Weight gain, carcass characteristics, and meat quality of native lambs fed in confinement with total rations

Abstract

A three-stage study was conducted to evaluate voluntary consumption (VC) and weight gain of lambs fed total rations (TR). It also compared the characteristics of the carcass and the quality of meat from lambs fed with total rations and grazing natural tropical grasses. The first part of the study consisted of a feeding test lasting 43 days using native lambs in development (n=10) of approximately 20 kg average starting weight. The two total rations evaluated contained 50% hay from tropical pastures, and 50% commercial concentrate (TGH + CC) (n=5) or 50% of a mixture of corn grain and soybean meal (TGH + CGSB) (n=5). Both diets were offered at 4% of the lamb live weight (LW) on a dry matter basis (DMB) and were formulated for a content of 13% crude protein (CP) and 53% of total digestible nutrients. The effect of the diets on VC and weight gain in lambs was evaluated. The second stage of the investigation assessed the effect of the two TR and the grazing feed on the characteristics of the carcass and yield of wholesale and retail cuts. The five wholesale cuts evaluated included the nape, front leg with shoulder, ribs 5 to 12, loin and rear leg. The retail cuts were the shoulder chops, Frenched chops, loin chops, hind leg, shanks and stew meat. The third stage determined the effect of the three diets on the quality of meat using as criteria its nutrient content, color and tenderness. The lambs in both TR consumed 3.1% LW/DMB of the feed offered. However, animals on the TGH + GCSB diet obtained a greater total and daily weight gain (P<0.05) than the TGH + CC diet (9.1 kg and 213.58 g vs. 6.0 kg and 139.58 g, respectively). The percentage yield of the hot carcass (% HCY) and cold carcass (% CCY), wholesale and retail cuts was similar in lambs fed with the two TR. The percentage CCY was lower (P<0.05) in lambs fed on pasture than with TR. The weight and percentage yield of the loin relative to the cold carcass was also higher (P<0.05) in lambs under the TR feed regimen than in grazing, but the yield percentage of the front leg and shoulder (ribs 1 to 4) was lower. The weight of some retail cuts and the performance of the shoulder chops and ossobuco was greater in grazing lambs than in lambs on TR diets, but the stew meat yield was lower. As expected, grazing-fed lamb meat had a higher (P<0.05) percentage of moisture and lower content of crude protein (CP), fat and minerals. The meat of lambs fed with TR was lighter, according to the value of L* of luminosity, and more tender than that of grass-fed lambs. In short, it is possible to obtain LW gains between 139 and 213 g/d in native lambs fed TR. The feeding system (TR vs. grazing) affects the weight and yield percentage of wholesale cuts (front leg and ribs 1 to 4) and retail cuts (shoulder chop, loin chop and shanks) and meat quality.