Animal performance and economic implications of alternative production systems for dairy bulls slaughtered at 15 months of age

Abstract

The objectives of this experiment were to investigate (i) the influence of varying levels of concentrate supplementation during the grazing season, (ii) alternative finishing strategies for dairy bulls slaughtered at 15 mo of age and (iii) economic implications of these management strategies. Bulls were assigned to a 2 (level of concentrate supplementation during the grazing season: 1 kg [LA] and 2 kg [HA] dry matter [DM]/head daily) × 2 (finishing strategies: concentrates ad libitum group [AL] or grass silage ad libitum plus 5 kg DM of concentrates/head daily group [SC]) factorial arrangement of treatments. Average daily gain (ADG) during the grazing season was greater (P < 0.01) for HA than for LA. Consequently, HA bulls were 16 kg heavier at housing: 214 and 230 kg, respectively (P < 0.05). During the finishing period, ADG tended (P = 0.09) to be greater for LA than for HA. Carcass weight tended (P = 0.08) to be greater for HA than for LA. Fat score was greater for HA. Live weight at slaughter (P < 0.001) and carcass weight (P < 0.001) were 41 and 23 kg greater for AL than for SC, respectively. Conformation (P < 0.05) and fat score (P < 0.05) were greater for AL than for SC. The Grange Dairy Beef Systems Model simulated whole-farm system effects of the production systems. Net margin/head was greater for LA than for HA and greater for SC than for AL. Sensitivity analysis of finishing concentrate price, calf purchase price and beef price showed no re-ranking of the systems on a net margin basis. Although greater animal performance was observed from the higher plane of nutrition, overall profitability was lower.