Naslov
Estimation of genetic parameters for dairy traits in Pag sheep with single and multi – trait test–day models

Autori
Špehar, M. ; Mulc, D. ; Barać, Z. ; Mioč, B. ; Kasap, A.

Izvornik
Small Ruminant Research (0921-4488) 183 (2020); 1, 6

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Pag sheep ; Dairy traits ; Test–day records ; Multi– trait model ; Genetic parameters

Sažetak
The objective of the study was to estimate genetic parameters and other estimable sources of phenotypic variability for daily milk yield (DMY), fat content (FC), and protein content (PC) in the Pag sheep breed reared in predominantly outdoor breeding environment. A total of 79, 937 phenotypic records from 7132 ewes were used in the analysis. After pruning of the pedigree, a total of 7870 animals were included in the additive relationship matrix. Single – trait (ST) and multi – trait (MT) approaches were applied in the statistical analysis using fixed regression repeatability test–day model. Parity, litter size, season of lambing, flock, stage of lactation, and age at lambing were fitted as fixed effects, while additive genetic, permanent environment, and flock–test–day as random effects. The estimates of heritabilities with MT model were 0.32, 0.19, and 0.40 for DMY, FC, and PC, respectively. Repeatabilities for DMY, FC, and PC were 0.46, 0.21, and 044, respectively. Negative genetic correlations were found evident between DMY and FC (–0.35), and DMY and PC (–0.36), while positive between FC and PC (0.66). The average reliabilities of breeding values (BVs) for DMY, FC, and PC for ewes were 0.771, 0.788, and 0.846, and for rams 0.675, 0.677, and 0.708, respectively. Estimates of genetic parameters and reliabilities of BVs with ST approach were very similar to MT approach as well as ranking of the animals based on BVs. Rank correlations of BVs between examined approaches (ST and MT) for DMY, FC, and PC were 0.995, 0.987, and 0.999 for ewes, and 0.991, 0.984, and 0.998 for rams, respectively. The use of the MT approach provided small gain in accuracy of genetic evaluation, but we encourage its usage wherever possible, particularly taking into account small size of dairy sheep populations and negligible extra computational costs. 1.

Izvorni jezik
Engleski

Znanstvena područja
Poljoprivreda (agronomija)

POVEZANOST RADA