Genetic analysis of udder score and milk traits in test day records of Sfakia dairy ewes
Abstract. A total of 4466 monthly test day records of 555 Greek Sfakia dairy ewes were used to estimate heritabilities as well as genetic and phenotypic correlations for udder score (US), average daily milk yield (MY), fat percentage (FC) and protein percentage (PC) of milk. Genetic parameters were estimated with a multitrait animal model with correlated residuals. Heritabilities were between 0.17 and 0.24, 0.41 and 0.47, 0.32 and 0.52 and 0.44 and 0.55, for test day US, MY, FC and PC, respectively. Within traits, genetic correlations between test days were between 0.54 and 0.57, 0.71 and 0.96, 0.79 and 0.99 and 0.85 and 0.99 for US, MY, FC and PC, respectively. Genetic correlations between milk traits and US were negative and of very low magnitude (−0.04 to −0.06). Genetic correlations between MY – FC and MY – PC were negative and of varying magnitude, from −0.37 to −0.52 and from −0.44 to −0.50, in the four test days, respectively. Fat and protein percentages were found to be highly, positively, correlated.