Effect of the Net Energy Concentration of Total Ration on Milk Production and Composition1

EFFECT

OF THE NET ENERGY CONCENTRATION OF TOTAL RATION ON I~IILK PRODUCTION AND COMPOSITION x

D. ZEREMSI(I, ~ K. It. VAIN- HORN, A. D. McGILLIARD, AND N. L. JACOBSON Department of Animal Science, Iowa State University, Anles ABSTRACT

Eighteen Holstein cows were assigned, after a 17-day preliminary period, to three rations, using a double 3 × 3 Latin-square design. The pounds of alfalfa-orchard grass hay and corn silage offered each cow during the experimental periods were, respectively: Ration A - - 6 , 24; Ration B--1O, 40; Ration C--14, 56. Concentrate was added to each ration so that total feed energy offered supplied maintenance needs plus 0.39 therm estimated net energy p e r pound 4% FCM. Each experimental period was 4 wk, the last 3 wk being used to evaluate ration effects. Average daily intakes of hay, silage, and concentrate, respectively, for the rations were: A--5.6, 23.3, 26.6 lb; B--8.5, 36.4, 20.5 lb; C--10.9, 45.9, 14.6 lb. Average 4% FCM was 46.7, 46.2, and 43.8 lb daily for Rations A, B, and C, respectively. Milk production on Rations A and B was significantly higher (P < .01) than on C, but gross and net efficiencies were essentially the same for all rations. There was a significant increase (P < .05) in S N F with increasing proportions of concentrate in the ration. There was no depression of fat level in milk on any of the rations. Cows on Ration C gained the most weight, but weight changes on all rations were small, suggesting that the level of feeding employed herein approximated the needs of the animals.

The effect of varying the proportion of energy in the ration which is supplied by concentrate has been studied by several investigators (2, 4, 5, 9, 13, 14). These data show that increasing the proportion of concentrates in the diet generally increases milk production. Although it appears that solids-not-fat ( S N F ) varies slightly in direct relationship to the proportion of energy supplied by concentrates, the effect of proportion of concentrates is quite small as compared to the effect of level of feeding (5). Most of the increase in production on rations with a higher proportion of energy supplied by concentrates is undoubtedly due to greater energy intake by cows on the more concentrated rations (2, 5). When forage quality is uniform, high-producing cows need a higher proportion of their energy supplied in the form of concentrate than do low-producing cows. However, since a variation in the energy value of the forage also has been shown to have an effect on energy ~ntake and milk production (15), it appears that the energy concentration of the :Received for publication July 8, 1965.

total ration in therms per pound of dry matter (D~[) is a more important consideration than the proportion of energy supplied by concentrate. Bloom et al. (2) and Hotchkiss (5) provide data easily converted to energy concentrations. However, the energy concentration fed in their experiments varies over a wide range. The present experiment was conducted to obtain a more precise estimate of the optimum energy concentration of the total ration for high-producing cows than can be obtained from previously conducted research. E X P E R I I ~ E N T A L PROCEDURE

Design of the experiment. Eighteen Holstein cows, second lactation or later, from the Iowa State University herd were used in this experiment started November 12, 1963, and terminated F e b r u a r y 19, 1964. The experiment consisted of a 17-day preliminary period and three comparison peri9ds , each of 4 wk duration. The design of the experiment involved two 3 X 3 Latin squares, as described by Patterson (12). At the start of the experiment the cows had been milking an average of 12 wk in their current lactation periods. The cows were grouped into blocks of three on the basis of date of calving, production of 4% FCM, and age. Allocation to treatments was random. The amount of feed offered daily was based on

1 Journal Paper no. J. 5021 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. -1541. '2Present address: Faculty of Agriculture, University of Belgrade, Belgrade, Yugoslavia. 1467

1468

i). Z E R E ~ S K I

Morrison's (11) feeding standards (higher values), except that allowances for production were increased by 30% to .39 theizn per pound of I~CM. Net energy requirements for Comparison Period I were calculated from the average production and body weight of each cow during the preliminary period. The level of feeding in subsequent periods was reduced on the basis of the average decline of all cows in relation to the preliminary period, rather than on the basis of the individual cow's decline, i.e., the principle of equalized feeding was applied (8). Feeding and ~anage~nent. The amount of feed offered and refused was weighed and recorded daily for each cow. Samples of feedstuffs and refusals were taken weekly for DM analysis. During each 4-wk period, equal amounts of dried samples from every week of each 4-wk period were pooled for analysis. Chemical analyses of the feedstuffs are presented in Table 1. During the preliminary period all cows were offered 14 lb alfalfa-orchard grass hay, 56 lb corn silage, and 21-24 lb of concentrate mixture per day. During the experimental periods the cows were offered 6 lb hay, 24 lb corn silage (Ration A ) ; 10 lb hay, 40 lb corn silage (Ration B) ; and 14 lb hay, 56 lb corn silage (Ration C). I n addition, enough concentrate was fed to meet maintenance requirements plus 130% of Morrison's ENE requirements for milk production. The concentrate mixture had the following composition in pounds: ground yellow corn, 1,000; roiled whole oats, 300; wheat bran, 300; soybean oil meal, 200; steamed bonemeal, 20; and salt, 20. Cows were kept indoors in a conventional barn during the entire experiment, and were fed individually. Roughages were fed two times and the concentrate mixture three times daily.

ET AL

Refused feed was removed from the manger before the next feeding. Water was available at all times. Milk weights were recorded at each milking. Analyses of fat, SNF, and protein were obtained weekly, using composite (evening and morning) samples. F a t was analyzed by the Bahcock method, S N F was obtained by subtracting fat per cent from the total solids per cent which was determined gravimetrically, and protein was determined by formol titration. Milk production data were converted to FCiV[ values. Body weights were taken at the beginning of the experiment and at the end of each period, always at the same hour and on three consecutive days. Thus, averages for three weighings have been used in analyses of the changes in body weight during the experiment. A digestion trial was carried out during the last ten days of each experimental period. Chromic oxide, used as an indicator, was fed (18 g in Periods I and I I and 30 g in Period I I I per cow daily) in the form of shredded chromic oxide paper, which was added to the concentrate at each feeding. During the last five days, grab samples of feces were collected at 6 AM and 6 P ~ a n d stored at --20C. At the end of each period, aliquots of each sample for each cow were composited. Determination of chromic oxide in feces was done by the method described by Kimura and Miller (7). RESULTS

Feed consumption. Average consumption of feed in all experimental periods was relatively uniform. Of the feed consumed, the concentrates were eaten most readily, whereas the hay and silage were refused in increasing amounts as more roughage was offered. Cows on Ration A refused only the coarsest parts of silage and hay. Refusals on Ration B were

TABLE 1 Chemical composition of feedstuffs Feedstuff

Expt. period

Dry matter

Ash

Protein

Fat

Fiber

N.F.E.

(%JAlfalfa-orchard grass hay

I II III

89.0 90.6 90.1

6.3 5.9 5.9

12.8 13.4 13.1

1.3 1.5 1.4

37.3 34.1 34.6

31.2 35.6 35.1

Corn silage

I II III

31.0 31.1 31.3

1.6 ].5 1.6

2.8 2.6 2.7

1.1 1.0 1.1

7.3 7.1 7.0

19.2 19.0 19.0

Concentrate mixture

I II III

90.3 90.3 90.3

4.4 4.6 4.2

14.9 15.5 14.8

3.2 3.2 3.1

7.0 5.8 5.3

60.9 61.2 62.9

ENERGY

A N D I~ILK P R O D U C T I O N

also mainly limited to the coarser parts of the forage, whereas on Ration C the refusals were similar in composition to the feed offered. Data on feed and nutrient intake are presented in Table 2. Increased feeding of roughages lowered total intake of energy (Table 2). The differences in total energy were significant (P < .01), with the greatest differences occurring between Rations A and C, and B and C. The amount of protein consumed was well above Morrison's allowances on all rations. Milk production. The cows fed Ration A, the more highly concentrated ration, produced the most milk, both on an actual and on an FCS~ basis. The differences in actual production and in production of 4% FCM were significant (P < .01) between Rations A and C and between Rations B and C (Table 3). Composition of mille. Statistical analyses of the data show no significant differences among rations in fat or protein content in the milk, but do show significant differences (P < .05) in the percentage of SNF and total solids (Table 3). Mean milk fat percentage varied little among rations. The percentage of protein in milk was the same when rations of low and of medium levels of concentrate were fed (Diets B and C), but was slightly higher for the high-concentrate ration.

1469

Energy utilization. The gross efficiency (pounds FCh[ × 0.340 therm per p o u n d therms ENE consumed) was nearly the same on all rations (Table 3). ttowever, there were small differences in the therms available for milk production after an estimated maintenance requirement of 7.6 therms was subtracted from the total energy intake. The amount of energy, above maintenance, utilized for the production of 1 lb of 4% FCM was practically the same as that allowed (0.39 therm). Digestion trial. Nutrient digestibility in all experimental periods was relatively uniform (Table 4). Cha~)gcs in digestibility were rather closely associated with changes in ration composition. As the amount of roughage increased, digestibility of crude fiber increased. However, in spite of the marked drop in the amount of concentrate consumed, from an average of 26.6 (Ration A) to 14.6 lb (Ration C), digestibilities of DM, fat, protein, and N F E decreased by only i to 2%. At the same time, digestibility of crude fiber increased from 62.7% (Ration A) to 66.6% (Ration C). Percentage of roughage in the rations is shown in Table 5. Since mechanical separation of grain from corn silage probably was not complete, the percentage of DM from grain actually may have been higher than that shown.

TABLE 2 Average daily feed and nutrient intake 1Cation Ingredient Hay (lb) Silage (tb) Concentrate (lb) Total DM (lb) Total ENE (themes) Digestible protein (lb) Energy concentration (therms ENE/IO0 lb DM)

A 5.6(6) a 23.3(24) 26.6 36.3 26.1 4.3 71.9

B 8.5(10) 36.4(40) 20.5 37.7 25.7 4.2 68.3

C 10.9(14) 45.9(56) 14.6 37.4 24.5 3.9 65.5

Numbers in parentheses represent the amounts of hay or silage offered to cows. TABLE 3 Average daily milk production, milk composition, and efficiency Ration Item Actual milk (lb)

FCI~ (lb)

Fat (%) SNF (%) Total solids (%) Protein (%) Gross efficiency (%) Therms ENE/]b FCM above maintenance ~

A

]3

C

Standard error

52.4 46.7 3.31 8.24 11.55 3.01 60.8 0.40

51.5 46.2 3.35 8.20 11.55 2.94 61.1 0.39

49.1 43.8 3.31 8.13 11.44 2.94 60.9 0.39

0.5 0.4 0.03 0.03 0.04 0.08 ...... ....

No correction was made for body weight changes.

D. ZEI~E~c[SKI E T AL

1470

TABLE 4 ~Iean coefficients of digestibility Treatment

Period

Dry matter

Protein

Fat

Fiber

N.F.E.

A

I II III Average

75.6 78.1 78.5 77.4

79.2 82.2 81.8 81.1

79.0 81.8 80.7 80.4

64.8 61.2 62.2 62.7

77.5 81.2 81.8 "80.2

B

I II

74.3 78.3 76.0 76.2

77.8 82.2 79.5 79.8

77.5 82.3 79.7 79.8

65.5 66.0 63.8 65.1

77.0 81.5 79.2 79.2

74.8 76.8 75.3 75.7

78.0 80.7 78.8 79.1

80.2 79.5 80.0 79.9

66.7 68.0 65.0 66.6

78.3 79.2 79.7 79.1

III

Average C

I II III

Average

Body weight. The mean body weights for the cows during the experimental periods were 1,217, 1,226, and 1,233 for Rations A, B, and C, respectively. The average body weight changes were --4, +6 , and + 1 2 for Rations A, B, and C, respectively. Increased feeding of roughages was reflected in increased (P < .10) body weights of cows. This likely was due in part to fill; whether there was also a difference in body composition is not known. DISCUSSIO~

The energy concentrations of 71.9, 68.3, and 65.5 for Rations A, B, and C, respectively, lie between the concentrations of rations with hay:concentrate ratios of ]5:85 and 35:65 fed by Bloom et ah (2) and Hotchkiss (5), whose data were reviewed and energy concentrations calculated (Table 6). These data show both energy concentration and level of feeding to have an effect on milk production. The F C M production in the present experiment was appreciably higher than in Bloom's and ttotchkiss' experiments. The level of feeding was also higher, which no doubt helped support a higher level of milk production; also, corn

silage was included in these rations. It appears that in this experiment an energy concentration of 68.3 (Ration B) was high enough to permit an energy intake sufficient to support milk production consistent with the abilities of these cows, since there was no significant difference in milk production between Rations A and B. This is an energy concentration intermediate between the two higher levels fed by Bloom and tIotchkiss. Recently, similar milk production on rations containing 90, 70, 50, and 30% of E N E in the form of concentrates has been reported (4). However, this was likely due to the comparatively low level of production (33.8 lb per day) and the high quality of the hay (20.6% crude protein and 26.9% crude fiber). Regardless of level of production, a higher proportion of energy can be supplied from high-quality forage than from poor-quality forage, which is taken into account when calculating rations on an energy concentration basis. J a r l (6) proposed specific concentrations of energy in the total ration ( E N E / D M ) for cows at various production levels (e.g., 59.1 for cows producing 44 ]b FC~I daily). I t is quite

TABLE 5 Per cent of dry matter supplied by different feedingredientsin ~ e rations Ration Source of dry matter Hay Silage with grain Silage without grain Grain from silage ~ Grain mixture Hay + silage with grain Hay q- silage without grain Grain mixture q- grain from silage

A

B

C

13.9 20.1 13.6 6.5 66.0 34.0 27.5 72.5

20.3 30.4 20.6 9.9 49.2 50.8 40.9 59.1

26.2 38.6 26.1 12.5 35.2 64.8 52.3 47.7

Amount of grain which could be separated manually from the silage averaged 32.2% of the silage dry matter.

ENERGY

AND MILK

PRODUCTION

1471

TABLE 6 Summary of the pooled data of Bloom et aL (2) and Hotchkiss (5) 4 Level of feeding

:Forage-toconcentrate ratio

Energy concentration

(therms/ew~ DM )

Daily DM intake

Daily ENE intake

Daily I~CM

(lb )

( therms )

(lb )

High Medium Low

15 : 85 15 : 85 15:85

73.6 73.7 74.0

30.6 27.5 25.0

22.5 20.3 18.4

40.9 40.4 37.0

Average

15:85

73.8

27.7

20.4

39.8

High Medium Low

35 : 65 35 : 65 35:65

64.2 64.2 64.2

34~6 31.8 28.0

22.2 20.4 18.0

38.4 35.8 37.4

Average

35 : 65

64.2

31.5

20.2

37.2

High Medium Low

55:45 55:45 55:45

56.7 57.1 56.7

38.6 35.6 30.5

22.0 20.4 17.3

38.6 37.8 32.2

Average

55:45

56.8

34.9

19.9

36.2

High Medium Low

75:25 75:25 75:25

51.0 50.8 50.8

37.0 35.2 34.2

18.8 17.8 17.4

31.7 32.0 29.6

Average

75:25

50.9

35.5

18.0

31.1

These two experiments were designed in the same manner, with each experiment including three cows in each cell of the design. A total of 72 cows are included in the above summary. They were continuously fed rations of one of four forage-t0-concentrate ratios at a high, medium, or low level of total intake. obvious, however, that the energy concentration that might be recommended depends on estimated DM consumption and total energy needs. Since J a r l did not allow f o r as great an energy requirement as is currently being recommended in the U.S.A. (10), it is readily evident why his energy concentration estimates are lower than those suggested in this experiment. Results of this study show increased consumption of energy with increased energy concentration in the r a t i o n ; this increase was reflected in higher milk production. However, the rations were not fed ad libitum and the differences in energy intake were due p r i m a r i l y to the failure of animals on the higher forage rations to consume all of the forage offered. Cows on Ration C, which had an energy concentration of 65.3, consumed an average of 24.5 therms daily and cows on Ration A, which had an energy concentration of 71.9, consumed 26.1 therms per day. Efficiency, both gross and net, was equally as good, however, f o r the highf o r a g e ration as f o r the other two. Although a p p a r e n t digestibility coefficients obtained in this experiment (Table 4) are higher than those obtained by Bloom et al. (1) and P u t n a m and Loosli (13), they have the same general trend, i.e., digestibility of DM,

protein, fat, and nitrogen-free extract increased as rate of concentrate feeding increased, whereas digestibility of crude fiber decreased. The a p p a r e n t digestibilities of DM and protein obtained in this experiment agree more closely with results presented by Martin et al. (9). I n the latter experiment D M and protein digestibilities were above 80% when the ration consisted of 20 to 30% hay, on a DM basis, and were 50 to 60% when hay represented 80% of the ration. I n the present experiment, the hay equivalent in Ration A was 27% of the total DM and digestibilities of DM and protein were 77 and 81%, respectively. The ration, especially the level of feeding, has a marked effect on the S N F and total solids of milk (1, 5, 16). However, it is difficult to determine f r o m the data in this experiment whether energy concentration of the ration or level of feeding effected the changes in S N F and total solids, since the energy intakes were not constant on all rations. I t would appear, as Hotchkiss (5) found, that level of feeding has the g r e a t e r effect with energy concentration p e r se having only a minor effect. No depression of milk f a t percentage was associated with any of the rations in this experiment or those of Bloom (2) and Hotehkiss (5). There-

1472

D. Z E a ~ S K I

fore, i t is a p p a r e n t t h a t e n e r g y c o n c e n t r a t i o n s as h i g h as 72 can be used w i t h o u t affecting f a t levels in the milk, a t least w i t h the r a t i o n ing r e d i e n t s f e d in these e x p e r i m e n t s . The n e t m e a n w e i g h t c h a n g e p e r cow d u r i n g the 12 wk on e x p e r i m e n t a l r a t i o n s was + 1 4 lb. This suggests t h a t the level of feeding ( 3 0 % above M o r r i s o n ' s h i g h levels f o r milk p r o d u c t i o n ) was n o t excessive a n d s u p p o r t s the suggestions o f others (10) t h a t p r e s e n t s t a n d a r d s are n o t a d e q u a t e f o r h i g h - p r o d u c i n g cows. The L a t i n - s q u a r e design used in this experinlent h a s l i m i t a t i o n s f o r use in lactation studies, because of the p o s s i b i l i t y of a r a t i o n causing a more r a p i d t h a n n m ~ a ] decline in p r o d u c tion which is n o t completely recovered in subs e q u e n t periods. This, in general, would t e n d to minimize differences in t r e a t m e n t s . Therefore, it is f e l t t h a t the differences in milk p r o duction s h o w n between the r a t i o n s fed in this e x p e r i m e n t would h a v e been a t least as g r e a t h a d the t r i a l been c o n t i n u o u s r a t h e r t h a n a Latin-square. I n general, c o n t i n u o u s t r i a l s would be favored, except t h a t much l a r g e r n u m b e r of a n i m a l s are r e q u i r e d f o r c o m p a r a b l e precision.

(1)

(2)

(3)

(4)

REFERENCES BL00IVf, S., JACOBSON, N. L., ALLEN, R. S., MCGILLIARD, L. D., AND H01VIEYER, P. G. 1957. Effects of Various tIay-Concentra~e Ratios on Nutrient Utilization and Production Responses of Dairy Cows. II. Observations on Ration Digestibility and on the Excretion P a t t e r n of Chromic Oxide. J. Dairy Sci., 40: 240. BL001~[, S., JACOBSON, N. L., McGILLIARD, L. O., HOMEYER, P. G., AND HEADY, E. O. 1957. Effects of Various Hay-Concentrate Ratios on Nutrient Utilization and Production Responses of Dairy Cows. L Relationships Among Feeding Level, Predicted Producing Ability, and Milk Production. J. Dairy Sci., 4 0 : 8 1 . COCHRAN, W. G., AUTREY, K. M., AND CANNON, C. Y. ]941. A Double Changeover Design for Dairy Cattle Feeding Experiments. J. Dairy Sci., 24: 937. HINDEaS, R. G., AND OWEN, F. G. 1963. Relationships Between Effieiency of Milk

~T An

(5)

(6) (7)

(8) (9)

(I0)

(11) (12) (13)

(14)

(15)

(16)

Production and Ruminal Volatile F a t t y Acids of Cows Fed Isocaloric ( E N E ) Rations of Varied Concentrate Levels. J. Dairy Sci., 46: 1246. liD,re,Kiss, D. K. 1960. Effect of Various Dietaries on Milk Composition and EffÉciency of Production of Dairy Cows. Ph.D. thesis, Iowa State University, Ames. JAI~L, F. 1952. Use of Forage in Dairy Production. 6th Intern. Grassland Congr., 2 : 1179. ]~II~iURA, F. T., AND MILLER, V. L. 1957. Improved Determination of Chromic Oxide in Cow Feed and Feces. J. Agr. Food Chem., 5: 216. LUCAS, H. L. 1943. A Me~hod of Equalized Feeding for Studies with Dairy Cows. J. Dairy Sci., 26: 1011. MARTIN, T. G., STODDARD, G. E., AND ALLEN, R . S . 1954. The Effect of Varied Rates of Hay Feeding on Body Weight and Production of Lactating Dairy Cows. J. Dairy Sci., 37: 1233. MOE, P. W., TYRI%ELL, H. F., AND REID, J. T. ]963. F u r t h e r Observations on Energy Requirements of Milking Cows. Proc. Corne]l Nutrition Conf. Feed Mfrs. pp. 66-70. Corne]l University, Ithaca, New York. M0~RRIS0N, F. B. 1959. Feeds and Feeding. 22nd ed. Morrison Publ. Co., Clinton, Iowa. PATTERSON, H. D. 1950. The Analysis of Change-over Trials. J. Agr. Sci., 40: 375. PUTNAm, P. A., AND LO0SLI, J. K. ]959. Effect of Feeding Different Ratios of Roughage to Concentrate upon Milk Production and Digestibility of the Ration. J. Dairy Sci., 42:1070. REID, J. T. 1956. Some Nutritional Effects of Varying Concentrate-Roughage Ratios in Relation to Feed I n p u t - M i l k Output by Dairy Cows. Memoir 344, Cornell University, Ithaca, New York. S'PONE., J. B., TRIMBERGER, G. W., HENDERSON, C. 1:~.,I~EID, J. T., TURK, ]<. L., AND LOOSLI, J. If. 1960. Forage Intake and Efficiency of Feed Utilization in Dairy Cattle. J. Dairy Sci., 43: 1275. ZEREi~SKI, D. 1960. Effect of Ration Composition on Production Responses of Dairy Cows, Milk Quality and Dry Matter Consumption. (Translated title.) Ph.D. thesis, Faculty of Agriculture Library, Belgrade University, Yugoslavia.