Pasture-finishing of late-maturing bulls or steers in a suckler calf-to-beef system: Animal production, meat quality, economics, greenhouse gas emissions and human-edible food-feed efficiency

Abstract

CONTEXTDemand for efficient sustainably-produced ‘grass-fed’ beef is increasing. Steers predominate in pasture-based systems. Bulls are inherently more efficient than steers but are usually produced indoors on concentrate-based rations rather than at pasture. OBJECTIVEEvaluate the animal productivity, meat quality, financial performance, greenhouse gas (GHG) production and human-edible protein (HEP) efficiency of suckler calf-to-beef systems, in which male progeny were finished as bulls or steers at pasture, with or without concentrate supplementation, at 19.5 months-of-age. METHODSWeaned suckler male cattle, produced as either bulls or steers, were offered grass silage and supplementary barley-soybean meal-based concentrates during a ‘backgrounding’ phase, and then assigned to one of two finishing strategies: grazed pasture-only for 192-days (G-O) or pasture-only for 95 days followed by pasture supplemented with 3.2 kg concentrate dry matter daily for 97 days (G-C). The experimental data generated were used to parameterise a whole-farm systems model and the productivity, profitability and GHG production of suckler calf-to-beef systems (encompassing cows, replacement heifers, female and male - bulls vs. steers - progeny) were evaluated. RESULTS AND CONCLUSIONSBulls had a heavier carcass (+44 kg), greater kill-out proportion (+14 g/kg) and carcass conformation score (+1.6 units, scale 1–15), a lower carcass fat score (−2.3, scale 1–15), darker muscle and less yellow subcutaneous fat than steers. Concentrate supplementation increased daily live-weight gain (+0.36 kg), carcass weight (+37 kg), kill-out proportion (+12 g/kg), carcass conformation score (+1.1 units) and fat score (+1.0). Meat tenderness, texture and acceptability were lower for bulls than steers. Profitability of suckler calf-to-beef systems was greater where male progeny were finished as bulls rather than steers, and for G-C than G-O. The GHG emissions (CO2 eq) per cow were lower for steer compared to bull systems, and for G-O than G-C; however, when expressed per kg live-, carcass- and meat- weight, the opposite was found. Half of the GHG emissions within the calf-to-beef systems were attributed to the cow. The HEP ratio for G-O exceeded 1.0, but for G-C declined to 0.9 for steers and 1.0 for bulls: replacing cereal and soya-bean meal with by-products resulted in all systems having HEP efficiencies >1.0. Bull systems had lower meat eating quality, greater profit, lower GHG emissions intensity, and superior HEP efficiency than steers. Concentrate supplementation did not affect meat quality, increased profitability, and reduced GHG emission intensity and HEP. SIGNIFICANCEConsideration of unavoidable trade-offs in sustainability-related metrics between suckler beef systems is necessary.