Milk Production Response of Dairy Cows Fed High-Moisture Grass Silage. I. Effect of Varying Levels of Hay and Concentrate1

Milk Production Response of Dairy Cows Fed High-Moisture Grass Silage. I. Effect of Varying Levels of Hay and Concentrate ~ F. R. MURDOCK and A. S. HODGSON

Department of Animal Sciences, Washington State University, Western Washington Research and Extension Center. Puyallup Abstract

Although research has demonstrated reduced dry-matter (DIV[) losses and increased acceptability of partially wilted silages, the effects of these harvesting procedures on the nutritive value of the resulting silages have not been clearly defined. Gordon et al. (7) compared the nutritive value of direct-cut silage, haylage, and barn-dried hay during three successive years. The three types of forage were prepared from the same crops of alfalfa. Animal acceptance, milk production, and live weight gains showed barn-dried hay to have, generally, the highest feeding value and direct-cut silage the lowest, ttaylage surpassed high-moisture, direct-cut silage in acceptance by the cattle and, as a result, live weight gains were higher. However, milk production was about equal on the two types of silage. Kesler and Cloninger (10) found slightly higher milk production by cows fed haylage (53.4% DM) as compared with direct-cut silage (25.4% DM). Feeding experiments at the South Dakota Station (16) with third-cutting alfalfa preserved as silage (35.5% DM) and haylage (59.7% DM) indicated an increase in DM consumption of approximately 26% when the haylage was fed. In spite of this large difference in DlV[ intake, differences in body weight gain and in milk production were negligible. Likewise, Byers (5) has recently reported no significant differences in DM consumption, milk production, or body weight gain by cows fed wilted silage (37.7% D)2[), low-moisture silage (50.1% D1VI), and hay (88.0% DM). The purpose of this feeding experiment was to ascertain milk production responses of dairy cows when a high-moisture grass silage ration was supplemented with varying levels of hay and concentrate.

Varying levels of bay and concentrate were fed in conjunction with high-moisture grass silage ad tibitum to 16 lactating cows, to determine the effects of these ration variables on milk production and composition. Feeding the higher level of concentrate (0.6 kg/kg 4% FCM over 8.16 kg) resulted in the production of more 4% FCM (P < 0.01), as well as higher percentages of milk protein (P < 0.01) and solids-notfat (P < 0.01) than produced when the lower level of concentrate (0.3 kg/kg 4% FCM over 8.16 kg) was fed. Varying the level of hay fed between 0.5 and 1.0 kg/100 kg body weight had no significant effect on the amount of milk produced or its composition. Likewise, no significant effects on the per cent of milk fat were observed by varying levels of either hay or concentrate within the limits fed in this study. Increasing the level of concentrate fed was more effective than increasing the level of hay for maintaining high dry-matter intake and in meeting the estimated TDN requirements of the cows. The TDN system of feed evaluation provided a reliable estimate of the relative nutritive value of these rations. Grass silage is the principal winter forage fed dairy cattle on many farms. The bulk of the silage made on farms in the north Pacific coastal area is harvested by direct-cut methods, in spite of research evidence that partial wilting of immature, succulent forages before ensiling reduces dry-matter losses in storage (7, 13, 17) and increases silage dry matter intake when fed (10, 14, 16). Cool, damp weather prevailing during first-cutting harvest makes wilting a questionable practice on most farms in this area.

Experimental Procedure

Grass silage fed during this study was prepared by direct-cut methods. The forage, predominantly orchardgrass and red clover, was harvested with a sickle-type harvester between May 23 and June 3, 1960, and ensiled in a wood-stave, tower silo. No preservative was added to the forage.

Received for publication June 17, 1966. ~Seientific Paper no. 2833, College of AgriOllture, Washington State University, Pullman. Work conducted under Project 1366. 57

5~

5IURDOCK AND HODGSON

Sixteen Holstein cows in early lactation were fed similarly during a 2-wk preliminary period. The preliminary ration consisted of grass silage, ad libitum; grass-clover hay, 0.75 kg/100 kg body weight; and concentrate at the rate of 0.45 kg//kg of 4% F C h l over 8.16 kg. At the conclusion of the preliminary period, the 16 cows were allocated to four squares and four treatment groups in a Latin-square change-over design, with an extra period as suggested by Lucas (11). An orthogonal set of squares with a balanced single square was used. Animals within each square were balanced as nearly as possible according to their stage of lactation and according to milk production and body weight during the last week of the preliminary period. I n this design each treatment was preceded by every other treatment, including itself. The four rations fed during the five 4-wk experimental periods are shown in Table 1. Grass silage was fed in amounts so that refusals were about 10%. The hay was a good-quality, second-cutting mixture of orchardgrass and red clover. The concentrate mixture consisted of ground barley, 38.8%; rolled oats, 20.4%; millrun, 19.4%; soybean oit meal (44%), 14.6%; molassesdried beet pulp, 4.8%; trace-mineralized salt, 1 % ; and steamed bonemeal, 1%. All cows were fed individually. Daily allotments of silage and hay were weighed and fed separately in two compartment mangers in a stall-type loafing shed. Silage was fed twice daily and hay once daily. The concentrate was fed in individual mangers in the milking barn, twice daily. Samples of grass silage and hay were taken weekly with a Penn State core sampler. I n sampling the silage, numerous cores were taken over the area of the silo to the estimated depth that would be fed during the ensuing week. Equal portions of the weekly silage samples were oven-dried at 80 C and composited for proximate analysis by 4-wk periods comparable to the feeding periods. One quarter of the hay bales fed during each period was sampled. Individual silage and hay refusals were TABLE 1 Experimental rations and rates of feeding

l~ation no. Grass silage 1 2 3 4

Ad Ad Ad Ad

Mixed Concentrate hay kg/kg kg/100 kg 4% FCf~¢I body over weight 8.16 kg ~

libitum libitum libitum libitum

1.0 1.0 0.5 0.5

Converted from 18 Ib avoirdupois. J. D A I R ~ Sex~,~e~ RrOL. 50, NO. i

0.6 0.3 0.6 0.3

weighed three times weekly, but only one proportionate sample of each was accumulated for all cows for each 4-wk period. These samples were kept frozen during the sampling periods in double, 4-mil polyethylene plastic bags. The DM content of silage and silage refusal samples was determined by the toluene distillation method of Perkins (15), modified for use with 50-g samples. Concentrates fed and refused were sampled weekly and samples combined by feeding periods. Proximate analyses were conducted on ovendried samples of all feeds and refusals by AOAC procedures (2). All cows were milked twice daily and the milk weighed and sampled. Weekly composite samples were tested for milk fat by standard Babcock procedures and for solids-not-fat ( S N F ) by the densitometer method of Gelding (6). Milk protein was determined weekly on a combined sample of one consecutive night and morning milking by the Orange G dye-binding method of Ashworth et al. (1). Cows were weighed on two consecutive days, at the end of the preliminary period and eaeh of the experimental periods, and these weights averaged. The effect of rations on milk production and composition was determined by the analysis of variance, by the methods of Lucas (11). Results and Discussion

The mean DM content of the forage as ensiled was 16.2% (SD = 4.1%) and of the preserved silage from the entire silo, 23.6% (SD = 1.4%). DM loss in storage due to seepage and fermentation was 14%. A plastic seal on the surface prevented any top spoilage. Mean proximate analyses of feeds and of feed refusals during the 20-wk feeding experiment are shown in Table 2. Average daily feed consumption, milk production and composition, and body weight changes of all cows while subjected to each of the ration treatments are shown in Table 3. Mean squares and statistical significances as determined by an analysis of variance of the milk production and composition data are presented in Table 4. The mean difference of 2.04 kg of 4% F C M / c o w / d a y between the two highconcentration rations (1 and 3) and the lowconcentrate rations (2 and 4) was significant (P < 0.01). Also, the higher level of concentrate feeding resulted in higher percentage of protein (P < 0.01) and S N F (P < 0.01) in the milk produced. These results are in agreement with those of Holmes et el. (8) and t t u b e r

PRODUCTION RESPONSE OF COWS

59

TABLE 2 Average chemical composition of feeds and weighbacks

(% as-fed basis) Moisture

Crude protein

Crude fiber

Ether extract

Ash

N.F.E.

Feeds Grass silage Mixed ha0~ ConcerLtra~e

75.6 '~ 9.2 10.3

3.0 11.8 18.4

8.7 24.6 5.4

1.3 3.5 3.2

1.8 9.2 5.3

9.6 41.7 57.4

Weighbacks Grass silage Mixed hay Concentrate

75.0 ~ 9.8 14.2

3.0 9.7 19.3

9.5 29.7 5.2

1.2 2.6 2.9

1.9 8.9 6.0

9.4 39.3 52.4

Moisture determined by toluene distillation. TABLE 3 Average feed consumption, milk ]production, composition, and body weight £hanges by rations Ration

1

Feed consumption, as-fed basis (kg/vow/day) Mixed h a y 6.08 Grass silage 26.72 Concentrate 8.82 Dry m a t t e r consumption Grass silage Mixed hay Total ration

2

3

4

6.12 30.39 3.96

3.22 34.38 8.54

3.08 36.20 4.02

(kg/lO0 kg body weight~day) 1.03 0.88 3.17

1.19 0.89 2.65

1.31 0.45 2.95

1.44 0.46 2.48

Milk production and composition F C M / c o w / d a y (kg) 23.16 Fat (%) 3.67 Protein ( % ) 3.03 SNF (%) 8.62

20.99 3.65 3.00 8.59

22.76 3.66 3.01 8.65

20.85 3.64 2.84 8.48

Body weight change A v g / c o w / d a y (leg)

-0.17

+0.25

--0.55

+0.35

TABLE 4 Mean squares and levels of significance of average daily milk production and composition d a t a Mean squares FCM

Fat 13.59 b 1.68 b 4.28 b 0.05 0.00 0.14 0.02 0.!4 0.21 3.2

Source of variation

df

(kg)

Squares Periods w / i squares Cows w / i squares Direct effect of t r e a t m e n t Level of hay Level of concentrates ]~ay × concentrate Residual effect Error C.V. (%)

3 16 12 3 1 1 1 3 42

69.63 b 28.82 b 68.18 b 23.15 b 0.22 69.21 b 0.01 0.64 1.80 6.1

. . . .

Protein

~(%)5.67 b 0.35 1.74 b 1.64 b 1.33 2.74 b 0.85 0.42 0.37 5.1

SNF 9.39 h 0.21 4.10 b 1.50 a 0.50 3.26 b 0.73 0.73 0.35 1.7

a Significant at P ~ 0.05. b Significant at P ~ 0.01. a n d B o m ~ n ( 9 ) , who o b s e r v e d s i m i l a r i n c r e a s e s i n p r o t e i n a n d S N F c o n t e n t of m i l k w h e n ene r g y in t h e r a t i o n w a s increased. T h e y differ, however, w i t h those o f B r o w n et al. ( 4 ) , who r e p o r t e d no effect of v a r y i n g c o n c e n t r a t e levels on mil]~ p r o t e i n a n d S N F content. T h e p e r -

e e n t a g e o f m i l k f a t w a s n o t affected s i g n i f i c a n t l y b y t h e c o n c e n t r a t e levels i m p o s e d in these rations. Differences in levels of h a y f e d in these rat i o n s h a d no significant ( P ~ 0.05) effects on m i l k p r o d u c t i o n or its p e r c e n t a g e c o m p o s i t i o n J. DAIRY SCIEI~OE VOL. 50, NO. 1

~0

MURDOCK

of fat, protein, or SNF.

AND ttODGSON

Also, interactions of hay and concentrate levels were insignificant (P > 0.05). A second analysis of variance was computed on the 4% FCM data after deletion of the production during the first week after ration changes. The purpose of this analysis was to determine the effect of using the first week after ration changes as change-over periods, thereby shortening the experimental periods to 3 wk. Although the mean squares for direct effects of ration treatments were increased slightly by this method of analysis, differences were not sufficient to change the significance, as indicated in Table 4. Although silage consumption was reduced by feeding higher levels of either hay or concentrate, reduction in silage DM consumption was not commensurate with the higher DM supplied by these other feeds. As a result, higher DM intakes were maintained when higher levels of /)()tit hay and concentrate were fed. A t the higher concentrate level, increasing the amount of hay fed from 0.5 to 1.0 kg/100 kg body weight resulted in a decrease of silage D~{ intake of 0.71 kg per kilogram of additional hay DM fed. At the lower concentrate level, decrease in silage DS{ intake was 0.52 kg per kilogram of hay DM fed. Similarly, an increase in the level of concentrate intake resulted in a decrease of silage DM intake of 0.20 and 0.11 kg per kilogram of concentrate DM when cows were fed at the higher and lower levels of hay, respectively. ~father et al. (12) reported a decline of silage DM intake of 0.26 kg per kilogram of grain fed when the rate of grain feeding was increased from a grain-milk ratio of 1:6 to 1:3 and cows were fed limited hay

and grass silage ad libitum. Brown et al (3) also observed a decrease in silage DM consumption as the level of hay was increased, but noted that total DM consumption increased with increasing levels of hay fed. Although milk production followed a trend similar to total DM consumption in this Michigan work, production differences were not significant, except in one feeding trial in which cows consuming silage produced significantly (P < 0.01) more milk than cows consuming hay. Estimated mean daily TDN requirements for maintenance and body weight change, as well as the estimated TDN consumed by ration treatments, are shown in Table 5. From these data the kilograms of TDN available for milk production and the grams of TDN per kilogram of nfilk produced were derived by computation. These cmnputations indicate no appreciable differences in the efficiency of TDN utilization for milk production between rations varying in roughage and concentrate levels within the limits of this experiment. I t is of interest to note that the mean efficiency value of all ration treatments (378 gm TDN/kg 4% I~CM) is very close to the requirement of 370 g recommended for cows producing at this level, in the Third Revised Edition of Nutrient Requirements of Dairy Cattle, National Academy of Sciences-National Research Council, Washington, D.C. These relationships indicate satisfactory reliability of the TDN system for evaluating the relative nutritive value of these mixed rations for dairy cows. Calculations of returns over feed cost from the feed consumption and milk production data indicate returns of $1.29, $1.39, $1.30, and $1.42 per cow per day on Rations 1 through

TABLE 5 Estimated mean daily TDN requirements and intakes by rations and efficiency of TDN utilization for milk production Ration Mean body wt ( k g ) Est. TDN req. for maintenance (I~g) ~ Est. TDN req. for body gain (+) or available from body loss (--) ( k g ) ~ Est. TDN cons. ( k g ) ¢ Est. TDN available for milk production ( k g ) TDN/kg FCM ( g )

]

2

3

4

631.4

622.3

641.8

615.1

4.10

4.06

4.16

4.03

+1.24 14.19

--0.46 11.16

+0.88 13.75

--1.51

8.85 382

7.56 360

8.71 383

8.07 387

10.59

a Estimate computed from Nutrient Requirements of Dairy Cattle, Third Revised Edition, National Academy of Sciences--National Research Council, 1966. b Estimate computed from body weight changes shown in Table 3 by applying factors of 3.53 for weight gain a~d 2.73 for weight loss, as suggested by Knott, J. C., ttodgson, tk E., and Ellington, E. Y. 1934. Methods of Measuring Pasture Yields with Dairy Cattle. Washington Agr. Expt. Sta., Bull. 295. c Estimate based on hay, 52.0%; silage, 16.5% ; and concentrate 75.0% TDN as fed. J . DAliI~Y SCIENCE VOL. 50, NO. 1

PRODUCTION I%ESPONSE OF COWS 4, respectively. These computations were based on 4 % milk at $10/100 kg, hay at $3.09/100 kg, silage at $0.77/100 kg, and concentrate at $7.16/100 kg. Although these comparisons indicate greater economy of milk production f r o m the lower level of concentrate feeding, they ignore differences in body weight changes. D a t a in Table 3 indicate mean weight gains of a p p r o x i m a t e l y 0.30 kg p e r day for cows while being fed the high-concentrate rations and mean weight losses of a p p r o x i m a t e l y 0.36 kg when fed the low-concentrate rations. These results suggest that cows were metabolizing body tissue to meet maintenance and milk production requirements while being fed the lowconcentrate rations. This is substantiated by the T D N balances, as indicated in Table 5. Therefore, it is a p p a r e n t that economic considerations of rations should not be established on the basis of short-time, change-over-type f e e d i n g experiments without taking into consideration body weight changes. A total of seven incidences of mastitis were recorded during the experimenL Three of these occurred in one cow during three separate periods. The f o u r other cases involved f o u r cows and were of short duration. Inasmuch as milk production was affected by these mastitic infections, some adjustments in milk production were made. The mean rate of production decline by the other cows receiving the same ration treatment during each affected period was used to adjust production decline of the mastitic cow f o r that period. F o u r of the incidences of mastitis occurred while cows were receiving the high rate of concentrate and three while receiving the low rate of concentrate. Incidences of mastitis were distributed as equally between the higher and lower levels of hay feeding.

Acknowledgments The authors appreciate tile assistance of Dr. T. S. Russell in conducting the statist.ical analyses.

References (1) Ashworth, U. S., Seals, R., and Erb, R. E. 1960. An Improved Procedure for the Determination of Milk Protein by Dye Binding. J. Dairy Sei., 43: 614. (2) Association of Official Agricultural Chemists. 1960. Official Methods of Analysis. 9th ed. Washington, D. C. (3) Brown, L. D., Hillman, D., Lassiter, C. A., and Huffman, C. F. 1963. Grass Silage vs. Hay for Lactating Dairy Cows. J. Dairy Sci., 46:407.

61

(4) Brown, L. D., Thomas, J. W., Emery, 1~. S., MeGilliard, L. D., Armstrong, D. ¥., and Lasslter, C. A. 1962. Effect of High-Level Grain Feeding on Milk Production Response of Lactating Dairy Cows. J. Dairy Sci., 45 : 1184. (5) Byers, J. H. 1965. Comparison of Feeding Values of Alfalfa Hay, Silage, and LowMoisture Silage. J. Dairy Sci., 48:206. (6) Golding, N. S. 1959. A Solids-not-fat Test for Milk Using Density Plastic Beads as Hydronleters. J. Dairy Sei., 42:899. (7) Gordon, C. H., Derbyshire, J. C., Wiseman, tI. G., Kane, E. A., and Metln, C. G. 1961. Preservation and Feeding ¥a]ues of Alfalfa Stored as Hay, Haylage, aud Direct-Cut Silage. J. Dairy Sci., 44 : 1299. (8) Holmes, W., Reid, D., MaeLusky, D. S., Walte, R., and Watson, J. N. 1957. Winter Feeding of Dairy Cows. IV. The Influence of Four Levels of Concentrate Feeding in Addition to a Basal Ration of Grass Products on the Production Obtained from Milking Cows. J. Dairy Research, 24:1. (9) ttuber, J. T., and Boman, R. L. 1966. Effect of Grain Level and Protein Content of the Grain for Grazing Cows on Milk Composition and Yield, and Certain Blood and Rumen Constituents. J. Dairy Sci., 49: 395. (10) Kesler, E. M., and ClonJnger, W. H. 3965. Haylage--A Way to Store High-Quality Forage. Science for the Fa~'mer, 2 : 10. (11) Lucas, H. L. 1957. Extra-Period LatinSquare Change-Over Designs. J. Dairy Sei., 40 : 225. (12) Mather, R. E., Breideustein, C. P., Poulton, B. R., and Bonnington, G. H., Jr., 1960. High Levels of Grass Silage for Milk Production with No Grain, Medium, and High Grain Feeding. I. Intake, Milk Production, and Body Weight Changes. J. Dairy Sci., 43 • 358. (13) Murdock, F. R., Hodgson, A. S., and tIarris, J. ]~. 1958. Nutrient Losses and Feeding ¥a]ue of Wilted and Direct-Cut Forages Stored in Tower Silos. J. Dairy Sei., 41: 1483. (14) Murdock, J. C. 1960. The Effect of PreWilting Herbage on the Composition of Silag~ and Its Intake by Cows. J. Brit. Grassland See., 15: 70. (15) Perkins, A. E. 1943. Dry Matter Determination in Green Plant Material and in Silage. J. Dairy Sci., 26:545. (16) ¥oelker, H., and Bartle, E. 1961. Supplen~enting ttaylage in Feeding Dairy Cattle for Efficient Milk Production. South Dakota Farm and Home Research, 12:4. (17) Woodward, T. E., and Shepherd, J. B. 1938. Methods of Making Silage from Grasses and Legumes. USDA. Tech. Bull. 611.

J. DAIRY S¢IEXCE Vob. 50, NO. 1