Genetic and Environmental Influences on Growth Performance of Jersey and Friesian Crossbred Dairy Cattle in Central Ethiopia

Abstract

This study was undertaken to evaluate the growth performance and estimate their genetic parameters for the crossbred of Jersey and Friesian with Boran breeds. Traits analyzed included birth weight (BW), weaning weight (WW), six-month weight (SMW), yearling weight (YW), pre-weaning weight gain (PRWWG), and post-weaning weight gain (PTWWG). Correlations of growth traits with age at first calving (AFC) were also computed to identify a better indicator of growth traits for AFC. Data collected from Boran (B) and crosses of Friesian (F) and Jersey (J) with Boran during 1978 to 2020 were used. A general linear model procedure (Models 1 and 2) was used for analysis. The first model was used to estimate the effect of fixed factors, while the second model calculated the crossbreeding parameters by fitting the coefficients of breed additive, heterosis, and recombination as covariates. In addition, multivariate analysis with fixed and random effects (model 3) was performed using WOMBAT to estimate genetic parameters. The overall least squares means of B and crosses of F and J with B were 27.09±0.1 kg for BW, 64.42±0.2 kg for WW, and 385.35±2 g for PRWWG. The corresponding estimates for post-weaning traits were 88.87±0.4 kg for SMW, 142.10±0.8 kg for YW, and 284.75±2 g for PTWWG. Genotype, birth year, birth season, and sex of calves significantly (p < 0.05) influenced all studied traits except for the effect of sex on WW. For instance, 1/2F:1/2B (F1) crossed calves gain approximately 80 -100 g more weight per day than B and other F x B crosses. Furthermore, 1/2F:1/2B (F1) attained 131 g and 119 g more PRWWG and PTWWG per day than their J counterparts, respectively. The contribution of the additive effect of the F breed was positive and significant (p < 0.001) for BW (11.99±0.7 kg) and WW (12.64±2). Likewise, heterosis from the F x B cross resulted in substantial improvement for all traits (p < 0.01). However, the weight gain obtained through heterosis was not sustained in subsequent generations of F x B crosses because of recombination loss in all traits. Estimates of recombination loss varied from -19.92±2 kg for WW to -68.49±7 kg for YW. Heritability estimates varied across traits and were reduced by approximately 26% to 56% for all traits expressed after BW. Strong genetic correlations were obtained between WW and SMW (0.86±0.03), WW and PRWWG (0.84±0.03), PRWWG and SMW (0.80±0.04), and YW and PTWWG (0.94±0.10). The results also showed desirably higher negative genetic correlations between YW and AFC (-0.77±0.09) and PTWWG and AFC (-0.80±0.09). The moderate to high estimated variances and h² indicate sufficient genetic variation within the population and the potential for genetic response to selection if an appropriate breeding program is implemented in the farm. The significant effect of year and season of calving and reduction in h² for growth traits expressed at later ages suggest these traits are highly influenced by environmental factors, highlighting the need for appropriate management and environmental interventions to optimize performance and complement genetic strategies.