No abstract

a b s t r a c tAt present, the Assaf is the main dairy sheep in Spain. The Spanish Assaf (Assaf.E) was formed by male-mediated absorption of native Spanish sheep. Here we assess the genetic relationships among the Assaf.E and major native Spanish dairy breeds using microsatellites to contribute to the knowledge of the formation and within-population genetic variability of the breed. Blood samples from 44 unrelated Assaf.E individuals from 23 different Assaf.E flocks spread throughout 6 different Spanish provinces were obtained and genotyped using 14 microsatellites. Up to 312 additional samples belonging to the Awassi and Milchschaf sheep breeds and to six native Spanish dairy sheep breeds (Castellana, Churra, Latxa, Manchega, and Rubia de El Molar) as well as samples from Merino individuals to be used as the outgroup were also analysed observed (H o ) and expected (H e ) heterozygosity, rarefacted number of alleles per locus and distances based on molecular coancestry information were computed. Probabilities of assignment of the Assaf.E individuals to native Spanish dairy sheep breeds and cryptic genetic structure in the whole dataset were also assessed. It can be concluded that the Assaf.E breed has low genetic variability and high genetic distance with respect native Spanish dairy sheep breeds. From our results, the formation of the Assaf.E breed basically occurred via the absorption of individuals belonging to the Entrefino type, particularly to the Castellana and Manchega populations. Furthermore, Churra individuals may have participated in the formation of the Assaf.E breed at an early moment of the introduction of the breed into Spain.

This work describes an outbreak of clinical mastitis affecting 13 of 58 lactating ewes due to Streptococcus equi subsp. zooepidemicus. S. equi subsp. zooepidemicus was isolated in pure culture from all milk samples. All the clinical isolates had identical biochemical profiles and antimicrobial susceptibility patterns and also exhibited indistinguishable macrorestriction patterns by pulsed-field gel electrophoresis, indicating that all cases of mastitis were produced by a single strain.

A total of 42,197 records of test-day milk yield (TDY) and 7654 lactations from 3854 individuals belonging to the Spanish Assaf (Assaf.E) breed were analysed using univariate and multivariate models to estimate genetic parameters affecting TDY, total milk yield standardised to 180 days (MY 180 ) and lactation length (LL) in order to asses their possibilities of use in the selection scheme of the Assaf.E population. Estimates of h 2 were, in general, on the lower limit of those usually reported for the three analysed traits. Estimates of heritability for MY 180 varied from 0.131 to 0.177. Estimates of h 2 for LL and TDY were consistent regardless the estimation model being of, roughly, 5% and 10%, respectively. The estimates for the permanent environmental effect (c 2 ) of TDY were consistently the same (0.27-0.28) regardless the fitted model whilst they showed large differences for LL and MY 180 . Genetic correlations were always positive and high ranging from 0.792 for the pair LL-TDY to 0.999 for the pair MY 180 -TDY. Correlations between permanent environmental effects were even higher ranging from 0.932 for the pair LL-MY 180 and 0.999 for the pair MY 180 -TDY. The advantages of using TDY as selection criterion in the Assaf.E improvement scheme are discussed.

The relationship between 17 body and 8 udder measurements and phenotypic dairy performance were studied using information from 280 Spanish Assaf ewes from 2 to 4 years old belonging to 18 flocks. The influence of the environmental area on the dairy traits was assessed by fitting a fixed model including the flock effect and the age effect. A factor analysis was also carried out to determine the lowest number of independent factors that account for most of the variation in the traits. The flock was statistically significant for performance trait and predicted breeding value (PBV) while the age was only significant in 150 days standardized milk yield (MY150) and daily milk yield (DMY). In general, not much association was found between morphological and dairy performance traits. Few body traits showed significant phenotypic correlations; mainly those related to height, diameters, ears and tail, with the latter being the most correlated but unfavourable for DMY and PBV. Among udder conformation, udder depth and length were the most correlated traits to milk production, while deep udders and short teats were related to lower somatic cell counts. The different traits were classified for analyses into six factors relating mainly to: live weight; production and udder traits; cheese production; stature; teats and udder health; and udder dimensions. Trade of animals was concluded to be unreasonably based on morphological or even on performance traits. The participation of breeders in an appropriate breeding scheme based on accurate genetic evaluations is encouraged.