Estimation of Carcass Tissue Composition from the Neck and Shoulder Composition in Growing Blackbelly Male Lambs.

This study was designed to develop predictive equations estimating carcass tissue composition in growing Blackbelly male lambs using as predictor variables for tissue composition of wholesale cuts of low economic value (i.e., neck and shoulder). For that, 40 lambs with 29.9 ± 3.18 kg of body weight were slaughtered and then the left half carcasses were weighed and divided in wholesale cuts, which were dissected to record weights of fat, muscle, and bone from leg, loin, neck, rib, and shoulder. Total weights of muscle (CM), bone (CB) and fat (CF) in carcass were recorded by adding the weights of each tissue from cuts. The CM, CF and CB positively correlated (p < 0.05; 0.36 ≤ r ≤ 0.86), from moderate to high, with most of the shoulder tissue components, but it was less evident (p ≤ 0.05; 0.32≤ r ≤0.63) with the neck tissue composition. In fact, CM did not correlate with neck fat and bone weights. Final models explained (p < 0.01) 94, 92 and 88% of the variation observed for CM, CF and CB, respectively. Overall, results showed that prediction of carcass composition from shoulder (shoulder) tissue composition is a viable option over the more accurate method of analyzing the whole carcass.

Residual Feed Intake and Rumen Metabolism in Growing Pelibuey Sheep.

This study was carried out to evaluate the residual feed intake (RFI), volatile fatty acid (VFA) production and enteric methane (CH4) from growing Pelibuey sheep. In this case, 12 non-castrated Pelibuey with an initial average live weight (LW) of 21.17 ± 3.87 kg and an age of 3 months, were housed in individual pens and fed a basal diet with 16% of crude protein and 11 MJ ME for 45 days. Dry matter intake (DMI) was measured and the daily weight gain (DWG) was calculated using a linear regression between the LW and experimental period. Mean metabolic live weight (LW0.75) was calculated. RFI was determined by linear regression with DWG and LW0.75 as independent variables. Lambs were classified as low, medium, and high RFI. Feed efficiency was determined as DWG/DMI. For determining rumen pH, ammonia nitrogen concentration NH3-N), and VFA, ruminal fluid was obtained using an esophageal probe on day 40. Feed intake of low RFI lambs was approximately 16% lower (p < 0.05) while growth rate was not significantly different. Their average energy loss, expressed as CH4 production per kilogram of metabolic weight, was 17% lower (p < 0.05).

Interplay between feed efficiency indices, performance, rumen fermentation parameters, carcass characteristics and meat quality in Pelibuey lambs.

Feed efficiency was measured in thirty Pelibuey noncastrated male lambs using the residual feed intake (RFI) and residual intake and gain (RIG). The lambs were fattened for 92 d and then slaughtered, with the aim of identifying the interplay between feed efficiency indices (FEIs) and performance, rumen fermentation parameters, carcass characteristics and meat quality traits from the 15 intermediate and most extreme lambs for each FEI. The mean values of the classes were -0.09, 0.00, and 0.09 kg DM/d for low, medium and high RFI, respectively. The RIG indicators were 2.6, -0.1, and -2.7, for high, medium and low, respectively. The lambs with high-RIG had a higher (P ≤ 0.05) average daily gain and improved feed conversion. Lambs with low-RFI and high-RIG had higher (P < 0.05) values of meat cooking loss. Efficient lambs had improved feed utilization without affecting the carcass characteristics or meat quality (except for cooking loss).