Abstract:
THE MILK PRODUCTION OF TWO YEAR OLD HEREFORD AND FRIESIAN COWS G.R. SAUL* and J.H.L. MORGAN* Eight Hereford (H) and eight Friesian (F) cows were selected from a larger herd of two year old cows after calving in May 1971 and grazed together. The cows had previously been inseminated with semen from Hereford, Friesian, Charolais or Brahman bulls. The 16 cows were selected to provide one heifer and one steer calf of each breed or cross, all calves being born within 16 days. Mean birth weights of the calves from H and F cows were 27.4 and 31.2 kg, respectively (PxO.05). The milk production of the cows was measured on ten occasions by the Plunket method which involved weighing the calves before and after suckling following a 17 hour separation period. In addition, on six occasions the milk production of the cows was measured by handmilking following a five hour separation period and an injection of 20 I.U. of oxytocin (Pitocin - Parke Davis and Company). Milk from each cow was sampled at each milking and analysed for butterfat (BF) and solids not fat (SNF). The estimates of milk production were adjusted pro rata to a 24 hour milk rate and the results were analysed by analysis of variance. The F cows provided their calves with more than twice as much milk as H cows and this difference persisted until weaning. Estimates of milk production by hand milking were higher than those by Plunket in September and October but were very similar in later months (Table l), TABLE 1 Mean milk production (kg day') according to cow breed and method of estimation 4.1% (ns) and the mean SNF contents 9.3 and 8.9% respectively (P~0.05). Weaning weights (240 day adjusted) of the calves from the H and F cows The mean BF contents of the milk of the H and F cows were 4.5 and were 176 and 235 kg, respectively (P~0.01). Average estimates of milk production by Plunket and by handmilking were highly correlated with growth rate from birth to weaning, r = 0.92 and 0.84, respectively. These high correlations were largely attributable to differences between dam breeds in milk production. * Department of Agriculture, Victoria, Pastoral Research Station, Hamilton. 3OP
