Efeito do fotoperíodo na detecção do estro em fêmeas bovinas Nelore (Bos taurus indicus) e cruzadas Red Angus x Nelore e Limousin x Nelore (Bos taurus taurus x Bos taurus indicus) manejadas em diferentes regiões do Brasil / Photoperiod effect on estrus detection in Nellore, Red Angus x Nellore and Limousin x Nellore cows, raised on different Brazilian regions
AUTOR(ES)
Paulo Eduardo Fonseca Loureiro
DATA DE PUBLICAÇÃO
2005
RESUMO
The artificial insemination (IA) technique is growing in beef cattle herds from all regions of Brazil, especially to obtain Bos t. taurus x Bos t. indicus crossbreds in large herds were the European bulls are not adapted. One of the difficulties of the IA program is the low efficiency of heat detection. In other countries this was avoided through studies of the sexual behavior of the cows. Brazilian beef cattle herds are distributed in all over the territory, but are concentrated mainly in the Southeast, Middle West and North regions, with large climatic differences and day duration (photoperiod), rain seasonality and temperatures that alter the sexual behavior of the cows and heifers. In this way this study used the heat observation in four farms in the North and Middle West regions to study the photoperiod effect on heat detection. A total of 4202 heats were detected in 3358 Nellore, 662 crossbred Limousin x Nellore and 182 crossbred Red Angus x Nellore females, managed under the same detection procedure. The mean daylight duration was 730,3, 750,8, 771,0 and 795,6 minutes, respectively in the farm 1 (Para State), 2 (Tocantins State), 3 (Goias State) and 4 (Mato Grosso do Sul State). As the daylight increased more estrus were detected in the morning. There were differences in cattle categories in estrus detection, with the heifers heat detected in the morning in all farms and in all genetic groups. There was no significant difference between genetic groups inside categories. Cows without calves behaved in a similar way to the heifers and showed no significant difference in heat detection. Cows with calves had a tendency to show estrus in the afternoon.
ASSUNTO(S)
reproduction beef cattle crossbred reprodução cruzamento industrial gado de corte estro fotoperíodo estrus photoperiod
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