Effect of winter feeding level and season on herbage intake in dairy breed steers on perennial ryegrass/white clover pasture

Summary

The objectives of this study were (1) to estimate herbage intake in spring and late summer in Danish Friesian steers during their first grazing season on ryegrass / white clover pasture and (2) to investigate the effect of different winter feeding levels on subsequent herbage intake in Danish Friesian steers weighing more than 450 kg. In experiment 1 (exp.1), herbage intake was estimated in 18-20 steers of a mean live weight of 210 kg (s.e. 8.0 kg) and 312 kg (s.e. 8.9 kg) in May/June and August respectively. In experiment 2 (exp.2), twenty-two steers were allocated to 2 feeding treatments in their second winter with expected daily liveweight gain of 500 g (LOW) and 800 g (HIGH). The steers weighed 483 kg (s.e. 13.1 kg) (LOW) and 542 kg (s.e. 8.2 kg) (HIGH) at the time of turn-out on a ryegrass / white clover pasture. Herbage intakes were estimated in June using the alkane bolus technique. Faeces and herbage samples were analysed for alkanes to estimate herbage intake, digestibility and botanical composition of intake. The weight gains (kg/day) were 1.156 (s.e. 0.69) and 1.054 (s.e. 0.80) in May/June and August respectively (exp. 1) and 1.592 (s.e. 0.137) and 1.273 (s.e. 0.116) in June in LOW and HIGH respectively (exp. 2). Daily herbage intake (kg dry matter (DM)/steer) estimated by alkanes C32 /C33 were 5.2 (s.e. 0.26), 9.4 (s.e. 0.28) in May/June and August (exp.1) (P<0.001) and 12.0 (s.e. 0.50) and 10.4 (s.e. 0.41) in LOW and HIGH (exp.2) (P<0.05) respectively. The diet of steers contained primarily ryegrass leaves (0.70-0.90) and ryegrass stems (0.10-0.30) and clover (0-0.02 and 0.18 in exp.1 and exp.2 respectively). It was concluded that (1) steers during their first grazing season can maintain herbage intake per kg liveweight during the grazing season from May to August, and (2) steers weighing more than 450 kg are able to increase herbage intake along with compensatory growth.