The influence of winter nutrition, grazing system and stocking rate on the performance of spring-calving Hereford × Friesian cows and their calves 1. Winter nutrition

Abstract

ABSTRACTIn three experiments the effects of giving Hereford × Friesian cows 61 to 64 MJ/day of metabolizable energy in the last 8 weeks of pregnancy, followed by either 49 to 56 (L) or 85 to 100 (H) MJ/day for the first 8 weeks of lactation, were determined. A further comparison was made in experiment 3, in which energy intakes were restricted to 46 and 64 MJ/day (M) in the two periods respectively. The L and M groups had a similar average weight loss of approximately 55 kg over winter whereas the H groups maintained their weight. The L and M treatments had a negligible effect on milk production at 3 weeks post calving but they caused a significant depression at 6 weeks in experiments 2 and 3. Milk energy and protein concentrations were reduced in all three experiments. Calf growth was similar on both treatments in experiment 1 but was 9 to 13% lower in experiments 2 and 3 for the L and M groups compared with the H group. Reproductive performance was not significantly affected. There was a substantial increase in milk production for all groups on turnout to grazing. This was greater for the L and M groups so that their summer milk production was almost equal to that of the H group. Cows from L and M groups gained more weight at pasture. By the end of the trials cows and calves from all treatments had similar weights except in experiment 3, when cows from the L and M treatments were still lighter than those from the H treatment.