The effect of genotype, feeding system and slaughter weight on the quality of light lambs: 1. Growth, carcass composition and meat quality

Abstract

One-hundred and eight Merino Branco (MB) and crossbred Ile de France x Merino Branco (IFxMB) ram lambs were used to evaluate the effects of genotype, feeding system and slaughter weight on growth, carcass composition and meat quality traits. At an average age of 53 days, lambs were randomly assigned to three feeding systems: P, pasture with dams; SP, pasture with dams, plus concentrate ad libitum; C, weaning, and concentrate ad libitum. Lambs were slaughtered at 24 or 30 kg live weight. The carcass left sides were partially dissected and the Longissimus thoracis and Longissimus lumborum muscles were used for meat quality determinations. Genotype had only minor effects on lamb growth as well as on carcass composition and meat traits. Growth rate was higher, and muscle proportion was lower in C than in SP, and in SP than in P. When lambs were fed only pasture (P), carcasses were mainly classified as very lean (class 1), especially when lambs where slaughtered at 24 kg. For SP and C, carcasses were mainly graded in class 2. Lambs in P, showed lower water-holding capacity. When slaughter weight increased, muscle proportion decreased but carcasses were still considered to be lean (class 2). Meat colour became darker and redness increased with slaughter weight, but shear force remained unchanged.