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Effect of Feeding Buffers to Dairy Cows Fed a High-Concentrate, Low-Roughage Ration1
EFFECT
OF FEEDING
BUFFERS
HIGH-CONCENTRATE,
TO D A I R Y C O W S F E D
LOW-ROUGHAGE
A
RATION ~
R. W. MILLER : AND R. W. HEMKEN University of Maryland, College Park AND
D. R. WALDO, M. OKAMOTO, AND L. A. MOORE Dairy Cattle :Research Branch--Animal Husbandry Research Division USDA, Beltsville, Maryland ABSTRACT
Eight lactath~g cows were grouped and assigned to one of two 4 X 4 Latin squares. Cows were offered concentrates ad libitum and 2 lb of hay daily. The four treatments consisted of an unsupplemented control ration, 1.00 lb XHC03, 0.84 lb NaHCO~, and 0.42 lb MgC03 per day. Addition o£ any one of the buffers prevented the depression in milk fat test that occurred while the cows were on the control ration (2.92 vs. 3.62%). Cows while on the control ration had an average daily gain in body weight of 2.46 lb per day, greater (P < .01) than the average of 0.04 lb while on the buffered rations. When the control ration was fed, cows had a lower (P < .05) molar per cent of rumen acetic acid (49.2 vs. 54.0), higher (P < .05) molar per cents of propionic acid (37.4 vs. 31.3) and n-valeric acid (2.8 vs. 1.8) than when fed the buffered rations. Rumen p H and Eh were not significantly affected by ration.
Milk fat depression that occurs when dairy cows are fed a high-concentrate, low-roughage ration can be prevented by feeding NaHCO~ or KHCO~, or a combination of the two (2-4, 7). Emery and Brown (3) reported that KHCO~ and NaHCO, increased the rumen p H but did not alter the proportion of rumen volatile fatty acids ( V F A ) . Subsequently, these workers (4) found a shift in the proportion of rumen VFA. Davis et al. (2) reported that the feeding of 3.0% NaHCO~ and I ( H C Q prevented the depression in milk fat test and increased the acetic :propionic acid ratio in cows fed a highconcentrate, low-roughage diet. One and a half per cent NaHCO~ and KHC03 gave trends similar to that when 3.0% was fed, but did not fully prevent the depression in milk fat test. The present study was undertaken to further investigate the mechanism by which NaHCO~ and KHCO~ prevent the depression in milk fat test Received for publication May 19, 1965.
of cows fed a high-concentrate, low-roughage diet and also to test the effect of MgC08. E X P E R I M E N T A L PROCEDURE
Seven Holsteins and one Guernsey-Ayrshire cross were grouped according to production and assigned to one of two 4 × 4 Latin squares. During a 3-wk preliminary period and a 3-wk post-experimental period the cows were on the normal herd ration, considered adequate in roughage. After the preliminary period, the roughage (mainly grass silage) in each cow's ration was gradually reduced and the concentrate mixture increased. The concentrate mixture consisted of 48% ground barley, 15% corn and cob meal, 10% molasses, 10% wheat bran, 15% soybean oil meaI (44% protein), 1% salt, and ] % steamed bone meal. At the end of the changeover period, the cows were receiving 2 lb alfalfa hay daily and essentially ad libitum concentrates. I n addition, the cows were offered steamed bone meal ad libitum and received 225,000 I U vitamin A per week via capsule. The four treatments consisted of a control (no added buffers), 1.00 lb XHCO.~, 0.42 lb MgC03, and 0.84 lb NaHC03 per day. The weights of the buffers were calculated on the ratios of their equivalent weights. These supplements were added to the concentrate mixture fed three times daily. Amounts of concentrates to be fed were adjusted frequently so the ani-
1Data from a thesis presented by R. W. Miller in partial fulfillment of the requirements for the M.S. Degree, University of Maryland. Scientific Article no. A-1190, Contribution no. 3685 of tile ~[aryland Agricultural Experiment Station, Department of Dairy Science. Address : Dairy Cattle Research ]~raneh, Animal Itusbandry Research Division, ARS, USDA, Beltsville, ]YIaryland. 1455
1456
a.w.
~¢iILLER
mals would receive all the concentrates they would eat without having large weighbacks. Periods were 21 days in length, with the last 14 being used for calculations; the first seven days were considered an adjustment period. Milk from individual cows was weighed at each milking and one-day composite milk samples taken from all cows twice weekly for milk fat, SNF, and protein determinations, by methods used previously (8). Cows were weighed three consecutive days at the start of each period for calculation of body weight changes. Seventeen days after the start of each period, rumen samples were taken by stomach tube approximately 4 hr after the morning concentrate feeding. These samples were processed as previously described (8). I n addition, Eh measurements were made using a Beckman (Model H-2) p t I meter equipped with saturated calomel and platinum electrodes. Eh measurements were standardized to a p H of 7, using the regression equation of Baldwin and Emery (1). Statistical analyses of the data were conducted, using methods described by Snedecor (11). The three degrees of freedom for treatmerits were broken down into individual degrees of freedom comparing control vs. NaHC03, KHCO.~, and MgC03; MgC03 vs. NaHCO~ and KHCO.~; and NaHCO~ vs. KHCO.~. I n addition, a covariance analysis of the acctatc-propionate ratios and nfilk fat tests was performed. RESULTS AND DISCUSSION Average consumption of concentrates was 32.8, 31.3, 29.6, and 27.5 lb for the control, NaHCO~, KHCOz and MgCO~ treatments, respectively. No statistical analysis was done on the consumption data, since there were occasionally no concentrate weighbacks; however, the depression in concentrate intake due to NaHCO.~ in the ration is not as great as that reported by Emery et al. (4). The average daily milk production, milk fat production, and the per cents of milk fat, protein, and SNF are presented in Table 1. The
ET A L
difference in milk production between the control and buffered rations was significantly different at the 10% level of probability. Milk protein values of cows while on MgCO~ were lower (P < .05) than when on NaHCO~ and KtIC03 and can probably be explained by a lower intake of concentrates (6). In comparison to the values for tile criteria presented in Table 1, average values of all cows in the preexperimental and post-experimental periods, respectively, for milk production, per cent SNF, and per cent protein were 47.3, 9.07, 3.35, and 32.4, 9.04, and 3.34. From Table 1 it can be seen that all three buffered rations increased the pounds of milk fat produced as well as increased the milk fat test over that of the control ration. That all three buffers increased the milk fat test to an essentially normal level was noted when the values obtained for the buffered rations were compared to the pre- and post-experimental values for milk fat test. These were 3.64 and 3.56% for the pre-experimental and post-experimental periods, respectively. The observation that the NaHCO.~ and KHCO~ prevented the depression in milk fat test is in agreement with other workers (2-4, 7). I n this experiment MgC03 was also effective in preventing a decrease in milk fat test; however, Emery et al. (4) reported no effect from feeding CaCO~. A possible explanation for this is that CaCO~ may be less soluble in the rumen fluid than MgCO~. Mean changes in body weight arc presented in Table 1. The gain of over 2 lb per day for aninmls while on the control ration is rather striking for lactating dairy cows. This observation does fit well into a theory discussed by Van Soest (12). This theory maintains that the raeehanisms of synthesis of body fat and milk fat are different. Body fat but not milk fat synthesis is promoted by an execs of reduced enzymes such as NADP. The metabolism of propionate would produce an excess of N A D P H which would suppress fat mobilization in the tissues and deprive the udder of essential
TABLE 1 Milk production, milk constituents, and body weight changes Criteria
Control
NattCO~
K IICO.~
MgCO~
Milk (lb/day) 38.6 37.5 36.2 34.7 Fat (%) 2.92 3.56 3.53 3.78 Fat (lb/day) 1.07 1.26 1.21 1.25 SNF (%) 9.11 9.16 9.06 9.04 Protein (%) 3.49 3.54 3.46 3.41 Body weight change (lb/day) +2.46 +0.76 --0.36 --0.29 Control and buffered rations significantly different (P ~ .01). b MgCO3 significantly different from NattCO~ and KtICO3 (P ~ .05).
SE of a mean 1.3 0.16 ~ 0.05 a 0.05 0.03 b 0.52"
FEEDING BUFFERS TO COWS materials for fat synthesis; however, fat synthesis in the tissues would be promoted. Whether this type of scheme is operating in dairy cows fed high-concentrate, low-roughage rations can not be ascertained from this experiment. Other workers have not shown weight gains of the magnitude Obtained in this experiment (2, 5, 8) in cows depressed in milk f a t test. From the rumen volatile fatty acid ( V F A ) data presented in Table 2 it can be seen that
1457
high-concentrate, low-roughage diet. This same group (4), however, in a later experiment reported that NaHC03 did widen the acetic :propionic acid ratio but that CaC0~ did not. Davis et al. (2) also reported that a mixture of NaItC0~ and K H C0 ~ increased the acetic :propionic ratios of dairy cows on a high-concentrate ration. Miller et al. (8) observed no changes in the proportions of tureen V F A when K H C 0 3 or MgCO~ was fed to dairy cows grazing Pearl
TABLE 2 Concentration of rumen WFA Control
NattCO3
KItCO~
MgCO~
SE of a mean
(meq/1 O0 ml tureen, f l u i d ) Acid C.~ C3 C4 C~ (iso) C5 Total Control and buffered rations
5.79 6.41 4.38 3.96 1.14 1.43 0.11 0.17 0.32 0.23 11.64 12.19 significantly different (P
cows while on the fat-depressing control diet had lower concentrations of acetic, butyric, and isovaleric acids and higher concentrations of propionic and n-valeric acids; however, only the difference in the concentration of isovaleric acid was significantly different at the 5% level of probability. Concentrations of acetic and n-valerie acids were different at the 10% level. When these results were expressed as molar per cents (Table 3), the differences in acetic and propionic acids between the control and buffered rations were significantly different at the 5% level, and that of n-valeric acid at the 1% level of probability. Reported effects of buffers on the rumen V F A appear to be contradictory. With dairy cows, Emery and Brown (3) found no differences in the molar per cents of V F A due to the feeding of NaHC0~ or KHCO~ to cows on a
6.38 3.52 1.26 0.17 0.22 11.55 ~ .05).
6.47 4.05 1.37 0.17 0.26 12.32
0.33 0.46 0.12 0.02 ~ 0.04 0.76
Millet or Sudangrass pastures. In all the above experiments the major protein source of the concentrate mixtures was soybean oil meal. With beef cattle results obtained with buffer feeding have been different. Nieholson, Cunningham, and Friend (9) reported that addition of buffers to beef cattle fed a high-concentrate ration (linseed meal-protein source) resulted in a decrease in the molar per cent of rumen acetic acid and an increase in the molar per cent of propionic acid. Results similar to those of Nicholson et al. (9) were obtained by 01tjen and Davis (10) when soybean oil meal was the major protein constituent of the concentrate mixture for beef cattle. When urea was the major protein constituent, Wise et al. (13) and 0]tjen and Davis (10) reported that addition of buffers increased the molar per cent of acetic acid and lowered the molar per cent of pro-
TABLE 3 Per cent rumen YFA Control
Na~ICOa
KttCOa
MgCOa
SE of a mean
53.1 32.2 11.2 1.4 2.0
1.6 a 2.5 ~ 1.0 0.2 0.2 b
(molar % of total) Acid C~ Ca C~ C~ (iso) C~
49.2 37.4 9.8 0.9 2.8
53.5 3].0 12.3 1.5 1.7
55.4 30.6 10.8 1.4 1.8
Control and buffered rations significantly different (P ~ .05). Control and buffered rations significantly different (P ~ .01).
1458
R.w.
MILLER ET AL
p i o n i c acid. I t would a p p e a r f r o m this discussion t h a t i f a n a t u r a l p r o t e i n source is used i n a c o n c e n t r a t e m i x t u r e , a d d i t i o n of buffers will widen the acetic : p r o p i o n i c acid r a t i o w h e n f e d to d a i r y cows, b u t will n a r r o w i t w i t h beef cattle. W h e t h e r this is true, or i f some o t h e r f a c t o r is responsible, r e m a i n s to be elucidated. To see i f changes in the acetic : p r o p i o n i c r a t i o could a c c o u n t f u l l y f o r the i n c r e a s e in milk f a t t e s t w h e n buffers were fed, a covariance analysis u s i n g the a c e t i c : p r o p i o n i c acid r a t i o as the X v a r i a b l e a n d m i l k f a t test was conducted. A f t e r the milk f a t tests were a d j u s t e d f o r differences in the a c e t i c : p r o p i o n i c ratios, statistically sign i f i c a n t ( P < .05) differences a m o n g t r e a t m e n t s remained. Thus, the buffers p r o b a b l y h a d some effect in i n c r e a s i n g the milk f a t test o t h e r t h a n t h a t m e d i a t e d t h r o u g h changes in the acetic: p r o p i o n i c acid ratios. E m e r y et al. (4) concluded f r o m t h e i r work t h a t sodium b i c a r b o n a t e controlled the milk f a t p e r cent via control of r u m i n a l acids. Table 4 shows results of r u m e n p t t a n d E h m e a s u r e m e n t s a n d Eo calculations. T h e r e were no statistically significant differences a m o n g a n y of the e x p e r i m e n t a l r a t i o n s f o r p t { , E h , or Eo. T h e r e has been a t r e n d t o w a r d s increased t u r e e n p H values w h e n buffers a r e a d d e d to high-conc e n t r a t e r a t i o n s ; however, as in this experiment, differences were usually n o t significantly different (4, 9, 10). I t m a y be t h a t r u m i n a l V F A p r o d u c t i o n is controlled b y r u m i n a l p H , as p r o p o s e d b y E m e r y a n d B r o w n (3), a n d t h a t f a i l u r e to o b t a i n significant differences was due to errors in r u m e n s a m p l i n g , especially b y stomach tube.
(3)
(4)
(5)
(6) (7)
(8)
(9)
(10)
ACKNOVCLEDGMENT The authors t h a n k Dr. Richard Lehmann, Biometrical Services, ARS, for advice on the statisticM analysis of this experiment.
(11)
(12)
REFERENCES (1) BALDWIN, R. L., AND EMERY, R. S. 1960. The Oxidation-Reduction Potential of Rumen Contents. J. Dairy Sci., 43: 506. (2) DAVIS, C. L., BROWN, R. E., ANn BEITZ, D. C. 1964. Effect of Feeding High-Grain Re-
(13)
strictcd Roughage Rations with and Without Bicarbonates on the F a t Content of Milk Produced and Proportions of Volatile F a t t y Acids in the Rumen. J. Dairy Sci., 47 : 1217. EMERY, R. S., AND BROWN, L. D. 1961. Effect of Feeding Sodium and Potassium Bicarbonate on Milk Fat, Rumen pH, and Volatile F a t t y Acid Production. J. Dairy Set., 44: 1899. EMERY, R. S., BROWN, L. D., AND THOMAS, J . W . 1964. Effect of Sodium and Calcium Carbonates on Milk Production and Composition of Milk, Blood, and Rumen Contents of Cows Fed Grain ad Libltum with Restricted Roughage. J. Dairy ScL, 47: 1325. KING, R. L., AND HEM~:EN, R. W. 1962. Composition of Milk Produced on Pelleted Hay and Heated Corn. J. Dairy Sci., 45: 1336. LABEN, R. C. 1963. Factors Responsible for Variation in Milk Composition. J. Dairy Set., 46: 1293. LO0SLI, J. K., ELLIOT, J. M., AND MYERS, G. S., fiR. 1963. Effect of Temperature and Additives on Pelleted Concentrates Fed to Dairy Cows at Different Ratios of Grain to Hay. Proe. Cornell Nutrition Conf. for Feed Mfrs. p. 44. MILLER, R. W., HEMKEN, R. W., VANDERSALL, J. H., WALDO, D. R., OKAI~t0T0, M., AND MOORE, L. A. 1965. Effect of Feeding Buffers to Dairy Cows Grazing Pearl Millet or Sudangrass. J. Dairy Set., 48: 1319. NICHOLSON, J. W. G., CUNNINGHAM, H. M., AND F~IEND, D. W. 1963. Effect of Adding Buffers to All-Concentrate Rations on Feedlot Performance of Steers, ]%ation Digestibility and Intra-Rumen Environment. J. Animal ScL, 22:368. OLTJEN, R. R., AND DAVIS, 1~. E. 1965. Factors Affecting the Rumlnai Characteristics of Cattle Fed All-Concentrate Rations. J. Animal Set., 24: 198. SNEDEC0t~, G. W. 1956. Statistical Methods. 5th ed. The Iowa State College Press, Ames. VAN SOEST, P. J. 1963. Ruminant F a t Metabolism with Particular Reference ¢o Factors Affecting Low Milk F a t and Feed Efficiency. A Review. J. Dairy Set., 46: 204. WISE, M. B., BLUI~ER, W. I~., MATRONE~ G.~ AND BARalCI~, E. R. 1961. Investigations on the Feeding of All-Concentrate Rations to Beef Cattle. J. Animal Sci., 20: 561.
TABLE 4 Rumen pI-I, Eh, and Eo Criteria
Control
NaHCOa
KHCOz
MgCO,
SE of a mean
pH E h (mv) a Eo (my) b
5.85 --372 --441
6.00 --378 --437
6.08 --366 --421
5.92 --371 --436
0.12 13 11
Relative to saturated calomel. b Eo = E h + 60 (pt{ -- 7.00).
OF FEEDING
BUFFERS
HIGH-CONCENTRATE,
TO D A I R Y C O W S F E D
LOW-ROUGHAGE
A
RATION ~
R. W. MILLER : AND R. W. HEMKEN University of Maryland, College Park AND
D. R. WALDO, M. OKAMOTO, AND L. A. MOORE Dairy Cattle :Research Branch--Animal Husbandry Research Division USDA, Beltsville, Maryland ABSTRACT
Eight lactath~g cows were grouped and assigned to one of two 4 X 4 Latin squares. Cows were offered concentrates ad libitum and 2 lb of hay daily. The four treatments consisted of an unsupplemented control ration, 1.00 lb XHC03, 0.84 lb NaHCO~, and 0.42 lb MgC03 per day. Addition o£ any one of the buffers prevented the depression in milk fat test that occurred while the cows were on the control ration (2.92 vs. 3.62%). Cows while on the control ration had an average daily gain in body weight of 2.46 lb per day, greater (P < .01) than the average of 0.04 lb while on the buffered rations. When the control ration was fed, cows had a lower (P < .05) molar per cent of rumen acetic acid (49.2 vs. 54.0), higher (P < .05) molar per cents of propionic acid (37.4 vs. 31.3) and n-valeric acid (2.8 vs. 1.8) than when fed the buffered rations. Rumen p H and Eh were not significantly affected by ration.
Milk fat depression that occurs when dairy cows are fed a high-concentrate, low-roughage ration can be prevented by feeding NaHCO~ or KHCO~, or a combination of the two (2-4, 7). Emery and Brown (3) reported that KHCO~ and NaHCO, increased the rumen p H but did not alter the proportion of rumen volatile fatty acids ( V F A ) . Subsequently, these workers (4) found a shift in the proportion of rumen VFA. Davis et al. (2) reported that the feeding of 3.0% NaHCO~ and I ( H C Q prevented the depression in milk fat test and increased the acetic :propionic acid ratio in cows fed a highconcentrate, low-roughage diet. One and a half per cent NaHCO~ and KHC03 gave trends similar to that when 3.0% was fed, but did not fully prevent the depression in milk fat test. The present study was undertaken to further investigate the mechanism by which NaHCO~ and KHCO~ prevent the depression in milk fat test Received for publication May 19, 1965.
of cows fed a high-concentrate, low-roughage diet and also to test the effect of MgC08. E X P E R I M E N T A L PROCEDURE
Seven Holsteins and one Guernsey-Ayrshire cross were grouped according to production and assigned to one of two 4 × 4 Latin squares. During a 3-wk preliminary period and a 3-wk post-experimental period the cows were on the normal herd ration, considered adequate in roughage. After the preliminary period, the roughage (mainly grass silage) in each cow's ration was gradually reduced and the concentrate mixture increased. The concentrate mixture consisted of 48% ground barley, 15% corn and cob meal, 10% molasses, 10% wheat bran, 15% soybean oil meaI (44% protein), 1% salt, and ] % steamed bone meal. At the end of the changeover period, the cows were receiving 2 lb alfalfa hay daily and essentially ad libitum concentrates. I n addition, the cows were offered steamed bone meal ad libitum and received 225,000 I U vitamin A per week via capsule. The four treatments consisted of a control (no added buffers), 1.00 lb XHCO.~, 0.42 lb MgC03, and 0.84 lb NaHC03 per day. The weights of the buffers were calculated on the ratios of their equivalent weights. These supplements were added to the concentrate mixture fed three times daily. Amounts of concentrates to be fed were adjusted frequently so the ani-
1Data from a thesis presented by R. W. Miller in partial fulfillment of the requirements for the M.S. Degree, University of Maryland. Scientific Article no. A-1190, Contribution no. 3685 of tile ~[aryland Agricultural Experiment Station, Department of Dairy Science. Address : Dairy Cattle Research ]~raneh, Animal Itusbandry Research Division, ARS, USDA, Beltsville, ]YIaryland. 1455
1456
a.w.
~¢iILLER
mals would receive all the concentrates they would eat without having large weighbacks. Periods were 21 days in length, with the last 14 being used for calculations; the first seven days were considered an adjustment period. Milk from individual cows was weighed at each milking and one-day composite milk samples taken from all cows twice weekly for milk fat, SNF, and protein determinations, by methods used previously (8). Cows were weighed three consecutive days at the start of each period for calculation of body weight changes. Seventeen days after the start of each period, rumen samples were taken by stomach tube approximately 4 hr after the morning concentrate feeding. These samples were processed as previously described (8). I n addition, Eh measurements were made using a Beckman (Model H-2) p t I meter equipped with saturated calomel and platinum electrodes. Eh measurements were standardized to a p H of 7, using the regression equation of Baldwin and Emery (1). Statistical analyses of the data were conducted, using methods described by Snedecor (11). The three degrees of freedom for treatmerits were broken down into individual degrees of freedom comparing control vs. NaHC03, KHCO.~, and MgC03; MgC03 vs. NaHCO~ and KHCO.~; and NaHCO~ vs. KHCO.~. I n addition, a covariance analysis of the acctatc-propionate ratios and nfilk fat tests was performed. RESULTS AND DISCUSSION Average consumption of concentrates was 32.8, 31.3, 29.6, and 27.5 lb for the control, NaHCO~, KHCOz and MgCO~ treatments, respectively. No statistical analysis was done on the consumption data, since there were occasionally no concentrate weighbacks; however, the depression in concentrate intake due to NaHCO.~ in the ration is not as great as that reported by Emery et al. (4). The average daily milk production, milk fat production, and the per cents of milk fat, protein, and SNF are presented in Table 1. The
ET A L
difference in milk production between the control and buffered rations was significantly different at the 10% level of probability. Milk protein values of cows while on MgCO~ were lower (P < .05) than when on NaHCO~ and KtIC03 and can probably be explained by a lower intake of concentrates (6). In comparison to the values for tile criteria presented in Table 1, average values of all cows in the preexperimental and post-experimental periods, respectively, for milk production, per cent SNF, and per cent protein were 47.3, 9.07, 3.35, and 32.4, 9.04, and 3.34. From Table 1 it can be seen that all three buffered rations increased the pounds of milk fat produced as well as increased the milk fat test over that of the control ration. That all three buffers increased the milk fat test to an essentially normal level was noted when the values obtained for the buffered rations were compared to the pre- and post-experimental values for milk fat test. These were 3.64 and 3.56% for the pre-experimental and post-experimental periods, respectively. The observation that the NaHCO.~ and KHCO~ prevented the depression in milk fat test is in agreement with other workers (2-4, 7). I n this experiment MgC03 was also effective in preventing a decrease in milk fat test; however, Emery et al. (4) reported no effect from feeding CaCO~. A possible explanation for this is that CaCO~ may be less soluble in the rumen fluid than MgCO~. Mean changes in body weight arc presented in Table 1. The gain of over 2 lb per day for aninmls while on the control ration is rather striking for lactating dairy cows. This observation does fit well into a theory discussed by Van Soest (12). This theory maintains that the raeehanisms of synthesis of body fat and milk fat are different. Body fat but not milk fat synthesis is promoted by an execs of reduced enzymes such as NADP. The metabolism of propionate would produce an excess of N A D P H which would suppress fat mobilization in the tissues and deprive the udder of essential
TABLE 1 Milk production, milk constituents, and body weight changes Criteria
Control
NattCO~
K IICO.~
MgCO~
Milk (lb/day) 38.6 37.5 36.2 34.7 Fat (%) 2.92 3.56 3.53 3.78 Fat (lb/day) 1.07 1.26 1.21 1.25 SNF (%) 9.11 9.16 9.06 9.04 Protein (%) 3.49 3.54 3.46 3.41 Body weight change (lb/day) +2.46 +0.76 --0.36 --0.29 Control and buffered rations significantly different (P ~ .01). b MgCO3 significantly different from NattCO~ and KtICO3 (P ~ .05).
SE of a mean 1.3 0.16 ~ 0.05 a 0.05 0.03 b 0.52"
FEEDING BUFFERS TO COWS materials for fat synthesis; however, fat synthesis in the tissues would be promoted. Whether this type of scheme is operating in dairy cows fed high-concentrate, low-roughage rations can not be ascertained from this experiment. Other workers have not shown weight gains of the magnitude Obtained in this experiment (2, 5, 8) in cows depressed in milk f a t test. From the rumen volatile fatty acid ( V F A ) data presented in Table 2 it can be seen that
1457
high-concentrate, low-roughage diet. This same group (4), however, in a later experiment reported that NaHC03 did widen the acetic :propionic acid ratio but that CaC0~ did not. Davis et al. (2) also reported that a mixture of NaItC0~ and K H C0 ~ increased the acetic :propionic ratios of dairy cows on a high-concentrate ration. Miller et al. (8) observed no changes in the proportions of tureen V F A when K H C 0 3 or MgCO~ was fed to dairy cows grazing Pearl
TABLE 2 Concentration of rumen WFA Control
NattCO3
KItCO~
MgCO~
SE of a mean
(meq/1 O0 ml tureen, f l u i d ) Acid C.~ C3 C4 C~ (iso) C5 Total Control and buffered rations
5.79 6.41 4.38 3.96 1.14 1.43 0.11 0.17 0.32 0.23 11.64 12.19 significantly different (P
cows while on the fat-depressing control diet had lower concentrations of acetic, butyric, and isovaleric acids and higher concentrations of propionic and n-valeric acids; however, only the difference in the concentration of isovaleric acid was significantly different at the 5% level of probability. Concentrations of acetic and n-valerie acids were different at the 10% level. When these results were expressed as molar per cents (Table 3), the differences in acetic and propionic acids between the control and buffered rations were significantly different at the 5% level, and that of n-valeric acid at the 1% level of probability. Reported effects of buffers on the rumen V F A appear to be contradictory. With dairy cows, Emery and Brown (3) found no differences in the molar per cents of V F A due to the feeding of NaHC0~ or KHCO~ to cows on a
6.38 3.52 1.26 0.17 0.22 11.55 ~ .05).
6.47 4.05 1.37 0.17 0.26 12.32
0.33 0.46 0.12 0.02 ~ 0.04 0.76
Millet or Sudangrass pastures. In all the above experiments the major protein source of the concentrate mixtures was soybean oil meal. With beef cattle results obtained with buffer feeding have been different. Nieholson, Cunningham, and Friend (9) reported that addition of buffers to beef cattle fed a high-concentrate ration (linseed meal-protein source) resulted in a decrease in the molar per cent of rumen acetic acid and an increase in the molar per cent of propionic acid. Results similar to those of Nicholson et al. (9) were obtained by 01tjen and Davis (10) when soybean oil meal was the major protein constituent of the concentrate mixture for beef cattle. When urea was the major protein constituent, Wise et al. (13) and 0]tjen and Davis (10) reported that addition of buffers increased the molar per cent of acetic acid and lowered the molar per cent of pro-
TABLE 3 Per cent rumen YFA Control
Na~ICOa
KttCOa
MgCOa
SE of a mean
53.1 32.2 11.2 1.4 2.0
1.6 a 2.5 ~ 1.0 0.2 0.2 b
(molar % of total) Acid C~ Ca C~ C~ (iso) C~
49.2 37.4 9.8 0.9 2.8
53.5 3].0 12.3 1.5 1.7
55.4 30.6 10.8 1.4 1.8
Control and buffered rations significantly different (P ~ .05). Control and buffered rations significantly different (P ~ .01).
1458
R.w.
MILLER ET AL
p i o n i c acid. I t would a p p e a r f r o m this discussion t h a t i f a n a t u r a l p r o t e i n source is used i n a c o n c e n t r a t e m i x t u r e , a d d i t i o n of buffers will widen the acetic : p r o p i o n i c acid r a t i o w h e n f e d to d a i r y cows, b u t will n a r r o w i t w i t h beef cattle. W h e t h e r this is true, or i f some o t h e r f a c t o r is responsible, r e m a i n s to be elucidated. To see i f changes in the acetic : p r o p i o n i c r a t i o could a c c o u n t f u l l y f o r the i n c r e a s e in milk f a t t e s t w h e n buffers were fed, a covariance analysis u s i n g the a c e t i c : p r o p i o n i c acid r a t i o as the X v a r i a b l e a n d m i l k f a t test was conducted. A f t e r the milk f a t tests were a d j u s t e d f o r differences in the a c e t i c : p r o p i o n i c ratios, statistically sign i f i c a n t ( P < .05) differences a m o n g t r e a t m e n t s remained. Thus, the buffers p r o b a b l y h a d some effect in i n c r e a s i n g the milk f a t test o t h e r t h a n t h a t m e d i a t e d t h r o u g h changes in the acetic: p r o p i o n i c acid ratios. E m e r y et al. (4) concluded f r o m t h e i r work t h a t sodium b i c a r b o n a t e controlled the milk f a t p e r cent via control of r u m i n a l acids. Table 4 shows results of r u m e n p t t a n d E h m e a s u r e m e n t s a n d Eo calculations. T h e r e were no statistically significant differences a m o n g a n y of the e x p e r i m e n t a l r a t i o n s f o r p t { , E h , or Eo. T h e r e has been a t r e n d t o w a r d s increased t u r e e n p H values w h e n buffers a r e a d d e d to high-conc e n t r a t e r a t i o n s ; however, as in this experiment, differences were usually n o t significantly different (4, 9, 10). I t m a y be t h a t r u m i n a l V F A p r o d u c t i o n is controlled b y r u m i n a l p H , as p r o p o s e d b y E m e r y a n d B r o w n (3), a n d t h a t f a i l u r e to o b t a i n significant differences was due to errors in r u m e n s a m p l i n g , especially b y stomach tube.
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(4)
(5)
(6) (7)
(8)
(9)
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ACKNOVCLEDGMENT The authors t h a n k Dr. Richard Lehmann, Biometrical Services, ARS, for advice on the statisticM analysis of this experiment.
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REFERENCES (1) BALDWIN, R. L., AND EMERY, R. S. 1960. The Oxidation-Reduction Potential of Rumen Contents. J. Dairy Sci., 43: 506. (2) DAVIS, C. L., BROWN, R. E., ANn BEITZ, D. C. 1964. Effect of Feeding High-Grain Re-
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strictcd Roughage Rations with and Without Bicarbonates on the F a t Content of Milk Produced and Proportions of Volatile F a t t y Acids in the Rumen. J. Dairy Sci., 47 : 1217. EMERY, R. S., AND BROWN, L. D. 1961. Effect of Feeding Sodium and Potassium Bicarbonate on Milk Fat, Rumen pH, and Volatile F a t t y Acid Production. J. Dairy Set., 44: 1899. EMERY, R. S., BROWN, L. D., AND THOMAS, J . W . 1964. Effect of Sodium and Calcium Carbonates on Milk Production and Composition of Milk, Blood, and Rumen Contents of Cows Fed Grain ad Libltum with Restricted Roughage. J. Dairy ScL, 47: 1325. KING, R. L., AND HEM~:EN, R. W. 1962. Composition of Milk Produced on Pelleted Hay and Heated Corn. J. Dairy Sci., 45: 1336. LABEN, R. C. 1963. Factors Responsible for Variation in Milk Composition. J. Dairy Set., 46: 1293. LO0SLI, J. K., ELLIOT, J. M., AND MYERS, G. S., fiR. 1963. Effect of Temperature and Additives on Pelleted Concentrates Fed to Dairy Cows at Different Ratios of Grain to Hay. Proe. Cornell Nutrition Conf. for Feed Mfrs. p. 44. MILLER, R. W., HEMKEN, R. W., VANDERSALL, J. H., WALDO, D. R., OKAI~t0T0, M., AND MOORE, L. A. 1965. Effect of Feeding Buffers to Dairy Cows Grazing Pearl Millet or Sudangrass. J. Dairy Set., 48: 1319. NICHOLSON, J. W. G., CUNNINGHAM, H. M., AND F~IEND, D. W. 1963. Effect of Adding Buffers to All-Concentrate Rations on Feedlot Performance of Steers, ]%ation Digestibility and Intra-Rumen Environment. J. Animal ScL, 22:368. OLTJEN, R. R., AND DAVIS, 1~. E. 1965. Factors Affecting the Rumlnai Characteristics of Cattle Fed All-Concentrate Rations. J. Animal Set., 24: 198. SNEDEC0t~, G. W. 1956. Statistical Methods. 5th ed. The Iowa State College Press, Ames. VAN SOEST, P. J. 1963. Ruminant F a t Metabolism with Particular Reference ¢o Factors Affecting Low Milk F a t and Feed Efficiency. A Review. J. Dairy Set., 46: 204. WISE, M. B., BLUI~ER, W. I~., MATRONE~ G.~ AND BARalCI~, E. R. 1961. Investigations on the Feeding of All-Concentrate Rations to Beef Cattle. J. Animal Sci., 20: 561.
TABLE 4 Rumen pI-I, Eh, and Eo Criteria
Control
NaHCOa
KHCOz
MgCO,
SE of a mean
pH E h (mv) a Eo (my) b
5.85 --372 --441
6.00 --378 --437
6.08 --366 --421
5.92 --371 --436
0.12 13 11
Relative to saturated calomel. b Eo = E h + 60 (pt{ -- 7.00).