Beef production from the dairy herd

Abstract

The involvement of New Zealand dairy farmers in beef production is outlined as a perspective for this series of papers. Objectives of the experiment reported in this series are described. Data are reported on calving difficulties, cow and calf mortalities, birth weights, and gestation lengths of 2188 single-born calves out of Friesian (F) cows sired by Friesian, Hereford (H), Simmental (S), Angus (A), Limousin (L), South Devon (SD), Blonde d'Aquitaine (BA), Red Devon (RD), and Charolais (C) bulls, born on 21, 18, 16, and 19 South Auckland dairy farms in the spring seasons of 1973–76 respectively. First-calving heifers, 2 years old at calving, were not used. In each year 10 F bulls were used, together with 10 from each of 2 of the other sire breeds listed. Relative to the F in each year, cows in-calf to C, BA, SD, or S bulls required more frequent assistance at calving than those in-calf to L, A, or H bulls in the descending order given. Dystocia was positively associated with sire breed mean birth weight but not gestation length. Calving assistance scores did not differ significantly among bulls of the same breed over all years, but dairy farm environment was a significant source of variation. Heavier male calves received more assistance at calving than lighter female calves. Age of the cow at calving did not consistently affect dystocia incidence. Few cows died at parturition. Calf losses within 48 h of birth ranged from 2.6% in 1975 to 7.1% in 1974 for F×F calves, with only small differences between sire breeds. A higher proportion of assisted calves died at birth compared with calves from unobsedved, or observed but unassisted, calvings. Birth weights of H × F and A × F calves were lower than the F × F; other breeds were heavier than F × F. All breeds, except A × F, had longer gestations than the F × F. Sires within breeds exerted significant effects on birth weight and gestation length, and heritability estimates were derived. Calf birth weight was significantly affected by dairy farm environment. Bull calves tended to have a longer gestation, and were heavier at birth, than heifers. Age of cow did not consistently affect either birth weight or gestation length of calves. Results are discussed in relation to the breeding strategy of dairy farmers.