Performance, carcass characteristics and non-carcass components of Santa Ines and crossbred (Santa Ines x Dorper) lambs finished in different confinement strategies.

Genetic group, age at entry into confinement and at slaughter, are characteristics that have an important influence on lamb performance and carcass. The aim of this study was to evaluate the performance, carcass characteristics and non-carcass components from different genetic groups (Santa Inês and ½ Dorper x ½ Santa Inês) sheep, submitted to different feedlot entry and exit strategies. Were used 72 lambs males and castrated; 36 Santa Inês (SI) and 36 crossbred (Dorper x Santa Inês-DSI), with 6 months of average initial age. The groups were established in a completely randomized experimental design, in a 2x3x4 factorial arrangement, from the combination of genetic groups (GG), body weight at the beginning of confinement (WBC) and length of stay in confinement (LSC). The body weight classes at the beginning of confinement were: light (25 kg), intermediate (28 kg) and heavy (31 kg), for Santa Inês and crossbreeds, respectively. Slaughters were carried out every 28 days of confinement, in four LSC: 0, 28, 56 and 84 days. The GG did not influence performance, carcass and non-carcass component traits of lambs (p > 0.05). There was an effect of the WBC on the weights: final (FW), metabolic (MW), body at slaughter (BWS), empty body (EBW), hot carcass (HCY) and cold (CCW), loin, shoulder, leg musculature; loin eye area (LEA) and loin fat (p < 0.05). There was also an effect on LSC, for FW, average daily weight gain (ADG), MW, weight and yield of body components, weight of cuts and tissue ratio components of cuts (p < 0.05). In non-carcass components, effect on full and empty weight of: omasum, rumen-reticulum, small intestine; empty large intestine, liver and kidneys, paws and skin, and perirenal, pelvic and inguinal fat (p < 0.05). Interaction double effect on the tissue muscle/fat:bone ratio (MF:B) and for the full omasal component (p < 0.05). And triple interaction effect for ADG, full omasum and perirenal fat (p < 0.05). Weight at the beginning of confinement and confinement time are the characteristics that most influence performance, quantitative characteristics of carcass and non-carcass components. Regardless of the genetic group and age class, the animals reach the same weight after 84 days of confinement. Thus, the confinement of heavier lambs (31 kg) can be a profitable alternative, as they presented the highest weights for the most commercially valued cuts (shank and loin). The confinement strategy must adapt to market situations.

Tissue composition and allometric growth of carcass of lambs Santa Inês and crossbreed with breed Dorper.

This study aimed to assess the tissue composition and allometric growth of carcasses of Santa Inês and crossbred Dorper x Santa Inês lambs confined for different periods at three body weight classes. Sixty-four lambs from Santa Inês (SI) and crossbred Dorper x Santa Inês (DSI) were slaughtered. The carcasses were refrigerated at 4 °C for 24 h, and half of the right side carcass was divided into five primary cuts, which were then dissected into bone, muscle, and fat. The corrected cold carcass weight (CCWc) was calculated based on the sum of the cuts. There was no effect of the interactions evaluated (P > 0.05) among the factors tested. CCWc, muscle (kg), fat (kg), bone (%), M:F, M:B, F:B, and M+F:B were influenced by the lambs' genetic group (P < 0.05). An effect of body weight at the beginning of confinement was found only for CCWc, muscle (kg), fat (kg), bone (kg), bone (%), and M:F. The crossbreeding of Santa Inês with breeds Dorper promotes improvements in the qualitative characteristics of the carcass. To obtain better relationships of the quantitative characteristics of the carcass, of sheep introduced in confinements with larger weights, the slaughter weight must be adjusted to that initial weight.