The effects of sire breed on calving difficulty and weaning weight in a beef breeding herd.

Abstract

THE EFFECTS OF SIRE BREED ON CALVING DIFFICULTY AND WEANING WEIGHT IN A BEEF BREEDING HERD J.H.L. MORGAN*; G.R. SAUL* and D.W. McKEOWN* Summary Hereford (H), Friesian (F), Charolais (C) and Brahman (B) sires were mated to H and F cows aged from one year in 1970 to four years in C and B sires increased gestation length, birth weight, calving 1973. Differences difficulty and calf mortality relative to H and F sires. in the weaning weight of the progeny of the different sires varied between years and between dam breeds but tended to increase with cow age. In H cows, the mean advantages in weaning weight of F, C and B sires over H sires were 9, 8 and 1% while in F cows, the mean advantages of H, Mean heterosis in HF C and B sires over F sires were 1, 7 and -4%. crosses was 1% in birth weight and 4% in weaning weight. I. INTRODUCTION Differences between breeds of cattle represent a valuable source of genetic variation which beef producers can exploit either by changing from one breed to another or by crossbreeding. The intermediate types produced by crossing are not only representative of the breed mix but ' also tend, on average, to be superior to straightbreds in performance, due to heterosis or hybrid vigour (reviewed Piper and Latter 1974). There is a need, however, for more information on the productive characteristics of the breeds available, and on the degree of heterosis expressed by crossbreds, when assessed under the conditions of production' in southern Australia. This paper reports the gestation lengths, birth weights, calving difficulty, perinatal mortality and weaning weights of the progeny of Hereford (H), Friesian (F), Charolais (C) and Brahman (B) sires mated to H and F cows when grazed together in western Victoria. II. MATERIALS AND METHODS H and F cows, aged one year in 1970, two years in 1971, three years in 1972 and four years in 1973, were inseminated during August and September with semen from H, F, C and B bulls. The number of bulls Cows not rearused per breed varied from 4 to 25 in different years. ing calves were retained and remated. The management of the cattle and the conditions of the experiment were described by Morgan, Cummins and Saul (1974). The mean pre-calving live weights of the cows were 371, 451, 495 and 518 kg in the years 1971 to 1974 respectively. The cows were treated with broad spectrum anthelmintic thrice yearly. During calving in May, June and July, or three times per day and new born calves vided if calving was prolonged beyond three of the placental membranes. The,cows were 109 the cows were inspected two weighed. Assistance was prohours after the appearance not inspected nor assisted * Department of Agriculture, Pastoral Research Station, Hamilton Vic. at night (i.e. from 6 p.m. till 8 a.m.). The following scoring system, based on that of Sagabiel et al. (1969) was used as an index of calving difficulty - no assistance (1); pulled, not difficult (3); pulled, difficult (5); embryotomy or caesarian (7); cow dead or destroyed (9). Even scores from 2 to 10 represented corresponding situations in which the addition of one score was given for the death of the calf either at birth or within three days. All calves were weaned simultaneously when their mean age was about eight months and their weights at weaning were adjusted to a constant age of 240 days. Data for gestation length, calving difficulty score, birth weight and weaning weight were analysed within years using a program designed to conduct least square analysis with unequal subclass numbers. Calving difficulty score was also analysed using pooled data for the four years. Calf mortality was analysed by chi square using accumulated data for the four years and pooling C with B sires and H with F sires. III. RESULTS TABLE 1 110 sired 1). also than The gestation periods of B sired calves were longer than those of C calves which were longer than those of H and F sired calves (Table C sired calves were the heaviest at birth; B sired calves were heavier than H and F sired calves. F sired calves were heavier H sired calves in 1971, 1973 and 1974 but were lighter in 1972. Sire breed differences in calving difficulty score attained significance only when the results for the four years were pooled; mean calving difficulty scores for H, F, C and B sires were 1.27, 1.39, 1.63 and 1.55, respectively (P < 0.05). Over the four years, mortality at birth and up to three days of age was higher in C and B sired calves (11.1%) than in H and F sired calves (4.5%) (P < 0.01). Sire breed did not significantly affect weaning weight in 1971; in the three subsequent years, C and F sired calves ranked heavier than B sired calves but the relative ranking of H sired calves varied, depending on year and breed of dam. In 1974, there was a significant (P < 0.05) interaction between the effects of sire breed and dam breed. Percentage heterosis in crosses of H and F breeds in 1971 to 1974 were 0.2, 1.3, 2.1 and 1.4 in birth weight and -0.3, 3.2, 4.7 and 7.8 in weaning weight. IV. DISCUSSION Long gestation periods and high birth weights for C sired calves have been reported elsewhere (Everitt and Jury 1972; Anon 1975). Of interest is the finding that the progeny of B sires and Bos taurus dams PP have even longer gestation periods than C sired calves. Other reports of high birth weights and a high incidence of calving difficulty and calf mortality in this cross (Ellis, Cartwright and Kruse 1965; Anon 1975) support the results of this study. C sired calves were little or no heavier than H sired calves at weaning in 1971 and 1972 but were appreciably heavier in 1973 and 1974. Such variation may have been due to the increasing age of the cows, or alternatively, due to the effect of seasonal conditions or to chance. In H cows in this experiment, no weaning weight advantage was found for C sires over F sires while Haycock and Stewart (1973) reported a 3% advantage for C sires over F sires when mated to Angus cross Shorthorn cows. To what extent the weaning weight advantage of C over F sired calves when bred from F cows in this experiment was due to a breed effect or due to heterosis cannot be determined. The lack of any advantage in weaning weight for B sired calves in a temperate climate supports the results of Deland, Jakes and Giles (1974) and of Kellaway and Colditz (1975) but contrasts with the preliminary findings of Barlow at Grafton N.S.W. (pers. comm.) and Anon (1975). The relative growth performance to weaning of C and B sired calves is less than indicated by the age adjusted weaning weights if allowance is made for (i) their advantage of heterosis relative to straightbred H and F calves (ii) their heavier birth weights and (iii) their longer gestation periods. Mean values of 1.3 and 3.9% heterosis for birth weight and weaning weight, respectively, in crosses of H and F breeds are of similar magnitude to those reported in Angus-Friesian crosses by Hight, Everitt The sire breed x dam breed interaction in 1974 can be and Jury (1973). attributed primarily to the effects of heterosis in crosses of H and F breeds. 111 . It is concluded that C sires will produce heavier calves at weaning than H sires, at least when mated to cows older than three years of age, but a similar result could probably be achieved in H cows by using F -The use of either C or B sires on Bos taurus dams will increase sires. Furthermore, the progeny of B calving difficulty and calf mortality. sires appear to have no growth advantage to weaning over the progeny of H sires under 'the climatic and pastoral conditions of the far south of Australia. In the breeds studied, breed of sire had on weaning weight than did breed of dam; this of the dam where beef is produced from breeding role of the breeds and crosses studied will be relative performance of the female progeny, as evaluated. v. ACKNOWLEDGMENTS a muchsmaller influence highlights the importance The potential herds. further assessed when the beef dams, has been The contributions of all those who assisted in this project are gratefully acknowledged; in particular L.J. Cummins for veterinary attention, A.J. Clark for recording of data, R. Jardine for biometrical services and Victorian Artificial Breeders Co-op. for semen supplies. Financial support was provided, in part, by the Australian Meat Research Cormnittee. VI. REFERENCES ANON. (1975). Progress Report No.2; Germ Plasm Evaluation Program, U.S. Meat Animal Research Center, Nebraska. DELAND, M.P., JAKES, J.E., and GILES, W.G. (1974). Proceedings of the Australian Society of Animal Production 10:17. ELLIS, G.F. Jr., CARTWRIGHT, T.C., and KRUSE,T.E. (1965). Journal of Animal Science 24:93. EVERITT, G.E., and JEY, K.E. (1972). New Zealand Journal of Agricultural Research 15:228. HAYCOCK, R.E., and STEWART,D.A. (1973). Animal Production Z 17:267. HIGHT, G.K., EVERITT, G.C., and JURY, K.E. (1973). New Zealand Journal of Agricultural Research 16:519. KELLAWAY, R.C., and COLDITZ, P.J. (1975). Australian Journal of Agricultural Research 26:6151 MORGAN, J.H.L., CUMMINS, L.J., and SAUL, G.R. (1974). Proceedings of the Australian Society of Animal Production 2:21. PIPER, L.R., and LATTER, B.D.H. (1974). Proceedings of the Australian Society of Animal Production 10:8. SAGABIEL, JOE A., K&XUSE, G.F., SZIT, BOB, LANGFORD, I,., COMFORT, J.E., DYER, A.J., and LASLEY, JOHN F. (1969). Journal of Animal Science Z 29t245. 112