Effect of pasture type and supplementary feeding on the milk yield of Shorthorn and Brahman cross cows and the growth rate of their progeny in the dry tropics of north Queensland

Abstract

The milk yields of Brahman cross (Bx) or Shorthorn (Sh) cows and the birth weight and growth rate of their progeny to weaning were recorded over the four years 1970-73. Animals grazed either native pasture stocked at 1 breeder 4.9 ha-1 (NP) or native pasture oversown with Townsville stylo (Stylosanthes humilis) and fertilized with superphosphate and stocked at 1 breeder 2.4 ha-1 (TS). The animals on both pasture types were offered supplements of molasses, urea and phosphorus at various times of the year. Mating from September 1 to January 31 resulted in the cows commencing lactation during the dry season. Bx cows bore heavier calves than the Sh cows and had higher average daily milk yields. Bx calves grew faster from birth to weaning and were heavier at 180 days (P < 0.05 in both cases). Pasture type had a variable effect on milk yield in the two genotypes. Sh cows produced more milk on TS than on NP in all years (P < 0.05 for years 1 and 3). However, milk yields from the Bx were higher on NP than on TS in years 1 and 2 (P < 0.05 for year 1). Pasture type had little effect on birth weight but calves on TS generally grew faster and had higher weaning weights than those on NP. Supplements only increased milk yields in year 1 (P < 0.05 for urea and phosphorus fed during the dry season). Supplements caused no significant increases in birth weight, average daily gain (ADG), or weaning weight. In all years there were significant (P < 0.01) correlations of ADG with milk yield, birth weight and weaning weights. Male calves weighed more at birth and grew faster than female calves (P< 0.05)