Precision finishing of South African lambs in feedlots: a review

In the intensification of sheep production systems, feedlot finishing plays a fundamental role in preparing lambs for slaughter, as well as relieving the grazing pressure on pasture. The profit margins in feedlot operations are often narrow and require the economics of scale to generate a sufficient income. In order to minimise expenses, intensive management and precision rearing of lambs to an ideal slaughter weight is needed to obtain premium carcass prices. The South African sheep industry is made up of wool, dual-purpose as well as meat type breeds, which also vary in terms of maturity. In order to implement precision finishing of South African lamb, a complete understanding of the growth, intake and fat deposition trends of growing lambs of different breed types is needed. This review outlines feedlot lamb production within the Southern African context for the major commercial breeds, while also providing insight in the considerations necessary to develop a decision support system for lamb rearing. Integrating such a decision support system into a lamb feedlot operation can then be used for precision finishing of lambs by predicting the optimal length of the feeding period and ideal slaughter weights of lambs.

Growth, carcass characteristics, cut yields and meat quality of lambs finished with zilpaterol hydrochloride and steroid implant

Forty hairbreed male lambs were used to evaluate the effects of zilpaterol hydrochloride (ZH, 0 and 0.15 mg/kg BW) and steroid implant (SI, without and with 52.5 mg trenbolone acetate and 7.5 mg 17β-estradiol) on feedlot performance, carcass characteristics, non-carcass components, wholesale cut yield, and meat quality. Supplemental ZH increased growth rate, feed efficiency, carcass weight, and dressing percentage, with no effect on wholesale cut yields. Feeding ZH increased muscle pH at 24 h. Supplemental ZH increased meat shear force, but decreased lightness, redness, and yellowness after frozen storage followed by a 14-day aging period. The SI administration increased dressing percentage and neck yield, but decreased testicle weight and meat redness, without affecting other variables. The LT area was greater with ZH + SI administration than with individual application of ZH or SI. Compared to individual administration, simultaneous application of ZH and SI did not result in improved growth performance, carcass traits and wholesale cut yields in hairbreed male lambs.