EFFECT OF GENOTYPE AND ENVIRONMENTAL TEMPERATURE ON THE PERFORMANCE OF THE YOUNG MEAT RABBIT

Abstract

31, 35 and 36 male New Zealand White (NZW), or commercial hybrids Hyla (H) and Provisal (P) rabbits were studied respectively, and rearad until they were 85 days old. The test provided for two experiments: the first was carried out in winter (December - January) at an average temperatura of 11 ºC and a relativa humidity level approximately of 66 % , and the second in summer (July - August) at a temperatura of 27ºC and humidity level of 74 %. During the two trials the animals were fed "ad libitum" with a commercial pelleted feed. At the end of the study, 10 animals from each genetic group and for each season were slaughtered and jointed. As regards the effect of the genotype on growth performance, daily weight gain (32.8 g), intake (126.5 g/d) and fead efficiency (3.85 g/g) appeared similar for the three breeds considerad. As regards seasonal effects, the high summer temperaturas led to a significant reduction (P<.01) in daily live weight gain (29.5 vs 36.1 g/d), daily intake (102.6 vs 152.3 g/d) and feed efficiency (3.48 vs 4.22 g/g). Going on to consider the slaughtering data according to the genotypes, significant differences were observad with regard to the head and neck which appeared heavier in the purebred rabbits (11.16 vs 10.86 %, P<.05) than in the H whereas the P were intermediate (10.98 %). The commercial crossbreds provided significantly higher percentages (P<.01) with regard to the distal hind legs (2.47 vs 2.13 %) and empty stomach and guts (5.40 vs 5.24 %) comparad to the purebred rabbits. As regards the seasons, breeding in summer led to a tower inciclence on empty body weight of heart (0.39 vs 0.49 %, P<.01 ), liver (3.90 vs 4.24 %, P<.05), kidneys (0.59 vs 0.79 %, P<.01) and empty stomach and guts (5.18 vs 5.51 %, P<.01) and a higher warm carcass (65.64 vs 64.82 %, P<.05). Examinatlon of the carcass jointing data indicated a smaller head and neck for the H rabbit compared to the NZW (13.14vs 13.96%, P<01) with the P falling in the middle of the ranga (13.55 %). The percentage values for rumps, natas and thighs were lower (P<.05) in the purebreds than in the hybrids (33.06 vs 33.79 %). No significant differences were recordad between genotypes, but for the animals rearad in summer there was a significantly lower amount (P<.01) of perirenal fat (1.62 vs 2.63 %), perivisceral fat (2.46 vs 3.54 %) and scapular fat (0.68 vs 0.92 %).