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Effect of High-Level Grain Feeding on Milk Production Response of Lactating Dairy Cows1
EFFECT
OF HIGH-LEVEL RESPONSE
GRAIN FEE'DING
OF LACTATING
ON M I L K P R O D U C T I O N
DAIRY
COWS 1
L. D. BROWN, J. W. THOMAS, R. S. EMERY, L. D. IV[cGILLIARD, D. V. ARMSTRONG, ANI) C. A. LASSITER Dairy Department, 3£ichigan State University, East Lansing SUMMARY
E'ighteen lactating dairy cows were divided into three comparable groups approximately 36 days postpartum to study the effect of feeding high levels of grain for a complete lactation. Grain was fed at three levels : Group 1, 1.0 ]b grain p e r 3.5 lb milk; Group 2, 1.0 lb grain per 2.5 lb milk, and Group 3, grain ad libitum. The cows fed the two higher levels of grain produced considerably more milk than expected from the first part of lactation, whereas cows fed the low level of grain produced slightly less milk than expected. The averages of milk produced during the 260-day experimental period were 9,861, 10,650, and 12,543 lb per cow for Groups 1, 2, and 3, respectively. In the same order, the average percentages of milk fat, protein, and S N F were 3.7, 3.8, 8.9; 3.6, 3.8, 8.9; and 3.7, 3.8, 9.0, respectively. The average gains in body weight were 0.64, 0.91, and 0.94 lb per cow per day for Groups 1, 2, and 3, respectively.
F o r many years roughages have played the predominant role in dairy cattle rations, primarily because they were recognized as the most economical sources of energy. However, in recent years much has been done to increase the yield of corn which, at least in the Corn Belt, is rapidly becoming the Number One economy feed. In ninny cases, the cost of 100 lb of TDN from ear corn is less than that from hay-crop silage or hay. Therefore, from an economic standpoint, maximum use should be made of the cheapest source of energy within the physiological limits of the cow. High-level grain feeding of dairy cows has recently been reviewed by Huffman (4). Castle and Watson (2) reported increased milk yields of cows fed high levels of concentrates over those fed low levels of concentrates. The increased nfilk yield amounted to approximately 1.0 lb of milk per 1.0 lb additional starch equivalent. In a 10-wk field trial in New York State, Charron (3) observed that 95% of the cows responded in milk production to increased grain feeding, with approximately 40% showing a profitable response. This experiment was conducted to determine the milk production response of cows fed high
levels of grain for the major portion of the lactation period. E X P E R I M E N T A L PROCEDURE
Eighteen Holstein cows were divided into three comparable groups on the basis of milk production, age, and body weight, and assigned to one of three experimental treatments approximately 36 days postpartum. During the subsequent 260-day experimental period all cows were fed 40 Ib c.orn silage per day. I n addition, cows in Group 1 received alfalfa hay ad libitum and grain at the rate of 1.0 lb grain for each 3.5 lb of milk. Cows in Group 2 were limited to 15.0 lb of alfalfa hay per day and the grain feeding increased to 1.0 lb of grain for each 2.5 lb of milk. Group 3 cows were limited to only 5.0 lb of alfalfa hay per day and grain was fed ad libitum. The hay and corn silage were considered to be of excellent quality. The grain mix was composed of 1,500 lb of corn and cob meal, 500 lb of soybean oil meal (44% C.P.), 20 lb of trace mineralized salt, 20 Ib of dicaleium phosphate, and 100 lb of feedgrade molasses. Milk samples were collected bi-weekly for milk fat analyses and monthly for solids-notfat ( S N F ) and protein analyses. Milk fat l~eceived for publication May 24, 1962. was determined by the standard Babcock proPublished with the approval of the Director cedure; protein content was determined by of Michigan Agrieultural Experiment Station as formol titration (7); and S N F measurements were made by the lactometrie method (8). Journal Article No. 2985. 1184
EFFECT
OF GRAIN
FEEDING
ON PI~ODUCTION
1185
TABLE 1 Estimated and actual milk production of cows fed different levels of hay and grain
Group
I~ate of grain feeding
Estimated
260-Day production Actual
Act.-Est.
Std. error
] 2 3
1:3'.5 1 : 2.5 ad lib.
10,505 9,542 9,9'26
9,86.1 10,650 12,543
-- 644 +1,10,8 +2,617
444.1 627.8 926;5
RESI.rL~'S AND DISCVSSIOX Milk production was used as the principal criterion in evaluatitlg treatment effects. Since the amount of milk produced in a lactation is c!osely correlated with milk produced during the early stages of lactation, the amount of milk expected during the 260-day experimental period was estimated from the amount of nfilk produced during the prelinfinary period as follows : 1'~,,o = Pp
f~+o~o
1
, where P~o is the ex-
pected cunmlative production of milk for the 260-day experimental period, Pp is the cumulative milk production during the preliminary period, fp is the ratio factor (chosen for appropriate age, season of calving, and days in the preliminary period) for estinmting 305-day production from the preliminary production and L, .... is the ratio factor (chosen for appropriate age, season of calving, and number of days to the end of the 260-day experimental period) for estimating 305-day production from preliminary and 260-day experimental production. The response of milk production to treatment was measured by comparing the expected production with the actual production for the 260-day experimental period (Table 1). The estimated potential production of all three groups was relatively close, ranging from 9,542 to 10,505 lb per cow. However, when the actual production of each cow was compared with the expected production, the milk response definitely increased as the level of grain feeding increased. Cows in Group 1 produced 644 lb less milk than expected, whereas cows in Groups 2 and 3 produced 1,108 and 2,617 lb, respectively, more milk than expected. This difference was significantly higher (P < 0.01) for cows in Group 3 than for cows in Group 1. Differences between Groups 1 and 2 or 2 and 3 approached significance (P < 0.05). I f the accuracy of the production equation was constant for all three groups, the average net increase in milk production from feeding higher levels of grain would be 1,'752 and 3,261 for Groups 2 and 3, respectively.
Difference
All cows did not respond to high-level grain feeding. Four of the six cows in Group 3 produced from 2,550 to 4,970 lb more milk than expected, whereas the two other cows produced at their respective calculated level. The reason these two cows did not respond is not known, but may have been due to the lack of genetic potential for high-level production. These data indicate that increasing the nutritional level of cows that do not have the genetic potential for high-level milk production will not result in increased milk production for a major portion of the lactation period. The average daily milk production, feed consumption, and changes in body weight by groups are given in Table 2. The differences in hay and gTMn consumption among groups were primarily due to experimental treatment. The highest daily grain consumption for any one cow was 46.0 lb per day, with an average of 43.2 lb per day for the 260-day period. I n no case was difficulty encountered with digestive disturbance or cows going off feed. Corn silage consmnption decreased as the level of grain in the ration increased. There were no significant differences in corn silage consumption between Groups I and 2; however, both groups consumed significantly more corn silage than Group 3 (P < 0.05). Cows consuming the two higher levels of grain gained slightly more in body weight than the low-level grain group, tiowTABLE 2 Average daily milk production, feed consumption, and body weight change for the 260-day experimental period Group
1
2
3
Milk production Actual FCM
37.9 36.6
4.1.0 39.9
48.2 46.0
Feed consumption Grain Hay Cor~l silage
11.9 24.4 38.2
17.0 13.9 37.7
36.0 4.9 34.2
Bodyweight change +0.64
+0.91
-g0.94
(Ib/day)
1186
L.D.
BROWN
ever, due to considerable within-group variation the differences among treatment groups in body weight gain were not statistically significant. Cows in Group 3 produced significantly (P < 0.01) more milk and FCIVl than cows in Groups :[ or 2. I n general, the response to added grain was through a slight initial increase in production and increased persistency throughout the 260-day period (Figure 1). The average group 70
70
a~ GO
60 50
Q.
40
5 40 u. 3G o
;
~
GROUP ~3 ~
" "~ GROUP ~2
zo
\ ~ GROUP *1
0 J j -15 0 i5
i 45
50 20 I0
J i ] i ] i ] ] 75 105 135 165 195 225 255 285 DAYS ON EXPERIMENT
FIG. 1. Actual milk production by 30-day periods for the three experimental groups. persistency values were 85.0, 92.7, and 94.0% for Groups 1, 2, and 3, respectively. The increased persistency of cows in Groups 2 and 3 was somewhat more evident in late lactation than in early lactation. The average initial milk production values were slightly higher for Groups 1 and 3 than for Group 2. However, due to the lower persistency of Group 1 cows, at the end of 90 days the average daffy milk production was approximately the same as Group 2 and declined rather rapidly throughout the remainder of the 260-day period. The relationship between increased grain feeding and total milk production is evident.
ET
AL
This experiment was not designed to study the efficiency of milk production in terms of pounds of TDN required per pound of milk. However, when net efficiency was calculated, the cows in Group 2 required 0.39 lb of TDN per pound of FCM as compared to 0.49 and 0.52 lb, respectively, for Groups i and 3 (P < 0.05). I n this calculation the following assumptions regarding TDN values o£ feeds were made: grain, 72% TDN; hay, 52% TDN; and corn silage, 19% TDN. The TDN requirements for maintenance were taken from ~1orrison (6) and the requirements for body weight gain from Brody (1). A correlation of --0.79 was observed between level of milk production for the 260-day period and pounds of TDN required per pound of milk. The increased efficiency of the higher-producing cows over the lower-producing cows may have been partially due to over-feeding the cows of inherent low production. The specific reason for the high correlation between level of milk production and efficiency of production cannot be ascertained from these data. The pounds of TDN required per pound of FC~¢I for cows producing over 10,000 lb of milk averaged 0.44 lb, as compared to 0.32 lb recorded in various feeding standards (5, 6). I n this comparison, however, the limitation of the calculations employed, as well as the fact that the cows receiving ad libitum grain were overfed in late lactation, should be considered. The average milk fat, protein, and solids-notfat percentages are shown in Table 3. Each period represents 30 days, with the exception of Period 9, which represents only 20 days. I n general, the protein, fat, and solids-not-fat content of milk increased with stage of lactation. The small differences observed among
TABLE 3 Effect of high-level grain feeding on milk composition Group 1
.o
Periods
Protein
:Fat
SNF
Protein
1 2 3 4 5 6 7 8 9
3.14 3.31 3.40 3.60 3,.80 3.80 4:00 3.90 4.10
3.4 3.5 3.6 3.9 3.8 3.8 4.0 4.3 4.3
8.8 8.9 8.8 8.8 8.8 8.9 8.9 9.2 9.2
3.7
3.8
8.9
Average
3
SNF
Protein
Fat
SNF
3.34 3.38 3.2'0 3.42 3.74 4.00 4.00 4.14 3.64
Fat (%) 3.8 3.6 3.7 3.9 3'.7 4.0 3.8 4.0 4.1
8.8 8.6 8.9 8.9 8.8 9.0 9.0 9.0 9.2
3.25 3.30, 3.60 3.60 3.90 4.00 3.90 3.80 3.81
3.4 3.5 3.4 3.6 3.9 4.0 3.9' 4.1 4.0
8.9 8.9 8.9 9.0 9.3 9.0 8.9 8.0 9.1
3.6
3.8
8.9
3.7
3.8
9.0
EFFECT OF GRAIN FEEDING ON PRODUCTION treatment groups were not significant and did not appear to be associated with the feeding regime. From the economic standpoint, cows in Groups 2 and 3 returned approximately $35 more over feed cost than cows in Group ]. When only the four highest producers from each group were considered, the return over feed cost was approximately $60 per cow higher for Group 3 than for Groups 1 and 2. In these calculations the following prices were assumed: grain, $40 per ton; hay, $20 per ton; corn silage, $7 per ton; and 4% FCM, $4.60 per 100 lb. Without question, the return over feed cost could have been increased considerably f o r cows in Group 3 by reducing grain to the lowest possible level without affecting milk production after cows reached their peak of production. Based on this work, it appears that feeding grain to appetite will increase milk production markedly and thus will aid in determining the genetic potential of the cow for high milk production. ACI~NOWLEOG~ENT The authors express appreciation to Cooperative Grange League Federation Exchange, Inc., Ithaca, New York, for a grant-in-aid as partial support of this experiment.
1187
REFER1~N CES
(1) BKODY,S. Bioenergetics and Growth. Rein(2)
(3)
(4) (5)
(6) (7)
(8)
hold Publishing Corporation, New York. 1945. CAS~L~:,M. E., AND WATSON,J. N. The Effect of Level of Concentrate Feeding Before and After Calving on the Production of Dairy Cows. J. Dairy Research, 28: 221. 1961. CHAmRO~, E. C. Higher TDN Feeding of Dairy Cows. Applied Research Department, G.L.F. Exchange, Inc., Ithaca, New York. July 12, 1960. ttv~'~, C. F. High Level Grain Feeding for Dairy Cows. J. Dairy Sei., 44: 2114. 1961. LOOSLI,J. i . , BF-X~x~a,R. B., HU~MAN, C. F., PI-I[I~IPS, P. H., AND SHAW, J. C. Nutrient Requirements of Dairy Cattle. Natl. head. Sci., Nail. Research Counc. Publ. 464. 1958. Mo~Iso~, F. B. Feeds and Feeding. 22nd ed. Morrison Publ. Company, Ithaca, New York. 1956. RICHAI~SOlV, G. A., YOnNQ, J. O., D ~ L , S. H., P ~ c ~ , S. J., Am) N ~ U ~ , P. N. The Use of Protein Test (Formol Titration) to Estimate the Solids-not-fat Content of Milk. Proc. 3~th Ann. Meet,, Western Din., Am. Dairy Sei. Assoc. 1953. WATS0~r, P. D. Determination of the Solids in Milk by a Lactometric Method at 102 ° F. J. Dairy Sei., 40: 394. 1957.
OF HIGH-LEVEL RESPONSE
GRAIN FEE'DING
OF LACTATING
ON M I L K P R O D U C T I O N
DAIRY
COWS 1
L. D. BROWN, J. W. THOMAS, R. S. EMERY, L. D. IV[cGILLIARD, D. V. ARMSTRONG, ANI) C. A. LASSITER Dairy Department, 3£ichigan State University, East Lansing SUMMARY
E'ighteen lactating dairy cows were divided into three comparable groups approximately 36 days postpartum to study the effect of feeding high levels of grain for a complete lactation. Grain was fed at three levels : Group 1, 1.0 ]b grain p e r 3.5 lb milk; Group 2, 1.0 lb grain per 2.5 lb milk, and Group 3, grain ad libitum. The cows fed the two higher levels of grain produced considerably more milk than expected from the first part of lactation, whereas cows fed the low level of grain produced slightly less milk than expected. The averages of milk produced during the 260-day experimental period were 9,861, 10,650, and 12,543 lb per cow for Groups 1, 2, and 3, respectively. In the same order, the average percentages of milk fat, protein, and S N F were 3.7, 3.8, 8.9; 3.6, 3.8, 8.9; and 3.7, 3.8, 9.0, respectively. The average gains in body weight were 0.64, 0.91, and 0.94 lb per cow per day for Groups 1, 2, and 3, respectively.
F o r many years roughages have played the predominant role in dairy cattle rations, primarily because they were recognized as the most economical sources of energy. However, in recent years much has been done to increase the yield of corn which, at least in the Corn Belt, is rapidly becoming the Number One economy feed. In ninny cases, the cost of 100 lb of TDN from ear corn is less than that from hay-crop silage or hay. Therefore, from an economic standpoint, maximum use should be made of the cheapest source of energy within the physiological limits of the cow. High-level grain feeding of dairy cows has recently been reviewed by Huffman (4). Castle and Watson (2) reported increased milk yields of cows fed high levels of concentrates over those fed low levels of concentrates. The increased nfilk yield amounted to approximately 1.0 lb of milk per 1.0 lb additional starch equivalent. In a 10-wk field trial in New York State, Charron (3) observed that 95% of the cows responded in milk production to increased grain feeding, with approximately 40% showing a profitable response. This experiment was conducted to determine the milk production response of cows fed high
levels of grain for the major portion of the lactation period. E X P E R I M E N T A L PROCEDURE
Eighteen Holstein cows were divided into three comparable groups on the basis of milk production, age, and body weight, and assigned to one of three experimental treatments approximately 36 days postpartum. During the subsequent 260-day experimental period all cows were fed 40 Ib c.orn silage per day. I n addition, cows in Group 1 received alfalfa hay ad libitum and grain at the rate of 1.0 lb grain for each 3.5 lb of milk. Cows in Group 2 were limited to 15.0 lb of alfalfa hay per day and the grain feeding increased to 1.0 lb of grain for each 2.5 lb of milk. Group 3 cows were limited to only 5.0 lb of alfalfa hay per day and grain was fed ad libitum. The hay and corn silage were considered to be of excellent quality. The grain mix was composed of 1,500 lb of corn and cob meal, 500 lb of soybean oil meal (44% C.P.), 20 lb of trace mineralized salt, 20 Ib of dicaleium phosphate, and 100 lb of feedgrade molasses. Milk samples were collected bi-weekly for milk fat analyses and monthly for solids-notfat ( S N F ) and protein analyses. Milk fat l~eceived for publication May 24, 1962. was determined by the standard Babcock proPublished with the approval of the Director cedure; protein content was determined by of Michigan Agrieultural Experiment Station as formol titration (7); and S N F measurements were made by the lactometrie method (8). Journal Article No. 2985. 1184
EFFECT
OF GRAIN
FEEDING
ON PI~ODUCTION
1185
TABLE 1 Estimated and actual milk production of cows fed different levels of hay and grain
Group
I~ate of grain feeding
Estimated
260-Day production Actual
Act.-Est.
Std. error
] 2 3
1:3'.5 1 : 2.5 ad lib.
10,505 9,542 9,9'26
9,86.1 10,650 12,543
-- 644 +1,10,8 +2,617
444.1 627.8 926;5
RESI.rL~'S AND DISCVSSIOX Milk production was used as the principal criterion in evaluatitlg treatment effects. Since the amount of milk produced in a lactation is c!osely correlated with milk produced during the early stages of lactation, the amount of milk expected during the 260-day experimental period was estimated from the amount of nfilk produced during the prelinfinary period as follows : 1'~,,o = Pp
f~+o~o
1
, where P~o is the ex-
pected cunmlative production of milk for the 260-day experimental period, Pp is the cumulative milk production during the preliminary period, fp is the ratio factor (chosen for appropriate age, season of calving, and days in the preliminary period) for estinmting 305-day production from the preliminary production and L, .... is the ratio factor (chosen for appropriate age, season of calving, and number of days to the end of the 260-day experimental period) for estimating 305-day production from preliminary and 260-day experimental production. The response of milk production to treatment was measured by comparing the expected production with the actual production for the 260-day experimental period (Table 1). The estimated potential production of all three groups was relatively close, ranging from 9,542 to 10,505 lb per cow. However, when the actual production of each cow was compared with the expected production, the milk response definitely increased as the level of grain feeding increased. Cows in Group 1 produced 644 lb less milk than expected, whereas cows in Groups 2 and 3 produced 1,108 and 2,617 lb, respectively, more milk than expected. This difference was significantly higher (P < 0.01) for cows in Group 3 than for cows in Group 1. Differences between Groups 1 and 2 or 2 and 3 approached significance (P < 0.05). I f the accuracy of the production equation was constant for all three groups, the average net increase in milk production from feeding higher levels of grain would be 1,'752 and 3,261 for Groups 2 and 3, respectively.
Difference
All cows did not respond to high-level grain feeding. Four of the six cows in Group 3 produced from 2,550 to 4,970 lb more milk than expected, whereas the two other cows produced at their respective calculated level. The reason these two cows did not respond is not known, but may have been due to the lack of genetic potential for high-level production. These data indicate that increasing the nutritional level of cows that do not have the genetic potential for high-level milk production will not result in increased milk production for a major portion of the lactation period. The average daily milk production, feed consumption, and changes in body weight by groups are given in Table 2. The differences in hay and gTMn consumption among groups were primarily due to experimental treatment. The highest daily grain consumption for any one cow was 46.0 lb per day, with an average of 43.2 lb per day for the 260-day period. I n no case was difficulty encountered with digestive disturbance or cows going off feed. Corn silage consmnption decreased as the level of grain in the ration increased. There were no significant differences in corn silage consumption between Groups I and 2; however, both groups consumed significantly more corn silage than Group 3 (P < 0.05). Cows consuming the two higher levels of grain gained slightly more in body weight than the low-level grain group, tiowTABLE 2 Average daily milk production, feed consumption, and body weight change for the 260-day experimental period Group
1
2
3
Milk production Actual FCM
37.9 36.6
4.1.0 39.9
48.2 46.0
Feed consumption Grain Hay Cor~l silage
11.9 24.4 38.2
17.0 13.9 37.7
36.0 4.9 34.2
Bodyweight change +0.64
+0.91
-g0.94
(Ib/day)
1186
L.D.
BROWN
ever, due to considerable within-group variation the differences among treatment groups in body weight gain were not statistically significant. Cows in Group 3 produced significantly (P < 0.01) more milk and FCIVl than cows in Groups :[ or 2. I n general, the response to added grain was through a slight initial increase in production and increased persistency throughout the 260-day period (Figure 1). The average group 70
70
a~ GO
60 50
Q.
40
5 40 u. 3G o
;
~
GROUP ~3 ~
" "~ GROUP ~2
zo
\ ~ GROUP *1
0 J j -15 0 i5
i 45
50 20 I0
J i ] i ] i ] ] 75 105 135 165 195 225 255 285 DAYS ON EXPERIMENT
FIG. 1. Actual milk production by 30-day periods for the three experimental groups. persistency values were 85.0, 92.7, and 94.0% for Groups 1, 2, and 3, respectively. The increased persistency of cows in Groups 2 and 3 was somewhat more evident in late lactation than in early lactation. The average initial milk production values were slightly higher for Groups 1 and 3 than for Group 2. However, due to the lower persistency of Group 1 cows, at the end of 90 days the average daffy milk production was approximately the same as Group 2 and declined rather rapidly throughout the remainder of the 260-day period. The relationship between increased grain feeding and total milk production is evident.
ET
AL
This experiment was not designed to study the efficiency of milk production in terms of pounds of TDN required per pound of milk. However, when net efficiency was calculated, the cows in Group 2 required 0.39 lb of TDN per pound of FCM as compared to 0.49 and 0.52 lb, respectively, for Groups i and 3 (P < 0.05). I n this calculation the following assumptions regarding TDN values o£ feeds were made: grain, 72% TDN; hay, 52% TDN; and corn silage, 19% TDN. The TDN requirements for maintenance were taken from ~1orrison (6) and the requirements for body weight gain from Brody (1). A correlation of --0.79 was observed between level of milk production for the 260-day period and pounds of TDN required per pound of milk. The increased efficiency of the higher-producing cows over the lower-producing cows may have been partially due to over-feeding the cows of inherent low production. The specific reason for the high correlation between level of milk production and efficiency of production cannot be ascertained from these data. The pounds of TDN required per pound of FC~¢I for cows producing over 10,000 lb of milk averaged 0.44 lb, as compared to 0.32 lb recorded in various feeding standards (5, 6). I n this comparison, however, the limitation of the calculations employed, as well as the fact that the cows receiving ad libitum grain were overfed in late lactation, should be considered. The average milk fat, protein, and solids-notfat percentages are shown in Table 3. Each period represents 30 days, with the exception of Period 9, which represents only 20 days. I n general, the protein, fat, and solids-not-fat content of milk increased with stage of lactation. The small differences observed among
TABLE 3 Effect of high-level grain feeding on milk composition Group 1
.o
Periods
Protein
:Fat
SNF
Protein
1 2 3 4 5 6 7 8 9
3.14 3.31 3.40 3.60 3,.80 3.80 4:00 3.90 4.10
3.4 3.5 3.6 3.9 3.8 3.8 4.0 4.3 4.3
8.8 8.9 8.8 8.8 8.8 8.9 8.9 9.2 9.2
3.7
3.8
8.9
Average
3
SNF
Protein
Fat
SNF
3.34 3.38 3.2'0 3.42 3.74 4.00 4.00 4.14 3.64
Fat (%) 3.8 3.6 3.7 3.9 3'.7 4.0 3.8 4.0 4.1
8.8 8.6 8.9 8.9 8.8 9.0 9.0 9.0 9.2
3.25 3.30, 3.60 3.60 3.90 4.00 3.90 3.80 3.81
3.4 3.5 3.4 3.6 3.9 4.0 3.9' 4.1 4.0
8.9 8.9 8.9 9.0 9.3 9.0 8.9 8.0 9.1
3.6
3.8
8.9
3.7
3.8
9.0
EFFECT OF GRAIN FEEDING ON PRODUCTION treatment groups were not significant and did not appear to be associated with the feeding regime. From the economic standpoint, cows in Groups 2 and 3 returned approximately $35 more over feed cost than cows in Group ]. When only the four highest producers from each group were considered, the return over feed cost was approximately $60 per cow higher for Group 3 than for Groups 1 and 2. In these calculations the following prices were assumed: grain, $40 per ton; hay, $20 per ton; corn silage, $7 per ton; and 4% FCM, $4.60 per 100 lb. Without question, the return over feed cost could have been increased considerably f o r cows in Group 3 by reducing grain to the lowest possible level without affecting milk production after cows reached their peak of production. Based on this work, it appears that feeding grain to appetite will increase milk production markedly and thus will aid in determining the genetic potential of the cow for high milk production. ACI~NOWLEOG~ENT The authors express appreciation to Cooperative Grange League Federation Exchange, Inc., Ithaca, New York, for a grant-in-aid as partial support of this experiment.
1187
REFER1~N CES
(1) BKODY,S. Bioenergetics and Growth. Rein(2)
(3)
(4) (5)
(6) (7)
(8)
hold Publishing Corporation, New York. 1945. CAS~L~:,M. E., AND WATSON,J. N. The Effect of Level of Concentrate Feeding Before and After Calving on the Production of Dairy Cows. J. Dairy Research, 28: 221. 1961. CHAmRO~, E. C. Higher TDN Feeding of Dairy Cows. Applied Research Department, G.L.F. Exchange, Inc., Ithaca, New York. July 12, 1960. ttv~'~, C. F. High Level Grain Feeding for Dairy Cows. J. Dairy Sei., 44: 2114. 1961. LOOSLI,J. i . , BF-X~x~a,R. B., HU~MAN, C. F., PI-I[I~IPS, P. H., AND SHAW, J. C. Nutrient Requirements of Dairy Cattle. Natl. head. Sci., Nail. Research Counc. Publ. 464. 1958. Mo~Iso~, F. B. Feeds and Feeding. 22nd ed. Morrison Publ. Company, Ithaca, New York. 1956. RICHAI~SOlV, G. A., YOnNQ, J. O., D ~ L , S. H., P ~ c ~ , S. J., Am) N ~ U ~ , P. N. The Use of Protein Test (Formol Titration) to Estimate the Solids-not-fat Content of Milk. Proc. 3~th Ann. Meet,, Western Din., Am. Dairy Sei. Assoc. 1953. WATS0~r, P. D. Determination of the Solids in Milk by a Lactometric Method at 102 ° F. J. Dairy Sei., 40: 394. 1957.