Ganho em peso, morfometria e caracterização de carcaças de cordeiros Santa Inês e F1 Dorper x Santa Inês em regime de pasto

Abstract

This work was carried out in order to evaluate the weight gain, the morphometry and the carcasses traits of two sheep genotypes, Saint Ines (SI) and F1 Dorper x Saint Ines (DxSI).In the experiment 32 animals were used divided into two genotypes (SI and DSI), being 8 females and 8 males of each genotype, with two ages of slaughter (120 and 150 days) at Volta da Serra stall, in Januária, North of Minas gerais. The design was entirely at random, in a factorial scheme 2 x 2 x 2 (two genotypes, two sexes and two slaughter times). Statistical analyses of central tendency were carried through and Scott-Knott test was used at 5% of probability for averages comparison. For weight gain characteristics, were collected the birth weight (BW), wean weight (WI) and final weight (FW), with weighting carried through every fifteen days. For morphometry, the body measures were: wither height (EH), back length (HB), hindquarter height (HC), body length (LB), thorax perimeter (CP), chest width (WC) and hindquarter width (WTC), collected before slaughtering the animals. The evaluated carcass characteristics were: live weight at slaughtering (WA), warn carcass weight (WHC), cold carcass weight (WCC), warn carcass yield (IHC), cold carcass yield (ICC), cooling loss (LC), conformation (C), carcass compactness index (CCI), carcass internal length (ILC). In the cold carcass were evaluated the commercial cuts yield of neck, shoulder, rib, loin, leg. The F1 DSI animals were statistically (P < 0,05) superior to SI in PN and PD while PF did not present significant difference, since the real weight gain to wean in the slaughtering was superior for the SI genotype, what demonstrated higher adaptation capacity to pasture system. The sex did not influence the weight traits. The F1 GPT was greater (P<0,05) than the SI one, but the same did not occur with GPMD that did not show difference between the evaluated genotypes. Amongst the carcass traits, the PCQ was superior (P<0,05) for DSI females at 150 days in relation to SI ones; while the PCF was higher for DSI males slaughtered at 120 days (P<0,05). The PR was more accentuated (P < 0,05) for the animal slaughtered at 150 days, and the SI lambs slaughtered at 120 days presented larger PR (P < 0,05) than F1 DSI ones. The COF of the DSI females slaughtered at 150 days was superior (P < 0,05) to females slaughtered at 120 days. There was no significant effect for ICC and CIC between the genotypes. For commercial cuts yield of more relevance, as shoulder and leg, there was no significant difference between the genotypes. As for loin yield, the F1 DSI were greater (P < 0,05) and the slaughter time influenced only shoulder yield with superiority for the animal slaughtered at 150 days. Concerning morphometry, the animal slaughtered at 120 days showed higher PET (P < 0,05) than those slaughtered at 150 days. The ALC and ALG were larger for SI animals while the CCO was higher (P < 0,05) for the F1 ones. The implantation of the Dorper breed as improved must be evaluated in a discerning way when it is intended to keep its products in systems exclusively to pasture, since the increment in weight gain, carcass characteristics and morphometry were irrelevant although the superiority in loin yield. More studies are necessary with those genotypes under the feedlot system to evaluate the bioeconomic return, as well as the reproductive and economic indices.