Genetic parameters of weeping teats in Italian Saanen and Alpine dairy goats and their relationship with milk production and somatic cell score

摘要

This paper reports a quantitative genetics analysis ofweeping teats (WT), an abnormality of the mammarygland in goats. Weeping teats are characterized by milkoozing out of the teat or by the presence of multiplecysts near its base. This abnormality has been routinelyrecorded in Italian Alpine and Saanen goats since 2000using a score of 0 or 1 (0 = defect not present, 1 = defectpresent). No information is available on the geneticbackground of WT or its relationship with productionor other udder-related traits. Data obtained by theItalian National Sheep and Goat Breeders Association(Rome, Italy) were used to estimate both heritabilityof WT and its genetic correlation with milk yield, somaticcell score, and udder traits. The final data setused in the analysis included 2,178 Saanen and 2,309Alpine primiparous goats kidding from 2009 to 2014.The pedigree data included 7,333 Saanen and 7,421Alpines, respectively. A threshold–linear multivariateanimal model was used to estimate variance and covariancecomponents. A genealogical data analysis was alsoimplemented, including genealogical data completeness,inbreeding, and identification of possible most recentcommon ancestors. On average, around 4 and 13% ofprimiparous Saanen and Alpine females kidding from2009 to 2014 showed mammary gland abnormality,respectively. Weeping teats heritability was 0.27 and0.26 for Saanen and Alpine, respectively. Genetic correlationsbetween milk production or somatic cell scoreranged from −0.16 in Saanen to 0.43 in Alpine, but thestandard error of the estimates was very large. Positivegenetic correlations were observed among WT and teatcharacteristics in both Saanen and Alpine. The averageinbreeding of abnormality carriers was 2.4 and 5.1 forSaanen and Alpine, respectively. The genealogical dataanalysis identified 4 common ancestors of affected doesin Saanen and 2 in Alpine. These results indicate thatWT have a possible genetic background. A genomewideassociation study might help in understanding thepolygenic or monogenic determination of this abnormality.