Lactation and Sample Test-Day Multi-trait animal model for genetic evaluation of somatic cell scores in Hungarian Holstein-Friesian crossbreeds
Abstract. Genetic and phenotypic correlations were estimated for means of log2 SCC (somatic cell scores: SCS) with milk production traits using complete lactation and sample test-day data sets. Data of SCS and milk production traits for six genetic groups of Holstein-Friesian (HF), Hungarian Native Breed (NHB) and four of their crossbreeds were used. Multi trait animal model was used for the estimation of all genetic and phenotypic (co)-variances All estimates of correlations either genetic (Rg) or phenotypic (Rp) between SCS and milk production traits were mostly negative except with protein percentage. Lactation (L) estimates of Rg between SCSL and total milk yield (MY), fat (FL), protein (PL) and lactose (LcL) percentages were -.11 ±10, -.12 ± .04, .09 ± .03, and -.18 ± .09, respectively and the corresponding sample test-day estimates (STD) were -. 13 ± .07, -. 13 ± .08, -.11 ± 04, -.11 ± 08 respectively. L and STD Rp estimates of SCS with MY and protein were higher than the corresponding R. L-Rg of SCS with MY and protein and L-Rp with fat and lactose were increased with parity. Rg either L or STD with fat decreased with the parity. The highest estimates of L-Rg of SCS with MY were negative for HF in the 2nd and the 3rd parity and were ranged from −0.13 to −0.17. Rg of SCSSTD with daily milk yield (DY) across parity in different genetic groups were higher than the corresponding with MY. All correlations of SCS with protein were positive. L-Rg ranged from .17 to .22 for HF vs. .01 to .04 for NHB. While L-Rp ranged from 06 to 15 for HF vs. .04 to .11 for NHB. It could be concluded that, trend of the relationship for SCS with milk production may had some change in crossbred than purebred aecording to percentage of crossing.