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ThesisItem Open Access GENETIC ANALYSIS OF PRODUCTIVE AND REPRODUCTIVE TRAITS IN FARM BRED NELLORE JODIPI SHEEP(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517502. (A.P.) INDIA, 2019-07) BHAKTHAVATCHALAM, S; PUNYA KUMARI, B (MAJOR); SUDHAKAR, K; JAGADEESWARA RAO, S; RAMANI PUSHPA, R.N.The data collected on 5008 production records and 2965 breeding records of Nellore Jodipi sheep maintained at the Network Project on Sheep Improvement, Livestock Research Station Palamaner, Chittoor district was utilized in the present investigation to study the effect of various factors including inbreeding on productive and reproductive traits and also to predict and compare the breeding values by using Least Squares (LS), Best Linear Unbiased Prediction (BLUP) and Restricted Maximum Likelihood (REML) methods. The overall least squares means for BW (Birth Weight), 3M (3 Months), 6M (6 Months), 9M (9 Months) and 12 M (12 Months) body weights were 3.03 ± 0.01, 13.29 ± 0.07, 17.86 ± 0.10, 21.34 ± 0.12, 24.96 ± 0.15 kg, respectively. Period, season, sex and parity had significant influence (P<0.01) on all the growth traits under study. The overall least square means for AGR i.e. from birth to 3, 3 to 6, 6 to 9, 9 to 12 and 3 to 12 months were 114.95 ± 0.76, 50.01 ± 0.65, 38.50 ± 0.64, 38.00 ± 0.72 and 40.19 ± 0.46 gms, respectively. Period and sex had significant influence on AGR for all age intervals. Both pre-weaning AGR and post-weaning AGR’s were significantly (p < 0.01) influenced by season of birth except post-weaning AGR 3-12 months. The overall least squares means for age at first lambing (AFL) in Nellore Jodipi sheep was 794.2 ± 6.9 days. Period of birth of ewe but not season of birth was found to be significant on AFL. The overall least squares means for lambing interval was 371.6 ± 11.9 days. Parity of ewe at lambing was found to be significant. The overall least squares mean lambing percentage (ewe covered) was 63.1 ± 2.30. Contemporary Group (CG) at breeding, but not parity of ewe at lambing had a highly significant influence on lambing percent. The mean generation interval, inbreeding coefficient (F), proportion of population inbred, individual increase in inbreeding, equivalent number of generations (EqGi) and effective population size based on birth year were 3.37y, 0.97 %, 31 %, 0.48 %, 2.54 and 1260.52, respectively. The regression coefficients of most of the traits on inbreeding coefficient (F), were negative and non-significant. Maximum and significant effect (p < 0.01) of ‘F’ was noticed on 9M, with a decrease of 0.075 kg of mean value per every 1 per cent increase in inbreeding. Effect of inbreeding was significant on post-weaning AGR 3-6 months. There was a decrease of 0.411 grams mean value in pre-weaning AGR, for every 1 per cent increase in ‘F’. The regression of age at first lambing on F was positive and significant. There was an increase of 5.565 days in AFL per every 1 per cent increase in F. The regression of lambing interval on F was negative (-1.223 days) and insignificant. The regression of lambing percent on F was positive and non-significant (0.001%). When inbreeding coefficient (F), included as fixed class in the analysis it exhibited highly significant effect on BW (p < 0.01), 3-6 months and 6-9 months post-weaning AGR; while significant (p < 0.05) on 3M, 12M body weights and 3-12 months post-weaning AGR. Effect of level of inbreeding on all reproductive traits was also found to be insignificant. The direct heritability estimates for BW, 3M, 6M, 9M and 12M from the best models in Nellore Jodipi sheep were 0.076, 0.194, 0.208, 0.199 and 0.136, respectively. The maternal heritability (m2), estimated from best models for body weights in which it was important, were 0.046, 0.038, 0.063 and 0.082 at 3M, 6M, 9M and 12M of age, respectively in Nellore Jodipi sheep. The estimates of h2 were moderate for pre-weaning (0.210) and all post weaning AGR (0.158 to 0.263) traits. The maternal heritability (m2), estimated from best models for the AGR traits in which it was important were 0.032, 0.025 and 0.029 for pre-weaning; post weaning 6-9 and 3-12 months AGR, respectively. The heritability estimates obtained for age at first lambing (0.082) and lambing percent (0.013) were low. For lambing interval, the estimated heritability was near to zero (0.0002). Repeatability for repeatable reproductive traits like lambing per cent (per ewe covered) was low (0.059) and for lambing interval, the value was near to zero (0.00018). All the estimates of genetic correlations among body weight traits were positive. Estimates of genetic correlations for birth weight with weight at later ages were medium (0.212 to 0.508). The correlation coefficients for 3M, 6M and 9M, with weights at later ages were medium to high (0.449 to 0.894). All the estimates for phenotypic correlations among body weight traits were positive. Birth weight had the lowest phenotypic correlation with the other traits (0.260 to 0.371), whereas, the remaining weights had moderate correlations (0.577 to 0.873). High estimates greater than 0.7 were observed for WW, 6M and 9M with subsequent ages. All the body weight traits (6M, 9M and 12M) had strong positive relationship with pre weaning AGR with medium to high range of values (0.393 to 0.855). Phenotypic correlations also followed the similar trend as genetic correlations (0.545 to 0.778). Genetic association between birth weight with age at first lambing (AFL) was positive and low in magnitude (0.07). Whereas, all body weight traits with lambing interval (LI) showed negative trend. Lambing interval recorded highest and lowest correlations with birth weight (-0.211) and 3 months body weight, respectively (-0.502). Phenotypic association between birth weight and age at first lambing (AFL) was negative and low in magnitude (-0.036). Highest value was noticed between birth weight with lambing interval (-0.031) and lowest between 3 months with lambing interval (-0.153) on phenotypic scale. The estimated overall average breeding values of sires for BW, 3M, 6M, 9M and 12 M body weights were found to be 3.09, 14.36, 19.04, 22.78, 24.73 kg by LSM; 2.96, 13.20, 18.12, 21.59 and 24.62 kg by BLUP method and 2.96,13.19, 18.11, 21.60 and 24.63 kg by DFREML methods, respectively. BLUP method was adjudged to be the most efficient method followed by LS and DFREML methods, because of its least error variance. LSM was best fitted model over the other two methods of sire evaluation based on coefficient of determination (R2), but the accuracy of BLUP was much closer to LSM than DFREML. The rank correlations among breeding values of sires estimated from different methods of sire evaluation were all high, and highly significant (P<0.01). The values ranged from 0.487 (LSM with DFREML for 9M) to 0.999 (BLUP with DFREML for BW). The rank correlations between BLUP and DFREML were greater than 0.9 for all the traits. BLUP or DFREML could select the same set of sires with almost similar ranking for unbiased estimates of breeding values for production traits. The direct genetic trends for BW, 3M, 6M, 9M and 12M were 0.003, 0.067, 0.084, 0.038 and 0.030, respectively in Nellore Jodipi sheep and the corresponding phenotypic trends were 0.010, 0.044, 0.083, 0.201 and 0.248, respectively.