Genetic parameters of milk traits in Latxa dairy sheep

Abstract

A total of 7444 lactation records which include milk, fat and protein yields (MY, FY, PY) and fat and protein content (F%, P%) from 6429 Black-Faced Latxa ewes were employed to estimate genetic parameters for milk traits. Traits were standardized to 120 days of lactation. For the calculation of composition traits, not all test-days had their composition measured and therefore a correction taking this into account was included in the analysis. A first-derivative restricted maximum likelihood algorithm was used on an animal model with repeatability analysis, using models including fixed effects (flock-year-season of lambing, age-parity at lambing, number of lambs, interval between lambing and first milk recording and the combination of sampled test-days) and random effects (the additive genetic effect and the permanent environmental effect). The resulting heritabilities were 0·20, 0·16, 0·18, 0·14 and 0·38 for MY, FY, PY, F% and P% respectively. Heritability of F% was much lower than expected, probably due to problems derived from the recording method. Genetic correlations were high and positive between yields and moderately positive between F% and P%, and negative or null between yields and composition, as has been reported for other European dairy sheep breeds. As most of the milk produced by Latxa dairy sheep is processed into cheese, the inclusion of milk sampling in official milk recording and a change in the selection criterion are recommended to avoid a long-term worsening in milk composition.

Genetic parameters affecting 180-days standardised milk yield, test-day milk yield and lactation length in Spanish Assaf (Assaf.E) dairy sheep

“…Serrano et al (2003) recently reported a heritability estimate of 0.18 for standardised milk yield (120 days) in Manchega ewes. However, heritability estimated for total milk yield in native Spanish dairy sheep breeds such as those of 0.23 and 0.24 for the Churra breed (ElSaied et al, 1998a;Othmane, 2000) and 0.20 and 0.21 for the Latxa breed (Ugarte et al, 1996;Legarra and Ugarte, 2001) are usually higher than those reported here Table 4 Genetic, permanent environmental, residual and phenotypic covariances and genetic (r g ), permanent environmental (r c ) and phenotypic (r p ) correlations among lactation length (LL) in days, 180 days adjusted milk production (MY 180 Barillet, 1997) or Sarda (0.30; Sanna et al, 1997). However, Portolano et al (2001), in Barbaresca siciliana sheep, reported heritability estimates for milk yield standardised to different lactation lengths that always ranged from 0.14 to 0.15 and Nikolau et al (2004) reported different estimates for total milk yield in Lesbos dairy sheep ranging from 0.16 to 0.20.…”

Genetic relationship between milk score and litter weight for Targhee, Columbia, Rambouillet, and Polypay sheep1

“…Generally larger estimates of heritability have been previously reported for MS at mature ages for the same four breeds . Legarra and Ugarte (2001) reported an estimate of heritability of 0.20 for Latxa dairy sheep using 120-d repeated lactation records. Baro et al (1994) andEl Saied et al (1999) estimated heritability to be 0.34 and 0.18 for multiple-lactation, test-day milk yield of Spanish Churra milking sheep, respectively.…”

Improving performance of Zackel sheep through cross-breeding with prolific Bluefaced Leicester under semi-intensive and extensive production systems

“…Average milk production could be considered low or medium, with yields varying from 70 to 150 kg of milk/lactation (Padeanu 2001). Although, some strains, due to selection and proper nutrition, may be able to produce yields higher than 200 kg of milk/lactation, taking into account the heritability for milk yield that ranges between 0.20 and 0.29 (El-Saied et al 1998;Legarra & Ugarte 2001). The most prominent breeds of this group are Comisana, Karagouniko, Lesvos, Podhale Zackel, Pramenka, Sarda, Sfakion, Turcana, Valachian and Vlahico.…”