Archivos de medicina veterinaria
versión impresa ISSN 0301-732X
WEBB, C. et al. Effect of two types of weaning and the application of a progestagen on the fertility in Bos indicus cattle. Arch. med. vet. [online]. 2004, vol.36, n.2, pp.147-154. ISSN 0301-732X. http://dx.doi.org/10.4067/S0301-732X2004000200005.
A total of 55 Zebu females, on average of 67 days postpartum, were synchronized with synthetic progesterone (Crestar, Lab Intervet, México). At the moment of implant withdrawal the calves were separated for 72h and mothers and calves were divided into three groups: Group A (n = 20) mantained visual and olfatory with their calves (CCV). Group B (n = 20) had neither visual nor olfatory contact with their calves (SCV) and the control group C (n = 15) contained synchronized cows wich were not separated from their calves (SS). For the CCV group the percentage of animals cycling at hhe onset of the experiment was 10% (2/20). When exposed to bulls the percentage increased to 85% (17/20). In the group SCV 20% (4/20) showed an active corpus luteum (CL) at the beginning and this percentage increased to 70% (14/20). In the SS group the percentages were 33.3% (5/15) and 80% (12/15) respectively. Oestrous duration was on average 6.9h (P 0.05) and has to be traslated following Crestar withdrawal was the same with 43h . There was no significant statistical difference between the groups (P 0.05). In the SCV group the number of mounts per oestrus (1.5 ± 0.1) was less than in the other groups (CCV 2.2 ± 0.5 and SS 2.5 ± 1.0) and was statistically significantly different (P<0.05) than the groups. Fertility index for day 43 in group SS was 53.3% (8/15), in the group SCV 55% (11/20) and in group CCV 70% (14/20) There was no significant statistical difference between the groups (P 0.05). The body condition did not influence these percentages P0.05. The best reproductive response was found in groups CCV and SS, six days after exposure to a bull when 74% of the cows were already cycling. However, the best percentage of accumulated pregnancies against time was obtained in the SCV. Sixty-nine point one (69.1%) of the experimental animals, including the control group, ovulated.
Palabras clave : synchronization; artificial insemination; male behaviour; bioestimulation.