Resumo

VERA, M. et al. Impact of management factors on days to conception in dairy heifers. Agriscientia [online]. 2020, vol.37, n.1, pp.33-40.  Epub 01-Jun-2020. ISSN 1668-298X.  http://dx.doi.org/10.31047/1668.298x.v37.n2.25979.

Increasing the number of pregnant heifers per time unit improves reproductive efficiency in dairy herds. The objective of this work was to analyze the effect of management factors on conception. Reproductive events of 2532 heifers throughout 37 years were analyzed adjusting proportional risk models. The interval from the first service to conception (IPSC) was defined as the days passed from the start of the service period (IPS) to conception. The observation period per animal was 90 days. Models adjusted for IPSC include effects of age at the start of the service period (IPS), year, number and season of Services, conception rate of bulls, and year-to-season interaction with services. The Weibull model adjusts the IPSC variation pattern. Conception was lower in heifers under 18 months, in the 2nd and 3rd service, and when bulls with less conception rate were used. Conception was higher in fall services by 1.17 times compared to spring services. Identifying management factors affecting days to conception in heifers allows developing strategies to improve reproductive efficiency in dairy herds.

Palavras-chave : Proportional hazard models; reproductive efficiency; conception rates.

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