Optimising compensatory growth in pastoral beef production systems: insights into feed efficiency, body composition,...

Exploitation of compensatory growth (CG) is a widely practised management strategy in beef production, especially under pastoral conditions due to its potential to reduce feed costs. The aim of this experiment was to evaluate the effect of nutritional restriction during backgrounding in Angus steers slaughtered at either similar age and/or similar BW on feed efficiency, body composition, carcass characteristics and meat quality attributes under either a forage or feedlot-based finishing diet. Eighty steers (BW: 444 ± 39 kg, age: 18 ± 1 months) were blocked and randomly assigned within block to either an optimal (0.6-0.7 kg/day) or suboptimal (0.3-0.4 kg/day) growth rate, during 97 days of backgrounding. Following, half of the steers in each group were finished on a forage diet while the other half were finished on feedlot-based diet. Half of the steers in each treatment were then slaughtered at similar age (24 months), whilst all remaining steers were slaughtered at similar BW (∼620 kg). Two extra slaughters were done with other representative steers on day 0 and day 97, to provide baseline parameters for carcass and non-carcass measurements. During the backgrounding period, optimal steers gained more than suboptimal (P < 0.01), resulting in higher BW and hot carcass weight (HCW; P < 0.01). During the finishing period, the suboptimal group increased BW gain (P < 0.01) and displayed an improved feed conversion ratio (FCR; P < 0.01). Differences (P < 0.01) in BW and HCW remained between the treatments when slaughtered at a similar age. When the steers were slaughtered at similar BW, after additional days of finishing for the suboptimal groups, no differences (P > 0.05) in backgrounding treatment on HCW, carcass grading, body composition or FCR for the entire period (backgrounding and finishing) were apparent. Indeed, no differences (P > 0.05) by backgrounding growth strategy were observed for any meat quality variables assessed using instrumental or sensory evaluations. During the finishing period, feedlot steers had increased (P < 0.01) BW and HCW gains, improved (P < 0.05) FCR and carcass grading, and had higher (P < 0.05) HCW compared to forage finished steers. However, no differences (P > 0.05) were observed for any meat quality variables assessed by finishing system. Overall, exploiting CG within pasture-based beef cattle production systems improves growth rate and FCR in both forage and feedlot finishing. Suboptimal backgrounded steers required additional days on feed to achieve similar BW to their contemporaries. Nevertheless, at similar BW, there were no residual differences in body composition, FCR during the entire period, meat tenderness or overall meat liking because of the backgrounding conditions.