Dr. K. AnilkumarM.PRIYADHARSHINI2024-03-182024-03-182022-02-10https://krishikosh.egranth.ac.in/handle/1/5810207543The objective of the present study was to assess the sire evaluation methods in crossbred cattle of Kerala by using age at first calving (AFC) and first lactation milk yield (FLMY). The records of 898 crossbred cows sired by 203 bulls spread over a period of 18 years (2002-2019) were collected from different field centres of ICAR-FPT, KVASU. The effect of genetic factors such as genetic group, sire batches and non-genetic factors including the period of birth and season of birth for AFC and period, season, age at first calving for FLMYand source of sires from for both traits were analyzed through Least squares analysis. The present study revealed that overall least square means (±standard error) for AFC was 1041.66± 6.73 days and for FLMY 2780.17 ± 15.72 kg. The sire batches had significant influence (P<0.01%) on AFC and FLMY. The period and season of birth was found to have non significant effect on AFC. Effect of calving period was significant (P<0.05%) on FLMY. However, season of calving and AFC was found to have non-significant influence on FLMY. The genetic group of sire and sources of sire showed non-significant influence on both traits under study. The genetic parameters for AFC and FLMY were estimated using Harvey and REML method. The breeding values of sires with four models were estimated and compared for both traits. BLUP-SM showed lowest error variance and highest coefficient of determination when compared to other models. Relative efficiency of both these traits was estimated with respect to error variance i.e. BLUP-SM. The rank and product moment correlation was statistically significant (P<0.01%) by all four models. The high correlation between BLUP-SM and BLUP-AM indicate higher degree of similarity between both models. So the BLUP-SM and BLUP-AM were equally effective for sire evaluation based on AFC and FLMY. The sires were ranked based on most efficient method for both the traits. Since low AFC is preferred, the sires with lowest AFC value ranked first and the sire with highest AFC value was ranked last in that order and vice versa for FLMY. In conclusion, BLUP-SM was better model when different models were evaluated based on accuracy measures R2, C.V, RMSE, MAE and MAPE for evaluation of bulls of crossbred cattle.EnglishThesis