The aim of this experiment was to determine the interval between the beginning of the spontaneous or induced oestrus and the ovulation in females buffaloes using ultrasonography. This will be useful in the determination of the most proper moment for the pre-fixed artificial insemination. In the reproductive season, autumn in the South of Brazil (march-june), 132 clicling females were divided in 3 groups: Group A: 53 females were treated with auricular subcutaneous implant of norgestomet or intravaginal device of progesterone. In the moment that the devices were removed, 250mg of cloprostenol were applied for intravulvar submucosis (ivsm). Group B: 48 buffaloes females were treated twice with 250mg of cloprostenol for ivsm with interval of 11 days. Group C: 31 buffaloes females remained without any treatment (control group). All of them were inseminated in the moment that was observed the biggest diameter of pre-ovulatory follicle determinated by ultrasonography. In the 3 groups, there was significative difference between pregnant and non-pregnant females in the oestrus-ovulation interval and in the A.I.-ovulation interval. The pregnancy rates were 41.5%, 52.1% and 54.8% in the groups A, B amd C, respectively. The variation in the oestrus-ovulation in buffaloes is the major obstacle to achieve high pregnancy rates using pre-fixed artificial insemination in spontaneous and induced oestrus.
buffaloes; progestogen; prostaglandin F2 alpha; ovulation; ultrasonography; artificial insemination
