Quantitative Trait Loci Underlying Udder Morphology Traits in Dairy Sheep

Abstract

A genome scan was conducted on the basis of the daughter design to detect quantitative trait loci (QTL) influencing udder morphology traits in Spanish Churra dairy sheep. A total of 739 ewes belonging to 11 half-sib families were genotyped for 182 microsatellite markers covering 3,248.2 cM (Kosambi) of the ovine autosomal genome. Phenotypic traits included scores for 5 linear udder traits: udder depth, udder attachment, teat placement, teat size, and udder shape. Quantitative measurements for the QTL analysis were calculated for each trait from evaluation scores using within-family yield deviations corrected for fixed environmental effects. Joint analysis of all families using Haley-Knott regression identified 5 regions that exceeded the 5% chromosome-wise significance threshold on chromosomes 7, 14, 15, 20, and 26. Based on the across-family results, a within-family analysis was carried out to identify families segregated according to the QTL and to estimate the QTL effect. The allelic substitution effect for individual families ranged from 0.47 to 1.7 phenotypic standard deviation units for udder shape on chromosome 15 and udder depth on chromosome 14, respectively. These QTL regions provide a starting point for further research aimed at the characterization of genetic variability involved in udder traits in Churra sheep. This paper presents the first report of a sheep genome scan for udder-related traits in a dairy sheep outbred population.

Quantitative trait loci for resistance to trichostrongylid infection in Spanish Churra sheep

“…In this genome scan a total of 182 markers (181 microsatellites and 1 SNP) distributed along the 26 ovine autosomes were genotyped across 1,421 animals belonging to 11 half-sib families. The procedures used for the genotyping of the 182 markers have been described in detail elsewhere [16,17]. The linkage map used in the current work was that generated for the most complete Churra sheep population genotyped (1.421 ewes), which has been reported by Gutiérrez-Gil et al [18].…”

Estimation of Genetic and Phenotypic Parameters for Udder Morphology Traits in Different Dairy Sheep Genotypes

“…Udder depth, udder attachment, teat placement, teat size and udder shape are commonly used traits for the selection programmes. In dairy ewes, the most important functional traits are those related to udder morphology, because they determine the machine milking efficiency of the animal and have a substantial effect on its functional lifetime (Gutiérrez et al, 2008). The relationship between udder traits are known for dairy cattle (Seykora and McDaniel, 1986;Rogers and Spencer, 1991).…”

Detection of QTL Underlying Milk Traits in Sheep: An Update

“…The most significant of these QTL was that identified in the proximal end of OAR7 for teat placement (Gutiérrez-Gil et al, 2008). In the same population QTL have also been identified for body conformation, which are functional traits of great interest in dairy sheep because its correlation with functionally productive life and overall productivity of the flock (Vukasinovic et al, 1995).…”

“…Udder related traits may be considered the most important functional traits in dairy sheep, as they determine the machine milking efficiency of the animal (Labussière, 1998) and have a substantial effect on its functional lifetime (Casu et al, 2003). QTL for udder traits have been reported in the Sarda x Lacaune population, the Lacaune-Manech families and in Churra dairy sheep (Gutiérrez-Gil et al, 2008). In the Sarda x Lacaune population a detailed study of udder morphology traits was performed, with digital picture measures being recorded in the cross-bred animals and a large list of udder morphology related traits being analysed for QTL detection.…”

“…A total of 1421 ewes sired by 11 IA rams and distributed among 17 different flocks were used in this project for detection of QTL underlying classical milk traits (Gutiérrez-Gil et al, 2009a). Other traits of interest in dairy sheep production such as morphology traits (Gutiérrez-Gil et al, 2008; and resistance to mastitis and nematode gastrointestinal infections (Gutiérrez-Gil et al, 2007;2009b) were also recorded in the commercial population genotyped. The average family size in this daughter design was around 110, ranging from 47 to 223 daughters per sire.…”