Effects of accelerated growth during rearing on reproduction and lactation in ewes lambing at 13 to 15 months of age

THERIOGENOLOGY

EFFECTS

OF ACCELERATED

GROWTH

DURING

REARING

ON REPRODUCTION

AND

LACTATION IN EWES LAMBING AT 13 TO 15 MONTHS OF AGEa

S. H. Umbergerb, L. Goode, E. V. Caruolo, R. W. Harvey, J. H. Britt, and A. C. Linnerud' Department of Animal Science, Department of Statistics' North Carolina State University, Raleigh, NC 27695-7621 Received for publication: Septemhr 14, 1984 Accepted: December 7, 1984

ABSTRACT Three trials were conducted using ewe lambs to determine the effects of accelerated growth during rearing on reproduction and lactation. Data Early weaned ewe lambs were randomly assigned were obtained on 113 ewes. to the following prebreeding treatments: (1) thin (T, moderate gain) and at 13 to 15 (2) fat (F, accelerated gain). They were bred to lamb months of age. After breeding, one half of the ewea on the T and F treatments were switched to the other treatment so that postbreeding treatments were TT, TF, FF and FT. Prebreeding treatment did not affect conception rate (T, 95$; F, 96$), but lambing rates were 43, 28 and 27% higher (P
ewe lamb, growth, fattening, reproduction, lactation

aPaper No. 6726 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named nor criticism of similar ones not mentioned. bPresent address: Department of AnimalScience,Virginia Institute and State University, Blacksburg, VA 24061

MARCH 1985 VOL. 23 NO. 3

Polytechnic

555

THERIOGENOLOGY INTRODUCTION Numerous studies have shown that dairy heifers fed for accelerated growth during rearing produced less milk than those fed for moderate growth (l-6). In beef cattle, a negative relationship has been reported between the weaning weight of replacement heifers and their subsequent milk production (7-g). Creep feeding replacement beef heifers has also impaired milk production (10, 11). Similar data for sheep are limited and inconclusive (12, 13). The possibility that rapid growth and fattening reduces milk production in replacement ewe lambs has serious implications for the sheep industry since the present practice of selecting replacement females from those with the most rapid gains would be antagonistic to milk production. The primary objective of this study was to determine the effects of accelerated growth from early weaning to parturition on reproduction, milk production and mammary gland development in ewe lambs. Since it has been suggested that ewes suckling twins gave more milk during early lactation as a result of higher thyroid activity (14), an ancillary objective was to examine the relationship between thyroid activity and milk production.

MATERIALS AND METHODS Trial 1. Trial 1 was conducted at the Upper Mountain Research Station, Laurel Springs, NC. Thirty-two straightbred Suffolk and crossbred (3/4 Suffolk, l/4 Dorset, l/4 Blackbelly) ewe lambs were early weaned in April at approximately 20 kg. They were grouped according to breed and randomly assigned to the following prebreeding treatments: (1) thin (T) fed for moderate gain (100 g/day, weaning to breeding), and (2) fat (F), fed for accelerated growth (200 g/day, weaning to breeding). After weaning, ewes were confined in dry-lot and fed 1.13 kg of alfalfa hay/head daily (IFN I-00-058). Ground corn (IFN 4-02-915) was fed ad libitum to F ewes whereas T ewes were fed 0.23 kg/head daily. After 30 days, ewes were allowed free access to pasture consisting of white clover, orchardgrass and Kentucky bluegrass. The F ewes continued to receive corn ad libitum but the T ewes were not supplemented. These feeding regimes were maintained until after the ewes were bred. Salt and minerals were fed ad libitum. From November 1 to December 8 ewes were checked twice daily for estrus with a vasectomized ram. They were randomly mated to Suffolk rams and were rebred if they returned to estrus. At the end of the breeding season, one half of the T and F ewes were randomly assigned to the alternate treatment so that postbreeding treatments were: TT, TF, FF and FT. During gestation all ewes were fed 1.81 kg of corn silage (IFN 2-02804) and 0.91 kg of alfalfa hay daily. In addition, ewes assigned to the FF and TF treatments were supplemented with 0.45 kg of ground corn daily Ewes assigned to the TT and FT treatments were also until lambing. supplemented with 0.45 kg corn during the last month of gestation.

556

MARCH

1985 VOL. 23 NO. 3

THERIOGENOLOGY

The daily lactation diet for all ewes was 3.18 kg of corn silage, 0.91 kg of alfalfa hay and 0.45 kg of an 80-20 mixture of corn and soybean meal (IFN 5-04-605). Ewe weights and shoulder heights were obtained at the beginning of the breeding season. Weight to height ratios were used as a measure of Conception rate and Litter size were obtained at body condition. lambing. Estimates of milk production were obtained at 20, 40, and 60 days of lactation, (+ 5 days). The weigh-suckle-weigh lamb nursing technique was used to estymate 4-hr milk yield at 20 and 40 days. The 60 day milk yield, and all subsequent yields, were obtained with a portable milking machine (specifications of 36 kPa of vacuum, 55:45 milk to rest ratio, 55 pulsations/min). Oxytocin (10 IU) was given i.v. immediately before each All 4-hr milk yields were converted to a 24-hr basis and milking. samples were analyzed for fat and protein with an infrared milk analyzer using performance specifications set forth by Biggs (15). Records were obtained on 29 of the 32 ewes and the these data were analyzed by least squares analysis of variance according to the Statistical Analysis System (16). Milk yields were adjusted for twin lambs by fitting general linear models for type of birth and solving for the solutions. This variation was removed from the data through use of the adjustment factors. The main effects in the milk yield model were treatement, breed and treatment X breed interaction. Separate analyses were carried out for the prebreeding and postbreeding treatments and the partial correlation coefficients of milk yield with weight to height rations were adjusted for breed and number of lambs. Trial 2. Trial 2 was conducted at the Upper Mountain Research Station during the second year of the study. Seventy-two grade Suffolk and grade Hampshire ewe lambs were weaned in late March at approximately They were stratified by breed and assigned to the T and F 16 kg. prebreeding treatments. Basic feeding, management, breeding, data collection and statistical analysis were as described in trial 1. Data were obtained on 46 ewes. Although sixteen ewes died of pregnancy toxemia and other causes and ten ewes did not conceive, the failure to breed and the death losses were not associated with treatments. Eight ewes, two from each postbreeding treatment, were euthanised at 20 days within three minutes after milking. Mammary glands were removed and separated through the medialsuspensary ligament. One half of the gland was infused with a 5% formalin solution and sliced sagitally at 4 mm thickness. Representative samples of tissue were removed from these slices, processed in a tissue processor, embedded in parafin, sectioned at 8 urn, placed on glass slides, and stained with hematoxylin and Rosin (17). Alveoli from three separate fields, each 4.23 mm2, were counted at 10x magnification and averaged for each gland.

MARCH

1985 VOL. 23 NO. 3

557

THERIOGENOLOGY Trial 3. Trial 3 was conducted at the North Carolina State University Research Unit at Raleigh, NC. Forty straightbred Suffolk, Dorset and Suffolk x Dorset ewe lambs were weaned in March at approximately 13.6 kg and assigned to T and F treatments as in trials 1 and 2. Feeding, management, and breeding were as previously described except that ewes were bred to Dorset rams. Mammary gland data were obtained as in trial 2. Blood samples for thyroxine (T4)analysis were collected from the jugular vein prior to breeding in August and November and at each milk collection period. These samples were refrigerated for 24 hr and allowed to clot. They were then centrifuged and the serum was removed and stored at -4c until assayed. Serum T4 concentrations were determined by a double antibody radioimmunoassay (18). Assay sensitivity was 2.5 ng of Crossreactivity of the T4 anti,body with T3, at 50% binding was 2.5%. T4' Intraassay and interassay coefficients of variation were 3.3 and 8.1$, respectively. No twins were raised by TT ewes in this trial. Therefore, least squares analysis of variance was performed on data for ewes suckling single lambs only. RESULTS AND DISCUSSION Since trials varied as to year, location and environment, separate analyses were carried out for each trial. Also, adjustments for type of rearing could not be made in a combined analysis because none of the TT ewes in trial 3 suckled twin lambs. Data on ewe performance from weaning to Prebreeding performance. breeding are summarized in Table 1. In each trial, ewes on the F prebreeding treatment were heavier (P
Least squares means and standard errors for ewe weight, shoulder height and weight to height ratios at the start of the breeding season, trials 1, 2 and 3.

_~~~~~__~~~~ Trial

Trt.

l_l

--___-_

No.

Weight kg

Shoulder----Weight to height ratio height cm kg/cm

1

T F

15 14

44.2 + 1.39 64.2 -+ 2.44

60.9 + 0.72 64.5 5 - 1.10

0.725 +0.03 0.993 zo.03

2

T F

25 21

45.6 + 1.29 57.6 5 - 2.37

60.4 + 0.71 63.5 5 - 1.05

0.755 0.02 0.905 LO.03

3

T F

19 18

42.8 + 1.64 63.8 5 - 2.40

62.4 + 0.85 65.1 T - 0.93

0.686 +0.03 0.948 zO.04

THERIOGENOLOGY ratios, the higher ratios for F result of greater fat deposition. and F ewes were 131, 217; 112, there respectively. At breeding, shoulder height, and weight to ration (TT treatment) and those These traits were also similar treatments. Reproduction. in table 2. Table

Means for Treatment

Least square 1, 2 and 3

2.

ewes were considered to be primarily the Gains from weaning to breeding for T 173; 113, 204 g/day in trials 1, 2 and 3 were no differences (P>O.O5) in weight, height ratio of ewes remaining on the T switched to the F ration (TF treatment). for ewes assigned to the FF and FT

conception differences

means

for

rate in conception

Treatments Item

No.

TT

No.

TF

and lambing conception rate

and

rate are presented rate were not litter

size,

trials

-__--__-__-___---.-_ No.

FF

No.

FT

7 11 8

100 31 100

Conception rate, 7 Trial Trial Trial

1 2 3

Number of Trial Trial Trial

aStandard

1 2 3

8 13 10

100 84 100

7 12

100

9

85 100

1 .25+0.26a 1.07yO.24 l.COTO -

7 12 9

1.14+0.11 1.08-/.o8 1.11+0.11 -

7 10 10

100 80 100

lambs 8 13 10

7 10 10

1.71+0.31 1.20~0.13 1.350.16

7 11 8

1 .57+0.23 1.24+0.14 1.38TO.18 -

error

significant in any of the trials. However, litter size was higher (P
MARCH

1985VOL.23 NO.3

559

THERIOGENOLOCY The results of this study show that ewe lambs can be successfuily bred in the Southeast at8 to 10 months of age, a practice which should increase lifetime productivity and economic return. Futhermore, if increases in lambing rate, such as those obtained in this study, can be obtained consistently, an accelerated growing period prior to breeding should be practical for commerical lamb production. Milk production, alveoli numbers and milk composition. Least squares means for milk production (Table 3) were similar (P>O.O5) for ewes Table

3.

Least squares means and standard errors for 24-hour production by periods, trials 1, 2 and 3.

milk

----_---___-----___------__------_---_-----~----24-hr milk yield --l_-(g)

--.__Trial 1

Trt. TT TF FF FT Tb F

2

3c

___-----_I

No.~ 8 7 7 7

Period 1

Period 2

2305 2250 I695 1708

1140 1414 1180 1221

I5 14

2305+257 1685z308

TT TF FF FT

13 12 10 11

1641

T F

25 21

1720~ 77 15582102

TT TF FF FT

10 9 7 5

1878 1806 1720 1597

T F

19 I2

1866+62+ 1672+78

_-----

Period 3 917 757 675 712

1287+114 1183~137

853+ 88 6807106 -

1542 1749 I378 1477

1178 1487 1027 1149

1889

1689 1574

1638+ 83 1435303

1355Lll7 1125_el45

1658 1689 1283 1263

1351 1220 1031 873

1695: 85++ 1313'106

--_----

1282: 81* 979+100 --_-

aNo. of ewes for first milking, numbers varied at subsequent milkings b Original prebreeding treatment groups 'Analysis performed on data for ewes with single lambs only +p
560

MARCH

1985 VOL. 23 NO. 3

THERIOGENOLOGY switched to their reciprocal treatment after breeding compared to those left on the original T and F treatments. Therefore, means for the prebreeding T and F treatments were considered to be the best estimates Milk yields were consistently higher for ewes on the of milk production. prebreeding T treatment compared to those on the F treatment. Treatment differences were not significant in trials 1 and 2. However, in trial 3 differences in daily milk production favoring T ewes were 193 g at 20, 40 and (P
F,

1373;

T,

1614,

F,

1321.

Similar depressions of milk yields have been reported in dairy heifers subjected to accelerated growth and fattening (l-6). However, In beef cattle, a negative other studies contradict these data (22, 23). relationship between the weaning weight of replacement heifers and their subsequent milk production has been reported (7-q). Creep feeding has also been shown to reduce milk production in replacement heifers (IO, The results of the present study show that accelerated growth and 11). fattening during rearing also depress milk production in ewe lambs. In trials 2 and 3, T ewes had more alveoli than F ewes. Overall least squares means and standard errors were T, 402+83 and F, 334+88 alveoli per 4.23 mm2 area. While this difference was not significant,-it is consistent with the lower milk production in F ewes. These data also agree with those of Sejrsen et al. (24) who found less ductular tissue in the mammary glands of prepubertal heifers raised on a high plane of nutrition. These authors also reported that there was no effect on the mammary glands of postpubertal heifers on a high plane of nutrition. Thus, it appears that the negative effect on mammary development occurred before or around puberty. Results of the present study are similar since switching ewes to the alternate treatment after breeding did not affect number of alveoli and milk production. Overall milk fat and protein percentages for the combined T and F treatments were 8.3, 5.7; 7.0, 5.3; 7.0, 4.7 in trials 1, 2 and 3, respectively, and were not affected by treatment. Correlations between milk production and weight to height ratios were negative in trials 1 and 3, but were positive in trial 2. A possible explanation is that there is a level of performance above which mammary development or function is impaired. Both daily gain and condition, measured by weight to height ratio, were lower in trial 2 than in trials 1 and 3. Amir et al. (3) found that gains above 800 g/day increased fat deposition and depressed milk yield in heifers. This is an important point, and information is needed to determine whether or not ewe lambs can be reared at some level of performance which permits adequate reproduction without decreasing milk production. Serum T levels. Least squares means and standard errors for serum T4 levels ram trial 3 are presented in Table 4. -8-----Thyroxine levels were higher (P
MARCH 1985 VOL. 23 NO. 3

561

Table 4.

Least squares means and standard errors for serum thyroxine concentrations (ng/ml), trial 3 -____I--

.-------II_---

Treatments Period

No.

T

F

NO.

Prebreeding August November

19 19

56.7+2.7 51.922.9

12 12

69.8~3.4 52.1~3.6

Lactation 20 days 40 days 60 days

IO 8 8

75*1+4.0 73.2T5.0 62.4z5.3

7 5 5

72.8+4.8 59.7T6.4 68.Pz7.5

No.

9 7 7

TF

70.6+4.3 70.4z5.4 59.1~5.6

NO.

5 3 3

FT

71.625.7 59.6+8.2 61.3z8.6

~FERENCES 1.

Hasson, A. Influence of rearing intensity on body development and milk production. Proc. Brit. Sot. Anim. Prod. pp. 51-55 (1956).

2.

Swanson, E. W. Effect of rapid growth with fattening of dairy heifers on their lactation ability. J. Dairy Sci. 43:377-387 (1960).

3.

Influence of growth rate on Amir, S., Kali, J. and Volcani, R. 1n:Growth and reproduction and lactation in dairy cattle. Development of Mammals, edited by G. A. Lodge and G. E-Lamming. Butterworths, London. pp. 234-257 (1968).

4.

Rearing intensity and milk production Plum, M. and Harris, L. Holstein heifers. J. Anim. Sci. -27:1128 (Abstr.) (1968).

5.

Sejrsen, K. Mammary development and milk yield in relation to growth rate in dairy and dual-purpose heifers. Acta. Agr. Scand.8:41-46 (1978).

6.

The effects of rapid rearing and early Little, W. and Kay, R. M. calving on the subsequent performance of dairy heifers. Anim. Prod. -2g:131-142 (1979).

7.

Christian, L. L., Hauser, R. E. and Chapman, A. B. Association of preweaning and postweaning traits in cattle. J. Anim. Sci.a:652659 (1965).

8.

Mangus, W. L. and Brinks, J. S. Relationships between direct and maternal effects on growth in Herefords: I. Environmental factors during preweaning. J. Anim. Sci. -32:17-25 (1971).

9.

Koch, R. M. The role of maternal effects in animal breeding:VI. Maternal effects in beef cattle. J. Anim. Sci. -35:1316-1323 (1972).

562

MARCH 1985 VOL. 23 NO. 3

of

THERIOGENOLOCY 10.

Relationship between preweaning Holloway, J. W. and Totusek, R. nutritional management and subsequent performance of Angus and Hereford females through three calf crops. 3. Anim. Sci. -37:807-812 (1973).

11.

Martin, T.G., Lemenager, R. P., Srinivasan, G. and Alenda, R. Creep feed as a factor influencing performance of cows and calves. J. Anim. Sci. -53:33-39 (1981).

12.

Owen, their Comb.

J. B. A study of the lactation and growth of hill sheep in native environment and under lowland conditions. J. Agr. Sci. -48:397-411

(1957).

13.

Gould, M. B. and Whiteman, J. V. Relationship between preweaning growth of female lambs and the growth of their offspring. J. Anim. Sci. -40:585-589 (1975).

14.

Singh, 0. N., Henneman, H. A. and Reineke, E. P. The relationship of thyroid activity to lactation, growth and sex in sheep. J. Anim. Sci. -15:625-630 (1956).

15.

Biggs, D. A. Performance specifications for infrared milk analysis. J. Assoc. Official Anal. Chem. 63:1211-1214 (1979).

16.

Barr, A. J., Goodnight, J. H., Sail, J. P., Blair, W. H. and D. M. Chilko. Statistical Analysis System User's Guide. SAS Institute, Inc., Raleigh, NC pp. 244-263 (1979).

17.

Luna, L. G. Mayer's hematoxylin and eosin staining procedure. In Manual of Histologic Staining Methods of the Armed Forces Institute of Pathology (3rd Ed.) McGraw-Hill Book Co., New York. 1968. pp. 3839.

18.

for 3, 5, 3-Triiodothyronine May. J. D. A radioimmunoassay chicken serum. Poul. Sci. 57:1740-1745 (1978).

19.

Klosterman, E. W., Sanford, L. G. and Parker, C. P. Effect of cow size and condition and ration protein content upon maintenance requirements of mature cows. J. Anim. Sci. -27:242-246 (1958).

20.

El-sheikh, S. A., Hulet, C. V., Pope, A. L. and Casida, L. D. The effect of level of feeding on the reproducti.ve capacity of the ewe. J. Anim. Sci. -14:919-929 (1955).

21.

Foote, W. C., Pope, A. L., Chapman, A. B. and Casida, L. E. Reproduction in yearling ewes as affected by breed and sequence of feeding levels. I. Effect on ovulation rate and embryo survival. J. Anim. Sci.G:453-462 (1959).

22.

Reid, J. T., Loosli, J. K., Trimberger, G. W., Turk, K. L., Asdell, S. A. and Smith, S. E. Causes and prevention of reproductive failures in dairy cattle. IV. Effect of plane of nutrition during early life on growth, reproduction, production, health and longevity of Holstein cows. Cornell Bull. 987, Cornell University, Ithaca, N. Y. pp. 5-31 (1964).

MARCH

1985 VOL. 23 NO. 3

in

563

THERIOGENOLOGY

23.

Gardner, R. W. Scnun, J. D., and Vargres, L. G. Accelertaed growth and early breeding of Holstein heifers. J. Dairy Sci. -60:1941-1948 (1977).

24.

Sejrsen, K., Huber, J. T., Tucker, H. A. and Akers, R. M. Influence of nutrition on mammary development in pre-and postpuberal heifer. J. Dairy Sci. -65:793-800 (1982).

564

MARCH

1985 VOL. 23 NO. 3