Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Studies on dairy production of milking ewes I. - Estimates of genetic parameters for total milk composition and yield | Génét. Sél. Evol. 1987 19 3 459-474 Studies on dairy production of milking ewes I. - Estimates of genetic parameters for total milk composition and yield F. BARILLET and D. BOICHARD . Station d Amelioration Génétique des Animaux Toulouse BP 27 F 31326 Castanet-Tolosan . Station de Génétique quantitative et appliquée F 78350 Jouy-en-Josas Summary Genetic parameters for dairy traits in first lactation milk yield fat and protein yields fat and protein contents were estimated from records of 1487 Lacaune ewe lambs born from 102 young rams undergoing progeny test and 74 proven rams. Variance and covariance components were estimated by Henderson s methods I and III. According to the analysis information from proven rams was totally or partially used for estimating fixed effects or was excluded. Results appeared similar to the average literature data for dairy cows except the correlation between fat and protein contents which was rather high . The genetic standard deviation of fat was larger than that of protein the ratio being about for yields and for contents. Accordingly expected genetic change is likely to be smaller for protein matter than for fat matter. Whereas the genetic correlation between fat content and yield was positive the genetic correlations between protein content and yield or between content of one component and yield of the other seemed to be close to zero and maybe negative. Accordingly the selection criterion should include useful yield and content instead of the useful yield alone. Useful yield or content was defined as a combination of fat and protein yields or contents with weighting 1 and respectively. Key words Dairy ewes milk composition milk yield genetic parameters selection goal. Résumé Etudes sur la production laitière des brebis trades I. - Paramètres génétiques de la quantité et composition totale du lait à la traite Les paramètres génétiques des caractères laitiers quantité de lait de matière grasse et de
