Genetic Parameter Estimations Of Early Traits And Lamb Meat Performance Study Of Liangshan Semi-fine Wool Sheep

After revising pedigree by microsatellite DNA markers, the breeding data from 1996 to 2001 of nuclear breeding farm's Liangshan semi-fine wool sheep was used for this study. Analyzed the effect of year, birth season and sex on birth weight (BWT, n=1282), weaning weight (WWT, n=1000) and weaning staple length (WSL, n=909) by using LSMEAN; estimated the variances (covariances) and genetic parameters for these three traits by using MTDFREML. Simultaneously, three-level fatting experiment (high nutrition group, HNG; medium nutrition group, MNG; low nutrition group, LNG) was carried out on partial lambs that were born in 2001 to compare the fatting effect of each level on lambs; Then, randomly four chosen male lambs for each level were slaughtered to compare meat performance.The results of LSMEAN show: year, birth season and sex significantly influence BWT, WWT; year, birth season significantly influence WSL, but sex has little effect on WSL. The coefficients of variation about BWT, WWT, WSL are 22.36,28.02 and 24.31 %, higher coefficients indicate a great potential to improve for the three traits.According to the results of MTDFREML: The proportions of genetic variance, uncorrelated random effect variance (permanent environmental effect variance) about BWT, WWT, WSL are low, but the proportions of residual variance are high. The estimates of heritability about BWT, WWT and WSL are 0.24,0.06 and 0.13, respectively. Relate genetic correlation coefficients are 0.87, -0.53 and -0.52. The high residual variances indicate that we must consider other factors in later breeding analysis, the low heritabilities and high genetic correlations indicate that total selection is necessarily in early selection.Fatting experiment suggests that daily gain of HNG, MNG, LNG are 146.09, 137.74 and 117.78g, respectively. The difference of fatting effect between HNG and MNG is not significant, but are significant between HNG and LNG, MNG and LNG. Dressing percentage, net meat percent and meat-bone ratio of HNG, MNG and LNG are 47.66, 79.14, 4.39; 47.19, 78.82, 3.97; 46.71, 78.93, 4.30, respectively. Meat performance indexes of HNG are higher than MNG and LMG, but the difference is not significant. Dressing percentage of MNG is higher than LNG, but the net meat percent and the meat-bone ratio are lower than LNG. Eye muscle area of HNG, MNG, LNG are 17.7,16.5, 24.03cm2, relate GR values of HNG, MNG, LNG are 1.51,1.40,1.50cm, res. The percent of first grade meat for each level was over 58. Fatting experiment indicates medium nutrition can bring better economic benefit, and high nutrition can make carcass composition quality decline.