Genetic parameters of lactation cell counts and milk and protein yields indairy ewes

A total of 3231 lactation records of somatic cell counts (SCC), milk yield, and protein percentage for 2379 Spanish Churra ewes from 10 flocks were us ed to estimate genetic and environmental parameters. Genetic parameters wer e estimated by REML with a multitrait repeatability animal model. A lactati on measure of SCC was obtained as the mean of test day log SCC adjusted for stage of lactation. Heritabilities for SCC, milk yield, and protein percentage were 0.12, 0.24, and 0.17, respectively. The corresponding repeatabilities were 0.35, 0.49, and 0.38. Heritability and repeatability estimates of SCC obtained from th is study fell within the range frequently reported for dairy cows. Therefor e, as practiced for dairy cattle, future possibilities for sire evaluation to improve udder health status using lactation measures of SCC for dairy sh eep are not rejected, although hygienic practices are regarded as more impo rtant. Genetic correlations of SCC with milk yield and protein percentage were -0. 15 and -0.03, respectively. The genetic correlation between milk yield and protein percentage was -0.47. The low genetic correlations of SCC with milk yield and protein percentage may indicate that breeding decisions to impro ve milk and protein yields of Churra ewes are not expected to have an effec tive correlated response in SCC.