Artificial Insemination (AI) allows rapid genetic progress and removes the stresses of having to keep bulls. With good management practices and well trained inseminators and staff conception rates should equal those achieved by the bull. For successful breeding of both the beef and the dairy herd, there are however, management techniques to ensure maximum conception rates.
Advantages of AI
- Faster genetic progress
- No spread of venereal disease
- The farmer chooses when his cows become pregnant
- The farmer can select bulls for the traits wanted in the herd
- It is cheaper to buy semen than to keep a bull and much less stressful ! To ensure best results
- Purchase semen from a reliable renowned source to ensure you are not introducing undesirable traits into the herd
- Heat detectors must be well trained and understand the importance of good accurate detection. Early reporting of cows on heat.
- Management and level of nutrition of the female animals must be excellent. Cows and heifers must be on a rising plane of nutrition for maximum conception and have a Body Condition Score of 2.5 minimum.
- AI requires training and refresher courses for the inseminators
- Timing of insemination is essential. (See Best Time to Breed Chart)
- Good semen handling practices to ensure maximum life of the sperm
- AI technique and placement of semen on the uterus (slow withdrawal of the pipette, semen placed in the body of the uterus, calm quiet environment and hygiene practices.)
- Accurate record keeping of calving dates, dates of first service, dates served and by whom, to which bull, and PD results.
- Bulls must be controlled, preferably culled or castrated, but if kept must be well penned far from the cows that are cycling. Guidelines for Heat Detection (See Best Time to Breed Chart) The cow’s normal oestrus cycle is 18 – 24 days depending on breed. Heifers have a shorter cycle, about 19 days and indigenous breeds also have a shorter cycle and often cycle at night, for a shorter time. Heat can last from 12 – 30 hours; heifers, young cows and indigenous breeds can have a very short heat period. It is important to time the heat detection so that these ‘shy cyclers’ can be detected and served.
- Time of day – early morning and evening are the best times to detect for heat. This is the time when dairy cows are being brought in for milking and beef cows are being taken to and from grazing or being fed, so it is a convenient time to spend with the animals.
- The heat detector should spend at least 30 mins with the cows, at least twice a day. With bigger herds it may be necessary to spend more time detecting and to visit the herd 3 or 4 times a day.
- Identification – cows must be ear-tagged or easily identifiable. Mistakes occur when the heat spotter has not identified the correct cow.
- Place – small areas, such as the dairy holding pen, are not suitable. Cows under close confinement are less likely to try and mount others and show other heat signs. The best place is an open paddock, and the cows should be moved quietly and gently, with no rough handling or loud noises.
Time of Insemination (See Best Time to Breed Chart)
The heat cycle has three distinct phases.
- Pre-heat – lasts 4-6 hours. The cow bellows, is restless, milk production may be down, she will mount other cows but not stand to be mounted herself. The vulva may appear moist and red and she may show beginning signs of a bull-string. She may sniff the vulva area of other cows.
- Standing heat – lasts 6 – 30 hours, average for heifers and indigenous breeds 12 hours, cows 18 hours. The vulva is obviously swollen and red and there may be a bull-string. The cow is very restless, frequently bellowing. She will stand to allow other cows to mount her. The time to note is the beginning of this stage – ie the first time the cow is seen standing firm and allowing others to mount her. Maximum conception rate is achieved when AI occurs 12 hours after first standing heat.
- End of heat – although the cow is still restless and may attempt to sniff and mount others, she will no longer stand to be mounted. At this time she is ovulating and AI may be too late for best results. Occasionally a show of blood may be seen at the vulva, this does not mean that the cow is pregnant.
