Why use artificial insemination
A cattle breeder may choose to utilise artificial insemination (AI) in their herds for several reasons including:
- genetic improvement
- access to genetics from across the world
- access to genetics from bulls that they would not otherwise be able to afford to purchase
- to reduce the number of bulls required
- access to breeds that are not available locally
- to join a bull with more females than he would be able to serve naturally in one mating season
- to mate individual cows to specific sires
- potential increased value of progeny from AI sires
- to reduce the risk of infection from venereal diseases
What to think about
Before commencing on an AI program the breeding objectives for the herd and suitability of sires to individual dams should be carefully considered.
Costs and available facilities should also be considered including:
- labour- cost, availability and skill
- adequacy of handling facilities
- cost of semen and drugs
- cost of AI technician
Costs will vary depending on synchronisation protocol used as they differ in drug and labour requirements.
Costs should be weighed against savings such as reduced number of bulls needed to be purchased and maintained throughout the year. There may also be an increase in income due to heavier calves at weaning as more calves are born earlier in the calving period and an increased value of calves from certain sires.
Management advantages of a successful AI program
The use of synchronisation programs, often used in combination with AI programs, may have further management benefits including:
- potential increase in calf weights at weaning due to females conceiving earlier in the breeding season
- a more compact calving pattern
- a more even line of calves
- reduced number of cows and heifers not in calf at the end of the breeding season
The number of females not in calf may be reduced because:
- more conceive earlier in the breeding season, so they have more time to resume cycling after calving and before the breeding season the following year
- anoestrus (non cycling) cows and prepubertal heifers may be stimulated to cycle earlier in the breeding season (when progesterone devices are used in the synchronisation program) than would otherwise occur so they have more opportunities to get in calf during the breeding season
- Cows and heifers that are either have physiological or anatomical problems that stop them from going in calf are identified earlier and removed from the breeding herd
Which animals should be artificial inseminated?
AI programs are not a silver bullet for fertility problems due to management factors. If pregnancy rates (number of cows in calf from all cows exposed to the bull) have not been at least 85% or more (in a 60-80 day breeding period) in previous years then there are most likely other management factors affecting pregnancy that must be addressed before commencing an AI program.
To gain the best possible pregnancy rate from an AI program the animals in the program should:
- have been vaccinated or treated to prevent relevant diseases with all vaccinations/treatments finishing a minimum of 30 days before the commencement of the AI program
- be in a body condition score of 2.5-3 for cows and three for heifers at calving ( on a scale of 1 - 5)
- (for heifers) have reached at least 60-65% (depending on the breed) of mature weight at the commencement of the breeding season
- be on a rising plane of nutrition post calving consuming a balanced ration
- continue to be provided with an adequate ration following AI to support pregnancy
- have calved unassisted
- have been calved for an average of at least 40 days or more before the commencement of an AI program
Animals which meet these requirements are more likely to have resumed normal oestrous cycles by the start of the breeding period increasing the chances of conceiving to AI.
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.
What pregnancy rate to expect
It is unrealistic to expect a 100% pregnancy rate from an AI program. A pregnancy rate of 65% to a single insemination whether by natural service or AI is considered good but can be reduced due to a variety of factors.
From a potential 100% pregnancy rate loss occur at several points including:
- a percentage of cows will not respond to the synchronisation protocol and will not come into oestrus, will come into oestrus outside of the set time frame or have an unfertile oestrus.
- when artificially inseminated, although fertilization is often high, not all cows will go on to establish a pregnancy.
- in FTAI programs all cows in the program are inseminated, but in other AI programs where heat detection is required, pregnancy rate can be further reduced if animals in heat are missed, they are identified incorrectly as being in heat, or they are presented at the wrong time for insemination (i.e. too early or too late relative to oestrus)
FTAI programs eliminate the need for heat detection and therefore losses of pregnancy associated with this stage of the program.
Achieving good results in an artificial insemination program depends on a number of factors including:
- cow health and nutrition
- good cow handling techniques to minimise stress
- adequate facilities to ensure the number of cattle can be inseminated within the desired time frame
- correct storage and handling procedures of drugs involved
- accurate implementation of the synchronisation protocol including precise administration of the correct dose of the correct drug in the correct place (i.e. intramuscular injections actually go into the muscle) on the correct day at the correct time
- accurate heat detection (if required for the program)
- correct semen handling, storage, thawing and insemination technique
- avoiding transportation between days 5-42 after AI
Attention to detail in every aspect of an AI program cannot be underestimated if good pregnancy rates are to be achieved.
Embryo transfer
Due to the costs involved, embryo transfer is mainly used by seed stock producers to accelerate genetic gain. Embryo transfer allows a superior female to have many more offspring than she would have naturally and allows repetition of desired joinings.
In most cases the donor female is treated with hormones so that many more oocytes develop on the ovary than normal. Drugs are used to stimulate ovulation followed by timed insemination. The fertilised embryos are flushed a few days later from the animal and graded. Only quality embryos with a good chance of establishing a pregnancy are kept.
Some cows do not repond well to superovulation but are valuable enough to justify single flushings, where only one embryo is produced and flushed from the animal. Oocytes may also be collected directly from ovaries and then further developed and fertilized in vitro (outside the animal).
The embryos can be either frozen for transferring later or transferred directly into recipient animals. Recipient animals must be synchronised to be at the same stage of the oestrous cycle as the donor animal when the embryos were flushed. Not all recipient animals synchronised will have responded to the synchronisation program. Only those recipients at the correct stage of the oetrous cycle should receive an embryo. The recipient animals represent one of the largest costs to an embryo transfer program.