Estimates of genetic parameters and genetic trend for growth traits and Kleiber ratio of Holstein-Friesian calves.

Growth traits of calves, which are quantitative characteristics determining cattle business profitability, vary according to genetic and environmental factors. In other words, growth traits depend on the genetics of the individual and vary with farm management. The aim of this study was to investigate the effective environmental factors, genetic parameters, and genetic trends for some growth traits and the Kleiber ratio (KR) in Holstein-Friesian calves. For this purpose, the records of 724 calves, progeny of 566 dams and 29 sires, reared between 2017 and 2019 on a private dairy farm in Türkiye, were used. MTDFREML software was utilized to estimate genetic parameters and genetic trends of growth traits and KR. In this study, regarding weight, the mean of birth weight (BW), 60-day weight (W 60 ), and 90-day weight (W 90 ) were 39.76 ± 6.15 kg, 69.23 ± 10.93 kg, and 95.76 ± 16.48 kg, respectively. Concerning weight gain, 1-60 daily weight gain (DWG 1-60 ), 60-90 daily weight gain (DWG 60-90 ), and 1-90 daily weight gain (DWG 1-90 ) were 0.49 ± 0.16 kg, 0.91 ± 0.34 kg, and 0.63 ± 0.17 kg, respectively. With respect to KR, 1-60 daily KR (KR 1-60 ), 60-90 daily KR (KR 60-90 ), and 1-90 daily KR (KR 1-90 ) were 2.03 ± 0.48, 2.93 ± 0.89, and 2.02 ± 0.34, respectively. As a result of the GLM analysis, only the effect of the birth season on all traits was significant (p < 0.05 or p < 0.01). In addition, it was detected that sex had a significant effect on BW and W 60 (p < 0.05 or p < 0.01). For all traits, only the effect of parity on KR 1-60 was not significant. In REML analysis, direct heritability differed between 0.26 ± 0.16 and 0.81 ± 0.27 obtained at DWG 1-90 and DWG 1-60 , respectively. Also, the highest repeatability (0.100) was obtained in DWG 1-60 . It was detected that mass selection could be used in all traits for breeding program. In BLUP analysis, the current population had an increasing trend for BW and W 90 and a decreasing trend for W 60 . However, there was no significant change in other weight gain traits and KR over the years. Calves with high breeding values for BW, W 60 , W 90 , DWG 1-60 , DWG 60-90 , and DWG 1-90 should be chosen for selection programs. But for KR 1-60 , KR 60-90 , and KR 1-90 , calves with low breeding values should be selected for efficiency. Also, KR evaluated would contribute to the literature and other research should be studied regarding KR.