Lysine Supplementation of Low-Protein Diets for Broiler Breeder Males1 W. H. REVINGTON,2 E. T. MORAN, JR., S. F. BILGILI, and R. D. BUSHONG Poultry Science Department, Alabama Agricultural Experiment Station, Auburn University, Alabama 36849-5416 (Received for publication May 10, 1991) ABSTRACT Two experiments were conducted to assess the impact of supplemental L-lysine HC1 on N balance in broiler breeder males fed 8% CP corn-based diets (3,220 kcal ME„/kg; .15% supplemental DL-methionine; .24% basal lysine). In Experiment 1, 78-wk-old males were fed the basal diet with either 0, .05, .10, or .25% supplemental L-lysine HC1. Birds were allowed to eat for 1 h each day to a maximum intake of 325 kcal MEj, per bird per day. Total excreta were collected for 8 consecutive days. Nitrogen retention and balance were not different among treatments (P>.05) and responded neither linearly nor quadratically to dietary lysine level. Removing the variation due to differences in N intake with analysis of covariance did not change the response. In Experiment 2, 30-wk-old males were fed the same basal diet with supplemental lysine levels of 0, .15, .30, .45, .60, and .75% L-lysine HC3 for 5 consecutive days. Nitrogen balance and retention were different among diets, and both variates responded linearly to increases in dietary lysine. Removing the variation due to differences in N intake removed treatment effects, however, suggesting that at least part of the difference was the result of variable levels of intake. Regression analysis indicated a significant linear increase in both N balance and retention with increasing dietary lysine level (R2 = .82). These results suggest that young broiler breeder males can make better use of the protein of corn if supplemental lysine is provided. However, older birds do not demonstrate improved N balance as a result of supplemental dietary lysine. {Key words: broiler breeder male, protein, lysine, nitrogen retention, age) 1992 Poultry Science 71:323-330
INTRODUCTION Wilson et al, (1987a,b) reported improved reproductive performance in broiler breeder males fed low-protein feeds (12% CP). Although reports are inconclusive, there is some evidence to suggest that even lower protein levels can be used to improve the reproductive performance of males (Leveille and Fisher, 1958; Arscott and Parker, 1963; Wilson et
Alabama Agricultural Experiment Station Journal Number 12-902498P. 2 Present address: New-Life Mills, Ltd., 1400 Bishop St., Cambridge, ON, N1R 6W8, Canada.
al., 1965; Wilson et al., 1987b). Success of low-protein regimens seems to depend on provision of balanced dietary protein, and on the implementation of such regimens subsequent to the onset of sexual maturity (Wilson et ah, 1971). Practical diets formulated to low levels of dietary protein are likely to have a high proportion of grain and a high proportion of energy relative to protein. They may also be low in lysine, particularly when corn is the primary ingredient. Revington et al. (1991a) fed caged breeder males either an all-corn diet (AC, 8% CP) or a standard corn and soybean meal diet (ST, 12% CP) at a rate of 325 kcal MEn per bird per day from 24 to 68 wk of
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age. Although BW of males fed the AC diet was significantly less than BW of birds receiving the ST diet, there was no apparent detriment to reproductive performance. Carcasses from birds fed 8% CP were proportionally fatter than those from birds that received the 12% CP control diet. Furthermore, Revington et al. (1988) showed that N intake paralleled N retention as dietary regimens were proportionally shifted from ST to AC. However, the relative proportion of N retained by birds was less for the 8% CP diet than for the 12% CP feed despite equal energy intakes and positive N balance. Taken together, these results suggest the possibility of improving protein utilization by supplementing corn-based diets with specific essential amino acids. Because the lysine content of corn is low relative to energy, and this amino acid is easily supplemented in free form, two experiments were conducted to determine the effect of supplemental lysine on N utilization in low-protein, all-corn diets. MATERIALS AND METHODS Experiment 1 Sixteen 78-wk-old broiler breeder males (Ross) were divided into four groups of approximately equal average BW. Each group was assigned to a set of four individual male breeder cages in a lighttight breeder facility. Water was available for ad libitum intake through nipple drinkers and the birds received 15 h of light/day during the experiment. Temperature averaged 25 C throughout the experimental period. Each group was randomly assigned to one of four dietary treatments consisting of different levels of supplemental L-lysine HC1 at the expense of corn (.05, .10, .25% Llysine H O ) . The basal diet (0% added Llysine HC1; Table 1) was formulated to approximate the amino acid requirements as reported by Leveille et al. (1960) for the Single Comb White Leghorn (SCWL) male. Birds received their respective test diets for 3 days prior to formal excreta collections, and for 45 min/day. All diets were fed to provide approximately 325 kcal AME„ per bird per day. Actual intake was determined
TABLE 1. Composition of the basal diet fed to caged broiler breeder males Ingredients and composition Ground corn DL-methionine Dicalcium phosphate Limestone Salt Vitamin-mineral mix1 Total Assayed composition CP, % MEn, kcal/kg
Percentage 96.00 .15 1.25 1.75 .35 .50 100.00 82 3,070
Supplied the following to each kilogram of finished feed: vitamin A palmitate, 8,000 IU; cholecaldferoL 2,200 ICU; vitamin E (DL-a-tocopheryl acetate), 8.0 IU; menadione, 2.0 mg; riboflavin, 5.5 mg; pantothenic acid, 13.0 mg; niacin, 36 mg; choline, 500 mg; vitamin B12, .02 mg; folic acid, .50 mg; thiamine, 1.0 mg; pyridoxine, 22 mg; iron, 55 mg; copper, 6 mg; zinc, 55 mg.
by weighing the feeders before and after the feeding period, and correcting for spilled feed. Corrections for availability of natural (88%) and synthetic (92%) lysine sources were made according to the findings of Sibbald and Wolynetz (1985) and are reflected in Table 2. Total excreta collections were made by a cup-and-harness collection procedure previously described b y Revington et al. (1991b). Collections were made daily for 8 consecutive days. Individual daily samples were analyzed. Total daily excreta were weighed, then frozen at -20 C until completion of the experiment, when all samples were lyophilized to determine moisture content. Duplicate samples of feed and excreta were analyzed by semi-micro Kjeldahl for N content and by adiabatic oxygen bomb calorimetry for gross energy. The AME and AMEn values for the diets were calculated according to methods outlined by Wolynetz and Sibbald (1984). Nitrogen retention and balance data were also determined from these variables. Experiment 2 Twenty-four broiler breeder males at 30 wk of age were arranged into six groups of approximately equal average BW. Groups were then assigned at random to sets of
LYSINE FOR BROILER BREEDER MALES TABLE 2. Dietary supplemental L-lysine HC1 and total lysine intake of 78-wk-old caged broiler breeder males. Experiment 1 L-lysine HC1 Added Total1
Lysine intake
(mg/kg BW (mg/dayr per dayr 503 122 25.4 .05 239 184 40.0 .10 .275 198 41.2 35 .383 258 535 ^Based on the National Research Council (1984) value for corn of .24% lysine and 88% availability. Llysine H Q assumed 78.8% lysine and 92% available (Sibbald and Wolynetz, 1985). Based on mean DM intake for each diet. %ased on mean BW of birds in each treatment group-
(%)
individual metabolism cages located in a single 3 x 3 m room. Water was available for ad libitum intake, and temperatures averaged 25 C for the duration of the experiment. Six diets each containing different levels of supplemental L-lysine HC1 were fed (0, .15, .30, .45, .60, and .75%). The basal diet (0% added L-lysine H Q ) was a remix of the same diet used in Experiment 1, however the same corn source as in Experiment 1 was used. Birds were allowed to eat for 45 m i n / d a y to a maximum daily intake of 325 kcal AMEj! per bird. Total excreta collections were made daily for 5 consecutive days, and daily feed intake was recorded. Corrections for lysine availability were made as in Experiment 1. All other conditions were as reported in Experiment 1.
325
1...4 in Experiment 1; i = 1...6 in Experiment 2); (Dy X Dt)jj = the corresponding day by diet interaction term; and e ^ = a random error term associated with each individual observation (k = 1...4). Orthogonal polynomial contrasts were applied to diet means. Coefficients for four unequally spaced treatment levels (Gill, 1978) were used to test for first- and secondorder polynomial responses in Experiment 1, and coefficients for six equally spaced treatments were used in Experiment 2 (Snedecor and Cochran, 1980). The day by diet interaction was used for testing significance of all diet effects, in accordance with a random model. For specific variables, analysis of covariance (ANCOVA) was also employed. Least-squares means are reported in the tables when the covariate was significant, and regression techniques were applied where indicated.
RESULTS Experiment 1
As expected, supplementing the diet with L-lysine HC1 resulted in increased lysine intake (Table 2). However, variation in DM intake and BW resulted in levels of lysine intake that were not greatly different among some of the treatment groups. Daily DM intake, ME intake, and N intake were different among the four dietary treatments (P
INTRODUCTION Wilson et al, (1987a,b) reported improved reproductive performance in broiler breeder males fed low-protein feeds (12% CP). Although reports are inconclusive, there is some evidence to suggest that even lower protein levels can be used to improve the reproductive performance of males (Leveille and Fisher, 1958; Arscott and Parker, 1963; Wilson et
Alabama Agricultural Experiment Station Journal Number 12-902498P. 2 Present address: New-Life Mills, Ltd., 1400 Bishop St., Cambridge, ON, N1R 6W8, Canada.
al., 1965; Wilson et al., 1987b). Success of low-protein regimens seems to depend on provision of balanced dietary protein, and on the implementation of such regimens subsequent to the onset of sexual maturity (Wilson et ah, 1971). Practical diets formulated to low levels of dietary protein are likely to have a high proportion of grain and a high proportion of energy relative to protein. They may also be low in lysine, particularly when corn is the primary ingredient. Revington et al. (1991a) fed caged breeder males either an all-corn diet (AC, 8% CP) or a standard corn and soybean meal diet (ST, 12% CP) at a rate of 325 kcal MEn per bird per day from 24 to 68 wk of
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age. Although BW of males fed the AC diet was significantly less than BW of birds receiving the ST diet, there was no apparent detriment to reproductive performance. Carcasses from birds fed 8% CP were proportionally fatter than those from birds that received the 12% CP control diet. Furthermore, Revington et al. (1988) showed that N intake paralleled N retention as dietary regimens were proportionally shifted from ST to AC. However, the relative proportion of N retained by birds was less for the 8% CP diet than for the 12% CP feed despite equal energy intakes and positive N balance. Taken together, these results suggest the possibility of improving protein utilization by supplementing corn-based diets with specific essential amino acids. Because the lysine content of corn is low relative to energy, and this amino acid is easily supplemented in free form, two experiments were conducted to determine the effect of supplemental lysine on N utilization in low-protein, all-corn diets. MATERIALS AND METHODS Experiment 1 Sixteen 78-wk-old broiler breeder males (Ross) were divided into four groups of approximately equal average BW. Each group was assigned to a set of four individual male breeder cages in a lighttight breeder facility. Water was available for ad libitum intake through nipple drinkers and the birds received 15 h of light/day during the experiment. Temperature averaged 25 C throughout the experimental period. Each group was randomly assigned to one of four dietary treatments consisting of different levels of supplemental L-lysine HC1 at the expense of corn (.05, .10, .25% Llysine H O ) . The basal diet (0% added Llysine HC1; Table 1) was formulated to approximate the amino acid requirements as reported by Leveille et al. (1960) for the Single Comb White Leghorn (SCWL) male. Birds received their respective test diets for 3 days prior to formal excreta collections, and for 45 min/day. All diets were fed to provide approximately 325 kcal AME„ per bird per day. Actual intake was determined
TABLE 1. Composition of the basal diet fed to caged broiler breeder males Ingredients and composition Ground corn DL-methionine Dicalcium phosphate Limestone Salt Vitamin-mineral mix1 Total Assayed composition CP, % MEn, kcal/kg
Percentage 96.00 .15 1.25 1.75 .35 .50 100.00 82 3,070
Supplied the following to each kilogram of finished feed: vitamin A palmitate, 8,000 IU; cholecaldferoL 2,200 ICU; vitamin E (DL-a-tocopheryl acetate), 8.0 IU; menadione, 2.0 mg; riboflavin, 5.5 mg; pantothenic acid, 13.0 mg; niacin, 36 mg; choline, 500 mg; vitamin B12, .02 mg; folic acid, .50 mg; thiamine, 1.0 mg; pyridoxine, 22 mg; iron, 55 mg; copper, 6 mg; zinc, 55 mg.
by weighing the feeders before and after the feeding period, and correcting for spilled feed. Corrections for availability of natural (88%) and synthetic (92%) lysine sources were made according to the findings of Sibbald and Wolynetz (1985) and are reflected in Table 2. Total excreta collections were made by a cup-and-harness collection procedure previously described b y Revington et al. (1991b). Collections were made daily for 8 consecutive days. Individual daily samples were analyzed. Total daily excreta were weighed, then frozen at -20 C until completion of the experiment, when all samples were lyophilized to determine moisture content. Duplicate samples of feed and excreta were analyzed by semi-micro Kjeldahl for N content and by adiabatic oxygen bomb calorimetry for gross energy. The AME and AMEn values for the diets were calculated according to methods outlined by Wolynetz and Sibbald (1984). Nitrogen retention and balance data were also determined from these variables. Experiment 2 Twenty-four broiler breeder males at 30 wk of age were arranged into six groups of approximately equal average BW. Groups were then assigned at random to sets of
LYSINE FOR BROILER BREEDER MALES TABLE 2. Dietary supplemental L-lysine HC1 and total lysine intake of 78-wk-old caged broiler breeder males. Experiment 1 L-lysine HC1 Added Total1
Lysine intake
(mg/kg BW (mg/dayr per dayr 503 122 25.4 .05 239 184 40.0 .10 .275 198 41.2 35 .383 258 535 ^Based on the National Research Council (1984) value for corn of .24% lysine and 88% availability. Llysine H Q assumed 78.8% lysine and 92% available (Sibbald and Wolynetz, 1985). Based on mean DM intake for each diet. %ased on mean BW of birds in each treatment group-
(%)
individual metabolism cages located in a single 3 x 3 m room. Water was available for ad libitum intake, and temperatures averaged 25 C for the duration of the experiment. Six diets each containing different levels of supplemental L-lysine HC1 were fed (0, .15, .30, .45, .60, and .75%). The basal diet (0% added L-lysine H Q ) was a remix of the same diet used in Experiment 1, however the same corn source as in Experiment 1 was used. Birds were allowed to eat for 45 m i n / d a y to a maximum daily intake of 325 kcal AMEj! per bird. Total excreta collections were made daily for 5 consecutive days, and daily feed intake was recorded. Corrections for lysine availability were made as in Experiment 1. All other conditions were as reported in Experiment 1.
325
1...4 in Experiment 1; i = 1...6 in Experiment 2); (Dy X Dt)jj = the corresponding day by diet interaction term; and e ^ = a random error term associated with each individual observation (k = 1...4). Orthogonal polynomial contrasts were applied to diet means. Coefficients for four unequally spaced treatment levels (Gill, 1978) were used to test for first- and secondorder polynomial responses in Experiment 1, and coefficients for six equally spaced treatments were used in Experiment 2 (Snedecor and Cochran, 1980). The day by diet interaction was used for testing significance of all diet effects, in accordance with a random model. For specific variables, analysis of covariance (ANCOVA) was also employed. Least-squares means are reported in the tables when the covariate was significant, and regression techniques were applied where indicated.
RESULTS Experiment 1
As expected, supplementing the diet with L-lysine HC1 resulted in increased lysine intake (Table 2). However, variation in DM intake and BW resulted in levels of lysine intake that were not greatly different among some of the treatment groups. Daily DM intake, ME intake, and N intake were different among the four dietary treatments (P
