Silent oestrus manifestation in Nigerian Bunaji Zebu cows

Abstract

Silent oestrus was investigated in 68 postpartum Bunaji Zebu cows of 5–8 years of age. Following parturition, all cows were observed for behavioural oestrus daily by herdsmen from 07.00 to 18.00 h. In addition, a vasectomised bull harnessed with a chinball mating device ran continuously with the herd. Blood samples were collected from these animals by jugular vein puncture 2–3 times a week from calving until 90 days postpartum for progesterone analysis. Twenty cows (29.4%) exhibited silent oestrus while 30 cows (44.1%) were anoestrus as indicated by the serum progesterone concentrations. Eighteen cows (27.0%) manifested oestrous behaviour. For silent oestrus cows, the range and average duration of silent oestrus for first, second and third silent oestrous cycles, in days, were 15–23 (18.7 ± 4.3), 13–35 (23.9 ± 11.1) and 12–29 (20.4 ± 8.6), respectively. For the oestrus cows, the range and duration of oestrus for the first, second and third oestrous cycles, in days, were 13–26 (19.1 ± 6.9), 11–32 (21.1 ± 10.9) and 14–28 (20.6 ± 7.4), respectively. The differences in lengths (days) for the first, second and third oestrous cycles between the silent oestrus and the oestrus cows were not significant ( P > 0.05). It is concluded from the results of this study that silent oestrus and anoestrus occur in Nigerian Bunaji Zebu cows during the postpartum period and this may be one of the contributory factors causing the reported prolonged calving intervals in these breeds of cattle.