Prof. S.B.S. YadavPRAKASH2017-04-262017-04-262016http://krishikosh.egranth.ac.in/handle/1/5810010151The data for present investigation, were analyzed from records (1994-2011) of Chokla sheep research flock maintained at semi-arid region campus of the Central Sheep and Wool Research Institute (CSWRI), Avikanagar, Rajasthan. The overall least-squares means were observed to be 2.79 ± 0.015, 12.68 ± 0.119, 19.02± 0 .0152, 20.91 ± 0 .194 and 23.89 ± 0.199 kg at birth, 3, 6, 9 and 12 months of age, respectively. The overall least-squares means were observed to be 109.97 ± 1.242, 70.67± 1.082 and 29.66± .879 g/day at 0-3, 3-6 and 6-12 months of age, respectively. The overall least-squares means for greasy fleece weight of clip I was estimated as 0.915 ± 0 .017 kg. The sire effect was highly significant (P≤ 0.01) on all growth traits .The sex effect of lamb was highly significant (P≤ 0.01) on all growth but non-significant 12 months body weight, period effect was highly significant (P≤ 0.01) on all growth traits but non-significant on birth weight. The effect of dam’s age was highly significant (P≤ 0.01) on birth weight, 3 months weight, ADG3 and clip I and non- significant effect for 6, 9, 12 months body weights, ADG1 and ADG2. The effect of season of birth was highly significant (P≤ 0.01) on all growth traits but non- significant effect for 12 months body weights. The effect of dam’s weight as a covariate was highly significant (P≤ 0.01) on birth, 3, 6, 9 months body weights and ADG1 and significant (P≤ 0.05) on12 months body weights and non- significant for ADG2 and ADG3. The effect of sire, period of birth, sex, season of birth and dam’s age was highly significant (P≤ 0.01) for clip I. The effect of age of shearing as a covariate was highly significant (P≤ 0.01) for clip I. The heritability estimates from WOMBAT (animal model 1) method for body weights, average daily gains and greasy fleece weight at clip I were low to medium. Estimates of genetic correlations between body weights with weights at subsequent ages were positive and ranged from 0.065 to 0.885, and average daily gains during different phase ranged from 0.088 to 0.322.Estimates for phenotypic correlations between body weights with weights at subsequent ages ranged from 0.255 to 0.818, and average daily gains during different phase ranged from -0.22 to 0.141. Among 59 selection indices constructed by incorporating body weights at birth, 3, 6, 9 and 12 months of age, clip I in different combinations, the index I58 (0.0008 BWT + 0.0033 3WT + 0.2348 9WT +0.2257 12WT + 0.1803 CLIP I) was considered most useful for its reliability (rIH = 0.4181) and genetic gain (∆H = 2.3295). Among two stage selection indices, index MSI32 {(first stage = 1.1758 BWT + 0.1631 3WT + 0.0248 6WT) + (second stage= 0.8553 BWT + 0.4194 3WT - 0.7113 6WT + 0.7143 9WT + 0.1859 12 WT)} found more efficient (∆H = 2.5313) than others. Though the multistage selection resulted in slower gain but reduced the cost of selection.ennullThesis