Effect of Canola Fat on Ruminal and Total Tract Digestion, Plasma Hormones, and Metabolites in Lactating Dairy Cows G. R. KHORASANI, G. de BOER,1 P. H. ROBINSON,2 and J. J. KENNELLY Department of Animal SCience University of Alberta Edmonton, AB, Canada T6G 2P5 ABSTRACT

5% Jet-Sploded® canola seed, but the benefits of increased energy density associated with higher inclusion levels may be offset by reduced availability of energy in the rumen and decreased fat digestibility postruminally. The substantial effects of time postfeeding on ruminal fermentation and on concentrations of plasma hormone and metabolites in animals fed TMR demonstrate that infrequent sampling can result in misleading results and, thus, invalid interpretation of the influence of dietary fat on these parameters. (Key words: Jet-Sploding,® canola seed, lactating cows, digestion)

The effects of canola fat on digestion and metabolism were investigated by incorporating 0, 4.5, 9, 13.2, or 17.4% JetSploded® canola seed into a diet containing a 60:40 (OM) concentrate:forage ratio. The diets contained 16.5% CP, 30% alfalfa silage, and 10% whole-crop oat silage on a DM basis and were fed for ad libitum consumption as TMR to 10 ruminally cannulated Holstein cows in early lactation. Jet-Sploded® canola seed supplementation did not change ruminal pH or NH3 N concentrations, but VFA concentrations declined with increasing level of inclusion. Apparent digestibilities of DM, OM, CP, NDF, and ADF were unaffected by level of inclusion of Jet-Sploded® canola seed, but ether extra~t digestibility declined linearly, whIch resulted in similar ether extract absorption across the three diets supplemented with canola fat. Based on in sacco data, the percentages of ruminal digestion of OM and CP declined with increasing inclusion of Jet-Sploded® canola seed. Plasma glucose and FFA concentrations tended to respond in a quadratic fashion, plasma insulin concentration declined linearly, and plasma glucagon and somatotropin concentrations were unaffected by dietary treatment. The results indicate that a positive productive response may be expected from dietary inclusion of about

Abbreviation key: EE = ether extract, JWCS canola seed, NDR = neutral detergent residue, ST = somatotropin.

= Jet-Sploded®


Received April 23, 1991. t-ccepted August 22, 1991. Current address: Champion Feed Services Ltd Grand Prairie, AB, Canada TSV 6K1. ., 2cuuent address: Agriculture Canada Research Station, PO Box 20280, Fredericton, NB, Canada E3B 4Z7. 1992 J Dairy Sci 75:492-501

. High producing dairy cows in early lactation are unable to consume sufficient feed to meet their energy requirements, and substantial loss of BW generally occurs during the first trimester of lactation. Increasing the energy density of the diet through the addition of fat is gaining wide acceptance as a means of modulating the extent of mobilization of body reserves. However, substitution of fats for rapidly fermentable carbohydrates has both direct and indirect effects on ruminal fermentation. Because digestion of fats in the rumen is limited, dietary inclusion of fats will reduce the energy available to bacteria and, hence, decrease microbial protein synthesis and VFA production (8, 9). Fats also can depress rumen digestion through an inhibitory effect of fatty acids on fiber digestion (20), which also will be ~flected in decreased VFA production, especially acetate. Reduced VFA production can influence the synthesis of milk: components



(26). Propionate is a glucose precursor, and mammary uptake of glucose directly affects rate of milk secretion. Milk protein synthesis usually does not decline during fat supplementation, but depression in milk protein concentration associated with dietary addition of fat also has been related to reduced availability of glucose (26). Lower propionate production may increase the utilization of AA for gluconeogenesis and thus reduce the AA available for milk protein synthesis. Decreased plasma insulin concentrations associated with lower propionate concentrations also have been implicated as limiting mammary uptake of AA (26). Reduced acetate production also could increase the utilization of AA as an energy substrate; however, this may be offset by decreased utilization of acetate for milk fat synthesis from increased incorporation of dietary fatty acids into milk fat (13). In contrast, Casper and Schingoethe (2)proposed that milk protein concentration was depressed because of a negative effect of dietary fat on somatotropin (ST) release, which reduced mammary uptake of AA. Canola seed contains 40% fat, which consists primarily of oleic (51%). linoleic (25%), and linolenic (14%) acids (13). The intact seed is relatively resistant to digestion in both the rumen and intestine unless it is exposed to some form of processing. M e s s i n g (e.g., grinding) permits digestion of canola seed, but the dietary inclusion level should be limited to avoid adverse effects on ruminal digestion (12). We have successfully increased the extent of ruminal escape of the protein fraction in canola seed by the application of dry heat in a process known as Jet-Spl&g@ (California Pellet Mill,Crawfordsville, IN) (3).We postulated that reducing the rate and extent of digestion of the protein-rich matrix surrounding the fat droplets would allow increased dietary inclusion levels of canola seed without negative effects on ruminal digestion. Thus, the present study was designed to determine the influence of graded levels of Jet-Sploded* whole canola seed (JWCS) on feed intake, milk yield, milk composition, ruminal digestion, and concentrations of blood hormone and metabolites. Data for feed intake, milk yield, and milk composition were reported by Khorasani et al. (13).



Ten early lactation Holstein cows, fitted with large rumen cannulas (10 cm i.d., BarDiamond Inc., Pama, ID), were fed a TMR containing 0,4.5,9.0,13.2,or 17.4% of JWCS @M basis). Preparation of JWCS, experimental design, treatments, and feeding protocol have been described (13). Sampling and Analysis

Feed, feces, and rumen fluid samples were collected during the last week of the covariate and test periods. Feed samples were collected on each day of the collection week (2 kg/d), frozen, and composited for analysis of DM, OM, N, ether extract @E), NDF, and ADF (13). Feces were collected on six occasions by rectal sampling within 72-h ~0lleCti0nperiod at 0800 h on Tuesday; at 0300,1200,and 2000 h on Wednesday; and at 1900 and 2330 h on Thursday of the last week of the covariate and test periods. Apparent digestibilities of DM, OM, CP, EE, NDF, and ADF were determined; wholecrop oat silage soaked with the indigestible marker, ytterbium chloride, was placed in the rumen through the rumen cannula at 0700, 1500,and 2100 h, commencing 96 h prior to collection of feces and continuing for the collection p e r i d Ytterbium was analyzed by atomic absorption spectrophotometry as described by Robinson and Kenneuy (22). Rumen fluid was obtained at 0750, 0800, 0830, O900, 1O00, 1200, 1400, 1600, 1800, 1900,2000,2200,2400,0100,0400, and 0750 h. Sampling times were designed to represent equally the 72-h collection period as well as the 24-h daily cycle. Rumen fluid pH was measured immediately after sample collection. Samples then were stored at -20'C until analyzed for NH3 concentrations. For analysis, samples were thawed and centrifuged at 2000 x g for 10 min, and N H 3 was determined as described by Fawcett and Scott (6). Samples for VFA were preserved with 25% (voVv01) orthophosphoric acid (4:1,rumen fluid to orthophosphoric acid) stored at -20'C and assayed as described (23). Diurnal pattems in pH, NH3, and rumen metabolites were subjected to polynomial analysis where the day Jomnal of Dairy Science Vol. 75. No. 2, 1992



cycle began at 0800 h and consisted of two sectors: sector 1 (day cycle), 0800 to 1800 h; and sector 2 (night cycle), 1800 to 0800 h. The relationships between time and metabolite concentrations, including pH, by individual cow period in both sectors were fitted to linear, quadratic, cubic, and quartic components (24). Although sectors were fitted individually, common times between sectors (i.e., 0800 and 1800 h) were forced to equivalency (21). This was accomplished using Splines analysis. Thus, model parameters described eight characteristics of the diurnal pattern for each cow period. They were the metabolite values at 0800 and 1800 h, as well as the linear, quadratic, cubic, and quartic components of relationships between time and metabolite concentrations in each sector (21). Fitted lines were used to calculate weighted means, range (fitted maximum minus fitted minimum), and, where appropriate, total hours below specified values. The eight model parameters fitted for each cow period for each parameter were tested by ANOVA, described in the statistical analysis section, to determine effects from level of JWCS inclusion to the diets. Those with significance of P < .05 were included in a regression equation to predict pH conditions or levels of soluble metabolites for each time of sampling for each level of JWCS inclusion. Thus, differences between fitted diurnal patterns, presented in all figures, represent significant differences in one or more of these eight parameters. Nylon bag procedures (5) were used to estimate ruminal degradation of DM, CP, and EE in JWCS. These bags were incubated during the covariate period (cows fed diet with 9% added JWCS), and bags were incubated in the rumen for .1, 2, 4, 8, 16, 24, and 120 h to determine rate and extent of digestion. The nylon bag procedure also was used to estimate the ruminal degradability of the test diets (i.e., each test diet was incubated in the rumen of the cow that received that diet). Bags were incubated for 8, 16, and 24 h as described by Robinson and Kennelly (21); residual DM, CP, and neutral detergent residue (NDR) were determined for each diet. The NDR were determined by direct use of NDF procedure (13) from residual fiber before ashing. To estimate changes in microbial activity of each test diet, a standard sample of alfalfa and wheatgrass hay was incubated in the rumen for .1, 2,8,24, 48, and 120 h. Journal of Dairy Science Vol 75, No.2, 1992

Digestion parameters from nylon bags (soluble = S, degradable = D, undegradable = U, and rate of degradation of the degradable fraction =k) were determined for DM, CP, and EE for JWCS. The disappearance rate was fitted to the following equation (18): disappearance


+ D (1 - e-kt)

and U

= 100 -

(S + D)

where t = time of rumen incubation. The effective degradability of DM (EDDM), CP (EDCP), and EE (EDEE) were calculated by the equation (18): EDDM, EDCP, or EDEE = S + [k/(k x kp)] D where kp = estimated rate of outflow from the rumen. Blood samples were taken from the coccygeal vein of the cows six times per day during the last day of each collection period. Blood samples were kept on ice until centrifuged within 30 min at 2000 x g for 10 min. Aliquots of plasma were stored at -25°C until analyzed for glucose, insulin, glucagon, and ST as described by de Boer and Kennelly (4). Statistical Analysis

Standard ANOVA techniques (24) were used with a model that included diet and covariate (pre-experimental data). Diet effects were tested using orthogonal contrasts (24). The model used for the blood metabolite components to test effect of diet and time of blood sampling included diet tested against cow(diet), and time, and time x diet tested against residual. Diet or time of sampling effects were tested using orthogonal contrasts. For rumen metabolites, the model included diet and covariate. Significance was dermed at P < .05 unless otherwise noted RESULTS AND DISCUSSION

In Sacco and Rumlnal Digestion

Effective degradability of DM and CP (Table 1) was greater than previously reported for



TABLE 1. Parameters of the model used to describe in sacco ruminal degradation of DM, CP, and ether extract (EE) from let-SplodedllD whole canola seed. Item Ruminal disappearance Soluble, % of total Degradable, % of total Undegradable, % of total Rate of digestion/h Effective degradabilityl .05/h .08/h




19.5 70.5 10.1 .0769

14.3 77.9 7.8 .0975

14.0 86.0 .0 .0739

62.1 54.0

65.8 57.1

65.3 55.3

1At estimated rumen turnover rate of .05 and .08/11.

JWCS by Deacon et al. (3). These differences likely reflect differences in the processing conditions (i.e., temperature and duration of exposure to selected temperature) used to prepare JWCS. However, diet and animal variation also can influence degradability (5, 16). When mixed diets were incubated in the rumen of cows fed that diet, a linear increase in residual DM at 8 and 16 h of incubation was observed with increasing dietary level of JWCS (Table 2). The residual DM after 24 h of incubation was not affected (P = .14) by level of JWCS in the diet. Residual CP increased linearly with increasing level of JWCS inclusion in the diet (at 8, 16, and 24 h of

ruminal incubation), but residual NOR was not significantly altered (Table 2), although nonsignificant increases were observed (at 8 h of incubation, P = .12, linear; at 16 h of incubation, P = .06, linear). The absence of a significant effect of dietary fat on NOR may have been due to the relatively short duration of ruminal incubation. Extending mminal incubation time to permit more complete digestion of fiber was likely to have resulted in more pr0nounced treatment differences. The higher residual CP of the mixed diets was, at least in part, due to the reduced rate of canola seed digestion in the rumen as a result of JetSploding~ (3). Fat supplementation had no

TABLE 2. Influence of Jet-SplodedllD canola seed (JWCS) on in sacco residual DM, residual cp. and residual NOR! from mixed rations incubated in the rumen of cows fed that diet. Ruminal incubation time

JWCS. % of dietary DM 0


8 16 24

42.0 38.3 33.1

42.7 37.3 31.0

8 16 24

23.4 17.1 15.6

24.2 19.7 13.7

8 16 24

82.3 76.3 70.8

83.7 75.6 63.1


9 Residual DM (%) 47.4 42.3 35.6 Residual CP (%) 30.9 22.1 15.9 Residual NDR (%) 86.1 83.3 75.9




45.9 35.6 35.3

53.0 51.4 40.9


1.4 2.5 .9

30.0 18.9 18.6

38.0 34.4 25.8

Qr L L

.7 4.0 1.6

85.8 73.0 67.8

94.6 95.2 82.1



3.9 1.4 10.1

INDR = Neutral detergent residue. 2contrast when treatment effect was significant (P < .05); L = linear. Qr = quartic. Journal of Dairy Science Vol. 75, No.2, 1992

496 &.&

KHORASANI ET AL. -r::---------------,

,. - , - - - - - - - - - - - - - - - - - r




&.>-1 I

a ::1


::i· 5.7




.~,~-~-,-----,------r, - -.-~,---,-,,12 16 20






Figure 2. DiumaI patterns of ruminal NH3 N; 0% (~ 4.5% (+), 9% (0), 132% (&), and 17.4% (x) Jet-Sploded whole canola seed.

Figure 1. DiumaI patterns of rumen pH; 0% (0), 4.5% (+), 9% (0), 132% (&), and 17.4% (x) Jet-Sploded~ whole canola seed.

significant effect on soluble, degradable, or (fable 4). Lack of an effect of dietary fat on undegradable fractions of the OM and CP of a average mminal pH is in agreement with standard hay sample (fable 3). However, a others (10). Although significant differences trend (P = .08) for a linear effect on rate of were observed in the diurnal pattern of pH OM degradation and a quadratic effect on the (Figure 1), the differences were small. The pH rate of CP degradation was observed with patterns were similar in both feeding cycles. JWCS inclusion. Overall, in sacco data for Although mean daily ruminal NH3 N concenmixed rations and a standard hay sample indi- trations did not change as a result of dietary fat cate that addition of JWCS at 4.5 and 9.0% of addition, ruminal NH3 N concentrations dietary OM had little effect on rate or extent of (Figure 2) increased at 2 b postfeeding and ruminal digestion. At the highest levels of were lower at 8 h postfeeding. There were no JWCS inclusion (17.4% of dietary OM), the changes in the night cycle of mminal NH3 N rate and extent of ruminal digestion were concentrations. As with ruminal pH, these differences were very small and may not have reduced. Level of JWCS had no significant effect on biological significance. Finn et al. (7) reported average ruminal pH and NH3 concentration that mminal NH3 N concentrations at 2 to 3 h

TABLE 3. Parameters of the model used to descn"be in sacco degradation of DM and CP of a standard hay sample incubated in the rumen of cows fed different dietary levels of Jet-Sploded~ canola seed (IWCS). IWCS, % of dietary DM Item








DM Digestion, % of total Soluble Degradable Undegradable Rate of digestion2

35.1 37.7 27.4 .099

35.0 38.7 26.3 .113

34.6 40.5 25.1 .107

35.3 40.6 24.0 .086

36.3 39.5 24.0 .070


1.3 2.0

CP Digestion, % of total Soluble Degradable Undegradable Rate of digestion2

34.8 55.8 92 .145

36.8 51.3 11.9 206

33.8 56.6 10.1 .183

36.9 53.5 9.7 .139

36.7 53.1 9.8 .141


1.6 22

lContrast when treatment effect was significant (P < .05); L = linear, Q = quadratic. 2Rate of digestion of degradable fIactioD/h. JoumaI of Daily Science VoL 75, No.2, 1992







TABLE 4. Characteristics of rumen fermentation for cows fed different levels of Jet-Sploded® canola seed (JWCS). JWCS, % of dietary DM Item



pH NH3 N, mg/dl VFA Concentrations, mM Total VFA Acetate (A) Propionate (P) Isobutyrate Butyrate Valerate Caproate A:P



Contrast l




5.86 12.75

5.87 12.26

6.02 8.50

5.94 11.05

5.96 9.50



171.57 101.37 49.08 1.25 13.93 2.33 .24 2.06

154.10 89.77 45.08 1.32 17.58 3.06 .36 2.06

156.28 93.09 46.21 1.15 14.06 3.26 .37 1.84

139.03 81.76 37.01 1.03 14.55 2.96 .59 2.19

122.56 68.04 37.59 .90 12.71 2.64 .30 1.96


13.29 7.78 5.46 .12 .66 .32 .19 .07

lContrast when treatment effect was significant (P < .05); L = linear, Q = quadratic, Qr = quartic.

postfeeding tended to be higher in cows fed sunflower seeds than in cows fed the control diet. Mean ruminal acetate and total VFA concentrations decreased linearly, and propionate concentration tended (P = .15) to decrease with increasing dietary inclusion level of lWCS (fable 4). Ruminal isobutyrate also showed a linear trend (P = .07) for lower concentrations as the levels of dietary fat increased in the diet. Concentrations of butyrate in the romen showed a quadratic response, valerate showed a trend (P = .11) toward a quadratic response, and caproate concentrations were not altered because of level of inclusion of JWCS. Although acetate and propionate concentrations





~~d I .







decreased with increasing inclusion of JWCS, the acetate:propionate ratio exhibited a quartic response. Other researchers reported similar responses for ruminal acetate concentrations, but some have observed increased propionate concentrations (19, 27). However, Sharma et al. (25) reported that the molar percentage of acetate was increased and that of propionate was depressed in romen fluid of cows fed 15% protected tallow. These differences presumably are related to factors such as inclusion level of fat, extent of ruminal escape of fat, degree of saturation of fatty acids, forage:concentrate ratio, and forages source. Acetate concentration (Figure 3) immediately prior to the a.m. feeding was influenced quadratically by level of


90 80




70 60 50 40 0




-, 20





'" 24



Figure 3. Diurnal patterns of rumina! acetate; 0% ~ 4.5% (+), 9% (0), 13.2% (A), and 17.4% (x) Jet-Sploded whole cano1a seed.









Figure 4. Diurnal patterns of rumina! propionate; 0% (0), 4.5% (+), 9% (0), 13.2% (A), and 17.4% (x) JetSploded® whole canola seed. Journal of Dairy Science Vol. 75, No.2, 1992



TABLE 5. Apparent digestibility coefficients for diets varying in level of let-SplodedQ!) canola seed (IWCS). IWCS, % of dietary DM Item








58.5 60.0 64.5 43.8 45.1 47.3

54.0 56.4 59.5 35.9 36.2 44.8


5.9 5.7 5.2 10.2 12.6 3.5

Digestibility (%) DM OM CP



62.9 64.7 67.5 46.6 46.8 57.4

66.4 68.1 72.1 47.3 43.4 78.9

64.9 66.9 65.3 51.3 50.6 62.6

lContrast when treatment effect was significant (P < .05). 2Bther extract

dietary fat addition, and patterns in both the day and night cycle largely reflected this effect. The increase in concentration of propionate postfeeding was rapid. and the extent of the increase was reduced in the day cycle as level of JWCS substitution increased (Figure 4). No treatment differences were observed in the propionate patterns of the night cycle. Diurnal patterns for butyrate and isobutyrate followed the same patterns as acetate, but diurnal patterns of valerate were not influenced by treatment Oearly, addition of JWCS caused substan~ro~esin~alre~en~onro~~

istics, especially total VFA coocentrations and molar proportions of VPA These changes probably reflect decreased substrate availability for bacteria in the rumen. Decreased substrate availability arises from the diluting effect of added dietary fat and. at higher levels of dietary fat, a negative effect of fat on fiber digestion.

Whole Tract Digestion

Treatment differences in apparent digestibility coefficients for DM, OM, CP, NDF, and ADF (fable 5) were not significant; however, there was a trend for lower digestibility at 13.2 and 17.4% inclusion of JWCS. Digestibility coefficients for BE declined (P = .08) from 78.9 to 44.8% as dietary JWCS was increased from 4.5 to 17.4%. Sharma et al (25) and Vicente et al. (27) reported a significant increase in apparent digestibility of BE when cows were fed diets containing different amounts of protected tallow, but other nutrients were not affected. We observed a trend (P = .08) for a negative quadratic effect in response to higher level of JWCS. This trend and, to a lesser extent, similar trends on other components of the diet at the two highest levels of JWCS inclusion may have offset the benefits of increased energy density of the high fat diets. Thus, the benefits of increased

TABLE 6. Effect of dietary addition of let-SplodedQ!) canola seed (IWCS) on plasma honnone and metabolite and milk cholesterol concentrations. IWCS, % of dietary DM Item






Plasma Glucose, mg/d1 Insulin, ng/ml Glucagon, pg/ml Somatotropin, ng/ml PFA, mmol/ml Cholesterol, mmol/ml Milk cholesterol, mgldI

71.35 1.20 193.50 5.41 184.10 141.3 9.31

72.74 1.13 209.10 4.63 205.30 114.8 7.66

74.86 1.09 163.60 4.92 266.10 234.5 7.45

72.90 .89 187.00 5.08 266.90 222.8 6.63

68.27 .89 365.70 4.92 185.30 217.1 7.63

lContrast when treatment effect was significant (P < .OS); L = linear, Q = quadratic. loumal of Dairy Science Vol 75, No. 2, 1992



2.68 .16 19.49 .32 41.70 42.5 .75



TABLE 7. lDfluence of blood sampling time on honnone aDd metabolite concentratioos pooled across the four dietary treatments. Time postfeediDg

Oh Glucose. mgldl IDsulin, ng/dl

Glucagon. pg/dl Somatotropin, ngIml FFA, mmol/m1 ChoIesttroI, mmoVmI

74.44 .71 223.8 5.90 257.4 199.6

.75 h 74.01 .95 241.0

4.87 232.9 203.8



6.5 h

9.5 h

Contrast l SEM

68.89 1.06 234.1 4.61 227.9 202.1

66.68 1.27 210.9 4.63 2Q4..8 196.1

74.58 1.24 210.1 4.55 194.0 193.6

74.56 1.02 228.2 5.42 212.9 194.2


lContrast when treatment effect was significant (P < .OS); Q

energy density associated with fat supplementation may be progressively lost with increasing fat addition to the diet. Honnone and Metabolite PrOfIles

The effect of treatments on plasma glucose concentration tended (P = .08) to be quadratic (Table 6). A quadratic effect of time of sam~ ling on plasma glucose concentration also was observed (Table 7). Most previous studies (I, 11, 15) indicated that plasma glucose concentration does not change when fat is fed to dairy cows. Our results confirm those of Kronfeld et al. (14), who reported a higher plasma concentration of glucose. These results suggest that the impact of dietary fat on plasma glucose concentration will vary, depending on the dietaty inclusion level of fat. Mean plasma insulin concentration declined linearly with JWCS addition and time of sampling. The relation between plasma glucagon concentration and time of sampling was cubic, but plasma glucagon concentration was not affected by addition of JWCS to the diet. Concentration of plasma ST remained relatively constant, but the quadratic relationship between time of blood sampling and plasma ST concentration was significant. Plasma FFA concentration showed a quadratic response to JWCS inclusion and Ii. linear decline with time postfeeding. Several other studies (1, 25, 26, 27) reported plasma FFA increased with added dietary fat. The reason for the lower plasma FFA concentration at the highest inclusion level of JWCS in the diet may be due to the lower fat digestibility in animals fed this diet. The substantive effect of time postfeeding on

3.48 .187 9.4 .492 20.7 3.8

= quadratic, L = linear, C = cubic.

plasma hormone and metabolite concentrations (Table 7) undoubtedly contributes to the apparent lack of agreement in the literature on the effect of dietaty fat on these parameters. These data indicate that interpretation of the influence of dietary fat on plasma hormone and metabolite concentrations can be influenced rnarJredly by time of sampling relative to feeding. Clearly, frequent sampling is critical if spurious results are to be avoided. Total serum cholesterol concentration increased linearly as the level of JWCS substitution increased (at all times of blood sampling); the relation between blood serum total cholesterol concentration and times of sampling also was linear. Other studies (7, 14, 19, 25) also have demonstrated a positive relationship between serum cholesterol and dietary fat. Nestel et at (17) proposed that increasing dietary fat stimulates intestinal cholesterol synthesis to meet increased demands for absorption and transport of fat. Milk cholesterol concentration was not influenced by level of dietary fat, suggesting that endogenous cholesterol synthe~wasreOOcedorma~ODwasin~

in response to dietary fat. Alternatively, mammary uptake of cholesterol may be independent of plasma concentrations. CONCLUSIONS

Incremental addition of JWCS to the diet of early lactation dairy cows in~ dietary BE from 2.2 to 6.7%. Addition of fat caused a linear reduction in ruminal acetate concentration and a tend for lower propionate concentration. These changes reflected reduced enetgy available for digestion in the rumen both as a result of the diluting effect of fat addition to Journal of Daily Science Vol. 75, No.2, 1992



the diet plus a tendency for reduced ruminal DM digestion. Ether extract digestibility tended to increase with the lowest inclusion level of JWCS but declined with each incremental addition of JWCS thereafter. The overall result of these changes probably reduced the availability of acetate and, to a lesser extent, propionate for milk component synthesis. The reduction in acetate was alleviated in part by increased incorporation of dietary long-chain fatty acids into milk fat, as reported previously (13). The trend for a decline in fat digestibility at the higher levels of JWCS inclusion resulted in relatively small differences between diets in amount of fat absorbed per day. Thus, the benefits of greater dietary energy density associated with increasing level of dietary fat tended to be progressively lost because of the trend for a linear reduction in fat digestibility. The observed linear decline in milk. protein percentage observed with incremental dietary addition of fat in this study (13) may be related to lower ruminal VFA production causing increased utilization of AA for gluconeogenesis. The data presented here and previously (13) indicate that a positive effect on animal performance can be expected by including JWCS at about 5% of dietary DM; however, negative effects of fat on digestion may offset the increased energy density associated with greater dietary inclusion of JWCS. ACKNOWLEDGMENTS

The authors thank the Canola Council of Canada and the Alberta Agriculture Research Institute for financial support. The technical assistance of 1 Moffat, J. Dietrich, and L. Wright is gratefully acknowledged. Appreciation is expressed to the staff of the University of Alberta Dairy Research Unit for care of the animals and to M. Deacon for sample collection. REFERENCES 1 Bines, J. A., P. B. Brumby, J. B. Storry, R. J. Pulford. and G. D. Braithwaite. 1978. The effect of protected lipids on nutrient intakes, blood and rumen metabolites and milk secretion in dairy cows during early lactation. J. Agric. Sci. (Carob.) 91:135. 2 Casper, D. P., and D. J. Schingoethe. 1989. Model to Journal of Dairy Science Vol. 75, No.2, 1992

describe and alleviate milk protein depression in early lactation dairy cows fed a high fat diet. J. Dairy Sci. 72:3327. 3 Deacon, M. A., G. de Boer, and J. J. Kenuelly. 1988. Influence of Jel-Sploding~ and extrusion on rominal and intestinal disappearance of canola and soybeans. J. Dairy Sci. 71:745. 4 de Boer, G., and J. J. Kennelly. 1989. Effect of somatotropin and dietary protein concentration on hormone and metabolite responses to single injections of hormones and glucose. J. Dairy Sci. 72:429. 5 de Boer, G., J. J. Murphy, and J. J. Kennelly. 1987. A modified method for determination of in situ rumen degradation of feedstuffs. Can. J. Anim. Sci. 67:93. 6 Fawcett, J. K., and J. B. Scoll. 1960. Determination of ammonia nitrogen. J. Ciin. Pathol. (Lond.) 13:156. 7Finn, A. M., A. K. Clark, J. K. Drackley, D. J. Schingoethe, and T. SahIu. 1985. Whole rolled sunflower seeds with or without additional limestone in lactating dairy cattle rations. J. Dairy Sci. 68:903. 8 Henderson, C. 1973. The effects of fatty acids on pure cultures of rumen bacteria. J. Agric. Sci. (Carob.) 81: 107. 9 Jenkins, T. C., and D. L. PaImquisl. 1982. Bffect of added fat and calcium on in vitro formation of insoluble fatty acid soaps and cell wall digestibility. J. Anim. Sci. 55:957. 10 Jerred, M. J., D. J. Carroll, D. K. Combs, and R. R. Grwnmer. 1990. Effects of fat supplementation and immature alfalfa to concentrate ratio on lactation performance of dairy cattle. J. Dairy Sci. 73:2842. 11 Johnson, J. C., Jr., P. R. Utley, B. G. Mulinix, Jr., and A. Merrill. 1988. Effects of adding fat and Iasalocid to diets of dairy cows. J. Dairy Sci. 71:2151. 12 Kennelly, J. J., M. A. Deacon, and G. deBoer. 1987. Enhancement of the nutritive value of full-fat canola seed for ruminants. Proc. 7th Int. Refereed Congr. (Poznan, Poland) 7:1692. 13 Khorasani, G. R., P. H. Robinson, G. de Boer, and J. J. Kennelly. 1991. Influence of canola fat on yield. fat percentage, fatty acid profile, and nitrogen fractions in Holstein milk. J. Dairy Sci. 74:1904. 14Kronfeld. D. S., S. Donoghue, J. M. Naylor, K. Johnson, and C. A. Bradley. 1980. Metabolic effects of feeding protected tallow to dairy cows. J. Dairy Sci. 63:545. 15 Macleod, G. K., Y. Yu, and L. R. Schaeffer. 1977. Feeding value of protected animal tallow for high yielding dairy cows. J. Dairy Sci. 60:725. 16 Mehrez, A Z., and B. R. 0rskov. 1977. A study of the artificial fibre bag technique for determining the digestibility of feeds in the rumen. J. Agric. Sci. (Carob.) 88:645. 17 Nestel, P. J., A. Poyser, R. L. Hood. S. C. Mills, M. R. Willis, L. J. Cook, and T. W. Scott. 1978. The effect of dietary fat supplements on cholesterol metabolism in ruminants. J. Lipid Res. 19:899. 18 0rskov, B. R., and L McDonald. 1979. The estimation of protein degradability in the rumen from incubation melWUl'elDClllS weighed according to rate of passage. J. Agric. Sci. (Carob.) 92:499. 19 Palmquist, D. L., and H. R. Conrad. 1978. High fat

CANOLA FAT FOR LACTATING DAIRY COWS rations for dairy cows. Effecrs on feed intake, milk and fat production, and plasma metabolites. J. Dairy Sci. 61:890. 20 Palmquist, D. L., and T. C. Jenkins. 1980. Fat in lactation rations: review. J. Dairy Sci. 63: l. 21 Robinson, P. H., and J. J. Kennelly. 1988. Influence of ammoniation of high moisture barley on irs in situ rumen degradation and influence on rumen fermentation in dairy cows. Can. J. Anim. Sci. 68:839. 22 Robinson, P. H., and 1. 1. Kennelly. 1989. Influence of ammoniation of high-moisture barley on digestibility, kinetics of rumen ingesta turnover, and milk production in dairy cows. Can. J. Anim. Sci. 69:195. 23 Robinson, P. H., J. J. Kennelly, and G. W. Mathison. 1988. Influence of type of silage bag on chemical


composition of alfalfa silage. Can. J. Anim. Sci. 68: 83l. 24 SAS~ User's Guide: Statistics, Version 5 Edition. 1985. SAS 1Dst., Inc., Cary. NC. 25 Sharma, H. R. J. R. Ingalls, and J. A. McKirdy. 1978. Replacing barley with protected tallow in ration of lactating Holstein cows. J. Dairy Sci. 61:574. 26 Smith, N. E., W. L. Dunkley, and A. A. Franke. 1978. Effects of feeding protected tallow to dairy cows in early lactation. 1. Dairy Sci. 61:74. 27 Vicente, G. R, J. A. Shelford, R G. Peterson, and C. R Krisbnamurti. 1984. Effects of feeding canolameaI-protected-tallow or soybean-meaI-protecledtallow in the low-roughage diet of dairy cows in early lactation. Can. I. Anim. Sci. 64:81.

Journal of Dairy Science Vol. 75, No.2, 1992

Effect of canola fat on ruminal and total tract digestion, plasma hormones, and metabolites in lactating dairy cows.

The effects of canola fat on digestion and metabolism were investigated by incorporating 0, 4.5, 9, 13.2, or 17.4% Jet-Sploded canola seed into a diet...
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