Arquivo Brasileiro de Medicina Veterinária e Zootecnia
On-line version ISSN 1678-4162
FONSECA, V.O.; FRANCO, C.S. and BERGMANN, J.A.G.. Reproductive and economic potencial of Nellore bulls mating in the proportion bull: cow 1:80. Arq. Bras. Med. Vet. Zootec. [online]. 2000, vol.52, n.1, pp. 77-82. ISSN 1678-4162. http://dx.doi.org/10.1590/S0102-09352000000100017.
From 158 sexually mature Nellore bulls evaluated for sexual soundness using physical and morphological characteristics of semen and scrotal circumference (test 1) and sexual behavior (test 2) 15 were classified either as good or excellent and they were selected. Bulls were randomly divided into two experimental groups: group 1- with five bulls for mating 400 cows (1:80 ratio), and group 2- with ten bulls for mating 400 cows (1:40 ratio). Females were multipara, open and non-nursing Nellore. Pregnancy rates at 30, 60 and 90 days of the breeding season were 62.0 vs. 67.3% (P³ 0.05), 84.5 vs. 87.3% (P³ 0.05) and 93.5 vs. 97.5 (P³ 0.05), for groups 1 and 2, respectively. It was observed a reduction of 22.8% in management costs (cost of buying extra bulls), when using 1:80 over 1:25 bull:cow ratio.
Keywords : Cattle; Nellore; bull:cow ratio; fertility.