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Methionine Hydroxy Analog: Varying Levels for Lactating Cows
Methionine Hydroxy Analog" Varying Levels for Lactating Cows Abstract
(m~-a-hydroxy-gamma-methyhnercaptobutyratecalcium) or with intravenous infusion of Lmethionine. This finding seems particularly significant, since the analog represented a practical way of enhancing the methionine complement of the animal. I f methionine were limiting in the metabolism and productivity of a ruminant, feeding the analog might easily correct the deficiency. I n subsequent experiments, Pennsylvania data indicated that 40 or 80 g / d a y of analog stimulated milk production, but a breed X level interaction existed (7). No study has indicated the optimal dietary level o f the analog for lactating dairy cows. Therefore, it became the objective of this study to define the response from feeding different levels of the analog to cows in early stages of lactation.
Beginning two weeks before anticipated parturition and f o r 90 days post-partum, 24 Holstein cows received a concentrate (14.5% crude protein) containing either 0, 0.2, 0.4, or 0.8% methionine hydroxy analog. Concentrate was limited to 11 to 12 k g / d a y and corn silage-urea (0.5%) was offered free choice. A milk production response curve indicated peak production at approximately 25 g analog/day. F a t content of milk increased with analog intake. Reduced silage and concentrate consumption was common with the highest analog level. F r e e fatty acid and triglyceride content of serum a-lipoproteius and triglycerides of the fllipoproteins were reduced in cows fed analog from those with no analog.
Recently, the quality of the protein presented to the blood stream of the ruminant animal has received considerable attention. Australian workers (5, 12, 14) have shown marked increases in wool production when sheep were fed formaldehyde-treated protein or had sulfur amino acids administered in the abomasum. The response was attributed to post-ruminal absorption of native amino acids available from decreased solubility and degradation while in the tureen. Methionine supplementation has had similar effect on growth. Over 20 years ago Loosli and t I a r r i s (8) reported improved utihzation of nitrogen by supplementing methionine into the diet. Methionine is among the amino acids likely to be limiting for optimal growth or milk production or both (1, 2, 4, 7, 12, 18). Although different essential amino acids may be limiting under certain circumstances, supplementing amino acids into the diet has not always yielded beneficial results (2). The principal reasons for different responses due to amino acid supplementation are probably related to the extent of degradation in the rumeu and the current metabolic needs. Penn State workers (9-11) have proposed that methionine nutrition has a direct bearing on bovine lipoprotein structure and composition. I n this manner, they have implicated methionine with both bovine ketosis and depressed milk fat production (11). Similar alterations in serum lipid fractions were observed with the oral administration of the analog of methionine
Experimental Procedure
I n the fall of ]968, 24 Holstein cows from the University herd that had completed at least one lactation were placed into six groups of four cows each based on anticipated date of parturition. Cows within a group were then randomly assigned to receive a concentrate containing either 0, 0.2, 0.4, or 0.8% analog. Concentrate feeding began two weeks before anticipated parturition. The pelleted concentrates (approximately 14.5 % crude protein) were composed of, in percentages, 70 corn, ]2.5 soybean meal, 5 molasses, 5 wheat, 2.5 distillers grains, 2 clay-based pelletbinder, 2.0 dicalcium phosphate, 1 iodized salt, 0.4 trace minerals, and 6,600 and 8,800 I U of vitamin A and D p e r kilogram, respectively. By parturition, cows were normally consuming 5 to 6.5 kg of concentrate per day. They were then gradually increased in concentrate up to ]1.8 kg per day. Corn silage containing 0.5% urea was fed free choice to all cows. Concentrate containing varying amounts of analog was fed for 90 days after parturition. C'ontrol concentrate (0% analog) was fed to all cows between 90 to 120 days. Feed consumption and milk production were recorded daily. Milk f a t and ketone content were determined at two-week intervals. Blood samples were taken at intervals of 30 -~ 4 days of lactation and analyzed for methionine by microbiological assay procedures (3) with Leuconostoc mesenteroides ATCC 8042. Similar procedures were utilized to assay for serum analog plus methionine with Lactobacillus plan607
608
JOURNAL
OF D A I R Y SCIENCE
t a r u m Strain 17-5, ATCC 8014. This organism can meet its methionine requirement with the analog. Serum a- and fl-tipoproteins from blood sampled at 60 and 120 days of lactation were further fractionated. The fl-lipoproteins were removed by the dextran sulfate method of Sakagami and Zilversmit (16). A f t e r precipitation the lower fraction was separated by decanting the supernatant fraction, which contained what was considered the a-lipoprotein fraction. Both fractions were then extracted by Mojonnier procedures with diethyl and petrolemn ether. Both lipoprotein components were further fractionated by thin-layer chromatogr a p h y (TLC) into polar lipids, cholesterol, free f a t t y acids, triglycerides, and cholesterol esters. A f t e r separation on TLC by the following solvent system (petroleum ether:ethyl ether:acetic acid--150:30:2), the plates were s p r a y misted with 50% sulfuric acid and charred at 180 C for 25 minutes. The resulting separate spots were then quantitated by densitometer with purified standards as a reference. The values in Table i are somewhat high because they were quantitated from the weights of lipid extracts which contained some nonlipid material.
Where appropriate, data were statistically analyzed according to Snedecor (17). Results and Discussion
The response curve (Fig. 1) for milk production (P ~ .01) revealed a mild but maximum response for animals consuming 25 g of analog per day. The regression equation indicates a marked decrease in milk production when analog is consumed in excess of 45 g. Analysis of variance of 14-day production means for each animal showed there was no effect of time on milk production response to analog nor an interaction between time and level of analog intake. Therefore, Figure 1 shows the over-all production means for each treatment for days 6 to 89 postparturition. Individual comparisons among treatment means indicate significant differences between 0.8% analog versus the other treatments (P < .05). The lower milk production in the group consuming the most analog can be explained largely by marked refusals of the concentrate (P < .05) and decreased intake of corn silage by some cows (Table 1). Refusals of concentrate were rare except in that group where four of six cows frequently
TABLE 1. Effect of methionine analog on feed consumption and selected blood components of lactating cows. Analog in concentrate Intake (kg dry m a t t e r / d a y ) Silage 60 to 90 Days on treatment Post-treatment Concentrate 60 to 90 Days on treatment Post-treatment Serum methionine b (ppm)
0%
0.2%
0.4%
0.8%
12.4(].0) a 12.4 (1.0)
11.6(0.6) 12.4(0.7)
11.5(0.8) 12.9 (0.7)
10.2(1.2) 12.2 (0.8)
11.4(0.3) 11.4(0,3)
11.7(0.6) 11.8(0.7)
11.4(0.2) 11.5(0.2)
9.2(0.8) d 11.0(0.9)
7.18(0.36)
7.60(0.69)
7.28(1.03)
8.43(0.58)
17.13(2.32) 2.12 (0.44) 1.52(0.52) 0.92(0.68) 2.97(0.35)
14.92(2.71) 1.63 (0.49) 0¢ 0 5.08(2.46)
18.43(3.63) 1.15 (0.28) 0.08(0.05) 0.22(0.22) 4.53(1.55)
24.35(7.90) 1.02 (0.77) 0.40(0.40) d 0 5.73(1.19)
Serum fl-lipoproteinsb (mg/lO ml) Polar lipids 21.66(2.77) Cholesterol 6.63(1.23) Free fatty acids 0 Triglyceridcs 1.15(0.54) Cholesterol esters 6.33 ( 1.36 )
12.7(2.34) 3.43(0.78) 0 0 3.65 ( 0.80 )
14.25(3.83) 3.23(0.44) 0 0 3.62 ( 0.91 )
22.22(4.62) 5.98(1.15) d 0 0.15(0.15) d 7.52 (3.30)
Serum a-lipoproteinsb (rag/10 nil) Polar lipids Cholesterol Free fatty acids Triglycerides Cholesterol esters
a I n parentheses is the s t a n d a r d error of the b Serum from blood sampled on 60 ± 4 days ¢ Zero indicates levels less than 0.01 mg/10 ml d Significant differences i n treatment means , P JOURNAL OF DAIRY SCIENCE ~ 0 L . 53, NO. 5
mean of sLx observations. lactation. serum. < .05.
TECHNICAL NOTES
35-
34-4,8
32- 4.4
30; >.
28
o Milk Yield D Fat Corrected Milk
~. Milk Fat Content
2s
U
2b
4b
go
8b
Analog Consumed (g/da~
Fro. 1. Effect of analog consumption ( X )
on
milk yicht, fat test, and fat-corrected milk production. Regression equations for milk production and milk fat test were, respectively, ~ = 32.35 + 0.107 X - - 0.00212 X 2 (P ~ .01) and ~---- 3.78 + 0.0155 X -- 0.00007 X 2 (P .~ .05). Fat-corrected milk was ea]culated on individuals and treatment means plotted. Mean fat tests for cows during the same period in the previous lactation were 3.6, 3.5, 3.7, and 3.5 for the 0, 0.2, 0.4, and 0.8% analog groups, respectively. Sylnbols represent actual '~reatment means. refused concentrate. Cows whose intakes were depressed during the treatment period increased intakes to levels comparable to all groups when the control concentrate replaced the analog ration (90 days post-partum, Table 1). Response in milk fat content was most surprising (Fig. 1). The response curve (P < .05) which reveals the increased milk fat production with increased intake of analog cannot be explained physiologically with our present knowledge of bovine fat metabolism and milk fat secretion. I t does indicate that alterations occur in fat metabolism due to methionine as suggested by McCarthy et al. (11) but specific mechanisms are unclear. When individual fat tests were compared with tests at the same stage of the previous lactation, the mean fat test w a s markedly increased in the present lactation for the treated groups and only slightly increased for the controls (Description, ]~ig. 1). This provides additional evidence that. the response in fat test was real. The increase in fat test cannot be accounted for by a decrease in milk production alone. Production was lower (P < .05) in the high treatment group, but even there production exceeded 27 kg per day. The mean production of 4% fat-corrected milk is plotted (Fig. 1). Serum methionine tended
609
to increase (Table 1) in those animals with the highest analog intake (P > .05), but the response was not consistent with treatment level. Sermn levels of analog plus methionine were n o t different between controls and the highest analog treatment. Milk ketones were generally quite normal and not different among treatments. There appeared to be a definite effect on some fractions of the serum a- and fl-lipoproteins. I n the a-lipoproteins (Table 1), there was a tendency for a decrease in cholesterol and a simultaneous increase in the cholesterol ester fraction. Free fatty acids (P < .05) and trigiycerides were present in small quantities in animals where analog was not fed but were essentially below the limits of detection by TLC in the serum of those cows receiving any level of the analog. The fl-lipoprotein fraction, considered more important in milk fat synthesis because of its uptake and contribution to the milk lipid content (6), contained considerable triglycerides in the control yet essentially none in the animals receiving the analog (P < .05). The increased fat content in the milk reflected the fl-lipoprotein triglyceride levels. Rosser (15) observed significantly (P < .05) lower trigIycerides in the fl-lipoproteins fraction of cows consuming 40 g of analog daily when they were fed a ration containing an 85% concentrate compared to controls on a similar analog-free ration. Blood samples taken 120 days post-partum after all animals had been reverted to control rations for approximately 30 days showed that animals regained free fatty acid and triglyceride levels comparable to the controls. The analog in the ration did alter the lipid metabolism in the animal. The site of action of methionine is not known. Patton et al. (13) have reported an increase in fatty acid synthesis by tureen inicroorganisms in the presence of added mcthionine. Furthermore, these workers have shown alterations in the lipid metabolism as evidenced by alterations in the fatty acid compositions of the blood a- and fl-lipoproteins (11). We have shown alterations in fractions derived from the serum lipoproteins. All these data indicate that methionine is intimately involved in the mechanisms that control lipid metabolism in the ruminant. C. E. POLAN, P. T. CHANDLER, and C. N. MILLER, Department of Dairy Science, Virginia Polytechnic Institute, Blacksburg 24061 Acknowledgments Partial support was provided by E. I. duPont de Nemours and Company, Wilmington, Delaware 19898, and Monsanto Company, St. Louis, Missouri 63166. J O U R N A L OF D A I R Y S C I E N C E ~]-OL. 5 3 , ~ O . 5
610
JOURNAL OF DAIRY SCIENCE
References
(1) Abdo, K. M., K. W. King, and R. W. Engel. (2) (3)
(4)
(5)
(6)
(7)
(8)
(9)
1964. Protein quality of rumcn microorganisms. J. Animal Sci., 23: 734. Chalupa, William. 1968. Problems in feeding urea to ruminants. J. Animal Sci., 27: 207. Difco Manual. Dehydrated Culture Media and Reagents for Microbiological and Clinical Laboratory Procedures. 9th ed. Difeo Laboratories, Inc., Detroit, Michigan. Ellis, W. C., L. M. Flynn, W. A. Hargus, and W. H. Pfander. 1959. Tryptophan, methionine, and lysine content of rumen contents in relation to nitrogen utlization by lambs fed purified rations. Federation Proc., 18 : 524. Ferguson, K. A., J. A. Hemsley, and P. J. Reis. 1967. Nutrition and wool growth: The effect of protecting dietary protein from microbial degradation in the rumen. Australian J. Sci., 30: 215. Glaseock, R. F., V. A. Welch, C. Bishop, T. Davies, E. W. Wright, and R. C. Noble. ]966. An investigation of serum llpoproteins and of their contribution to milk f a t in the dairy cow. Biochem. J., 98: 149. Grie], L. C., Jr., R. A. Patton, R. D. McCarthy, and P. T. Chandler. 1968. Milk production response to feeding methionine hydroxy analog to lactating dairy cows. J. Dairy Sci., 51: 866. Loosli, J. K., and L. E. Harris. 1945. Mcthionine increases the value of urea for lambs. J. Animal Sci., 4: 435. McCarthy, R. D., P. T. Chandler, L. C. Griel, Jr., and G. A. Porter. 1968. F a t t y acid composition of blood serum lipoproteins from normal and ketotic cows. J. Dairy Sci., 51 : 392.
JOURNALOF DAIRY SCIENCE"VOL.53, NO. 5
(1O) McCarthy, R. D., P. S, Dimick, and S. Patton. 1966. Field observations on the lipids of cows with depressed milk f a t test. J. Dairy Sci., 49: 205. (11) McCarthy, R. D., G. A. Porter, and L. C. Griel, Jr. 1968. Bovine ketosis and depressed f a t test in milk: A problem o£ methionine metabolism and serum lipoprorein aberration. J. Dairy Sol., 51 : 459. (12) McDonald, I. W. ]968. Nutritional aspects of protein metabolism in ruminants. Australian Vet. J., 44: 145. (13) Patton, R. A., R. D. McCarthy, and L. C. Grie], fir. 1968. Lipid synthesis by rmnen microorganisms. I. Stimulation by methionine in vitro. J. Dairy Sci., 51: 1310. (14) Reis, P. J., and P. G. Schinchel. ]964. The growth and composition of wool. II. The effect of casein, gelatin and sulfur containing amino acids given per abomasum. Australian J. Biol. Sci., 17: 532. (15) Rosser, R. A. 1969. The effect of dietary solublc carbohivdrates and whey components on bovine lipid metabolism. Ph.D. thesis, Virginia Polytechnic Institute, Blacksburg, Virginia. (16) Sakagami, T., and D. B. Zilversmit. 1961. Separation of dog serum lipoproteins by ultracentrifugation, dextran sulfate precipitation, and paper electrophoresis. J. Lipid Rcs., 2: 271. (17) Snedeeor, G. W. 1956. Statistical Methods Applied to :Experiments in Agriculture and Biology. 5th ed. Iowa State University Press, Ames. (18) Virtanen, A. E. 1966. Milk production of cows on protein-free feed. Science, 153 : 1603.
(m~-a-hydroxy-gamma-methyhnercaptobutyratecalcium) or with intravenous infusion of Lmethionine. This finding seems particularly significant, since the analog represented a practical way of enhancing the methionine complement of the animal. I f methionine were limiting in the metabolism and productivity of a ruminant, feeding the analog might easily correct the deficiency. I n subsequent experiments, Pennsylvania data indicated that 40 or 80 g / d a y of analog stimulated milk production, but a breed X level interaction existed (7). No study has indicated the optimal dietary level o f the analog for lactating dairy cows. Therefore, it became the objective of this study to define the response from feeding different levels of the analog to cows in early stages of lactation.
Beginning two weeks before anticipated parturition and f o r 90 days post-partum, 24 Holstein cows received a concentrate (14.5% crude protein) containing either 0, 0.2, 0.4, or 0.8% methionine hydroxy analog. Concentrate was limited to 11 to 12 k g / d a y and corn silage-urea (0.5%) was offered free choice. A milk production response curve indicated peak production at approximately 25 g analog/day. F a t content of milk increased with analog intake. Reduced silage and concentrate consumption was common with the highest analog level. F r e e fatty acid and triglyceride content of serum a-lipoproteius and triglycerides of the fllipoproteins were reduced in cows fed analog from those with no analog.
Recently, the quality of the protein presented to the blood stream of the ruminant animal has received considerable attention. Australian workers (5, 12, 14) have shown marked increases in wool production when sheep were fed formaldehyde-treated protein or had sulfur amino acids administered in the abomasum. The response was attributed to post-ruminal absorption of native amino acids available from decreased solubility and degradation while in the tureen. Methionine supplementation has had similar effect on growth. Over 20 years ago Loosli and t I a r r i s (8) reported improved utihzation of nitrogen by supplementing methionine into the diet. Methionine is among the amino acids likely to be limiting for optimal growth or milk production or both (1, 2, 4, 7, 12, 18). Although different essential amino acids may be limiting under certain circumstances, supplementing amino acids into the diet has not always yielded beneficial results (2). The principal reasons for different responses due to amino acid supplementation are probably related to the extent of degradation in the rumeu and the current metabolic needs. Penn State workers (9-11) have proposed that methionine nutrition has a direct bearing on bovine lipoprotein structure and composition. I n this manner, they have implicated methionine with both bovine ketosis and depressed milk fat production (11). Similar alterations in serum lipid fractions were observed with the oral administration of the analog of methionine
Experimental Procedure
I n the fall of ]968, 24 Holstein cows from the University herd that had completed at least one lactation were placed into six groups of four cows each based on anticipated date of parturition. Cows within a group were then randomly assigned to receive a concentrate containing either 0, 0.2, 0.4, or 0.8% analog. Concentrate feeding began two weeks before anticipated parturition. The pelleted concentrates (approximately 14.5 % crude protein) were composed of, in percentages, 70 corn, ]2.5 soybean meal, 5 molasses, 5 wheat, 2.5 distillers grains, 2 clay-based pelletbinder, 2.0 dicalcium phosphate, 1 iodized salt, 0.4 trace minerals, and 6,600 and 8,800 I U of vitamin A and D p e r kilogram, respectively. By parturition, cows were normally consuming 5 to 6.5 kg of concentrate per day. They were then gradually increased in concentrate up to ]1.8 kg per day. Corn silage containing 0.5% urea was fed free choice to all cows. Concentrate containing varying amounts of analog was fed for 90 days after parturition. C'ontrol concentrate (0% analog) was fed to all cows between 90 to 120 days. Feed consumption and milk production were recorded daily. Milk f a t and ketone content were determined at two-week intervals. Blood samples were taken at intervals of 30 -~ 4 days of lactation and analyzed for methionine by microbiological assay procedures (3) with Leuconostoc mesenteroides ATCC 8042. Similar procedures were utilized to assay for serum analog plus methionine with Lactobacillus plan607
608
JOURNAL
OF D A I R Y SCIENCE
t a r u m Strain 17-5, ATCC 8014. This organism can meet its methionine requirement with the analog. Serum a- and fl-tipoproteins from blood sampled at 60 and 120 days of lactation were further fractionated. The fl-lipoproteins were removed by the dextran sulfate method of Sakagami and Zilversmit (16). A f t e r precipitation the lower fraction was separated by decanting the supernatant fraction, which contained what was considered the a-lipoprotein fraction. Both fractions were then extracted by Mojonnier procedures with diethyl and petrolemn ether. Both lipoprotein components were further fractionated by thin-layer chromatogr a p h y (TLC) into polar lipids, cholesterol, free f a t t y acids, triglycerides, and cholesterol esters. A f t e r separation on TLC by the following solvent system (petroleum ether:ethyl ether:acetic acid--150:30:2), the plates were s p r a y misted with 50% sulfuric acid and charred at 180 C for 25 minutes. The resulting separate spots were then quantitated by densitometer with purified standards as a reference. The values in Table i are somewhat high because they were quantitated from the weights of lipid extracts which contained some nonlipid material.
Where appropriate, data were statistically analyzed according to Snedecor (17). Results and Discussion
The response curve (Fig. 1) for milk production (P ~ .01) revealed a mild but maximum response for animals consuming 25 g of analog per day. The regression equation indicates a marked decrease in milk production when analog is consumed in excess of 45 g. Analysis of variance of 14-day production means for each animal showed there was no effect of time on milk production response to analog nor an interaction between time and level of analog intake. Therefore, Figure 1 shows the over-all production means for each treatment for days 6 to 89 postparturition. Individual comparisons among treatment means indicate significant differences between 0.8% analog versus the other treatments (P < .05). The lower milk production in the group consuming the most analog can be explained largely by marked refusals of the concentrate (P < .05) and decreased intake of corn silage by some cows (Table 1). Refusals of concentrate were rare except in that group where four of six cows frequently
TABLE 1. Effect of methionine analog on feed consumption and selected blood components of lactating cows. Analog in concentrate Intake (kg dry m a t t e r / d a y ) Silage 60 to 90 Days on treatment Post-treatment Concentrate 60 to 90 Days on treatment Post-treatment Serum methionine b (ppm)
0%
0.2%
0.4%
0.8%
12.4(].0) a 12.4 (1.0)
11.6(0.6) 12.4(0.7)
11.5(0.8) 12.9 (0.7)
10.2(1.2) 12.2 (0.8)
11.4(0.3) 11.4(0,3)
11.7(0.6) 11.8(0.7)
11.4(0.2) 11.5(0.2)
9.2(0.8) d 11.0(0.9)
7.18(0.36)
7.60(0.69)
7.28(1.03)
8.43(0.58)
17.13(2.32) 2.12 (0.44) 1.52(0.52) 0.92(0.68) 2.97(0.35)
14.92(2.71) 1.63 (0.49) 0¢ 0 5.08(2.46)
18.43(3.63) 1.15 (0.28) 0.08(0.05) 0.22(0.22) 4.53(1.55)
24.35(7.90) 1.02 (0.77) 0.40(0.40) d 0 5.73(1.19)
Serum fl-lipoproteinsb (mg/lO ml) Polar lipids 21.66(2.77) Cholesterol 6.63(1.23) Free fatty acids 0 Triglyceridcs 1.15(0.54) Cholesterol esters 6.33 ( 1.36 )
12.7(2.34) 3.43(0.78) 0 0 3.65 ( 0.80 )
14.25(3.83) 3.23(0.44) 0 0 3.62 ( 0.91 )
22.22(4.62) 5.98(1.15) d 0 0.15(0.15) d 7.52 (3.30)
Serum a-lipoproteinsb (rag/10 nil) Polar lipids Cholesterol Free fatty acids Triglycerides Cholesterol esters
a I n parentheses is the s t a n d a r d error of the b Serum from blood sampled on 60 ± 4 days ¢ Zero indicates levels less than 0.01 mg/10 ml d Significant differences i n treatment means , P JOURNAL OF DAIRY SCIENCE ~ 0 L . 53, NO. 5
mean of sLx observations. lactation. serum. < .05.
TECHNICAL NOTES
35-
34-4,8
32- 4.4
30; >.
28
o Milk Yield D Fat Corrected Milk
~. Milk Fat Content
2s
U
2b
4b
go
8b
Analog Consumed (g/da~
Fro. 1. Effect of analog consumption ( X )
on
milk yicht, fat test, and fat-corrected milk production. Regression equations for milk production and milk fat test were, respectively, ~ = 32.35 + 0.107 X - - 0.00212 X 2 (P ~ .01) and ~---- 3.78 + 0.0155 X -- 0.00007 X 2 (P .~ .05). Fat-corrected milk was ea]culated on individuals and treatment means plotted. Mean fat tests for cows during the same period in the previous lactation were 3.6, 3.5, 3.7, and 3.5 for the 0, 0.2, 0.4, and 0.8% analog groups, respectively. Sylnbols represent actual '~reatment means. refused concentrate. Cows whose intakes were depressed during the treatment period increased intakes to levels comparable to all groups when the control concentrate replaced the analog ration (90 days post-partum, Table 1). Response in milk fat content was most surprising (Fig. 1). The response curve (P < .05) which reveals the increased milk fat production with increased intake of analog cannot be explained physiologically with our present knowledge of bovine fat metabolism and milk fat secretion. I t does indicate that alterations occur in fat metabolism due to methionine as suggested by McCarthy et al. (11) but specific mechanisms are unclear. When individual fat tests were compared with tests at the same stage of the previous lactation, the mean fat test w a s markedly increased in the present lactation for the treated groups and only slightly increased for the controls (Description, ]~ig. 1). This provides additional evidence that. the response in fat test was real. The increase in fat test cannot be accounted for by a decrease in milk production alone. Production was lower (P < .05) in the high treatment group, but even there production exceeded 27 kg per day. The mean production of 4% fat-corrected milk is plotted (Fig. 1). Serum methionine tended
609
to increase (Table 1) in those animals with the highest analog intake (P > .05), but the response was not consistent with treatment level. Sermn levels of analog plus methionine were n o t different between controls and the highest analog treatment. Milk ketones were generally quite normal and not different among treatments. There appeared to be a definite effect on some fractions of the serum a- and fl-lipoproteins. I n the a-lipoproteins (Table 1), there was a tendency for a decrease in cholesterol and a simultaneous increase in the cholesterol ester fraction. Free fatty acids (P < .05) and trigiycerides were present in small quantities in animals where analog was not fed but were essentially below the limits of detection by TLC in the serum of those cows receiving any level of the analog. The fl-lipoprotein fraction, considered more important in milk fat synthesis because of its uptake and contribution to the milk lipid content (6), contained considerable triglycerides in the control yet essentially none in the animals receiving the analog (P < .05). The increased fat content in the milk reflected the fl-lipoprotein triglyceride levels. Rosser (15) observed significantly (P < .05) lower trigIycerides in the fl-lipoproteins fraction of cows consuming 40 g of analog daily when they were fed a ration containing an 85% concentrate compared to controls on a similar analog-free ration. Blood samples taken 120 days post-partum after all animals had been reverted to control rations for approximately 30 days showed that animals regained free fatty acid and triglyceride levels comparable to the controls. The analog in the ration did alter the lipid metabolism in the animal. The site of action of methionine is not known. Patton et al. (13) have reported an increase in fatty acid synthesis by tureen inicroorganisms in the presence of added mcthionine. Furthermore, these workers have shown alterations in the lipid metabolism as evidenced by alterations in the fatty acid compositions of the blood a- and fl-lipoproteins (11). We have shown alterations in fractions derived from the serum lipoproteins. All these data indicate that methionine is intimately involved in the mechanisms that control lipid metabolism in the ruminant. C. E. POLAN, P. T. CHANDLER, and C. N. MILLER, Department of Dairy Science, Virginia Polytechnic Institute, Blacksburg 24061 Acknowledgments Partial support was provided by E. I. duPont de Nemours and Company, Wilmington, Delaware 19898, and Monsanto Company, St. Louis, Missouri 63166. J O U R N A L OF D A I R Y S C I E N C E ~]-OL. 5 3 , ~ O . 5
610
JOURNAL OF DAIRY SCIENCE
References
(1) Abdo, K. M., K. W. King, and R. W. Engel. (2) (3)
(4)
(5)
(6)
(7)
(8)
(9)
1964. Protein quality of rumcn microorganisms. J. Animal Sci., 23: 734. Chalupa, William. 1968. Problems in feeding urea to ruminants. J. Animal Sci., 27: 207. Difco Manual. Dehydrated Culture Media and Reagents for Microbiological and Clinical Laboratory Procedures. 9th ed. Difeo Laboratories, Inc., Detroit, Michigan. Ellis, W. C., L. M. Flynn, W. A. Hargus, and W. H. Pfander. 1959. Tryptophan, methionine, and lysine content of rumen contents in relation to nitrogen utlization by lambs fed purified rations. Federation Proc., 18 : 524. Ferguson, K. A., J. A. Hemsley, and P. J. Reis. 1967. Nutrition and wool growth: The effect of protecting dietary protein from microbial degradation in the rumen. Australian J. Sci., 30: 215. Glaseock, R. F., V. A. Welch, C. Bishop, T. Davies, E. W. Wright, and R. C. Noble. ]966. An investigation of serum llpoproteins and of their contribution to milk f a t in the dairy cow. Biochem. J., 98: 149. Grie], L. C., Jr., R. A. Patton, R. D. McCarthy, and P. T. Chandler. 1968. Milk production response to feeding methionine hydroxy analog to lactating dairy cows. J. Dairy Sci., 51: 866. Loosli, J. K., and L. E. Harris. 1945. Mcthionine increases the value of urea for lambs. J. Animal Sci., 4: 435. McCarthy, R. D., P. T. Chandler, L. C. Griel, Jr., and G. A. Porter. 1968. F a t t y acid composition of blood serum lipoproteins from normal and ketotic cows. J. Dairy Sci., 51 : 392.
JOURNALOF DAIRY SCIENCE"VOL.53, NO. 5
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