The length of the oestrous cycle, oestrus and the time of ovulation were assessed in 20 adult, non-lactating @entity7040 @entity291 over 53 consecutive days of observation. Oestrus was detected at 30-minute observation periods daily. Peripheral blood samples were collected twice weekly for @entity1420 determination. To measure the length of the synchronised oestrous period, 10 @entity291 with a palpable corpus luteum were injected with @entity3774 alpha and continuously observed for 96 hours. Two @entity291 at a time were exposed to a bull with a deviated penis for five minutes every three hours during this period. To measure the length of the natural oestrus, eight of the 10 @entity291 from the previous experiment were continuously observed from day 21 after @entity3009 injection. They were kept during the daytime in a field with two teaser bulls and at night in a @entity291 pen where they were exposed to a teaser bull every three hours. Oestrus was considered to occur when the @entity291 stood to be mounted. Ovulation was detected by rectal palpation every three hours in five @entity291 starting six hours after receptivity commenced until ovulation took place. The length of the oestrous cycle was 20.1 +/- 1.9 days; 20 per cent of the animals did not show oestrus although their @entity1420 levels demonstrated that they were cycling. Two @entity291 showed oestrus following @entity3774 injection although they were cycling as revealed by serum @entity1420 . Five animals showed behavioural oestrus around 118 hours after injection and following their release. Oestrus duration was 15.3 +/- 6.0 hours and ovulation occurred 28.2 +/- 5.0 hours after the start of the period of sexual receptivity.

Oestrous cycles, oestrus and ovulation of the XXXX in the Mexican tropics.

@entity1420 :: ('MESH:D011374', 'Chemical') :: ['progesterone'] @entity3009 :: ('CHEBI:26333', 'Chemical') :: ['prostaglandin'] @entity3774 :: ('MESH:D015237', 'Chemical') :: ['prostaglandin F2', 'prostaglandin F2 alpha'] @entity7040 :: ('9915', 'Species') :: ['zebu'] @entity291 :: ('9913', 'Species') :: ['cows', 'cow', 'cattle']
@entity7040 :: (9915,Species) :: ['zebu']
