الفهرس 
ContentsOnly 14 pages are availabe for public view
Abstract
The present study was carried out incorporation between the Animal Production Research Institute and Animal Production Department, Faculty of Agriculture, Mansoura University. Data used in the present study were collected during the period from 1995 to 2006. Saidi lambs raised in Seds experimental Station, which represent a total number of 1644 Saidi lambs records was available for this study. This records basied on 788 male and 856 females at the start of the experiment. To investigate effects of genetic and non-genetics factors on production traits of lambs (Body weights from birth and monthly until 18 months) and average daily gain (ADG) which calculated for the stage of growth lambs, estimate the effect of inbreeding on body weight and average daily gain of lambs and estimate the Additive direct genetic effect using 6 models. The first model included only the random effect. Various combinations of maternal components (maternal genetic and maternal permanent environmental effects) were included in the other models. Model 2 included to maternal permanent environmental effect. Models 3 and 4 included to maternal genetic effect without and with covariance between direct and maternal effect, respectively. Models 5 and 6 included both maternal components without and with covariance between direct and maternal effect, respectively. Estimate the phenotypic variance (σ2p) of birth weight to 6month weight. Estimate Heritability for direct additive genetic effect. Estimate Heritability for the additive maternal effect. Data was analyzed using the GlM procedures of SAS (1998), the algorithm of SAS, (1998) was used to calculate the coefficients of inbreeding utilizing pedigree data of all individuals. The significant differences between fixed items were tested using Duncan. The results of the present study could be summarized as follows : The coefficient of variation (CV) of lamb weight increased with the advanced age up to two months weight (27.811) and thereafter declined till the 18th month (19.022), the average daily gain was high (108.73 ± 35.27) from birth to 3 months of age, then the average daily gains showed trend of gradual reduce, the coefficient of variation of average daily gains showed the lowest value (32.438 g) from birth to 3 months then increases (91.158 g) till the 15 to 18 months, lamb weights at different age stages (from birth to 11th months) were significantly (P<0.001) affected by lambing season, except weights at the last months (12, 16, 17 and 18), the average daily gain weight of Saidi lambs at all different periods of age were significantly (P<0.001) affected by lambing season except the two periods of 12 to 15 and 15 to 18, lambing year had significant effect (P<0.001) on all lamb weights at different periods, lambing year had significant effect on average daily gain of Saidi lambs at all studied periods form birth until 18 month of age, sex had significant effect on lambs weights at birth and monthly until 18th (P<0.0l). The male lambs were significantly heavier than female lambs at birth and at all examined months, the male lambs showed higher average daily gains than female lambs, single lambs at birth tended to be heavier in birth weights (2.88 kg) than in twins (2.53 kg) or in triplet (2.16 Kg). Inbreeding had a negative significant effect (P<0.05) on weights of lambs at 1 and 2 months and inbreeding had no effect on birth weight, weaning weight and other weights in the present study. The direct additive variance estimates (σ2a) of BW, W1, W2, W3, W4, W5 and W6 were 0 06±0.01, 0.84±0.27, 0.90 ±0.31, 1.76±0.51, 3.16±0.67, 5.21±1.15 and 6.91±1.40, respectively. The total phenotypic variance (σ2p) estimates of BW, W1, W2, W3, W4, W5 and W6 were 0.29, 5.07, 7.91, 10.60, 14.51, 21.44 and 26.34, respectively. The direct heritability (h2a) estimates of BW, W1, W2, W3, W4, W5 and W6 were 0.20±0.04, 0.17±0.05, 0.11±0.04, 0.17±0.04, 0.22±0.04, 0.24±0.05 and 0.26±0.05, respectively. Estimates of genetic correlations among body weights were higher than those of the phenotypic ones except the correlations between BW with other weights. The estimates of phenotypic correlations among body weights ranged from 0.05 to 0.84. The permanent environmental variance estimates (σ2c) of BW, W1, W2, W3, W4, W5 and W6 were 0.04±0.02, 0.02±0.04, 0.29±0.22, .0.28±0.27, 0.75±0.50, 1.31±0.97 and 1.83±1.39, respectively. Estimates of permanent environmental correlations (rc) effect among body weights were very high and range from 0.99 to 1.00. Estimates of genetic correlation between BW with other weights were low and ranged from -0.02±0.08 (between BW and W4) to 0.12±0.07 (between BW and W5). Estimates of maternal correlations among body weights were low to very high.CONCLUSION Birth weight will be very useful in better planning for herd management and breeding. On the basis of this fact, several studies were carried out to determine the effects of some factors such as lambing year, lambing season, type of birth and sex of lamb.The present results showed that inbreeding had negative significant effects on some weights from birth until 18th months and average daily gain at different ages. The genetic programs which needed for lead to improve sheep herds will be based on increasing the frequency of desirable genes by different breeding ways in staid of using inbreeding alone to avoid the economic losses. In this study we used 6 models, on the basis of the obtained results; it was found that the best model was the simple model 1 included direct additive genetic effect and it had high heritability for the traits studied compared with other models used. Whereas, the second best model was model 2 which included maternal permanent environmental effect. It is important to mention that using each of sex models reflect degree of improvement. However, model 1 was the practically and simple in using for the farmer and from the breeder side of view. This based on the low of heritability for weights of animals as a result of low effect of maternal, permanent and the interaction.