Published in Scientific Papers. Series D. Animal Science, Vol. LVII
Written by Ion BUZU
The research purpose was the factors which determine the variability of Karakul sheep body weight, heritability degree identification and repeatability of this character, determining the selection efficiency of the sheep by this important character. The research has been made on the Moldovan Karakul sheep flock INZMV, village of Maximovca, Anenii Noi district. The body weight of the sheep was determined with technical weighing scales: at birth, 20-90 days, at 6-18 months, adult age, annually. The research has shown that the body weight of Karakul sheep has a decisive impact on meat production and on fur skin surface obtained from new-born lambs. Thus, from the rams of 6 months, which were intensively fatted, with body mass 35-36 kg, it were obtained carcasses of 16.6 ± 0.3 kg, of R and U categories, according to UE classification scale. The slaughter yield of these ram lambs was 47.5 %. From reformed sheep, which were intensively fatted, with body mass of 64-65 kg, were obtained massive carcasses, with weight of 32.3 ± 1.0 kg, reported to R and U categories, according to UE classification scale. The slaughter yield of these sheep was 54.8 %. It has been found that, as bigger are the lambs at birth, that bigger is the standard surface of the fur skins. With increasing of lambs body weight at birth from 3.9 up to 4.4 kg, the share fur skins with big surface (> 1400 cm2),increase from 28.2 % up to 63.8 % or 2.3 times (P < 0.001). With further increase of lambs body weight up to 5.4 kg, increase substantially the share of fur skins with very big surface (> 1800 cm2), from 15.3 % up to 91.4 % or with 6.0 times (P < 0.001). Phenotypic correlation coefficient (rxy) between body weight of Karakul lambs and standard surface of fur skins is: rxy = 0.64 ± 0.04 (nst = 10-15-22; P < 0.001). From corpulent parents it were obtained progeny with a big body weight. The rams with big body weight 86-100 kg have given progeny with high body weight at birth of 5.16 ± 0.03 kg, rams with average body weight of 71- 85 kg, have given progeny with average body weight of 4.78 ± 0.04 kg, and rams with low body weight of 60 – 70 kg, have given progeny with lowest body weight – 4.45 ± 0.04 kg. The progeny of corpulent rams exceeded, after the body weight at birth, the progeny of average rams with 0.38 kg or 7.9 % (P < 0.001) and of the small ones with 0.71 kg or 16.0 % (P < 0.001). This shows that between body weight of ram fathers and body weight of lambs progeny exist a positive genotypic correlation. In good years with sufficient vegetation on the pasture, the body weight of the sheep achieved a high level, and was on average at breeding batch: at adult rams – 92.6 ± 3.0 kg, at sheep jelly – 57.8 ± 0.3 kg, at rams of 18 months – 63.6 ± 5.5 kg, at sheep of 18 months - 53,1 ± 0,4 kg, being significantly higher, than in bad years, respectively, with 11.7% (P < 0.05), 14.8% (P < 0.001), 16,1% (P < 0.05) and 7.6% (P <0.001). Based on the research results, it were made following conclusions: body weight of Moldovan Karakul sheep is one of the most important morph productive selection characters, because it has a direct impact on both, the meat production and on fur skins surface obtained from lambs at age of 2-5 days after birth; the internal factors which treat the phenotypic variability of body weight, the most important is heredity (genotype), and of external factors – nutrition and feeding (forage base); sheep of Moldovan Karakul type are more precocious, comparing to sheep of Asian Karakul, which represents one of the interior biological particularities of this interracial type of sheep. This type of sheep continue to grow in body until the age of 2.5-3.5 years. Selection of Moldovan Karakul sheep after the body weight is modestly efficient, thanks to heritability and moderate repeatability of this character. The coefficient of body weight heritability is not very high (h2 = 0.3), but quiet (tr = 2.6; P < 0.01). The coefficient of body weight repeatability (rw) at different age of young sheep and adult sheep varies within the precinct of 0.23 – 0.47.
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