Características de estro pós-parto associadas às chances de prenhez de vacas holandesas em lactação
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2020-03-03
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Universidade Federal de Goiás
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The detection of estrus remains a major problem in dairy cattle, despite the enormous progress in the knowledge of the reproductive physiology of the cow and in the development of auxiliary methods. The success of any estrus detection program will depend, at least in part, on the cows' ability to exhibit estrus, which is affected by a multitude of physiological and management factors that favor or suppress estrus behavior. Parity, number of days postpartum, body condition score, milk production, calving problems, postpartum disease is recognized for influencing estrus expression. In addition, heat stress, building and the size of the herd can also affect estrus behavior. The aim of this study was to evaluate the risk factors associated with estrus behavior, identified by an automated estrus detection system. Data from three experiments carried out between August 2015 and July 2018, in the state of Florida, United States of America, were collected and processed. The number of animals that participated in the experiments A, B and C was 565, 671 and 678, totaling 1914 lactation cows and 3029 estrus events. The animals enrolled in the experiments were monitored by an automated estrus detection device (SCR Inc., Netanya, Israel). Estrus was determined according to changes in activity and rumination patterns within the two-hour interval compared to the average activity and rumination for the same period in the previous five and seven days, respectively. Data were analyzed using ANOVA, logistic regression and Cox proportional regression using the SAS statistical software. The duration and intensity of estrus showed a negative correlation with the proportion of time cows were subjected to heat stress. The return to ovarian cyclicity before the end of the voluntary waiting period increased the chances of pregnancy at the first service and the pregnancy for artificial insemination up to 150 DIM. Uterine disease, subclinical ketosis and BCS were associated with delayed return to cyclicity, potentially negatively impacting reproductive performance.
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FROTA, W. V. Características de estro pós-parto associadas às chances de prenhez de vacas holandesas em lactação. 2020. 56 f. Dissertação (Mestrado em Zootecnia) - Universidade Federal de Goiás, Goiânia, 2020.