Behavioural compensation of extruded urea level and the effects of supplementation presencefor finished lambs in tropical grass pastures

Abstract

The objective was to investigate how different levels of soybean meal replacement with extruded urea (EU) in sheep supplementation affected pasture characteristics (Brachiaria spp.), consumption, ingestive behavior and animal performance. Sixty Texel crossbred lambs were randomly divided between treatments: 0, 6, 12, 18 and 24 g of 100 kg−1 body weight (BW) EU supplement under continuous stocking in Brachiaria spp. The animals receiving a supplement in the proportion of 24 g 100 kg−1 BW from the EU had the highest pasture height (39.5 cm) as compared with other treatments. The levels of replacement of soybean meal by the EU had no effect on the supply of forage, forage accumulation rate or structural characteristics. The forage dry matter intake (DMI) as percentage of BW and metabolic BW were adjusted to quadratic equations, and the minimum levels of DMI in relation to BW (1.5 %) and metabolic (55.6 g DM/kg0.75) were estimated at 10 g and 9.4 g 100 kg−1 BW of the EU, respectively. The grazing time of the lambs decreased linearly (P = 0.006) by 4.88 min for each increase in the EU level. In contrast, as EU levels in lamb supplementation increased, the time taken to consume the supplement and the bite rate increased by 4.38 min and 0.28 bites/minutes, respectively. The average daily gain increased linearly up to 18 g 100 kg−1 BW (146 g/day) (P = 0.034). For lambs finishing in Brachiaria spp., the EU can be used in place of soybean meal up to 18 g 100 kg-1 BW without altering animal performance, consumption, or the structural characteristics of the pasture.