AI programs
Many factors affect the success rate of an AI program. It is crucial that:
- drugs are administered in a timely and appropriate manner
- observations are carried out by experienced people for the correct length of time and at the correct times of day
- records are accurately kept
- insemination is carried out following appropriate techniques and drugs and semen are stored correctly
Hormones commonly used for AI programs in beef cattle include prostaglandin, progesterone, oestradiol and gonadotropin releasing hormone. Together these drugs given in a specifi order help synchronise follicular waves and the timing of ovulation.
There are various synchronisation programs. Some will concentrate oestrus (heats) into a few days, but still require heat detection (which is crucial for the program’s success), whilst others will synchronise oestrus into a few hours allowing for fixed time AI (FTAI) where all animals are inseminated in a few hours. FTAI programs eliminate the labour requirements and associated costs required for heat detection and only require one visit from an AI technician.
Adequate heat detection, which requires a time commitment and experienced personnel, can be very time consuming and therefore costly in terms of labour. Studies have shown that a large proportion of oestrus behaviour is shown at night and there is large variation in how long an animal is in heat. The definitive sign of an animal in oestrus is that she will stand to be mounted by another animal, but there are considerable variations between animals in how often this behaviour occurs during oestrus.
Animals should be artificially inseminated 8-12 hours after the start of standing oestrus being observed (i.e. if they are observed in oestrus in the morning they should be inseminated in the afternoon and if they are observed in oestrus in the afternoon, they should be artificially inseminated the following morning).
Tail paint and pressure mount detectors can assist with heat detection but visual observations are also necessary to ensure animals are artificially inseminated at the correct time. Animals may sometimes activate heat mount detectors or remove tail paint by scratching on low hanging branches so paddocks should be selected carefully for the heat detection period of the program. Additionally they may be partially activated or lost making it difficult to tell if the animal is in heat unless behaviour has also been observed.
Studies have shown that a large proportion of females may not have resumed regular fertile oestrous cycles by beginning of the breeding season. The use of progesterone in the synchronisation program is important in these situations as it can help stimulate resumption of normal fertile oestrous cycles and improve chances of conceiving.
Bos indicus cattle have several differences in their reproductive physiology in comparison to Bos taurus cattle. Bos indicus cattle take longer to resume cycling post calving, reach puberty at an older age and oestrus behaviour is of a much shorter duration and harder to detect. For this reason FTAI programs are more commonly used for Bos Indicus cattle as they eliminate the need for oestrus detection.
Talk to your vet or animal breeding centre to discuss the most appropriate synchronisation program for your situation.