Breed of sire influence on weight for age and age at sale of commercial steers.

Abstract

BREED OF SIRE INFLUENCE ON WEIGHT FOR AGE AND AGE AT SALE OF COMMERCIAL STEERS P.L. CORLIS*, G.W. SEIFERT** and T.H. RUDDER*** SUMMARY Live weights of tropically adapted steers born during two consecutive calvings were analysed to measure the effect of breed of sire and breed of dam on weight per day of age at 6, 12, 16, 23 and 29 months of age at sale, and age of sale. These steers were sired by Brahman, Hereford, Santa Gertrudis, Droughtmaster, and Belmont Red Bulls from low Brahman (about l/2 Brahman) and high Brahman (about 3/4 Brahman) cows. There was no consistent breed of sire effects, but year by breed of sire interactions were present for weight per day of age at 6 and 12 months of sale, and for age at sale (P < 0.01). There were no breed of dam, or breed of dam by breed of sire effects on weight per day of age of the steer progeny. This may be explained by previous selection practices in the breeding herd. Correlations of weight per day of age at sale, and age at sale (38 months) with 23 and 29 months weight per day of age indicate that either of the two later ages may be a reliable indicator of the commercial value of steers. INTRODUCTION The concept of using Bos indicus genotypes to breed tropically adapted cattle is widely accepted and adopted in central and northern Queensland (Anon. 1978). Research results that support this breeding policy are widely documented. Most tropically adapted herds are based on Brahman and Hereford or Shorthorn crosses. The choice of breed of sire to join with Brahman-British crossbreeds is debated widely in the beef industry. Lapworth et al. (1976) reported weight per day of age at 7, 23 and 29 months of steers by Brahman, Hereford and Santa Gertrudis bulls from approximately l/2 Brahman cows, approximately 3/4 Brahman cows and approximately l/2 Brahman cows respectively. The residual component of these cows was Hereford. The major trend in these data was a year by breed of sire interaction with little evidence of a consistent breed of sire effect over four calf groups. Data from steers produced by joinings of Brahman, Santa Gertrudis, Droughtmaster and Belmont Red with approximately l/2 Brahman cows; and Hereford bulls with approximately 3/4 Brahman cows showed a strong year by breed of sire interaction on weight per day of age at 5, 12 and 16 months (Rudder et al. 1976). There was no consistent breed of sire effect over the two calf drops. * QDPI, Beef Cattle Husbandry Branch, Biloela, Qld 4715. ** CSIRO, Division of Animal Production, Rockhampton, Qld 4700. *** QDPI, Beef Cattle Husbandry Branch, Rockhampton, Qld 4700. 369 Animal Production in Australia In both o const.ants for w This trend,comb may b e of littl herds . This pa sale, and age a uatio n of those f the previou eight per day ined with the e commercial per reports w t sale. With presented by s reports the magnitude of the breed of sire * of age decreased as the age of the steers increased. interactions with year, implied that breed of sire significance in many tropically adapted breeding eight per day at 6, 12, 16, 23 and 29 months of age, minor varation, the data presented are a continRudder - al. (1976).. et MATERIALS AND METHODS steers bred and grown at 'Mount Eugene', management programmes, and environment have et - a1.(1976). The data were collected from Jambin, Queensland. Breeding and been described previously Rudder Liveweight data from steers sired by Brahman,Hereford, Santa Gertrudis, Droughtmaster and Belmont Red bulls from 3/4 Brahmancontent, and l/2 Braham content cows were recorded from weaning to sale. Steers used in this observation were from two consecutive calvings and had a mean day of birth of September 27 2 35 days standard deviation. Liveweight data were analysed by the least squares method (Harvey 1960) using a model that included years, dam age, dam breed, sire breed, all first order interactions, and the partial regressions of weight per day of age on dam weight at weaning, and day of birth. This approach was taken to isolate environmental effects from dam breed and breed of sire effects. Time of sale was determined by live weight, seasonal conditions, and visual assessment of a suitable degree of fatness to present a product to meet apparent requirements. These cattle were sold at average live weight of 560 kgbecause the most reliable market in this region is for steers about this weight to satisfy export markets. RESULTS AND DISCUSSION Effects of breed of sire and breed of dam are given in Table 1. TABLE 1 Least squares means for weight per day of age at 6, 12, 16, 23 and 29 months at sale, and age at sale. 370 Animal Production in Australia There were no breed of sire effect over the two years' data, but year by breed of sire interactions were significant at 6 months (P<O.O05) and 12 months (P< O.Ol>, at sale (P<O.Ol), and age at sale (P< 0.005). Breed of dam, and breed of dam by breed of sire interaction had no effect on weight per day of age at any of the observations. The absence of breed of dam by breed of sire interactions'on weight per day of steer progeny may be a function of selection. In this herd, maiden heifers had to grow sufficiently to conceive and calve at approximately two years of age, and lactating cows had to conceive and calve the following year to remain in the herd. It is logical to suggest that only those cows having adequate environmental adaptation, remained in the herd. Therefore, it is possible that there was little genetic variation between the approximately 3/4 Brahmanand the approximately l/2 Brahman cows that produced these steers. The year by breed of sire interactions are probably a reflection of variation between genotypes in their ability to cope with annual variation in environmental factors. The interactions also demonstrate the need to repeat this type of work over years and at various ages of the steers. Year and breed of sire effects at sale are shown in Table 2, and illustrate how one year's data could be misleading. TABLE 2 Lea&squares means for year and breed of sire effects on weight per day of age at sale (kg/d) and age at sale (d) Simple correlations between weight per day of age at sale and age at sale with weight per day of age at 23 and 29 months were highly significant (P cO.01). The correlation coefficients ranged from 0.582 to 0.775 and the values associated with age at sale were negative. Weight per day of age at sale was strongly correlated with age at sale (P< O.Ol;r = -0.842) indicating there was no conflict between apparent market suitability and high weight per day of age. Correlations between the two parameters at sale and weight per day of age at the three earlier ages were significant (P< 0.01) but were generally too low to have reliable predictive value. These data indicate that weight per day of age through to sale, and age at sale will not vary markedly over a relatively wide range of Bos indicus component. It follows that choice of breed of sire to use over Brahman Hereford cows should be based on traits other than weight per day of age. ACKNOWLEDGEMENTS Support freely given by the Maynard family is gratefully acknowledged. Assistance given by other QDPI and CSIRO officers in collecting data has contributed to this work. Processing of these data was undertaken by Heather Animal production in Australia Burrow and Ken Bean and without their help, preparation of this paper would have been difficult. REFERENCES ANON. (1978). Queensland Meat Cattle Breeds, of Statistics, Brisbane 1978. HARVEY, W.R. (1960). United States Department Research Science, No. A.R.S. 20-8. LAPWORTH, J.W., BEAN, K-G., SEIFERT, G.W., and Exp. Agric. Anim. Husbandry. 16: 636. RUDDER, T.H., BEAN, K.G., LAPWOR;;, J.W., and Soc. Anim. Prod. 11: 89. C 31 March 1977, Australian Bureau of Agriculture, Agricultural RUDDER, T.H. (1976). Aust. J. SEIFERT, G.W. (1976). Proc. Aust. 372