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Effect of Abrupt Ration Changes on Milk and Blood Components1
Effect of Abrupt Ration Changes on Milk and Blood Components 1 L. D. SATTER and A. N. BRINGE
Department of Dairy Science, University of Wisconsin, Madison 53706 Abstract
The effect of abrupt change between a normal and a fat-depressing ration on milk composition and several blood components was examined. An abrupt ration change was accomplished by simultaneously switching rumen contents and rations between two cows, one fed a ration having a grainto-roughage ratio of approximately 1:2 and the other a fat-depressing ration with a 3:1 ratio. Feed intake was not altered when the cows were abruptly switched from one ration to the other. Five to six days were necessary to affect complete transition in the level of milk fat following a ration change. This was interpreted to mean that the ration effect on milk fat content was eventually mediated through time-cousnming metabolic adaptations by the host, rather than by immediate availability or supply of acetate, propionate, or butyrate from the tureen. Arterial levels of blood glucose, ketones, acetate, and triglycerides with the normal ration were 50.2, 2.13, 12.6, and 11.1 rag/100 ml, respectively. Corresponding values with the fat-depressing ration were 56.3, 2.44, 7.9, and 11.5 rag/100 ml. Values for blood glucose and acetate were significantly different (P < 0.05), whereas those for ketones and triglycerides were not. The only arterial-venous difference across the mamm a r t, gland tha~ approached significance was that for acetate. I ntroducfion
A period of one to three weeks has usually been required to affect complete depression in milk fat following change from a normal to a fat-depresslng ration (5, 6). Some of the delay can be attributed to the gradual change from one ration to another, usually requiring one week or less. Once complete ration substitution has occurred, additional time is probably
required for the rumen microbial population to stabilize and produce their characteristic end products. Finally, the host itself must undergo adaptive changes to accommodate the altered ruminal end products, and to utilize them in the synthesis of milk having low fat content. The following study was conducted to assess the relative length of time required for each of these adaptive changes. By simultaneous substitution of ration and rumen contents, the delay in rmneu environmental and microbial change was avoided. I t was further hoped that such a technique would sharpen the host response, and more clearly delineate changes in several blood components utilized for milk synthesis.
Experimental Procedure Two lactating Holstein cows possessing ruminal fistulas were placed respectively on a normal ration (6.36 kg of regular herd mix concentrate and alfalfa hay ad lib.) or a fatdepressing ration (three parts of pelleted concentrate and one p a r t alfalfa hay fed a~l lib.), as described by Jorgensen et al. (5). A t designated times each reticulo-rumen was emptied and the contents switched to the other cow. The ration was simultaneously switched, resulting in an abrupt transition from one dietary regime to another. This was repeated four times with a mininmm of three weeks between ration changes. I n addition, three ration changes were made without simultaneously changing rumen conteats. When going from the fat-depressing ration to the normal ration, an immediate change in ration was made. A gradual ration change lasting four days was made when switching from the normal ration to the fatdepressing ration. This was done to avoid problems of overeating. Blood samples were o b ~ i n e d from two of the periods of abrupt simultaneous switching of ration and tureen contents. Blood from the tail artery and mammary vein were obtained several hours before the ration change, and again on the first and third or seventh day following" ration substitution. Blood glucose, ketones, acetate, and triglycerides were de-
Received for publication March 28, 1969. 1 Published with the approval of the Director of the Wisconsin Agricultural Experiment Station, Madison, Wisconsin. 1776
ABRUPT
RATION
CHANGES
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FIa. 1. Milk production and per cent milk fat.
termined in the arterial and venous blood as reported by Bringe and Sehultz (3). Arterialvenous differences were determined and were assumed to represent mammary gland uptake of each component• Ruminal ingesta was sampled twice weekly for determination of volatile f a t t y acids. A representative sample of ruminal contents was acidified and strained through two layers of cheese cloth and centrifuged at 12,000 × g for 15 rain. Total volatile f a t t y acids were determined by steam distillation and the component f a t t y acids by gas chromatogr a p h y (2). Milk was sampled daily for milk fat determination one to two weeks after a ration change. Biweekly samples were obtained for solids-not-fat and protei~ analysis. Milk fat was determined by the Babcock method, solidsnot-fat by the Golding bead method (4), and protein by the dye-binding method (1). Results and Discussion
The mean levels for milk production and per cent milk f a t are shown in Figure 1. Each point on the milk production curve represents the mean of three days' milk production. Milk production values did not figure into the mean until the second day following a switch of
rations, and per cent milk f a t values were not included until the fifth day following a change. The fat-depressing ration supported a higher level of production (P < 0.005), particularly in Cow 1102. This cow responded to the fatdepressing ration by increasing milk production by 40% within five to seven days after placement on the ration; but then would immediately decline in production to an apparent normal level within one week following the peak production. This same response was noted in the other cow, but to a much lesser extent. I t is not a p p a r e n t what the stimulus of milk production was, and why it was not effective in sustaining the high level of production. The r a p i d i t y with which milk f a t adjusted to a new ration is illustrated in Table 1. These values indicate the extent of adjustment to the new mean milk fat percentage. When both rmnen contents and ration were switched abruptly, about 70% of the change that was to occur did so within three days and was essentially complete within five to six days. A slightly slower transition requiring one to two days' more time was noted when the tureen contents were not changed simultaneously with the ration. When the fat-depressing ration was introduced over a period of four days, about J.
DAIRY
SCIENCE
VOI,.
52,
NO.
11
TABLe. 1. Rate of milk fat test adaptation to new ration. Previous mean 1
2
3
4
Day following ration change 6 7 8 9
5
10
11
12
13
14
Approaching mean
(%) Abrupt ration change with rumen content change N a --> FD 2.77 2.80 2.27 2.00 1.90 F D b --> N 1.37 1.67 1.98 2.23 2.53
1.80 2.00
1.72 2.70
1.90 2.67
"~ Abrupt ration change without rumen content change FD --> N 1.96 1.80 2.05 2.47 2.57
2.73
2.65
3.03
3.70
....
3.23
............
3.00
3.07
Four-day period for ration change without rumen content change N --> F D 2.68 2.90 2.90 2.77 2.63 2.60 2.35
2.40
2.22
....
2.13
...........
1.60
2.07
•~
........................... ............................
1.55 2.72
a N, Normal ration. b FD, Fat-depressing ration. TABLE 2. Effect of alternate rations on feed intake, ruminal volatile acids, and milk composition. Feed intake Period
Na
FD b
Acetate N
FD
(kg/day)
Propionate N
FD
1 to 2 3 to 4 5 to 6 7 to 8 Average
17.5 19.7 20.1 17.3 18.7
18.9 20.2 19.9 14.6 18.4
7.70 9.25 8.70 8.11 8.44 ***c
7.24 7.63 6.11 7.27 7.06
(meq/100 ml) Cow 1163 2.75 4.86 2.48 3.82 2.48 4.79 2.37 4.06 2.52 ~ * 4.38
1 to 2 3 to 4 5 to 6 7 to 8 Average
21.1 19.6 18.7 16.7 19.0
20.2 20.8 19.1 16.2 19.1
8.97 9.05 7.32 9.72 8.77 **~
6.13 6.70 5.71 6.07 6.15
2.51 2.58 2.55 2.53 2.54 ~
a N, Normal ration. b FD, Fat-depressing. c Significant P < 0.005.
Cow 1102 5.24 4.69 4.32 4.62 4.72
Butyrate N
FD
Solids-not-fat N
Protein
FD
N
FD
(%) 1.22 1.45 1.67 1.39 1.43
1.38 1.51 1.83 1.39 1.53
8.37 7.56 7.90 7.77 7.90 * ~
8.28 8.35 8.42 7.90 8.29
3.02 2.98 2.98 3.26 3.06 ~**
3.05 3.28 3.45 3.33 3.28
1.36 1.72 1.49 1.46 1.51
1.21 1.55 1.24 2.01 1.50
8.50 8.29 8.42 8.85 8.52 **~
8.92 8.97 9.23 8.93 9.01
2.92 3.22 3.31 3.96 3.35 ~**
3.27 3.45 3.62 3.84 3.55
(DO
ABRUPT
1779
RATION CHANGES
11 days were required for the mean level of the subsequent period to be reached. F r o m this it appears that a minimum of five to six days is required for adaptive responses by the host itself, aside from the adaptive changes in the rumen. This certainly supports the view that change in milk fat content is eventually regulated by something more than the immediate availability or supply of acetate, propionate, or butyrate from the t u r e e n , and that timeconsuming metabolic adaptations are involved. Table 2 shows the effect of each ration on feed intake, ruminal volatile acids, and milk composition. Feed intake and ruminal fatty acid data are reported throughout the whole period, whereas milk composition data are not reported until the fifth day after each ration change. The consumption of air-dry feed wus the same for both rations, though the estimated net energy intake would have been 30% greater for the fat-depressing ration. I t was of interest to note that the abrupt ration and rumen changes did not seem to affect feed intake at all, in spite of the radical ration change. The ruminal concentration of acetate was lower, and that of propionate considerably higher with the fat-depressing ration. Ruminal butyrate concentration was about equal for both rations. I t required about two days for
ruminal fatty acid levels tQ reach their charaeteristie patterns when the ration, but not the ruminal ingesta, was abruptly changed. Milk solids-not-fat and protein were higher on the fat-depressing ration than on the normal ration. Ruminal f a t t y acid patterns and milk composition values resembled the observations made by others using similar rations (3, 5). I t was postulated that by inducing an abrupt change in the digestive end products being absorbed from the gastrointestinal tract a clearer response of several blood components associated with milk fat synthesis might be detected. Tail arterial and mammary venous levels o£ glucose, ketones, acetate, and triglycerides are shown in Table 3. The number in parentheses indicates the number of observations used to obtain each mean. Over-all arterial and venous glucose was higher (P < 0.05 and P ~ 0.10, respectively) on the fat-depressing ration, but the A-V difference was not significantly different from the normal ration. On only one occasion did it a p p e a r that blood glucose levels had responded by the first day following abrupt ration changes. Between one and seven days was required for most blood glucose changes to occur. Arterial and venous levels of ketones and triglycerides were not affected by the abrupt ration changes, nor were
TABLE 3. Effect of alternate rations on blood constituents. Normal Arterial
Fat-depressing A-V
Arterial
A-V
(rag/100 m l ) A b r u p t change from normal to fat-depressing ration (2) a 10.2 (2) 56.4 (4) 11.9
Glucose Ketones Acetate Triglyeeride
47.9 3.02 (2) 12.7 (1) 8.8 (2)
Glucose Ketones Acetate Triglyceride
A b r u p t change from fat-depressing to normal ration 51.8 (3) 11.6 (3) 55.9 (2) 14.6 1.53 (3) 0.43 (3) 2.01 (2) 0.52 12.6 (2) 7.5 (2) 8.4 (1) 5.1 11.7 (4) 4.8 (4) 13.0 (2) 5.5
Glucose Ketones Acetate Triglyceride
50.2 2.13 12.6
11.1
1.o
(2)
6.1 3.2
(1) (2)
11.0 0.66 7.1 4.3
2.50 (4) 7.6 10.7
Over-all mean values 56.3 * 2.44 7.9 ~ 11.5
(2) (4)
(4)
0.60 (4) 4.0 4.4
(2) (4) (2)
(2) (1) (2)
12.8 0.80 4.4 4.8
a Number of samples obtained. Significant, P ~ .05. *~ Significant, P < .01. J . DAIRY SCIENCE V O L 52, No. 11
1780
SATTER
AND BRINGE
the arteriovenous differences of either altered. Arterial and venous acetate was lower (P < 0.05) with the fat-depressing ration. I t did appear that blood acetate levels had changed within one day of the ration switch, but because of some missing data this observation must be considered tentative. I n summary, it appears that it takes longer for the host to complete the change of milk f a t levels (about six days) in response to an altered pattern of metabolites presented to it by the gastrointestinal tract than it takes for the rumen microorganisms effectively to change the rnminal fermentation (about two days) when a sudden ration change is made. This suggests that the extent of milk fat synthesis is controlled through time-consuming metabolic adaptations, and that it is more than a matter of immediate availability of acetate, propionate, or butyrate from the tureen.
Acknowledgment The authors acknowledge the assistance of Ralph Lance with animal care and the help of Dwight Sattler and Ruth Wolberg in sample analysis.
J . DAIRY SCIENCE ~rOL. 52, NO. 11
References (1) Ashworth, U. S., R. Seals, and R. E. Erb. 1960. An improved procedure for the determination of milk proteins by dye binding. J. Dairy Sei., 43: 614. (2) Baumgardt, B. R. ]964. Practical observations on the quantitative analysis of free volatile fatty acids (VFA) in aqueous solutions by gas-liquid chromatography. University of Wisconsin, Dep. Dairy Sol., Dep. Bull. 1. (3) Bringe, A. N., and L. H. Schultz. 1969. Effects of roughage type or added bentouite in maintaining test. J. Dairy Sci., 52: 465. (4) Golding, N. S. 1959. A sollds-not-fat test for milk using density beads as hydrometers. J. Dairy Sci., 42: 899. (5) Jorgensen, N. A., L. H. Schultz, and G. R. Burr. 1965. Factors influencing milk fat depression on rations high in concentrates. J. Dairy Sci., 48: 1031. (6) Storry, J. E., and J. A. F. Rook. 1965. The effects of a diet low in hay and high in flaked maize on milk fat secretion and on the concentrations of certain constituents in the blood plasma of the cow. Brit. J. Nutrition, 19: 101.
Department of Dairy Science, University of Wisconsin, Madison 53706 Abstract
The effect of abrupt change between a normal and a fat-depressing ration on milk composition and several blood components was examined. An abrupt ration change was accomplished by simultaneously switching rumen contents and rations between two cows, one fed a ration having a grainto-roughage ratio of approximately 1:2 and the other a fat-depressing ration with a 3:1 ratio. Feed intake was not altered when the cows were abruptly switched from one ration to the other. Five to six days were necessary to affect complete transition in the level of milk fat following a ration change. This was interpreted to mean that the ration effect on milk fat content was eventually mediated through time-cousnming metabolic adaptations by the host, rather than by immediate availability or supply of acetate, propionate, or butyrate from the tureen. Arterial levels of blood glucose, ketones, acetate, and triglycerides with the normal ration were 50.2, 2.13, 12.6, and 11.1 rag/100 ml, respectively. Corresponding values with the fat-depressing ration were 56.3, 2.44, 7.9, and 11.5 rag/100 ml. Values for blood glucose and acetate were significantly different (P < 0.05), whereas those for ketones and triglycerides were not. The only arterial-venous difference across the mamm a r t, gland tha~ approached significance was that for acetate. I ntroducfion
A period of one to three weeks has usually been required to affect complete depression in milk fat following change from a normal to a fat-depresslng ration (5, 6). Some of the delay can be attributed to the gradual change from one ration to another, usually requiring one week or less. Once complete ration substitution has occurred, additional time is probably
required for the rumen microbial population to stabilize and produce their characteristic end products. Finally, the host itself must undergo adaptive changes to accommodate the altered ruminal end products, and to utilize them in the synthesis of milk having low fat content. The following study was conducted to assess the relative length of time required for each of these adaptive changes. By simultaneous substitution of ration and rumen contents, the delay in rmneu environmental and microbial change was avoided. I t was further hoped that such a technique would sharpen the host response, and more clearly delineate changes in several blood components utilized for milk synthesis.
Experimental Procedure Two lactating Holstein cows possessing ruminal fistulas were placed respectively on a normal ration (6.36 kg of regular herd mix concentrate and alfalfa hay ad lib.) or a fatdepressing ration (three parts of pelleted concentrate and one p a r t alfalfa hay fed a~l lib.), as described by Jorgensen et al. (5). A t designated times each reticulo-rumen was emptied and the contents switched to the other cow. The ration was simultaneously switched, resulting in an abrupt transition from one dietary regime to another. This was repeated four times with a mininmm of three weeks between ration changes. I n addition, three ration changes were made without simultaneously changing rumen conteats. When going from the fat-depressing ration to the normal ration, an immediate change in ration was made. A gradual ration change lasting four days was made when switching from the normal ration to the fatdepressing ration. This was done to avoid problems of overeating. Blood samples were o b ~ i n e d from two of the periods of abrupt simultaneous switching of ration and tureen contents. Blood from the tail artery and mammary vein were obtained several hours before the ration change, and again on the first and third or seventh day following" ration substitution. Blood glucose, ketones, acetate, and triglycerides were de-
Received for publication March 28, 1969. 1 Published with the approval of the Director of the Wisconsin Agricultural Experiment Station, Madison, Wisconsin. 1776
ABRUPT
RATION
CHANGES
1777
35~ "'°
33
t
31 i t
29
"
,
i
a
.
• •
27
.
•
i
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I
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I
I M A R 17
FFO 4
I APR 8
I
I
29
JUN5
I
26
DATE
FIa. 1. Milk production and per cent milk fat.
termined in the arterial and venous blood as reported by Bringe and Sehultz (3). Arterialvenous differences were determined and were assumed to represent mammary gland uptake of each component• Ruminal ingesta was sampled twice weekly for determination of volatile f a t t y acids. A representative sample of ruminal contents was acidified and strained through two layers of cheese cloth and centrifuged at 12,000 × g for 15 rain. Total volatile f a t t y acids were determined by steam distillation and the component f a t t y acids by gas chromatogr a p h y (2). Milk was sampled daily for milk fat determination one to two weeks after a ration change. Biweekly samples were obtained for solids-not-fat and protei~ analysis. Milk fat was determined by the Babcock method, solidsnot-fat by the Golding bead method (4), and protein by the dye-binding method (1). Results and Discussion
The mean levels for milk production and per cent milk f a t are shown in Figure 1. Each point on the milk production curve represents the mean of three days' milk production. Milk production values did not figure into the mean until the second day following a switch of
rations, and per cent milk f a t values were not included until the fifth day following a change. The fat-depressing ration supported a higher level of production (P < 0.005), particularly in Cow 1102. This cow responded to the fatdepressing ration by increasing milk production by 40% within five to seven days after placement on the ration; but then would immediately decline in production to an apparent normal level within one week following the peak production. This same response was noted in the other cow, but to a much lesser extent. I t is not a p p a r e n t what the stimulus of milk production was, and why it was not effective in sustaining the high level of production. The r a p i d i t y with which milk f a t adjusted to a new ration is illustrated in Table 1. These values indicate the extent of adjustment to the new mean milk fat percentage. When both rmnen contents and ration were switched abruptly, about 70% of the change that was to occur did so within three days and was essentially complete within five to six days. A slightly slower transition requiring one to two days' more time was noted when the tureen contents were not changed simultaneously with the ration. When the fat-depressing ration was introduced over a period of four days, about J.
DAIRY
SCIENCE
VOI,.
52,
NO.
11
TABLe. 1. Rate of milk fat test adaptation to new ration. Previous mean 1
2
3
4
Day following ration change 6 7 8 9
5
10
11
12
13
14
Approaching mean
(%) Abrupt ration change with rumen content change N a --> FD 2.77 2.80 2.27 2.00 1.90 F D b --> N 1.37 1.67 1.98 2.23 2.53
1.80 2.00
1.72 2.70
1.90 2.67
"~ Abrupt ration change without rumen content change FD --> N 1.96 1.80 2.05 2.47 2.57
2.73
2.65
3.03
3.70
....
3.23
............
3.00
3.07
Four-day period for ration change without rumen content change N --> F D 2.68 2.90 2.90 2.77 2.63 2.60 2.35
2.40
2.22
....
2.13
...........
1.60
2.07
•~
........................... ............................
1.55 2.72
a N, Normal ration. b FD, Fat-depressing ration. TABLE 2. Effect of alternate rations on feed intake, ruminal volatile acids, and milk composition. Feed intake Period
Na
FD b
Acetate N
FD
(kg/day)
Propionate N
FD
1 to 2 3 to 4 5 to 6 7 to 8 Average
17.5 19.7 20.1 17.3 18.7
18.9 20.2 19.9 14.6 18.4
7.70 9.25 8.70 8.11 8.44 ***c
7.24 7.63 6.11 7.27 7.06
(meq/100 ml) Cow 1163 2.75 4.86 2.48 3.82 2.48 4.79 2.37 4.06 2.52 ~ * 4.38
1 to 2 3 to 4 5 to 6 7 to 8 Average
21.1 19.6 18.7 16.7 19.0
20.2 20.8 19.1 16.2 19.1
8.97 9.05 7.32 9.72 8.77 **~
6.13 6.70 5.71 6.07 6.15
2.51 2.58 2.55 2.53 2.54 ~
a N, Normal ration. b FD, Fat-depressing. c Significant P < 0.005.
Cow 1102 5.24 4.69 4.32 4.62 4.72
Butyrate N
FD
Solids-not-fat N
Protein
FD
N
FD
(%) 1.22 1.45 1.67 1.39 1.43
1.38 1.51 1.83 1.39 1.53
8.37 7.56 7.90 7.77 7.90 * ~
8.28 8.35 8.42 7.90 8.29
3.02 2.98 2.98 3.26 3.06 ~**
3.05 3.28 3.45 3.33 3.28
1.36 1.72 1.49 1.46 1.51
1.21 1.55 1.24 2.01 1.50
8.50 8.29 8.42 8.85 8.52 **~
8.92 8.97 9.23 8.93 9.01
2.92 3.22 3.31 3.96 3.35 ~**
3.27 3.45 3.62 3.84 3.55
(DO
ABRUPT
1779
RATION CHANGES
11 days were required for the mean level of the subsequent period to be reached. F r o m this it appears that a minimum of five to six days is required for adaptive responses by the host itself, aside from the adaptive changes in the rumen. This certainly supports the view that change in milk fat content is eventually regulated by something more than the immediate availability or supply of acetate, propionate, or butyrate from the t u r e e n , and that timeconsuming metabolic adaptations are involved. Table 2 shows the effect of each ration on feed intake, ruminal volatile acids, and milk composition. Feed intake and ruminal fatty acid data are reported throughout the whole period, whereas milk composition data are not reported until the fifth day after each ration change. The consumption of air-dry feed wus the same for both rations, though the estimated net energy intake would have been 30% greater for the fat-depressing ration. I t was of interest to note that the abrupt ration and rumen changes did not seem to affect feed intake at all, in spite of the radical ration change. The ruminal concentration of acetate was lower, and that of propionate considerably higher with the fat-depressing ration. Ruminal butyrate concentration was about equal for both rations. I t required about two days for
ruminal fatty acid levels tQ reach their charaeteristie patterns when the ration, but not the ruminal ingesta, was abruptly changed. Milk solids-not-fat and protein were higher on the fat-depressing ration than on the normal ration. Ruminal f a t t y acid patterns and milk composition values resembled the observations made by others using similar rations (3, 5). I t was postulated that by inducing an abrupt change in the digestive end products being absorbed from the gastrointestinal tract a clearer response of several blood components associated with milk fat synthesis might be detected. Tail arterial and mammary venous levels o£ glucose, ketones, acetate, and triglycerides are shown in Table 3. The number in parentheses indicates the number of observations used to obtain each mean. Over-all arterial and venous glucose was higher (P < 0.05 and P ~ 0.10, respectively) on the fat-depressing ration, but the A-V difference was not significantly different from the normal ration. On only one occasion did it a p p e a r that blood glucose levels had responded by the first day following abrupt ration changes. Between one and seven days was required for most blood glucose changes to occur. Arterial and venous levels of ketones and triglycerides were not affected by the abrupt ration changes, nor were
TABLE 3. Effect of alternate rations on blood constituents. Normal Arterial
Fat-depressing A-V
Arterial
A-V
(rag/100 m l ) A b r u p t change from normal to fat-depressing ration (2) a 10.2 (2) 56.4 (4) 11.9
Glucose Ketones Acetate Triglyeeride
47.9 3.02 (2) 12.7 (1) 8.8 (2)
Glucose Ketones Acetate Triglyceride
A b r u p t change from fat-depressing to normal ration 51.8 (3) 11.6 (3) 55.9 (2) 14.6 1.53 (3) 0.43 (3) 2.01 (2) 0.52 12.6 (2) 7.5 (2) 8.4 (1) 5.1 11.7 (4) 4.8 (4) 13.0 (2) 5.5
Glucose Ketones Acetate Triglyceride
50.2 2.13 12.6
11.1
1.o
(2)
6.1 3.2
(1) (2)
11.0 0.66 7.1 4.3
2.50 (4) 7.6 10.7
Over-all mean values 56.3 * 2.44 7.9 ~ 11.5
(2) (4)
(4)
0.60 (4) 4.0 4.4
(2) (4) (2)
(2) (1) (2)
12.8 0.80 4.4 4.8
a Number of samples obtained. Significant, P ~ .05. *~ Significant, P < .01. J . DAIRY SCIENCE V O L 52, No. 11
1780
SATTER
AND BRINGE
the arteriovenous differences of either altered. Arterial and venous acetate was lower (P < 0.05) with the fat-depressing ration. I t did appear that blood acetate levels had changed within one day of the ration switch, but because of some missing data this observation must be considered tentative. I n summary, it appears that it takes longer for the host to complete the change of milk f a t levels (about six days) in response to an altered pattern of metabolites presented to it by the gastrointestinal tract than it takes for the rumen microorganisms effectively to change the rnminal fermentation (about two days) when a sudden ration change is made. This suggests that the extent of milk fat synthesis is controlled through time-consuming metabolic adaptations, and that it is more than a matter of immediate availability of acetate, propionate, or butyrate from the tureen.
Acknowledgment The authors acknowledge the assistance of Ralph Lance with animal care and the help of Dwight Sattler and Ruth Wolberg in sample analysis.
J . DAIRY SCIENCE ~rOL. 52, NO. 11
References (1) Ashworth, U. S., R. Seals, and R. E. Erb. 1960. An improved procedure for the determination of milk proteins by dye binding. J. Dairy Sei., 43: 614. (2) Baumgardt, B. R. ]964. Practical observations on the quantitative analysis of free volatile fatty acids (VFA) in aqueous solutions by gas-liquid chromatography. University of Wisconsin, Dep. Dairy Sol., Dep. Bull. 1. (3) Bringe, A. N., and L. H. Schultz. 1969. Effects of roughage type or added bentouite in maintaining test. J. Dairy Sci., 52: 465. (4) Golding, N. S. 1959. A sollds-not-fat test for milk using density beads as hydrometers. J. Dairy Sci., 42: 899. (5) Jorgensen, N. A., L. H. Schultz, and G. R. Burr. 1965. Factors influencing milk fat depression on rations high in concentrates. J. Dairy Sci., 48: 1031. (6) Storry, J. E., and J. A. F. Rook. 1965. The effects of a diet low in hay and high in flaked maize on milk fat secretion and on the concentrations of certain constituents in the blood plasma of the cow. Brit. J. Nutrition, 19: 101.