Effect of level of feeding on growth, reproductive performance and milk production of beef females

Abstract

Fifty-nine Aberdeen Angus females, each weighing about 190 kg and 7 months old, were randomly assigned to five levels of feed intake (140, 100, 80, 60 and 40% of the recommended allowance for total digestible nutrients). Two groups of females were assigned to the 60% level, one of which was raised to the 100% level 45 days prepartum. All females except those fed at the 140% level were raised to the 100% level at parturition until 150 days postpartum and then returned to prepartum levels. The females were removed from the experiment at their first estrus after the second calving. Females (nine in this group) fed at the 40% level of feed intake ceased to cycle before their first breeding date and had to be raised to the 100% level until estrual cycles were reestablished. Raising feed intake levels 45 days prepartum increased average daily gain (1.24 vs 0.16 kg, P < 0.01) of the females but had no significant influence on calf birth weight, calf mortality, milk yield, average daily gain of calves, time to postpartum estrus and conception or conception rate. Both groups of females fed the 60% level of feed intake and those fed the 40% level gained faster (0.28 vs 0.02 kg daily, P < 0.01) during lactation but weighed less (290 vs 423 kg, P < 0.01) and gave less milk (2.8 vs 3.4 kg, P < 0.01) than females fed the other levels. Although postpartum estrus and conception were delayed slightly, none of the females fed the 60 and 40% levels ceased to cycle after calving. Females fed the 140% level of feed intake became extremely fat and their milk production was similar to that of the other groups, but calf mortality was higher. Raising levels of feed intake postpartum increased gains and reproductive performance of females on levels below recommended allowances, but increasing either feed intake 45 days prepartum or feed intake levels above recommended allowances had no measurable benefit.