Estimates of Genetic Parameters for Economic Traits of Holstein Friesian Dairy Cattle in Tropics: A multi-trait animal model

Abstract Background: In any genetic improvement program, multi-trait estimates of genetic parameters and breeding values of economically important traits are essential to facilitate total merit index selection objectives.Method: Data comprising 4,263 lactation records of 1,223 cows calved in the years between 1992 and 2017 were used to estimate genetic parameters and breeding values of lactation milk yield (LMY) and lactation length (LL) and fertility (age at first calving, AFC; calving interval, CI; and days open DO) traits. Preliminary analysis of fixed effects used in the mixed model analysis was tested for their significance using lm package of R software. C(o)variance components and resulting parameters were estimated by fitting single and multi-trait repeatability animal models using BLUPF90 software packages.Results: The heritability estimates of LMY and LL were 0.21±0.04 and 0.13±0.02, respectively. Heritabilities for AFC, CI, and DO were 0.53, 0.12, and 0.14±0.04, respectively. Repeatability estimates of production and fertility traits were low to moderate. The genetic correlation between LMY and LL was high (0.53) whilst, among fertility traits, the estimates were ranged from 0.09±0.03 (between AFC and CI) to 0.99±0.01 (between CI and DO). Genetic correlations of productive traits with fertility traits were ranged from -0.01 to 0.99. The phenotypic correlations between production and fertility traits ranged from 0.06±0.02 for LL and AFC to 0.43±0.02 for LL and DO. The genetic trends for LMY and LL were positive and genetically improved by 15.80 kg year−1 and 0.92 days year−1, respectively. Regarding fertility traits, favorable trends of -0.56 and -0.65 days year-1 were observed for CI and DO, respectively. However, unfavorable trends of 0.04 month year−1 were obtained for AFC.Conclusion: With this small herd size, the study highlighted that a high response to selection for LMY and AFC would be expected in this population. Furthermore, aggregate selection of both production and fertility traits should take into account their antagonistic genetic correlations in future improvement programs.