Genetic Analysis of Herd Life Traits and its Relationship with Production and Reproduction Traits in Jersey Crossbred Cattle

Abstract

Background: Herd life is a crucial economic trait, since it affects both total milk yield over a lifetime and the expenses associated with herd replacement. The genetic improvement of longevity traits is frequently challenging due to their typically poor heritability. Consequently, employing indirect selection based on production and reproductive attributes genetically related to longevity may yield a more efficacious breeding strategy. Assessing genetic parameters and interrelations among these traits is crucial for developing effective breeding strategies in jersey crossbred cattle. Methods: This research examined the performance records of 357 Jersey crossbred cows over a span of 39 years (1980-2018). Genetic parameters were assessed for various longevity-related traits, including herd life (HL), productive herd life (PHL), total milk production (TMP), number of days in lactation (NDL) and number of lactations completed (NLC). Their correlations with production traits, including first lactation 305-day milk yield (FL305MY) and first lactation total milk yield (FLTMY), alongside reproductive traits. [Age at first calving, service period and calving interval] were examined. Heritability estimations were derived via the paternal half-sib approach and a restricted maximum likelihood (REML)-based animal model. Covariance component analysis was employed to determine genetic and phenotypic associations among characteristics. Result: Estimates of heritability obtained from paternal half-sib analysis were 0.08±0.15 for HL, 0.06±0.14 for PHL, 0.23±0.17 for TMP, 0.26±0.17 for NDL and 0.38±0.18 for NLC. Estimates derived from the animal model varied between 0.05 and 0.18, signifying a modest to moderate additive genetic impact on longevity traits. The genetic correlations observed among longevity and productivity traits varied from 0.37 to 0.71, indicating positive correlations, although the phenotypic correlations were somewhat less. Most reproductive traits demonstrated low to moderate positive genetic associations with longevity traits, with the exception of the association between NLC and AFC. The identified correlation structure indicates that the selection for increased longevity may concurrently boost milk production without adversely impacting reproductive efficiency.