Infrequent winter supplementation with whole Lupin grain in grazing yearling steers on improved Lotus uliginosus cv. INIA E-Tanin pastures in Basaltic soils

Abstract

This study aimed to evaluate the effect of infrequent self-fed winter supplementation with whole lupin grain on growth performance and pasture-animal interactions in yearling Hereford steers grazing improved native pasture based on Lotus uliginosus cv. INIA E-Tanin. The trial was conducted over 98 days (August–November 2022) at the Glencoe Experimental Unit (INIA Tacuarembó), under a completely randomised design with two treatments and two replicates. Thirty-two steers (initial liveweight-LW: 302 kg) were allocated to either no supplementation (SL) or supplementation at 1% LW (CL). Pasture availability, structure, botanical composition, growth, and nutritive value were measured both before and after grazing. Animal variables included liveweight gain, productivity per hectare, ingestive behaviour, supplement intake, and feed conversion efficiency (FCE). Steers in the CL group showed significantly higher daily gains (1580 vs. 930 g/day; P<0.01), final LW (457 vs. 401 kg; P<0.01), and productivity per hectare (388 vs. 227 kg LW/ha; P<0.01), with an FCE of 5.3 kg lupin grain per kg extra LW gain. While pre-grazing forage conditions were similar, CL increased post-grazing forage mass (1384 vs. 1023 kg DM/ha; P<0.05) and height (5.0 vs. 4.1 cm; P<0.01), without major changes in pasture structure, quality or species composition. Supplemented steers also showed reduced grazing time and increased resting behaviour. These results indicate that combining INIA E-Tanin with strategic lupin supplementation in improved pastures is a promising alternative to enhance animal performance and accelerate growth in semi-extensive beef systems on basaltic soils.