부산대학교 도서관

Beef cattle breeding has developed in extensive grazing systems in Mexico, concerning the livelihood of over one million families and affecting the use of natural resources. Reproductive efficiency is a major determinant of both the environmental impact of the herd, and the economic viability of the cow-calf production system. As reproductive traits have low heritability, reproductive efficiency can be largely influenced by herd management practices. Thus, a questionnaire was administered as personal interviews to 3280 producers, to investigate the prevalence of practices that could directly influence the reproductive outcome of their cattle. Results show that yearround breeding (93%) and natural service by the bull (97.4%) are the most common mating methods. However, only 41% of producers evaluate the breeding soundness of their bulls, and diagnostic testing for specific reproductive diseases of the sires is barely performed in 20% of the farms. The main declared reason for replacing the bull is old age (26.8%), which is followed by to avoid inbreeding (68.4%). Less than 10% of the operations use methods for the synchronization of the estrous cycle, and most farmers breed their heifers for the first time after 2 years of age (73%). Diagnosis of pregnancy is performed in merely 31% of operations, with 23% of the producers declaring to discard non-pregnant cows. Energy or protein feed supplements are provided to the cattle in 63% of the production units, whilst mineral supplements are given in 79% of the farms. Calves are typically weaned between 6 months and a year of age (85%). Only 16% of operations vaccinate against brucellosis and 17.5% against other reproductive diseases (IBR-DVB-VSR and Leptospirosis). The present study showcases a low frequency of adoption of basic reproductive management practices by cow-calf operations in Mexico. Advancement of these practices, as well as implementation and promotion of associated technologies, denotes an area of opportunity to improve the reproductive efficiency of the national herd. [ABSTRACT FROM AUTHOR]