Factors affecting the performance of steers grown under commercial conditions in a sub-tropical environment

Abstract

Liveweights of steers born during four consecutive calving seasons were analysed to evaluate the effect of year of birth, breed of sire, age of dam, weight of dam, date of birth, and the year of birth by breed of sire interaction. Weight per day of age at 207 days (weaning), 698 days, and at 890 days was used as the basis for evaluation. Year effect was significant but tended to decrease with age. Constants for breed of sire effect were significant at each age but the magnitude of the differences decreased as age increased. Over all years steers sired by Santa Gertrudis bulls had higher weight per day of age than those sired by Brahman and Hereford bulls; but the significant year of birth by breed of sire interaction showed that breed of sire differences were inconsistent from year to year. Age of dam effect was significant at 207 days and 890 days. The magnitude of these differences decreased with age, and the ranking of dam age groups varied according to age of steers. The regression of weight per day of age on cow weight was significant at 698 days, and at 890 days. This regression indicated that heavier cows tended to produce steers with a higher weight per day of age. The regression on day of birth was significant at 207 days, and at 890 days, but the magnitude of this effect decreased markedly as age increased.