optimize performance
.180
,205
.230
.255
,230
CV
.32
.34 .50
.34 .51
.35 .53
.39 .64 .6 1 1.47
10.7 10.1 5.5
.4a .66 .86
.66
.66
.66
1.02
1.18
1.35
-
Broken line
Plateau
Quadratic
.19
.18 .18
.23 .23 .22
.19 .16
-
.18
-
the feedstuffs. Chromic oxide contents were determined using the procedure of Kimura and Miller (19571. Feces were analyzed for energy (adiabatic bomb calorimetry) and chromic oxide contents. Experiment 5 used a two-period crossover design. Four finishing barrows averaging 62 kg of BW, initially, were used to evaluate the basal diet from Exp. 3 containing .063% Trp and a similar diet containing .O8% added L-Trp. Pigs were fed approximately 3.6% BW/d. Environment, feeding schedule, collection, and analyses of diet, fecal, and ileal digesta samples were similar to those in Exp. 4, except that ileal digesta collection occurred for only 2 d. The experimental unit was the pen in Exp. 1, 2, and 3. Trial, block within trial, diet, and trial x diet interaction effects were evaluated in the statistical model. The trial x diet interaction was not significant (P > .25) in any analyses. Dietary Trp levels were partitioned into linear and quadratic effects (positive control deleted), and a single df contrast was performed to compare the positive control and the diet approximating the Trp requirement s u g gested by the NRC (1988). When a significant (P < .05) quadratic effect was found, the Trp requirement was estimated by fitting a broken-line to the data Bobbins, 19861, by using a plateau method (Anderson and Nelson, 1975) and by calculation of the inflection from the quadratic equation (SAS, 1985). In Exp. 3, the statistical model also included sex and the sex x diet interaction. The sex x diet interaction was not significant and estimated requirements using data from barrows or gilts were identical. Therefore, estimated requirements are based on combined data for barrows and gilts. In Exp. 4 and 5, the pig within a period was the experimental unit. Experiment 4 was analyzed as a 4 x 4 Latin square and Exp. 5 as a crossover design. Single df contrasts were used to evaluate the effect of Trp addition on amino acid digestibilities and to determine whether average digestibilities differed between starting and growing diets in
Exp. 4. Procedures of SAS (1985) were used for all analyses.
Results and Discussion Average daily gain, ADFI, and gain/feed increased linearly (P < .001) and quadratically (P < .0011 as dietary Trp content increased from .13 to .255% in Exp. 1 (Table 3). Growth rate and feed consumption were poorer (P < .0011 for pigs fed the diet containing .23% Trp than for those fed the control diet; however, gain/feed was greater (P .001) for pigs fed the .23% Trp diet. Estimates of the dietary Trp content required to optimize ADG, ADFI, and gain/feed (Table 3) by broken-line and plateau method estimates agreed well. Predicted values by the broken-line and plateau methods were, respectively, ADG, .19 and .l8%; ADFI, .19 and .l8%; and gain/feed, .16 and . l 8 % . The quadratic method estimated much higher requirements (.23, .23, and .22% for ADG, ADFI, and gain/ feed, respectively). Such curvilinear methods predict requirements adequate for maximum performance of all animals within the population, whereas the broken-line method estimates the requirements for the average individual of a population (Baker, 19861. The plateau method lacks the ability to interpolate between tested levels of a nutrient. At .19% dietary Trp, pigs consumed .96 g of Trp per day. Results of Exp. 1 agree with previous research that Trp is required a t .19% of the diet to optimize performance in 5- to 20-kg pigs (Gallo and Pond, 1966; Ball and Bayley, 1984). Borg et al. (1985a) reported that a slightly higher level (.20% 1 of dietary Trp was needed to maximize ADG in 6- to 14-kg pigs fed a 12% CP corn-sunflower oil meal diet. Lower estimates of .14% (LaRue et al., 19851, .15% (Zimmerman, 1975; Borg et al., 1985b1, .16% (Leibholz, 1981; Wahlstrom et al., 1985; Borg et al., 1987; Sato et al., 19871, and .17% (Lougnon, 1984) total dietary Trp have been reported. Varia-
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'Values are means of eight pens (six pigdpen). The trial lasted 28 d and began on the day of weaning when pigs averaged 28 d of age. Average initial weight was 6.2 kg. bDiets were based on corn, corn gluten meal, and fish meal, and contained 22% CP. %ingle df contrast between the control and the experimental diet containing .230% tryptophan (P e .001). dLinear and quadratic effects of dietary tryptophan (P < ,0011.
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DIGESTIBLE TRYPTOPHAN REQUIREMENTS OF PIGS
Table 4. Effect of dietary tryptophan level on performance of growing pigsa Control diet Trp,OO/
Dietary Trp, % b Item ADG, kgcd ADFI, kgd Gain/feedd Trp intake, g/d
Percentage of tryptophan determined to optimize performance
.OB
.10
.12
.14
.16
.18
.15
CV
Broken line
Plateau
Quadratic
.26 .84 .30 .87
.47 1.20 .39 1.20
.69 1.60 .43 1.92
.77 1.75 .44 2.45
BO 1.82 .44 2.92
.83 1.85 .45 3.33
.87 2.04 .43 3.05
24.8 20.1 9.7 -
.13 .13 .12
.14 .14 .12 -
.17 .17 .16 -
-
tion among reported estimates may be due to differences between research studies as previously mentioned, particularly initial and final pig weights and composition of basal diets. The .19% Trp found in this study to maximize performance of 6- to 16-kg pigs is higher than the .17% requirement of the NRC (1988) and the SCA (1987)for 5- to 10-kgpigs. The NRC (1988)suggested .14% Trp for 10- to 20-kg pigs, whereas the ARC (19811 suggested that .21% Trp is required. The ARC (1981) and SCA (1987) values were calculated using 3.60 Mcal of DE/kg of diet, the determined content of the basal diet (Table 2). Linear (P < .001) and quadratic (P e .0011 responses in ADG, ADFI, and gain/feed were found as dietary Trp increased from .08 to .18% in Exp. 2 (Table 4). Pigs fed the experimental diet containing .14% Trp grew more slowly (P e .01) than those fed the control diet (.77 vs. 87 kg/d, respectively). However, no differences (P > .lo) in ADFI or gain/feed were found. Estimates of the Trp requirement were .13, .14, and .17% Brokenline, plateau, and quadratic methods, respectively) when ADG was used as the response criterion. The intake of Trp needed to optimize ADG was 2.19 g/ d based on the broken-line estimate. The broken-line estimate of .13% Trp for growing pigs was substantially lower than the .18 and .15% recommended by the ARC (1981) and SCA (19871, respectively, and slightly higher than the .12% suggested by the NRC (1988). The estimated requirement of .13% Trp is consistent with previous research (Lin et al., 1986) and in good agreement with the .14% reported by others (Sharda et al., 1976; Russell et al., 1980, 1987; Batterham and Watson, 1985). Although broken-line analysis estimated the requirement to be .13%, the data suggest that 20- to 50-kg pigs may be able to utilize higher levels of Trp when the lysine content is 2 .90% of the diet. As Trp content increased to .18%, ADG, ADFI, and gain/feed continued to improve. Support for the hypothesis that growing pigs may need > .13% Trp can be found in reports of previous experiments. Estimated requirements of
.16% (Wahlstrom et al., 1985; Henry et al., 19861, .17% (Russell et al., 19831, and .18% (Stockland et al., 1971) have been reported. Even higher estimates of .2O% (Shelton et al., 1951) and .22%
(Lawrence, 1972) have been reported, but these estimates may be imprecise due to the large increments of Trp between dietary treatments. Performance (ADG, ADFI, and gain/feed) of finishing pigs in Exp. 3 increased linearly and quadratically (P e .001) as dietary Trp increased from .063 to .163% (Table 5). A cubic effect was found for ADG (P e .05) and gain/feed (P c .Oil, but not for ADFI (P > .lo). Pigs fed the experimental diet containing .103% Trp had performance similar (P > .lo) to those fed the control diet. Estimates of the Trp requirement were .09, .08, and .13% (broken-line, plateau, and quadratic methods, respectively). Daily Trp consumption was 2.75 g/d at the broken-line estimate of .09%. Response in performance of finishing pigs to dietary Trp content was not as large as that seen in starting and growing pigs. The larger responses of starting and growing pigs were probably due to the greater differences in Trp content between basal diets and estimated requirements (-06, .05, and .03% Trp for starting, growing, and finishing pigs, respectively). Our estimated requirement of .09% Trp is slightly lower than the . l o % suggested by the NRC (1988) and substantially lower than the .13 and .14% recommended by the SCA (1987) and ARC (19811, respectively. The .09% requirement is in close agreement with the .O8% (Sharda et al., 19761, .09% (Gallo and Pond, 19651, and .lo% (Corley and Easter, 19801 reported previously. Lewis et al. (19791 reported a higher estimate of .12% Trp when .38% lysine was added to an 11% CP, corn-soybean meal diet. In Exp. 4, Trp digestibility was 72% for the basal starting diet and was increased IP < .01) to 83% when . l o % crystalline Trp was added (Table 6). Digestibilities of leucine (90 vs 88%) and phenylalanine (89 vs 87%) were lowered (P c .051 by the addition of L-Trp. Addition of .O8% L-Trp to the
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'Values are means of 14 pens (two pigs per ped. The trials lasted 35 d. Average initial weight was 22 kg. bDiets were based on corn, corn gluten meal, and fish meal, and contained 15.5% CP. CSingle df contrast between the control and the experimental diet containing .14% tryptophan (P < .011. dLinear and quadratic effects of dietary tryptophan content P c .001).
BURGOON ET AL.
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Table 5. Effect of dietary tryptophan level on performance of finishing pigs" Control diet Trp, YO
Dietary Trp,YO Item
,063
,083 ~~
ADG, kgcde ADFI, kgCf Gain/feedcdg Trp intake, g/d
.87 2.48 .27 1.56
,103
~
.94 3.06 .31 2.54
,123
~~
.143
,163
Percentage of tryptophan determined to optimize performance CV
,120
Broken line
~~~~~~~~
1.00 3.12 .32 3.22
1.01 3.23 .31 3.97
~
.98 3.18 .31 4.55
1.00 3.14 32 5.11
.98 3.14 .31 3.77
~~
12.5 12.5 6.1 -
Plateau ~~
.09 .09 .09
~~
.08 .08 .08
-
-
Quadratic ~
~
.13 .13 .I3 -
growing basal diet increased (P e .01) Trp digestibility from 70 to 78% but had no effect ( P > .lo1 on other essential amino acids. Digestibilities of crystalline Trp, calculated by difference, were 98 and 87% based on starting and growing diets, respectively. In Exp. 5, the addition of .O8% L-Trp to the basal finishing diet increased ( P e .05) the digestibility of Trp from 59 to 8 4 % (Table 6).Lysine and histidine digestibilities tended to be greater (P e .081 when L-Trp was added to the basal diet. The remaining
essential amino acid and nitrogen digestibilities were similar (P > .lo1 between diets. Crystalline Trp digestibility was calculated by difference and found to be 105%. Energy digestibility was unaffected by the addition of Trp. Average digestibilities of gross energy were found to be 88, 90, and 87% for starting, growing, and finishing pigs, respectively. Comparisons of determined and calculated Trp digestibilities for the starting and growing basal diets show good agreement (72 vs 7 0 % and 70 vs
Table 6. Apparent digestibility of gross energy, N, and amino acids in diets used in growth trialsab Exp. 4 Starting Item,
oh
~ r p va: , ,131
GE N Amino acids Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine L-tryptophane
,230
Exp. 5
Growing
pc
.OB
.i8
Finishing pd
cv
.om
,143
87 83
80 82
90 81
89 80
1.7 2.2
86 69
87 78
89 86 86 90 88 88 89 83 72 85
88 84 84 88 88 87 87 82 83 82 98
86 85 83
87 84 82 88
1.4 1.7 1.9 1.2
78 74 73 78
87
85 86 87 78 78 81 87
1.8 1.6 1.2 2.4 3.0 1.9 -
78 75 78 88 59 71
82 80 79 a3 83 78 82 75 84 77 105
~~~~~
*
aa
88
* **
88 80 70 83
-
** ~~
-
P
cv .8 5.9
t t
3.8 3.3 5 .O 4.1 2.6 4.2 3.5 5.3 7.8 4.1
-
~
&Values are means of four observations. Mean initial and final weights were 28.8and 59 kg for Exp. 4, respectively, and 624 and 75.1 kg for Exp. 5 , respectively. Average daily feed intake averaged 3.8Y0 BW/d for each experiment. bAll digestibility values are based on ileal digesta collection except GE which is based on fecal collection. CComparison of diets containing 131 or .230% Trp. komparison of diets containing .OS or 16% ~ r p . eDigestibility of L-Trp was calculated by difference. +P < .lo.
* P < .OS. **P < .01.
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&Valuesare means of six pens of barrows and six pens of gilts (two pigs per pen). Average initial weight was 55.4kg and the trial lasted 42 d. bDiets were based on corn, corn gluten meal, and fish meal, and contained 12% CP. 'Single df contrast between the control and the experimental diet containing .103% tryptophan (P > .lo). dLinear and quadratic effects of dietary tryptophan content (P < .001). %ubic effect of dietary tryptophan content (P < ,051. fLinear and quadratic effects of dietary tryptophan content (P .011. BCubic effect of dietary tryptophan content (P .01).
DIGESTIBLE TRYPTOPHAN REQUIREMENTS OF PIGS
Implications The digestible tryptophan requirements of starting, growing, and finishing pigs were determined to be .15, .lo, and .O6%, respectively. Use of these values in conjunction with the digestible tryptophan content of feedstuffs should increase precision in diet formulation.
Literature Cited Anderson, R. L. and L. A. Nelson. 1975. A family of models involving intersecting straight lines and concomitant experimental designs useful in evaluating response to fertilizer nutrients. Biometrics 31:303. AOAC. 1984. Official Methods of Analysis (14th Ed.). Association of Official Analytical Chemists, Arlington, VA. ARC. 1981. The Nutrient Requirements of Pigs. Commonwealth Agricultural Bureaux, Slough, UK. Baker, D. H. 1986. Problems and pitfalls in animal experimentation designed to establish dietary requirements for essential nutrients. J. Nutr. 116:2339. Ball, R. O., and H. S.Bayley. 1984. Tryptophan requirement of the 2.5-kg piglet determined by the oxidation of a n indicator amino acid. J. Nutr. 114:1741. Batterham, E. S.,and C. Watson. 1985. Tryptophan content of feeds, limitations in diets and requirement for growing pigs. Anim. Feed Sci. Technol. 13:171. Borg, B. S., G. W. Libal, and R. C. Wahlstrom. 1985a. Effect of tryptophan and threonine supplementation of a corn-sunflower meal diet for weaned pigs. J. Anim. Sci. 61(suppl. 1): 99 (Abstr.). Borg, B. S., G. W. Libal, and R. C. Wahlstrom. 1985b. Effect of tryptophan supplementation of a low-protein, corn-sunflower meal diet for young growing pigs. J. Anim. Sci. 61(Suppl. 11:300 (Abstr.). Borg, B. S., G. W. Libal, and R. C. Wahlstrom. 1987. Tryptophan and threonine requirements of young pigs and their effects on serum calcium, phosphorus and zinc concentrations. J. h i m . Sci. 64:1070. Corley, J. R. and R. A. Easter. 1980. Lysine and tryptophan supplementation of low-protein diets for growing and fin ishing pigs. J. Anim. Sci. 51(Suppl. 1):lQl(Abstr.).
Gallo, J. T., and W. G. Pond. 1985. Lysine and tryptophan in corn diets for finishing pigs. J. Anim. Sci. 24:881 (Abstr.). Gallo, J. T., and W. G. Pond. 1966. Tryptophan requirement of early-weaned pigs from three to seven weeks of age. J. Anim. sci. 25:774. Henry, Y.,P. H. Duee, A. Rerat, and R. Ron. 1986. Determination of tryptophan requirement of growing pigs between 15 and 40 kg live weight. Nutr. Rep. Int. 34:565. Kimura, F. T., and V. L. Miller. 1957. Improved determination of chromic oxide in cow feed and feces. J. Agric. Food Chem. 5:216. Knabe, D. A., D. C. LaRue, E. J. Gregg, G. M. Martinez, and T. D. Tanksley, Jr. 1989. Apparent digestibility of nitrogen and amino acids in protein feedstuffs by growing pigs. J. Anim. Sci. 67:441. LaRue, D. C. 1985. Comparative alkaline hydrolysis for the determination of tryptophan in feedstuffs and determination of the tryptophan requirement for 5 to 20 and 20 to 50 kilogram pigs. Ph.D. Dissertation. Texas A&M Univ., College Station. LaRue, D. C., T. D. Tanksley, Jr., and D. A. Knabe. 1985. Tryptophan requirement of starter pigs fed a corn-soybean meal diet. J. Anim. Sci. 61(Suppl. 1):314 (Abstr.). Lawrence, T. L. 1972. High level cereal diets for the growing/ finishing pig. VII. The performance of weaned pigs grown to cutter weight (160 Ib. live weight) on iso-nitrogenous maize-based diets containing different levels of lysine and tryptophan. J. Agric. Sci. (Camb.) 79:161. Leibholz, J. 1981. Tryptophan requirements of pigs between 28 and 58 days of age. Aust. J. Agric. Res. 32:845. Lewis, A. J., E. R. Peo, Jr., B. D. Moser ,and T. D. Crenshaw. 1979. Additions of lysine, tryptophan, methionine and isoleucine to all-corn diets for finishing swine. Nutr. Rep. Int. 19:533. Lin, F. D., D. A. Knabe, and T. D. Tanksley, Jr. 1987. Apparent digestibility of amino acids, gross energy and starch in corn, sorghum, wheat, barley, oat groats and wheat middlings for growing pigs. J. Anim. Sci. 64:1655. Lin, F. D., T. K. Smith, and H. S. Bayley. 1988. Tryptohan requirement of growing swine as determined by the oxidation of a n indicator amino acid. J. Anim. Sci. 62:660. Lougnon, J. 1984. Nutritional importance and indispensability of tryptophan. In: 16’emes Journ. Rech. Porcine Fr. p 371. Martinez, G. M., and D. A. Knabe. 1990. Digestible lysine requirement of starter and grower pigs. J. Anim. Sci. 68:2748. NRC. 1988. Nutrient Requirements of Swine (9th Ed.). National Academy Press, Washington, DC. Robbins, K. R. 1986. A method, SAS program, and example for fitting the broken-line to growth data. Univ. of Tennessee Agric. Exp. Sta. Rep. 86-09. Knoxville, TN. Russell, L. E., G. L. Cromwell, and T. S. Stahly. 1980. L-tryptophan supplementation of low protein diets for growing pigs. J. Anim. Sci. 51(Suppl. 1):219 (Abstr.1. Russell, L. E., G. L. Cromwell, and T. S. Stahly. 1983. Tryptophan, threonine, isoleucine and methionine supplementation of a 12% protein, lysine-supplemented, corn-soybean meal diet for growing pigs. J. Anim. Sci. 56:1115. Russell, L. E., B. J. Kerr, and R. A. Easter. 1987. Limiting amino acids in a n 1 1 % crude protein corn-soybean meal diet for growing pigs. J. Anim. Sci. 65:1266. SAS. 1985. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC. Sato, H., T. Kobayashi, R. W. Jones, and R. A. Easter. 1987. Tryptophan availability of some feedstuffs determined by the pig growth assay. J. Anim. Sci. 64:191. Sauer, W. G., and L. Ozimek. 1986. Digestibility of amino acids in swine: results and their practical applications. A review. Livest. Prod. Sci. 15:367. SCA. 1987. Australian Agricultural Council. Feeding standards for Australian livestock: Pigs. CSIRO Editorial and Publish-
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73%), indicating that digestibilities of individual feedstuffs can be used to predict accurately the digestibility of complete diets. Such a,comparison for finishing diets (59 vs 71%) is not as favorable, however. The Trp digestibility of 59% may have been too low. One possible reason is the larger variability in Exp. 5 vs Exp. 4 (CV = 7.8 vs 3.0%, respectively). Also, the low Trp content of basal finishing diets may have contributed to a higher proportion of endogenous Trp in digesta samples, thereby lowering the apparent digestibility. The L-Trp digestibilities of 98, 87, and 105% for starting, growing, and finishing pigs, respectively, were averaged, producing a mean L-Trp digestibility of 97%. The mean digestibility for L-Trp was used in calculating the digestible requirements of .15, .LO, and .O6% Trp for starting, growing, and finishing pigs, respectively.
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ing, East Melbourne, Australia. Sharda, D. P., D. C. Mahan, and R. F. Wilson. 1978. Limiting amino acids in low-protein corn-soybean meal diets for growingfinishing swine. J. Anim. Sci. 42:1175. Shelton, D. C., W. M. Beeson, and E. T. Mertz. 1951. Quantitative DL-tryptophan requirement of the weanling pig. J. Anim. sci. 10:73. Stockland, W. L., R. J. Meade, and J. W. Nordstrom. 1971. Lysine, methionine and tryptophan supplementation of a corn-meat and bone meal diet for growing swine. J. Anim. Sci. 32:282.
Tmksley, T. D. Jr., and D. A. Knabe. 1984. Ileal digestibilities of amino acids in pig feeds and their use in formulating diets. In: W. Haresign and D.J.A. Cole (Ed.) Recent Advances in Animal Nutrition 1984. pp 75-94. Butterworths, London. Wahlstrom, R. C., G. W. Libal, and R. C. Thaler. 1985. Efficacy of supplemental tryptophan, threonine, isoleucine and methionine for weanling pigs fed a low-protein, lysine-supplemented, corn-sunflower meal diet. J. Anim. Sci. 60:720. Zimmerman, D. R. 1975. Tryptophan requirements of 5- to 15-kg pigs with semi-practical pig starters. J. Anim. Sci. 40: 875.
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ken-line regression analyses determined the total dietary Trp requirements needed to optimize performance to be .19, .13, and .09% (as-fed basis) for starting, growing, and finishing pigs, respectively. These concentrations equated to Trp intakes of .96, 2.18, and 2.88 g/d. A digestion trial using growing pigs (29 kg initially) determined the apparent ileal digestibility of Trp in the basal starting and growing diets to be 72 and 709'0, respectively; a similar trial with finishing pigs (55 kg initially) found 59% Trp digestibility for the basal finishing diet. Mean digestibility of L-Trp was 97%. Based on these values and the total Trp requirements given above, the digestible Trp requirements are .15, .lo, and .O6% for starting, growing, and finishing pigs, respectively.
Key Words: Pigs, Tryptophan, Requirements, Amino Acids, Digestibility
J. Anim. Sci. 1992. 70:2493-2500
Introduction Lysine (Lys) and tryptophan (Trp) are generally considered the first- and second-limiting amino acids in most corn-based pig diets. A large amount of research has been conducted to estimate the total dietary Lys and Trp requirements. Only recently was the digestible Lys requirement reported for starting and growing pigs (Martinez and Knabe, 1990). Estimates of the total dietary Trp requirements have been reviewed by the ARC (19811, SCA (19871, and NRC (1988). Results of experiments cited in these publications vary considerably for pigs within a given weight range. A number of factors may affect these results, including genotype, dietary energy and protein content,
'Publication T. A. 30219, Texas Agric. Exp. Sta. Appreciation is expressed to Heartland Lysine, for providing the crystalline amino acids used in this research. 2To whom correspondence should be addressed. Received September 18, 1991. Accepted March 18, 1992.
initial and final pig weights, feed intake, and variation in digestibility or availability of amino acids among feedstuffs. The apparent digestibilities of amino acids vary among feedstuffs used in pig diets (Sauer and Ozimek, 1986; Knabe et al., 1989). The ARC (19811, SCA (19871, and NRC (19881 acknowledge a need to formulate diets based on a digestible basis. Formulating diets on a digestible amino acid basis would improve feedstuff use and more accurately meet the requirements of swine (Tanksley and Knabe, 1984). The objective of this study was to determine the digestible Trp requirement of starting, growing, and finishing pigs.
Experimental Procedures Representative samples of the corn, soybean meal, menhaden fish meal, and corn gluten meal used in these studies were ground through a 1-mm screen and then analyzed for CP content IAOAC, 19841, amino acid content (Knabe et al., 19891, and Trp content (LaRue, 1985). Diets were
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ABSTRACT: Seven hundred eight crossbred pigs were used in growth and digestion trials to determine the digestible tryptophan ITrp) requirement of starting (6 to 16 kgl, growing (22 to 50 kg), and finishing (55 to 97 kg) pigs. Each growth trial evaluated a corn-fish meal-corn gluten meal basal diet, the basal diet with five incremental additions of L-Trp, and a control corn-soybean meal diet. The tryptophan content of the six incremental diets ranged from .13 to .255% for starting pigs, .08 to .18% for growing pigs, and .063 to .163% for finishing pigs. Lysine contents of basal diets were 1.38, .90, and .72% for starting, growing, and finishing diets, respectively. In all trials, ADG, ADFI, and gain/feed increased (P < .001) linearly and quadratically as dietary Trp increased. Bro-
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BURGOON ET AL.
Table 1. Chemical analyses of feedstuffsa Soybean meal
Corn Item
DM,% CP,Yo
-
Corn gluten meal
12
3
12
3
1.2,3
1.2
3
89.2 10.5
90.0 7.2
91.5 44.5
91.7 43.8
93.9 62.1
89.1 59.8
93.5 62.3
.51 .31 .40 .43 .28 .26 .26 .57 .40 .06 .53
.40 .22 .28 .95 .25 .38 .29 .05 .39
3.37 1.21 2.07 3.41 2.88 .66 .73 2.25 1.68 .54 2.18
3.44 1.23 2.23 3.66 2.94
2.37 1.88 .54 2.31
3.71 1.66 2.74 4.71 4.94 1.84
BO 2.62 2.69 .54 3.22
1.92 1.09 2.55 9.95 1.14 1.42 1.19 3.86 1.98 .22 2.80
2.01 1.20 2.73 10.60 1.20
4.20 2.14 .25 3.00
*Values are expressed on an as-fed basis. bAnalyses of methionine and cystine were conducted by Heartland Lysine, Eddyville, IA.
formulated using the analyzed CP and amino acid contents (Table 1). A total of seven dietary treatments were used in each growth trial. The basal diets were formulated to provide 22, 15.5, and 12% protein for starting, growing, and finishing pigs, respectively (Table 2). Calculated tryptophan contents of the corresponding basal diet were .13, .08, and .063%, respectively. Additions of crystalline lysine were made to basal diets to provide 120% of the lysine requirements (NRC, 1988). Crystalline threonine was added to provide an estimated dietary digestible threonine content equal to 70% of the estimated digestible lysine content. Digestible amino acid contents were calculated using apparent digestibilities reported by Lin et al. (1987) for corn and digestibilities reported by Knabe et al. (1989) for other feedstuffs. Dietary contents of remaining amino acids were a t least 120, 120, and 114% of the NRC (1988) requirements for 5- to 10-kg, 20- to 50-kg, and 50- to 110-kg pigs, respectively. Crystalline tryptophan (L-Trp)was added a t five incremental amounts to the basal diet in each trial to produce a titration effect. A glutamic acid/ glycine mixture (1.96:l) was substituted at the expense of cornstarch and L-Trp to ensure that experimental diets were isonitrogenous. Conventional corn-soybean meal diets (22, 17, and 13% CP, and 1.20, .80, and .65% lysine for starting, growing, and finishing pigs, respectively) were included in each trial to serve as a control. Experiment 1 consisted of two 28-d trials using 336 crossbred (Yorkshire-Landrace sows x DurocHampshire boars) pigs. The average initial weight was 6.2 kg. Trials started on the day of weaning when pigs were approximately 28 d of age. Each trial was arranged in a randomized complete
block design; blocks consisted of initial weight and pen location within the nursery. Littermates were balanced across treatments as much as possible without regard to sex. Pigs were housed six per pen (1.5-m x 1.5-m,with woven-wire flooring) in an enclosed nursery. Ambient temperature in the nursery was maintained at 29OC for the initial 7 d, and then gradually lowered to 24OC by d 21. Pigs were allowed a d libitum access to feed and water. Experiment 2 used 196 crossbred pigs (same genotype as Exp. 1) in two 35-d trials. Average initial pig weight was 21.9 kg. Each trial was arranged in a randomized complete block, with 14 replicates blocked according to initial weight and sex. Littermates were distributed as in Exp. 1. Pigs were housed two per pen (1.22-m x 4.9-m, with a solid concrete floor) in a n open-sided growing finishing building. Each pen was equipped with a fogger activated by a thermostat when the air temperature was > 29°C. The trials were conducted between April 7, 1989 and June 19, 1989; mean daily minimum and maximum temperatures were 19.1 and 30.1°C, respectively. Pigs were allowed a d libitum access to feed and water. Experiment 3 was identical in experimental design to Exp. 2 but only 12 replicates were used (168 total pigs) and the trials lasted 42 d. Average initial pig weight was 55.4 kg. The trials were conducted between November 17, 1989 and February 16, 1990; mean daily minimum and maximum temperatures were 5.3 and 11.8”C, respectively. Bedding was provided when temperatures were < 0°C. Experiment 4 was a digestion trial arranged in a 4 x 4 Latin square design. Diets consisted of the basal diets from Exp. 1 and 2 and the same diets with .10 or . O 8 % Trp added, respectively. Composi-
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Amino acids, TO Arginine Histidine Isoleucine Leucine Lysine Methionineb Cystine” Phenylalanine Threonine Tryptophan Valine
Fish meal
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DIGESTIBLE TRYPTOPHAN REQUIREMENTS OF PIGS
period, and feed intake was adjusted before the first meal of subsequent periods. Water was mixed with feed a t a 1:l feed:water ratio to form a moist mash. Pigs were allowed ad libitum access to water in stainless steel feeders after consumption of each meal. Experimental periods consisted of 5 d of diet adjustment, 2 d of feces collection, and 3 d of ileal digesta collection. Feces were collected at 12-hintervals; ileal digesta were collected between 0700 and 1800. Ileal digesta samples were collected, stored, and prepared using procedures described by Knabe et al. (1989). Ileal and diet samples were analyzed for protein and amino acid content as described for
Table 2. Percentage of composition and analyses of positive control and basal diets used in the growth trialsa Starting Item Corn Soybean meal Corn gluten meal Fish meal Dicalcium phosphate Limestone Vitamin premix” Trace mineral premixC Antibacterial mixd Salt 1.96:1 Glu:Glye L-LYs HCl, 98% L-Thr Calculated content, YO CP, Yo Lysine Tryptophan Threonine Isoleucine Calcium Phosphorus Analyzed content, % CP, 010 Lysine Tryptophan Threonine Isoleucine, DE, kcal/d
Growing
Finishing
Control
Basal
Control
Basal
Control
Basal
59.84 35.65 -
77.27 20.00
87.37
82.17 15.40
89.07
-
72.23 4.00 11.34 8.00 1.a5 .44 .50 .15 1 .oo .25 .14 .67 .23
22.15 1.20 .23 .84 .98 .85 .70
22.02 1.38 .13 1.03 .88 .85 .70
17.01
22.4 1.24 ,233 .94 1.03
22.41 1.39 .13gf 1 .OB .91 3.59
17.0 .81 ,156 .67 .74
-
1.61 1.00 .50 .15 1 .oo .25 -
-
-
1.12 .86 .25 .15 .10 .25
-
.EO
.15 .65 .72 .65 .55
-
-
6.80 2.50 1.12 .64 .25 .15 .10 .25 .ll .57 .14
-
-
.90
.88 .25 .15
-
.25
-
-
-
-
6.00 2.00 .90 .72 .25 .15 .25 .ll .42 .13
15.52 .90 .08 .70 .59 .65 .55
12.65 .65 .12 .51 .57 .60 .50
11.98 .72 .06 .54 .46
15.64 .92 ,0928 .09 .59 3.75
13.06
12.20 .73 .064h .56 .46 3.60
.66
.ll .52 .50 -
BO .50
‘Values are expressed on a n as-fed basis. bAdding .50% of the premix contributed the following per kilogram of diet: vitamin A,7,715IU; vitamin DB,770 IU; vitamin E,44 IU; menadione sodium bisulfate complex, 9 mg; riboflavin, 7.7 mg; d-calcium pantothenate, 33 mg; niacin, 33 mg; choline, 287 mg; vitamin BIZ,44 pg;and d-biotin 220
M.
‘Contributed the following per kilogram of diet: Cu, 10 mg; Fe, 100 mg;I, .3mg; Mn, 20 mg; Zn, 100 mg; Se, .3 mg. dContributed 25 mg of carbadox or 110 mg of chlortetracycline/kg of starter and grower diets,
respectively. eWeighted ratio provided equal N from Glu and Gly. ‘Analyzed total tryptophan contents of the six experimental starting diets were ,139,,160,,177, ,202,,213,and .235%. BAnalyzed total tryptophan contents of the six experimental growing diets were .092,,106,,125, .142 152, and .172%. ~ k a l y z e dtotal tryptophan contents of the six experimental finishing diets were ,064,,078,,093, ,107,.119,and .141%. ’Based on results of Exp. 4 and 5.
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tion of diets was identical to diets used in Exp. 1 and 2 except that .25% chromic oxide was substituted for corn. Four barrows, initially weighing 29 kg, were fitted with a simple T-cannula approximately 10 cm anterior to the ileo-cecal junction. Halothane gas was used to induce and maintain a surgical plane of anesthesia. Pigs were placed in 1-m x 2-m stainless steel metabolism cages immediately after surgery, and the trial was initiated after a 14-d postoperative recovery period. Ambient temperature was maintained a t 21 & 1°C. Pigs were fed approximately 3.8% BW/d in two equal meals at 0700 and 1800. Body weight of pigs was measured at the end of each experimental
BURGOON ET AL.
2496
Table 3. Effect of dietary tryptophan level on performance of starting pigsa Control diet Trp, YO
Dietary Trp,% Item
,130
,155
ADG, kgCd ADFI, kgCd Gain/feedcd Trp intake, g/d
.17
.25 .39 .64
.so .57 .40
.61
Percentage of tryptophan determined to optimize performance
.180
,205
.230
.255
,230
CV
.32
.34 .50
.34 .51
.35 .53
.39 .64 .6 1 1.47
10.7 10.1 5.5
.4a .66 .86
.66
.66
.66
1.02
1.18
1.35
-
Broken line
Plateau
Quadratic
.19
.18 .18
.23 .23 .22
.19 .16
-
.18
-
the feedstuffs. Chromic oxide contents were determined using the procedure of Kimura and Miller (19571. Feces were analyzed for energy (adiabatic bomb calorimetry) and chromic oxide contents. Experiment 5 used a two-period crossover design. Four finishing barrows averaging 62 kg of BW, initially, were used to evaluate the basal diet from Exp. 3 containing .063% Trp and a similar diet containing .O8% added L-Trp. Pigs were fed approximately 3.6% BW/d. Environment, feeding schedule, collection, and analyses of diet, fecal, and ileal digesta samples were similar to those in Exp. 4, except that ileal digesta collection occurred for only 2 d. The experimental unit was the pen in Exp. 1, 2, and 3. Trial, block within trial, diet, and trial x diet interaction effects were evaluated in the statistical model. The trial x diet interaction was not significant (P > .25) in any analyses. Dietary Trp levels were partitioned into linear and quadratic effects (positive control deleted), and a single df contrast was performed to compare the positive control and the diet approximating the Trp requirement s u g gested by the NRC (1988). When a significant (P < .05) quadratic effect was found, the Trp requirement was estimated by fitting a broken-line to the data Bobbins, 19861, by using a plateau method (Anderson and Nelson, 1975) and by calculation of the inflection from the quadratic equation (SAS, 1985). In Exp. 3, the statistical model also included sex and the sex x diet interaction. The sex x diet interaction was not significant and estimated requirements using data from barrows or gilts were identical. Therefore, estimated requirements are based on combined data for barrows and gilts. In Exp. 4 and 5, the pig within a period was the experimental unit. Experiment 4 was analyzed as a 4 x 4 Latin square and Exp. 5 as a crossover design. Single df contrasts were used to evaluate the effect of Trp addition on amino acid digestibilities and to determine whether average digestibilities differed between starting and growing diets in
Exp. 4. Procedures of SAS (1985) were used for all analyses.
Results and Discussion Average daily gain, ADFI, and gain/feed increased linearly (P < .001) and quadratically (P < .0011 as dietary Trp content increased from .13 to .255% in Exp. 1 (Table 3). Growth rate and feed consumption were poorer (P < .0011 for pigs fed the diet containing .23% Trp than for those fed the control diet; however, gain/feed was greater (P .001) for pigs fed the .23% Trp diet. Estimates of the dietary Trp content required to optimize ADG, ADFI, and gain/feed (Table 3) by broken-line and plateau method estimates agreed well. Predicted values by the broken-line and plateau methods were, respectively, ADG, .19 and .l8%; ADFI, .19 and .l8%; and gain/feed, .16 and . l 8 % . The quadratic method estimated much higher requirements (.23, .23, and .22% for ADG, ADFI, and gain/ feed, respectively). Such curvilinear methods predict requirements adequate for maximum performance of all animals within the population, whereas the broken-line method estimates the requirements for the average individual of a population (Baker, 19861. The plateau method lacks the ability to interpolate between tested levels of a nutrient. At .19% dietary Trp, pigs consumed .96 g of Trp per day. Results of Exp. 1 agree with previous research that Trp is required a t .19% of the diet to optimize performance in 5- to 20-kg pigs (Gallo and Pond, 1966; Ball and Bayley, 1984). Borg et al. (1985a) reported that a slightly higher level (.20% 1 of dietary Trp was needed to maximize ADG in 6- to 14-kg pigs fed a 12% CP corn-sunflower oil meal diet. Lower estimates of .14% (LaRue et al., 19851, .15% (Zimmerman, 1975; Borg et al., 1985b1, .16% (Leibholz, 1981; Wahlstrom et al., 1985; Borg et al., 1987; Sato et al., 19871, and .17% (Lougnon, 1984) total dietary Trp have been reported. Varia-
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'Values are means of eight pens (six pigdpen). The trial lasted 28 d and began on the day of weaning when pigs averaged 28 d of age. Average initial weight was 6.2 kg. bDiets were based on corn, corn gluten meal, and fish meal, and contained 22% CP. %ingle df contrast between the control and the experimental diet containing .230% tryptophan (P e .001). dLinear and quadratic effects of dietary tryptophan (P < ,0011.
2497
DIGESTIBLE TRYPTOPHAN REQUIREMENTS OF PIGS
Table 4. Effect of dietary tryptophan level on performance of growing pigsa Control diet Trp,OO/
Dietary Trp, % b Item ADG, kgcd ADFI, kgd Gain/feedd Trp intake, g/d
Percentage of tryptophan determined to optimize performance
.OB
.10
.12
.14
.16
.18
.15
CV
Broken line
Plateau
Quadratic
.26 .84 .30 .87
.47 1.20 .39 1.20
.69 1.60 .43 1.92
.77 1.75 .44 2.45
BO 1.82 .44 2.92
.83 1.85 .45 3.33
.87 2.04 .43 3.05
24.8 20.1 9.7 -
.13 .13 .12
.14 .14 .12 -
.17 .17 .16 -
-
tion among reported estimates may be due to differences between research studies as previously mentioned, particularly initial and final pig weights and composition of basal diets. The .19% Trp found in this study to maximize performance of 6- to 16-kg pigs is higher than the .17% requirement of the NRC (1988) and the SCA (1987)for 5- to 10-kgpigs. The NRC (1988)suggested .14% Trp for 10- to 20-kg pigs, whereas the ARC (19811 suggested that .21% Trp is required. The ARC (1981) and SCA (1987) values were calculated using 3.60 Mcal of DE/kg of diet, the determined content of the basal diet (Table 2). Linear (P < .001) and quadratic (P e .0011 responses in ADG, ADFI, and gain/feed were found as dietary Trp increased from .08 to .18% in Exp. 2 (Table 4). Pigs fed the experimental diet containing .14% Trp grew more slowly (P e .01) than those fed the control diet (.77 vs. 87 kg/d, respectively). However, no differences (P > .lo) in ADFI or gain/feed were found. Estimates of the Trp requirement were .13, .14, and .17% Brokenline, plateau, and quadratic methods, respectively) when ADG was used as the response criterion. The intake of Trp needed to optimize ADG was 2.19 g/ d based on the broken-line estimate. The broken-line estimate of .13% Trp for growing pigs was substantially lower than the .18 and .15% recommended by the ARC (1981) and SCA (19871, respectively, and slightly higher than the .12% suggested by the NRC (1988). The estimated requirement of .13% Trp is consistent with previous research (Lin et al., 1986) and in good agreement with the .14% reported by others (Sharda et al., 1976; Russell et al., 1980, 1987; Batterham and Watson, 1985). Although broken-line analysis estimated the requirement to be .13%, the data suggest that 20- to 50-kg pigs may be able to utilize higher levels of Trp when the lysine content is 2 .90% of the diet. As Trp content increased to .18%, ADG, ADFI, and gain/feed continued to improve. Support for the hypothesis that growing pigs may need > .13% Trp can be found in reports of previous experiments. Estimated requirements of
.16% (Wahlstrom et al., 1985; Henry et al., 19861, .17% (Russell et al., 19831, and .18% (Stockland et al., 1971) have been reported. Even higher estimates of .2O% (Shelton et al., 1951) and .22%
(Lawrence, 1972) have been reported, but these estimates may be imprecise due to the large increments of Trp between dietary treatments. Performance (ADG, ADFI, and gain/feed) of finishing pigs in Exp. 3 increased linearly and quadratically (P e .001) as dietary Trp increased from .063 to .163% (Table 5). A cubic effect was found for ADG (P e .05) and gain/feed (P c .Oil, but not for ADFI (P > .lo). Pigs fed the experimental diet containing .103% Trp had performance similar (P > .lo) to those fed the control diet. Estimates of the Trp requirement were .09, .08, and .13% (broken-line, plateau, and quadratic methods, respectively). Daily Trp consumption was 2.75 g/d at the broken-line estimate of .09%. Response in performance of finishing pigs to dietary Trp content was not as large as that seen in starting and growing pigs. The larger responses of starting and growing pigs were probably due to the greater differences in Trp content between basal diets and estimated requirements (-06, .05, and .03% Trp for starting, growing, and finishing pigs, respectively). Our estimated requirement of .09% Trp is slightly lower than the . l o % suggested by the NRC (1988) and substantially lower than the .13 and .14% recommended by the SCA (1987) and ARC (19811, respectively. The .09% requirement is in close agreement with the .O8% (Sharda et al., 19761, .09% (Gallo and Pond, 19651, and .lo% (Corley and Easter, 19801 reported previously. Lewis et al. (19791 reported a higher estimate of .12% Trp when .38% lysine was added to an 11% CP, corn-soybean meal diet. In Exp. 4, Trp digestibility was 72% for the basal starting diet and was increased IP < .01) to 83% when . l o % crystalline Trp was added (Table 6). Digestibilities of leucine (90 vs 88%) and phenylalanine (89 vs 87%) were lowered (P c .051 by the addition of L-Trp. Addition of .O8% L-Trp to the
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'Values are means of 14 pens (two pigs per ped. The trials lasted 35 d. Average initial weight was 22 kg. bDiets were based on corn, corn gluten meal, and fish meal, and contained 15.5% CP. CSingle df contrast between the control and the experimental diet containing .14% tryptophan (P < .011. dLinear and quadratic effects of dietary tryptophan content P c .001).
BURGOON ET AL.
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Table 5. Effect of dietary tryptophan level on performance of finishing pigs" Control diet Trp, YO
Dietary Trp,YO Item
,063
,083 ~~
ADG, kgcde ADFI, kgCf Gain/feedcdg Trp intake, g/d
.87 2.48 .27 1.56
,103
~
.94 3.06 .31 2.54
,123
~~
.143
,163
Percentage of tryptophan determined to optimize performance CV
,120
Broken line
~~~~~~~~
1.00 3.12 .32 3.22
1.01 3.23 .31 3.97
~
.98 3.18 .31 4.55
1.00 3.14 32 5.11
.98 3.14 .31 3.77
~~
12.5 12.5 6.1 -
Plateau ~~
.09 .09 .09
~~
.08 .08 .08
-
-
Quadratic ~
~
.13 .13 .I3 -
growing basal diet increased (P e .01) Trp digestibility from 70 to 78% but had no effect ( P > .lo1 on other essential amino acids. Digestibilities of crystalline Trp, calculated by difference, were 98 and 87% based on starting and growing diets, respectively. In Exp. 5, the addition of .O8% L-Trp to the basal finishing diet increased ( P e .05) the digestibility of Trp from 59 to 8 4 % (Table 6).Lysine and histidine digestibilities tended to be greater (P e .081 when L-Trp was added to the basal diet. The remaining
essential amino acid and nitrogen digestibilities were similar (P > .lo1 between diets. Crystalline Trp digestibility was calculated by difference and found to be 105%. Energy digestibility was unaffected by the addition of Trp. Average digestibilities of gross energy were found to be 88, 90, and 87% for starting, growing, and finishing pigs, respectively. Comparisons of determined and calculated Trp digestibilities for the starting and growing basal diets show good agreement (72 vs 7 0 % and 70 vs
Table 6. Apparent digestibility of gross energy, N, and amino acids in diets used in growth trialsab Exp. 4 Starting Item,
oh
~ r p va: , ,131
GE N Amino acids Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine L-tryptophane
,230
Exp. 5
Growing
pc
.OB
.i8
Finishing pd
cv
.om
,143
87 83
80 82
90 81
89 80
1.7 2.2
86 69
87 78
89 86 86 90 88 88 89 83 72 85
88 84 84 88 88 87 87 82 83 82 98
86 85 83
87 84 82 88
1.4 1.7 1.9 1.2
78 74 73 78
87
85 86 87 78 78 81 87
1.8 1.6 1.2 2.4 3.0 1.9 -
78 75 78 88 59 71
82 80 79 a3 83 78 82 75 84 77 105
~~~~~
*
aa
88
* **
88 80 70 83
-
** ~~
-
P
cv .8 5.9
t t
3.8 3.3 5 .O 4.1 2.6 4.2 3.5 5.3 7.8 4.1
-
~
&Values are means of four observations. Mean initial and final weights were 28.8and 59 kg for Exp. 4, respectively, and 624 and 75.1 kg for Exp. 5 , respectively. Average daily feed intake averaged 3.8Y0 BW/d for each experiment. bAll digestibility values are based on ileal digesta collection except GE which is based on fecal collection. CComparison of diets containing 131 or .230% Trp. komparison of diets containing .OS or 16% ~ r p . eDigestibility of L-Trp was calculated by difference. +P < .lo.
* P < .OS. **P < .01.
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&Valuesare means of six pens of barrows and six pens of gilts (two pigs per pen). Average initial weight was 55.4kg and the trial lasted 42 d. bDiets were based on corn, corn gluten meal, and fish meal, and contained 12% CP. 'Single df contrast between the control and the experimental diet containing .103% tryptophan (P > .lo). dLinear and quadratic effects of dietary tryptophan content (P < .001). %ubic effect of dietary tryptophan content (P < ,051. fLinear and quadratic effects of dietary tryptophan content (P .011. BCubic effect of dietary tryptophan content (P .01).
DIGESTIBLE TRYPTOPHAN REQUIREMENTS OF PIGS
Implications The digestible tryptophan requirements of starting, growing, and finishing pigs were determined to be .15, .lo, and .O6%, respectively. Use of these values in conjunction with the digestible tryptophan content of feedstuffs should increase precision in diet formulation.
Literature Cited Anderson, R. L. and L. A. Nelson. 1975. A family of models involving intersecting straight lines and concomitant experimental designs useful in evaluating response to fertilizer nutrients. Biometrics 31:303. AOAC. 1984. Official Methods of Analysis (14th Ed.). Association of Official Analytical Chemists, Arlington, VA. ARC. 1981. The Nutrient Requirements of Pigs. Commonwealth Agricultural Bureaux, Slough, UK. Baker, D. H. 1986. Problems and pitfalls in animal experimentation designed to establish dietary requirements for essential nutrients. J. Nutr. 116:2339. Ball, R. O., and H. S.Bayley. 1984. Tryptophan requirement of the 2.5-kg piglet determined by the oxidation of a n indicator amino acid. J. Nutr. 114:1741. Batterham, E. S.,and C. Watson. 1985. Tryptophan content of feeds, limitations in diets and requirement for growing pigs. Anim. Feed Sci. Technol. 13:171. Borg, B. S., G. W. Libal, and R. C. Wahlstrom. 1985a. Effect of tryptophan and threonine supplementation of a corn-sunflower meal diet for weaned pigs. J. Anim. Sci. 61(suppl. 1): 99 (Abstr.). Borg, B. S., G. W. Libal, and R. C. Wahlstrom. 1985b. Effect of tryptophan supplementation of a low-protein, corn-sunflower meal diet for young growing pigs. J. Anim. Sci. 61(Suppl. 11:300 (Abstr.). Borg, B. S., G. W. Libal, and R. C. Wahlstrom. 1987. Tryptophan and threonine requirements of young pigs and their effects on serum calcium, phosphorus and zinc concentrations. J. h i m . Sci. 64:1070. Corley, J. R. and R. A. Easter. 1980. Lysine and tryptophan supplementation of low-protein diets for growing and fin ishing pigs. J. Anim. Sci. 51(Suppl. 1):lQl(Abstr.).
Gallo, J. T., and W. G. Pond. 1985. Lysine and tryptophan in corn diets for finishing pigs. J. Anim. Sci. 24:881 (Abstr.). Gallo, J. T., and W. G. Pond. 1966. Tryptophan requirement of early-weaned pigs from three to seven weeks of age. J. Anim. sci. 25:774. Henry, Y.,P. H. Duee, A. Rerat, and R. Ron. 1986. Determination of tryptophan requirement of growing pigs between 15 and 40 kg live weight. Nutr. Rep. Int. 34:565. Kimura, F. T., and V. L. Miller. 1957. Improved determination of chromic oxide in cow feed and feces. J. Agric. Food Chem. 5:216. Knabe, D. A., D. C. LaRue, E. J. Gregg, G. M. Martinez, and T. D. Tanksley, Jr. 1989. Apparent digestibility of nitrogen and amino acids in protein feedstuffs by growing pigs. J. Anim. Sci. 67:441. LaRue, D. C. 1985. Comparative alkaline hydrolysis for the determination of tryptophan in feedstuffs and determination of the tryptophan requirement for 5 to 20 and 20 to 50 kilogram pigs. Ph.D. Dissertation. Texas A&M Univ., College Station. LaRue, D. C., T. D. Tanksley, Jr., and D. A. Knabe. 1985. Tryptophan requirement of starter pigs fed a corn-soybean meal diet. J. Anim. Sci. 61(Suppl. 1):314 (Abstr.). Lawrence, T. L. 1972. High level cereal diets for the growing/ finishing pig. VII. The performance of weaned pigs grown to cutter weight (160 Ib. live weight) on iso-nitrogenous maize-based diets containing different levels of lysine and tryptophan. J. Agric. Sci. (Camb.) 79:161. Leibholz, J. 1981. Tryptophan requirements of pigs between 28 and 58 days of age. Aust. J. Agric. Res. 32:845. Lewis, A. J., E. R. Peo, Jr., B. D. Moser ,and T. D. Crenshaw. 1979. Additions of lysine, tryptophan, methionine and isoleucine to all-corn diets for finishing swine. Nutr. Rep. Int. 19:533. Lin, F. D., D. A. Knabe, and T. D. Tanksley, Jr. 1987. Apparent digestibility of amino acids, gross energy and starch in corn, sorghum, wheat, barley, oat groats and wheat middlings for growing pigs. J. Anim. Sci. 64:1655. Lin, F. D., T. K. Smith, and H. S. Bayley. 1988. Tryptohan requirement of growing swine as determined by the oxidation of a n indicator amino acid. J. Anim. Sci. 62:660. Lougnon, J. 1984. Nutritional importance and indispensability of tryptophan. In: 16’emes Journ. Rech. Porcine Fr. p 371. Martinez, G. M., and D. A. Knabe. 1990. Digestible lysine requirement of starter and grower pigs. J. Anim. Sci. 68:2748. NRC. 1988. Nutrient Requirements of Swine (9th Ed.). National Academy Press, Washington, DC. Robbins, K. R. 1986. A method, SAS program, and example for fitting the broken-line to growth data. Univ. of Tennessee Agric. Exp. Sta. Rep. 86-09. Knoxville, TN. Russell, L. E., G. L. Cromwell, and T. S. Stahly. 1980. L-tryptophan supplementation of low protein diets for growing pigs. J. Anim. Sci. 51(Suppl. 1):219 (Abstr.1. Russell, L. E., G. L. Cromwell, and T. S. Stahly. 1983. Tryptophan, threonine, isoleucine and methionine supplementation of a 12% protein, lysine-supplemented, corn-soybean meal diet for growing pigs. J. Anim. Sci. 56:1115. Russell, L. E., B. J. Kerr, and R. A. Easter. 1987. Limiting amino acids in a n 1 1 % crude protein corn-soybean meal diet for growing pigs. J. Anim. Sci. 65:1266. SAS. 1985. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC. Sato, H., T. Kobayashi, R. W. Jones, and R. A. Easter. 1987. Tryptophan availability of some feedstuffs determined by the pig growth assay. J. Anim. Sci. 64:191. Sauer, W. G., and L. Ozimek. 1986. Digestibility of amino acids in swine: results and their practical applications. A review. Livest. Prod. Sci. 15:367. SCA. 1987. Australian Agricultural Council. Feeding standards for Australian livestock: Pigs. CSIRO Editorial and Publish-
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73%), indicating that digestibilities of individual feedstuffs can be used to predict accurately the digestibility of complete diets. Such a,comparison for finishing diets (59 vs 71%) is not as favorable, however. The Trp digestibility of 59% may have been too low. One possible reason is the larger variability in Exp. 5 vs Exp. 4 (CV = 7.8 vs 3.0%, respectively). Also, the low Trp content of basal finishing diets may have contributed to a higher proportion of endogenous Trp in digesta samples, thereby lowering the apparent digestibility. The L-Trp digestibilities of 98, 87, and 105% for starting, growing, and finishing pigs, respectively, were averaged, producing a mean L-Trp digestibility of 97%. The mean digestibility for L-Trp was used in calculating the digestible requirements of .15, .LO, and .O6% Trp for starting, growing, and finishing pigs, respectively.
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ing, East Melbourne, Australia. Sharda, D. P., D. C. Mahan, and R. F. Wilson. 1978. Limiting amino acids in low-protein corn-soybean meal diets for growingfinishing swine. J. Anim. Sci. 42:1175. Shelton, D. C., W. M. Beeson, and E. T. Mertz. 1951. Quantitative DL-tryptophan requirement of the weanling pig. J. Anim. sci. 10:73. Stockland, W. L., R. J. Meade, and J. W. Nordstrom. 1971. Lysine, methionine and tryptophan supplementation of a corn-meat and bone meal diet for growing swine. J. Anim. Sci. 32:282.
Tmksley, T. D. Jr., and D. A. Knabe. 1984. Ileal digestibilities of amino acids in pig feeds and their use in formulating diets. In: W. Haresign and D.J.A. Cole (Ed.) Recent Advances in Animal Nutrition 1984. pp 75-94. Butterworths, London. Wahlstrom, R. C., G. W. Libal, and R. C. Thaler. 1985. Efficacy of supplemental tryptophan, threonine, isoleucine and methionine for weanling pigs fed a low-protein, lysine-supplemented, corn-sunflower meal diet. J. Anim. Sci. 60:720. Zimmerman, D. R. 1975. Tryptophan requirements of 5- to 15-kg pigs with semi-practical pig starters. J. Anim. Sci. 40: 875.
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