Effect of beta-lactoglobulin polymorphism on milk-related traits of dairy ewes analysed by a repeated measures design.

Among specific genes that may affect economically important traits in sheep, the β-lactoglobulin (LGB) locus has been extensively studied. Polymorphism has been detected in several breeds, but studies of the effect of LGB alleles on milk production traits have given conflicting results. Some found that LGB polymorphism significantly affects milk yield (Bolla et al. 1989; Herget et al. 1995; Fraghì et al. 1996), fat and protein content (Garzon & Martínez 1992; Giaccone et al. 1997; Kukovics et al. 1998), only fat content (Pirisi et al. 1998) and cheese yield and composition (Di Stasio et al. 1997; Rampilli et al. 1997). However, other studies failed to detect any effect of the gene on mi…