Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học Journal of Biology đề tài: Genetic and environmental factors affecting some reproductive traits of Holstein cows in Cuba | Genet Sei Evol 1997 29 469-482 Elsevier Inra 469 Original article Genetic and environmental factors affecting some reproductive traits of Holstein cows in Cuba A Menendez Buxadera1 L Dempfle2 1 Centro de Investigation para el Mejoramiento Animal Carretera Central Km 21 1 2 Cotorro Havana Cuba 2 International Trypanotolerance Center PMB lị Banjul Gambia Received 6 March 1996 accepted 14 August 1997 Summary - A total of 226 651 fertility records of dairy cows obtained from 1980 to 1988 was studied in order to determine the environmental and genetic factors affecting the reproductive performance of Holstein cows under Cuban conditions. Only of the inseminated females were pregnant at first service however for heifers this value was . The seasonal variability was higher for heifers and for primiparous than for older lactating cows. The best performance was found from February to April whereas during the hot and humid summer July to September poorer results were obtained. Age at calving or number of calvings was another important environmental source of variation the earlier the calving the poorer is the next reproductive performance. The genetic analyses were made within calving number with the REML procedure. For heifers 226 sires 45 575 records the heritability and the genetic coefficient of variation were and and and and for conception rate CR numbers of services per conception SG and conception status CS 1 SG respectively. For first calving females 280 sires 43 647 records the results were and and and and for CR SG and cs respectively. For the second and third calving the results were poorer. For the calving interval and days open the heritabilities were between and . The results of SG were selected as the best and more useful traits showing high genetic correlations for the same traits in different calving number. Holstein cattle breed I reproduction traits genetic parameters
