Bioeconomic selection indexes for terminal lamb systems in tropical conditions

Abstract

The main challenge for sheep farming in Brazil is the regularity in the quantity and quality of animals destined for slaughter. The selection for several traits simultaneously, considering their economic relevance, can improve the production efficiency in the finishing systems, the quality of meat offered to the consumer market, and, consequently, the profitability. The objective was to develop selection indexes for three terminal lamb scenarios: extensive system (EXS), semi-intensive system (SIS), and intensive system (INS). The costs and revenues calculated were according to the national average prices in 2021. The economic values were determined by the partial derivatives of the profit function, changing one trait at a time, by 1 unit, while keeping the other traits constant. For the traits of the selection objective: feed conversion ratio, weight at 180 days, and dressing percentage, the economic values (US$) were, respectively, EXS: − 1.91, 1.13, 1.53; SIS: − 3.16, 1.35, 1.54; INS: − 6.30, 0.99, 1.55. Feed conversion ratio was the trait that presented the highest economic value for all systems, affecting production costs and production efficiency. Additive genetic variance and genetic correlation values obtained were in literature. The traits of selection criteria were: weight at 180 days, measured in kg, eye muscle depth, and subcutaneous fat depth, measured by the ultrasound. The selection index weight for the traits of the criterion of selection were, respectively, EXS: 7.850, 4.421, 1.079; SIS: 9.788, 3.988, − 0.711; INS: 10.087, 2.803, − 5.272. The prediction of economic gain per animal was US$6.21 (EXS), US$7.35 (SIS), and US$7.16 (INS). In addition, the accuracy of the indexes was 0.88 (EXS), 0.91 (SIS), 0.91 (INS). The selection for growth and carcass traits as selection criteria can improve the performance and dressing percentage of the animal. The accuracy of the index showed to be favorable to replicate these indexes in similar scenarios of terminal lamb, which can improve the genetic progress and profit of the herd.