Effect of level of feeding on growth, reproductive performance and milk production of beef females

Livestock Production Science, 5 (1978) 159--169 159 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

EFFECT OF LEVEL OF FEEDING ON GROWTH, REPRODUCTIVE PERFORMANCE AND MILK PRODUCTION OF BEEF FEMALES

J A M E S B O N D and B.T. W E I N L A N D

Ruminant Nutrition Laboratory, Nutrition Institute,ARS, U.S. Department of Agriculture, Beltsville, Md. 20705 (U.S.A.) (Received 18 May 1977)

ABSTRACT Bond, J. and Weinland, B.T., 1978. Effect of level of feeding on growth, reproductive performance and milk production of beef females. Livest. Prod. Sci., 5 : 1 5 9 - - 1 6 9 Fifty-nine Aberdeen Angus females, each weighing about 190 kg and 7 months old, were randomly assigned to five levels of feed intake (140, 100, 80, 60 and 40% of the recommended allowance for total digestible nutrients). Two groups of females were assigned to the 60% level, one of which was raised to the 100% level 45 days prepartum. All females except those fed at the 140% level were raised to the 100% level at parturition until 150 days postpartum and then returned to prepartum levels. The females were removed from the experiment at their first estrus after the second calving. Females (nine in this group) fed at the 40% level of feed intake ceased to cycle before their first breeding date and had to be raised to the 100% level until estrual cycles were reestablished. Raising feed intake levels 45 days prepartum increased average daily gain (1.24 vs 0.16 kg, P < 0.01) of the females but had no significant influence on calf birth weight, calf mortality, milk yield, average daily gain of calves, time to postpartum estrus and conception or conception rate. Both groups of females fed the 60% level of feed intake and those fed the 40% level gained faster (0.28 vs 0.02 kg daily, P < 0.01) during lactation but weighed less (290 vs 423 kg, P < 0.01) and gave less milk (2.8 vs 3.4 kg, P < 0.01) than females fed the other levels. Although postpartum estrus and conception were delayed slightly, none of the females fed the 60 and 40% levels ceased to cycle after calving. Females fed the 140% level of feed intake became extremely fat and their milk production was similar to that of the other groups, but calf mortality was higher. Raising levels of feed intake postpartum increased gains and reproductive performance of females on levels below recommended allowances, but increasing either feed intake 45 days prepartum or feed intake levels above recommended allowances had no measurable benefit.

INTRODUCTION L o w levels o f n u t r i t i o n i n h i b i t g r o w t h o f c a t t l e a n d c a n also c h a n g e b e h a vior and physiological functions; lowered efficiency of performance results

160 (Blaxter, 1945; Winchester et al., 1967). Also, results of several studies showed that undernutrition (Reid, 1960; Wiltbank et al., 1965) and excessive feeding {Swanson, 1960; Bond and Wiltbank, 1970) adversely influence reproductive performance in female cattle. Lodge et al. (1972) fed Holstein cows for 6 weeks prepartum at either maintenance or 1.8 × maintenance followed by ad libitum intake of hay and concentrates postpartum. Cows fed at the prepartum maintenance level recovered their initial postpartum weight loss and consumed more concentrates than cows fed at the 1.8 X maintenance level, but total dry matter intake, milk yield or calf birth weight were the same for cows fed both levels of feed intake. The experiment reported here was designed to observe (1) the effects of feeding 140, 100, 80, 60 and 40% of recommended allowances for total digestible nutrients (Morrison, 1956) on body weight, feed efficiency and reproductive performance of the beef female through two calving periods, (2) the effects on growth of the female and her calf and (3) the reproductive performance of the female when the level of feed was raised from 60 to 100% of recommended allowances for 45 days prepartum or during the postpartum period until their calves were weaned. EXPERIMENTAL PROCEDURE Fifty-nine open grade Aberdeen Angus heifers, about 7 months old and averaging 190 kg, were randomly assigned by weight to five levels of feed intake (140, 100, 80, 60, and 40% of approximated total digestible nutrients recommendations (Morrison, 1956) for growing, reproducing heifers). With only 59 females available for this study, nine were assigned by chance to the 40% level of feed intake and ten to each of the other levels. Two groups of females were assigned to the 60% level, one of which was offered the 100% level about 45 days prepartum (60% (100)). The females fed the 140% level were fed ad libitum and consumed about 40% more than those fed the recommended level of feed. The females fed the 40% level were fed to maintain their body weights. All females were individually fed a pelleted diet (Table I) with the amount of feed adjusted when necessary to meet the desired level of feed intakes. All females except the ad libitum (140% level) group were fed twice each day at about 09.00 and 14.00 h; the daily allotment of feed was divided into two equal portions. The females fed ad libitum had their feed replenished when necessary. Water, trace mineralized salt and steamed bone meal were available on a free choice basis. Females were housed in covered, concrete floor pens measuring 1.8 X 3.7 m and an outside area measuring 1.8 × 5.5 m. Sawdust bedding was used at both calvings. Females fed the 140% level were moved to dirt floor pens after they weaned their first calves; because they had a problem walking on the concrete floors at this body weight. All females were

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TABLE I Composition and chemical analysis of the experimental diet Item

I R N No.

Diet (%)a

Ingredient b Timothy hay Corn and cob meal Cottonseed meal Molasses, cane Dicalcium phosphate Trace mineralized salt c

1-09-003 4-02-849 5-01-632 4°04-696 6-01-080

24.5 49.0 14.7 9.8 1.0 1.0

Chemical analysis, dry basis Crude protein Ether extract Crude fiber Ash Nitrogen-free extract Gross energy (Mcal/g)

14.0 2.1 16.4 6.3 61.2 4.28

aDiet was ground, mixed and pelleted (16 m m in diameter). b4125 USP vitamin A units were added to each kilogram of feed. CThe trace mineralized salt was a commercial mixture that had a guaranteed analysis of: salt not more than 99% or less than 96%; manganese not less than 0.20%; iron not less than 0.15%; magnesium not less than 0.10%; sulfate sulfur not less than 0.05%; copper not less than 0.03%; cobalt not less than 0.01%; zinc not less than 0.008%; iodine not less than 0.007%.

allowed on a larger paved lot daily from 06.30 to 09.00 and 15.00 to 16.30 h. This time was used to clean pens and check the females for estrus. A vasectomized bull was used to check females for estrus twice daily. Reproductive organs were examined periodically b y rectal palpation. After a b o u t 360 days on test, all females were bred b y one of t w o proven Angus bulls at each estrus. Females were removed from the experiment at their first estrus after calving for the second time. Milk yield was obtained weekly starting at 14 days postpartum by the calf suckling method, as described b y Bond and Wiltbank (1970). Although this m e t h o d for estimating milk yield has a degree of error associated with it, it does give an approximation of the milk consumed by the calf. Unlimited creep feed (the experimental diet} was provided individually when the calf was 14 days old until it was weaned at 150 days. Fresh feed was added when necessary, and feed intake was measured each week. Calves had access to their dam's feed b u t appeared to eat little. All females except those fed the 140% level, were offered 100% of the r e c o m m e n d e d feed for lactating females of this t y p e from calving to weaning. At weaning each female was returned to the respective prepartum level of feed. All variables were statistically analysed; a one-way analysis of variance model was used to compare the six groups. The SAS General Linear Models

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procedure (Barr et al., 1976) which adjusts for unequal subclass numbers was used. Significant differences among the groups were determined by Duncan's Multiple Range Test (Duncan, 1955). RESULTS Weight gains of the females through first calving are shown in Table II. Eight females fed the 40% level of feed intake were offered the 100% level because only seven showed heat and five stopped cycling on the initial 40% feeding level. The interval from diet change to reestablishment of estrus was about 100 days. When the heifers reestablished estrual cycles, they were returned to the 40% level. At first breeding, body weights of the females were different (P < 0.01) among all feeding levels. Females fed the 60% (100) level of feed intake made the highest gains (P < 0.01) during the 45 day period before calving to calving for both gestations (Tables II and III). When the feed was raised to the 100% level during the period from calving to weaning females that were fed the 60, 60(100) and 40% levels gained faster (P < 0.01) than heifers fed the 140, 100 and 80% levels. Feed intake during lactation was lowest (P < 0.01) for females fed the 60 and 40% levels. After weaning of first calves and until second calving, those females fed the 140 and 100% levels of feed intake gained faster (P < 0.01} than the other groups (Table III). Females fed the 80% level gained faster than those fed the 60 and 40% levels. Females fed the 60 and 40% levels of feed intake gained the same when feed was increased during lactation. Females fed the 140% feed level lost weight during lactation while eating the most feed whereas those fed the 40% level ate the least (P < 0.01). Length of the estrual cycle, gestation length and calf birth weight were not different among treatments for the first and second calving (Tables II and III). However, the difference in postpartum interval to first estrus after the first calving was large but non-significant. Postpartum interval to first estrus was longer (P < 0.05) for the females fed the 60% level of feed intake than for those fed the 140, 100 and 80% levels. The females fed the 60(100) and 40% levels had postpartum intervals that were not statistically different from the other groups. During the first lactation, milk yield was lowest (P < 0.01) for females fed the 40% level of feed intake (Table IV). Milk yield for females fed the 140 and 80% levels peaked in lactation at about the same time (60 days) and then declined the last 90 days (Table IV). Milk yield for the females fed the 60 and 40% peaked at about 90 days. Milk yield for females fed the 100 and 60(100)% levels increased slightly over the 150 days of lactation. During the second lactation, milk yield was different (P < 0.05) among groups although the patterns of lactation, except those for females fed the 100 and 40% levels, were similar. For most groups milk yield peaked at 60 days and then declined the last 90 days; however, milk yield for the females fed the 100 and 40% levels peaked at 90 days.

163

T A B L E II B o d y weight, daily gain, feed i n t a k e a n d reproductive performance o f experimental females through first calving

Item

N u m b e r o f females Bred Pregnant Calved B o d y w e i g h t (kg) Beginning Conception 1 week before calving

Feed i n t a k e l e v e l ( % ) 140

100

10 8 8

10 8 8

10 10 10

10 9 9

10 9 9

9 9 9

193 " 390 a

1~9 335 b

191 296 c

192 247 d

191 240 d

191 207 e

458 b

394 c

314 d

339 d

305 d

430 b

361 c

289 d

304 d

285 d

523 a 24 h after 478 a calving Average daily gain (kg) 0.53 a B e g i n n i n g t o calving 45 days before 0.29 b calving t o calving 0.03 b calving t o weaning Average daily feed i n t a k e f (kg) 7.4 a Beginning t o calving 45 days before 7.2 a calving t o calving 10.0 a calving to w e a n i n g 20.6 Estrual cycle (days) Days to: 370 a Breeding 644 a Calving Calves living 5 A t birth 2 At weaning 23.7 Average birth weight (kg) 127.I Average w e a n i n g w e i g h t (kg) Calving to first 81.7 estrus (days) Calving to c o n c e p t i o n (days) 187.2

80

60

60(100)

40

0,42 b

0.33 c

0.18 d,e

0.23 d

0.14 e

0.13 b -0,01 b

0.21 b 0.12 b

0.11 b 0.29 a

1.24 a 0.28 a

0.04 b 0.31 a

4.3 c

3.1 d

3.2 d

2,9 d

4.8 b 8.0 b,c 21.2

3.0 c 7.6 d 20.5

4.6 b 8.2 b 20.9

2.5 c 7.7 ¢,d 20.8

5.2 b 5.2 b 8.2 b 21.5 363 a 640 a

362 a 634 a

425 b 702 b

379 a 652 a

503 c 782 c

7 6 25,0 130.8

9 8 26.0 129.7

9 7 21.9 116.9

8 7 23.2 106.6

9 8 22.9 110.8

68.4

72.6

136.6

100.6

111.6

136.9

152.1

180.1

163.7

171.2

a,b.c,d,e Means w i t h i n rows which have u n l i k e superscripts are different (P < 0.01). f As-fed basis.

Creep-feed intake of all calves (both lactations) was very low during the first 90 days of lactation but then increased (P < 0.01) dramatically to weaning. Average daily gains of the calves were not significantly different among groups but their gains were different (P < 0.01) over the 150
164

TABLE

III

Body weight, daily gain, feed intake and reproductive performance of experimental females through second calving Item

Number of females Bred Pregnant Calved Body weight after calving ( k g ) Average daily gain (kg) Weaning to calving 45 days before calving to calving calving to weaning Average daily feed intake f (kg) Weaning to calving 45 days before calving to calving calving to weaning Calves living At birth A t weaning

Average birth weight (kg) Average weaning weight (kg) Calving to first estrus (days) g

Feed intake level (%) 140

100

80

60

60(100)

40

7 3 3 508 a

8 8 8 456 b

10 9 9 386 c

8 8 8 321 d

9 9 9 342 d

8 8 8 275 e

0 . 2 3 a'b

0.23 a

0.14 b

0.05 c

0.03 c

0.01 c

0.01 b 0.12 a,b

0.17 a'b 0.22 a

0.55 a 0.28 a

0.09a, b 0.19a, b

0.01 a,b --0.21 b

0 . 1 6 a,b --0.03 b

7.9 a

5.3 b

4.2 c

3.3 d

3.3 d

2.8 e

8.2 a 9.7 a

5.2 b 8.2 b

4.1 c 8.1 b,c

4.0 c 8.2 b

5.3 b 8.2 b

2.6 d 8.0 c

9 7 23.6 121.7 75.7h~i

8 5 23.5 122.4 8 3 . 0 hA

3 0 17.7 59.0 i

8 4 28.3 145.2 47.91

9 7 23.9 133.0 55.7 i

8 7 22.1 136.3 1 1 0 . 0 I~

a,b,c,d,eMeans within rows which have unlike superscripts are different (P < 0.01). fAs-fed basis. gThe value reported for the 140% level is from only one female. h,iMeans within rows which have unlike superscripts are different (P < 0 . 0 5 ) .

by white muscle disease; and when the other calves were treated with selenium-vitamin E compound, no further problems occurred. DISCUSSION The females at the 40% level gained more to first calving than normal for this level of intake because the feed intake o f the anestrus females had to be raised. After an interval o f higher feed intake, these females reestablished estrual cycles and conceived. These data would indicate that the 40% level of feed intake was inadequate and the females needed additional energy and protein to maintain their estrual cycles. Raising the feed intake level of females fed the 60% level to the 100% level 45 days prepartum increased average daily gain to calving but had no significant influence on calf birth weight, calves alive at birth and at weaning, milk yield, average daily gain o f calves and postpartum interval to estrus and conception. However, after both calvings, the interval to estrus and conception was one full cycle less than that o f females fed the 60% level that was not raised before parturation. These females (60(100)%) probably used the additional energy for their own body growth rather than for either fetal growth or milk production and this probably affected postpartum interval.

165

TABLE IV M e a n s f o r m i l k yield, c r e e p - f e e d i n t a k e a n d average daily gain o f calves d u r i n g t w o lactations Item

Days o f l a c t a t i o n 30

Milk y i e l d ( k g / 1 2 h ) First lactation 140 100 80 60 60(100) 40 Second lactation 140 100 80 60 60(100) 40 Creep-feed i n t a k e ( g / d a y ) First lactation 140 100 80 60 60(100) 40 Second lactation 140 100 80 60 60(100) 40 Average daily gain o f calves (kg) First lactation 140 100 80 60 60(100) 40 Second lactation 140 100 80 60 60(100) 40

60

2.3 3.2 3.2 2.6 3.0 2.1 .

.

. 3.6 4.0 4.2 3.3 2.9

20 36 28 75 50 43 .

0.4 0.4 0.5 0.4 0.4 0.4 .

. 0.4 0.5 0.6 0.5 0.5

90

3.5 3.4 4.0 3.2 3.1 2.6

3.1 3.3 3.5 2.9 2.4

. 68 45 68 33 70

Mean 120

3.4 3.4 3.8 3.3 3.1 2.7 .

3.3 3.5 3.8 3.3 2.8 2.7 .

. 4.0 3.6 3.6 3.1 3.2

4.0 3.9 3.9 3.2 3.3

100 124 139 98 128 143

85 326 298 278 455 342

. 94 86 86 123 150

. 192 259 244 340 433

0.7 0.6 0.8 0.6 0.6 0.5

0.8 0.8 0.8 0.6 0.6 0.6

. 0.7 0.7 0.7 0.6 0.6

. 0.6 0.7 0.7 0.7 0.6

150

.

2.9 3.6 3.3 3.1 3.2 2.5

3.1 a'b 3.4 a 3.6 a 3.1 a~b 3.0 a~b 2.5 b

4.0 3.1 3.2 3.0 3.0

3.7 h 3.6 h 3.7 h 3.1 h,i 3.0 i

.

435 618 693 423 900 747

420 820 1033 724 1377 1399

233 385 461 328 750 645

. 715 936 956 672 860

. 1458 1740 1883 1506 1568

515 720 765 632 724

0.8 0.8 0.7 0.7 0.7 0.7 .

0.8 0.7 0.8 0.7 0.6 0.9

0.7 0.6 0.7 0.6 0.6 0.6

0.9 0.8 0.9 0.7 0.8

0.7 0.7 0.8 0.6 0.7

. 1.0 0.9 0.9 0.8 0.8

a, b M e a n s w i t h i n rows w h i c h h a v e u n l i k e s u p e r s c r i p t s are d i f f e r e n t (P < 0.01). h,iMeans w i t h i n r o w s w h i c h h a v e u n l i k e s u p e r s c r i p t s are d i f f e r e n t ( P < 0.05).

166

Although females fed the 60 and 40% levels of feed intake gained less from the start of the experiment to first calving and from weaning to second calving, the average birth weights of the calves they produced were similar to those of calves from females fed the higher levels of feed intake. These results agree with those of Hironaka and Peters (1969) who found no difference in birth weight of calves due to level of feeding of the darn. Even with additional feed, it appeared that postpartum estrus was delayed slightly in females fed the 60 and 40% levels of feed intake. Dunn et al. (1969) found that the pre-ealving energy level exerted the greatest influence on the first postpartum estrns. The females in the present study seemed to need the additional feed for milk production and to gain back some of the weight lost at calving before they reestablished their estrual cycle. Calving difficulties and high calf mortality in the females with 140% intakes agreed with results by Bond and Wiltbank (1970) for beef heifers but are contrary to those by Holland (1961) with mature cows. Because these fat females had problems with their legs and calving, their reproductive span would be reduced. Bond and Wiltbank (1970) reported that heifers fed low energy and low protein weighed 33 and 21% less and produced 50 and 28% less milk, respectively, during the first lactation than heifers fed medium levels of energy and protein. Data from the present study show that females fed the 60, 60(100) and 40% levels of feed intake weighed 33% less and produced 19% less milk than females fed the 100% level. The higher milk production of females in the present study than in other studies was due to the increased feed offered during lactation. Lodge et al. (1972) found that dairy cows fed at a maintenance level 6 weeks before parturition followed by ad libitum feeding gained back weight lost and produced the same amount of milk as cows fed 1.8 X maintenance followed by ad libitum feeding. The females fed the 60 and 40% levels in the present study gained more weight during lactation than heifers fed the 100% level as a result of a lower maintenance requirement, with more energy available for weight gain and milk production. The fact that growth of calves tended to follow the same pattern as that for milk production suggests that growth was limited by the milk production of the female. Creep-feed intake appeared to be related to milk intake in the present study. The patterns of creep-feed intake were similar among all calves from all females; small amounts of creep feed were eaten until about 90 days postpartum and then creep-feed intake increased dramatically during the rest of the lactation period when milk yield was decreased. This finding would agree with that of Lusby et al. (1976) who reported that non-milk nutrient intake, non-milk nutrient digestibility, milk intake and calf weight (reflecting age) are interrelated. Based on data from all diet treatments, 1.3 and 1.5 kg (first and second lactation) of dry matter (milk and creep feed) were required to produce 1 kg of calf gain. Although creep-feed intake appeared to have positive effect on calf growth, indications are that the calves that ate more creep feed because of lower amount of milk available to them were less efficient in feed conver-

167

sion (1.3 vs 1.5 kg dry matter/kg gain for the 100 and 40% levels of feed intake calves, respectively) than calves that received an adequate amount of milk. Results in the present study show that for females fed the 60% level of feed intake, raising the level of feed (100% of recommended allowances for TDN) 45 days prepartum allowed these females to gain weight and appeared to decrease the postpartum interval to estrus but did not influence birth weight or milk yield. For females fed the 60 and 40% levels, increasing the feed available postpartum allowed these females to regain weight lost at calving; and although postpartum estrus was delayed slightly, none of the females became anestrus. ACKNOWLEDGMENTS

The authors gratefully acknowledge the technical assistance of Mr. B. Phillips and the secretarial assistance of Ms. M.A. Grier in the preparation of this manuscript.

REFERENCES Barr, A.J., Sail, J.P., Goodnight, J.H. and Helwig, J.T., 1976. A Users Guide to SAS 76. SAS Institute Inc., Raleigh, N.C., pp. 127--144. Blaxter, K.L., 1945. F o o d preferences and habits in dairy cows. Meeting o f the Institute for the Study of Animal Behavior, 1945, pp. 85---94. Bond, J. and Wiltbank, J.N., 1970. Effect of energy and protein on estrus, conception rate, growth and milk production o f beef females. J. Anita. Sci., 30: 438--444. Duncan, D.B., 1955. Multiple Range and Multiple F Tests. Biometrics, 11: 1--42. Dunn, T.G., Ingalls, J.E., Zimmerman, D.R. and Wiltbank, J.N., 1969. Reproductive performance of 2-year-old Hereford and Angus heifers as influenced by pre- and post-calving energy intake. J. Anita. Sci., 29: 719--726. Hironaka, R. and Peters, H.F., 1969. Energy requirements for wintering mature pregnant beef cows. Can. J. Anim. Sci., 49: 323--330. Holland, G.L., 1961. The Influence of Excessive Body Fatness on the .Performance of Beef Females. Thesis, Oklahoma State Univ. Stillwater, Okla., 116 pp., mimeographed. Lodge, G.A., Lessard, J.R. and Fisher, L.J., 1972. Influence of prepartum feed intake on the performance of cows fed ad libitum during lactation. J. Dairy Sci., 55: 685. Lusby, K.S., Stephens, D.F. and Totusek, R., 1976. Effects of milk intake on range and creep intake and digestibility in drylot. J. Anim. Sci., 43: 1066--1071. Morrison, F.B., 1956. Feeds and Feeding. Morrison Publ. Co., Ithaca, N.Y., 22nd edn,' 1207 pp. Reid, J.T., 1960. Effect of energy intake upon reproduction in farm animals. Suppl. J. Dairy Sci., 43: 103--122. Swanson, E.W., 1960. Effect o f rapid growth with fattening of dairy heifers on their lactational ability. J. Dairy Sci., 43: 377--387. Wiltbank, J.N., Bond, J. and Warwick, E.J., 1965. Influence of Total Feed and Protein Intake on Reproductive Performance of the Beef Female through Second Calving. U.S.D.A., ARS Tech. Bull. 1314. Winchester, C.F., Davis, R.E. and Hiner, R.L., 1967. Malnutrition of Young Cattle: Effect on Feed Utilization, Eventual Body Size, and Meat Quality. U.S.D.A., ARS Teeh. Bull. 1374.

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RESUME Bond, J. et Weinland, B.T., 1978. Influence du niveau d'alimentation sur la croissance, les performances de reproduction et la production laiti~re des femelles bovines de race ~ viande. Livest. Prod. Sci., 5:159--169 (en anglais). Cinquante neuf femelles Aberdeen Angus pesant environ 190 kg et §g~es de 7 mois, ont ~t~ r~parties au hasard entre 5 niveaux d'ingestion alimentaire: 140, 100, 80, 60 et 4 0 % des apportsde T D N recommand~s. Deux groupes ont ~t~ mis au niveau 60, Fun d'eux passant au niveau 100, 45 jours avant la raise bas. Toutes les femelles, ~ l'exception de celles au niveau 140, ont ~t~ raises au niveau 100 pendant les 150 jours suivant la raise bas puis sont revenues au niveau ant~rieur. Elles ont routes dt~ retirees de l'exp~rience au premier oestrus faisant suite au deuxi~me v~lage. Les femelles (9) alimentdes au niveau 40 ont arretd leurs cycles oestriens avant la date prevue pour leur raise ~ la reproduction. Elles ont dfi ~tre raises au niveau 100 jusqu'au r~tablissement de leurs cycles. L'accroissement du niveau d'ingestion 45 jours avant la raise bas a augment~ le gain de poids vif journalier des femelles (1,24 au lieu de 0,16 kg, P < 0,1) mais n'a pas eu d'influence sur le poids des veaux ~ la naissance et leur natalitY, la production laiti~re,le cofit journalier des veaux, l'intervalleentre le v~lage et le premier oestrus et la conception, ni sur le taux de gestation. Les deux groupes de femelles au r~gime 60 et celui au r~gime 40 ont eu un croR plus ~lev~ (0,28 au lieu de 0,02 kg, P < 0,01) pendant la lactation mais elles avaient un poids plus faible (290 au lieu de 423 kg, P < 0,1) et ont produit moins de lait (2,8 au lieu de 3,4 kg, P < 0,1) que celles des autres lots. Aucune d'elles n'a arr~t~ ses cycles apr~s le v~lage bien que le premier oestrus post partum et la conception aient ~t~ l~g~rement retard&. Les femelles aliment~es au niveau 140 sont devenues extr~mement grasses; leur production laiti~rea ~t~ semblable ~ celle des aulzes groupes mais la mortalitd de leurs veaux a ~t~ plus ~lev~e. L'accroissement du niveau d'ingestion post-partum a augment~ le croft et les performances de reproduction des femelles qui avaient ~t~ aliment~es ~ des niveaux inf~rieurs 100 mais l'accrolsement du niveau pendant 45 jours pr~c~dant le v~lage n'a pas eu d'avantage mesurable, pas plus que les niveaux sup~rieurs aux recommandations. KURZFASSUNG Bond, J. und Weinland, B.T., 1978. Einfluss des Fiitterungsniveaus auf Wachstum, Fortpflanzungsleistung und Milchproduktion bei weiblichen Fleischrindern. Livest. Prod. Sci., 5:159--169 (in Englisch). 59 weibliche Tiere der Rasse Aberdeen Angus wurden fiinf verschiedenen Niveaus der Futteraufnahme zugeteilt (140, 100, 80, 60 und 4 0 % der empfohlenen Ration fttrgesamtverdauliche N~hrstoffe). Zwei Gruppen weiblicher Tiere wurden d e m 6 0 % Niveau zugeteilt. Hiervon wurde eine Gruppe 45 Tage vor d e m Abkalben auf das 1 0 0 % Niveau angehoben. Alle weiblichen Tiere ausser denen auf d e m 1 4 0 % Niveau wurden bei der Abkalbung auf das 1 0 0 % Niveau bis 150 Tage post partum angehoben und dann auf die FiitterungshShen vor der Abkalbung zuriickgenommen. Die Tiere wurden bei ihrem ersten Ustrus nach der zweiten Abkalbung aus d e m Versuch genommen. Die neun weiblichen Tiere, welchen ein Fiitterungsniveau yon 4 0 % verabreicht wurde, h~rten vor ihrer ersten Belegung auf, briinstig zu werden. Das Niveau musste auf 100% angehoben werden, bis sich der normale Brunstzyklus wieder einstellte. Das Anheben des Fiitterungsniveaus 45 Tage vor dem Abkalben hatte einen Anstieg des t~iglichen Zuwachses der Tiere zufolge (1,24 statt 0.16 kg, P < 0.01), aber es beein-

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flusste weder das Geburtsgewicht und die Mortalit~it der Kklber, noch die Milchproduktion, die durchschnittliche Gewichtszunahme der ICdlber pro Tag, den ersten post partum Ostrus, die Konzeption, und die Befruchtungsrate wesentlich. Die beiden Gruppen auf dem 60% Niveau und diejenige auf dem 40% Niveau hatten eine h~here Gewichtszunahme (0.28 statt 0.02 kg pro Tag, P < 0.01) w~hrend der Laktation als die anderen Gruppen, jedoch hatten sie ein geringeres Gewicht (290 statt 423 kg, P < 0.01) und produzierten weniger Milch (2.8 start 3.4 kg, P < 0.01 ). Obwohl post partum {3strus und Konzeption sich leicht verz~gerten, hat keine den Zyklus verfehlt. Die weiblichen Tiere auf dem 140% Niveau sind ausserordentlich fett geworden; die Milchproduktion war vergleichbar, abet die Sterblichkeit der K~lber war hier am h~chsten. Das Anheben des Fiitterungsniveaus post partum hat die Gewichtszunahme und die Fortpflanzungsleistung der mit der empfohlenen Ration gefiitterten Tiere erh~ht. Jedoch hatte weder erh6hte Futteraufnahme 45 Tage vor dem Abkalben, noch eine Uberschreitung der empfohlenen Ration einen messbaren Vorteil.