September 10, 2008

Getting top results with dairy cow Artificial Insemination (AI)

While the genetic merit of bulls in dairy AI programs is improving all the time, the costs of running an AI program are increasing due to factors like rising fuel charges, increasing wages and declining cow fertility. So it's very important to get the best from an AI program which requires a good knowledge of animal-human interaction.

When will a cow come on heat?
  • Cattle reach puberty about 6-9 months of age but some calves can come on heat as early as 4 months of age – especially rapidly-growing Friesian calves.
  • Puberty depends more on weight than age. If you ever have calves that get pregnant, it's best to have them aborted as soon as you notice excess udder development as there may be no other signs. Check with your veterinarian for the appropriate action.
  • Dairy heifers are mated as yearlings at 12-14 months old to calve around 24 months.
  • Gestation in the cow is 283 days but in the dairy industry 14 days either side of this time is accepted as normal variation in terms of deciding the sire of the calf.
  • Beef heifers have not traditionally been mated as yearlings, but this is changing if they are well grown to get more profit from the enterprise.
  • A cow will cycle (show oestrus or come on heat) about three weeks after calving, but it is more likely to be six weeks. Don't mate her at that first 3-week cycle: leave her to her second cycle.
  • She should then cycle every 21 days after that if not pregnant, with a range from 18-24 days.
  • An unmated cow will cycle all year round with slightly less activity in winter.
  • There are nymphomaniac cows that cycle every 3 weeks all year round and never get pregnant after mating. They are a great nuisance.
  • If a cow doesn't get pregnant after 3 cycles, then get rid of her.
How long does a cow stay on heat?
  • She normally stays on heat for about 8 hours but this can vary from 4-12 hours.
  • In the short days of winter heat periods can be at the lower end of the range
  • Oestrus will start off with low intensity, rising to a state of "standing heat" when the cow will stand quite still when mounted by other cows.
  • If a bull then tries to mount her she'll often not accept him straight away. This is nature's way of teasing the bull to concentrate his sperm before ejaculation.
  • After this, heat intensity declines as she goes off heat and she'll let nothing mount her.
What are the signs of heat in cattle?
Cows coming on heat
  • They will attempt to ride other cows but will not stand to be ridden themselves.
  • They smell other cows around the genital area.
  • Have a moist, red swollen vulva.
  • Are restless, walk a lot and bellow for company of other cows.
Cows on heat
  • Stand to be ridden and may also ride other cows.
  • Hair will be rubbed off her tail head and muddy feet marks will appear on her flanks from being mounted.
  • May stand with back arched and tail raised.
  • Are nervous and excitable and graze less.
  • Are restless, walk a lot and bellow for company of other cows.
  • Have a moist red vulva with clear mucus coming from it.
  • Dairy cows will hold their milk and often come into the parlour out of their normal order.
  • Also watch any friendly heifers as they may try to mount their owners. It's a bit scary to turn round and find a beast up on its hind legs about to land on you!
Cows going off heat
  • Will not stand to be ridden any more but may attempt to ride others
  • The still smell other cows around the genital areas.
Sexually Active Groups (SAGs)
  • Cows (especially in dairy herds) at various stages of their oestrus form groups of 2-6 sexually active cows referred to as a SAG.
  • They are made up of cows coming on heat, those on heat and cows going off heat.
  • They often rotate through the herd, forming, breaking up and reforming with new animals.
  • With AI programmes it pays to keep good records of which animals have been inseminated to avoid confusion by this group behaviour.
What are short cycles?
  • These are when a cow has been mated and comes on heat again after a shorter interval than the normal 18-24 days.
  • Returning to oestrus in 10 days is a common abnormal interval.
  • If this happens - mate the cow again and if possible use the same bull or semen to avoid confusion over parentage.
  • If parentage is important then you can always have the calf DNA profiling to be certain of the sire.
What is a "silent heat"?
  • This is when a cow fails to show outward heat signs but has ovulated (shed an egg).
  • This can be confirmed through palpation of the ovaries by a veterinarian who can feel a Corpus Luteum or yellow body. This is where the follicle on the ovary has burst when the egg was shed.
  • Silent heats are very frustrating as you have lost three weeks in time with no gain.
  • The cow may have a silent heat for the first one after calving, and then start normal cycling after that.
  • This problem has been reported to be more common in Friesian heifers than in Jerseys but the cause has not been fully investigated.
  • If you have a cow that never cycles and vet inspection shows that she has had many ovulations – then get rid of her.
  • Check her dam's records and any other relatives in the herd as it could be a genetic problem.
Why use tail paint?
  • Paint a short strip (100mm wide and 150mm long) along the tail head of the cow. Tail painting is a very cheap and easy way to identify cows coming into heat or on heat.
  • When the cow is mounted by another cow, the paint will be scuffed and some rubbed off. It can be a good indicator along with other signs.
  • She may also have skin rubbed off her backbone and muddy feet marks on her flanks.
  • Buy the proper approved tail paint and follow the instructions.
  • Use one colour and after the cow is mated change the colour.
  • Use the traffic light colour sequence.
Can suckling calves delay return to oestrus?
Yes it can. Suckling one calf will not delay heat much, but if you put more calves on a cow, then return to oestrus can be delayed by quite a few weeks due to the lactation drain on the cow.

Will a bull near by help cows come into heat?
  • Yes - sometimes. Some dairy farmer experience shows that if the herd is slow to start cycling after calving, the sight, smell and sound of a nearby bull when walking past for milking will sometimes help stimulate their breeding cycle.
  • Running a teaser bull with beef cows may also be worth trying but this means having access to one.
What is a teaser bull?
  • A teaser bull is vasectomised so he is sexually active but does not ejaculate fertile semen.
  • If fitted with a mating harness with coloured ink, teasers can identify cows on heat which can then be put up for AI.
  • Teasers have all the dangers and disadvantages of keeping entire bulls so beware.
  • Don't keep them for more than one season as they often lose libido.
  • If you get a bull vasectomised, get the vet to remove one testicle as a clear indicator of his status. It's a lot easier than looking for a scar on the neck of his scrotum!
What is AI and AB?
  • Artificial Insemination (AI) also called Artificial Breeding (AB) in Australia and New Zealand, and is where semen is collected from a bull and after dilution is used either fresh or frozen to inseminate a cow on heat.
  • For a successful programme you have to understand some facts about cow reproduction.
When is the best time to inseminate a cow?
  • The best time is when she is going off heat, or has just gone off heat because this is when ovulation occurs. So in practice - if you see a cow on heat in the morning, have her inseminated in the afternoon of that day.
  • If you see her on heat in the afternoon or evening, them inseminate her the next morning or early afternoon.
How to keep your AI technician happy?
  • This is important as experience shows that a stressed, frustrated technician will not achieve top results. Here are some points to consider:
  • Have a good road to where your cattle are and the gates open when the technician is due to call.
  • Have a good set of yards and a proper race so the technician can get behind the cow safely without risk of accident.
  • Remember your responsibilities under OSH to have a safe workplace as if the technician has an accident you could be liable.
  • Have a clear and clean bench space for the technician's equipment.
  • Have the cow or cows handy to the yard, or in the yard waiting. Have someone there to put the cows in to the yard and restrain them.
  • If you have ordered frozen semen, have a bucket of cold water handy to thaw the semen straw. Don't change your mind from the semen you have ordered when the technician arrives.
  • Have a rubbish bin at the yards and keep the place tidy.
  • Provide a washing facility or tap and hose for the technician to wash hands and boots.
  • Provide a clean towel or some paper towels.
  • Remember technicians have to keep moving so don't hold them up. But a flask of coffee and a chocolate bar could be tempting and help the conception rate – at the next farm if not at yours!
  • For some humorous insights, read my post on the earliest days of AI on the farms of the North Tyne where I grew up - The Bull in the Bowler Hat.
Avoid what sperm hate:
  • Smoke - no smoking
  • Sunlight - provide shade
  • Chemicals –don't spread disinfectant around
  • Cow muck –keep the place clean
How to treat a cow after insemination?
  • Quiet handling is important after insemination. Let her out of the bail into a small area on her own if she will stay there.
  • If she's getting upset at being on her own, give her a mate for company.
  • Try to avoid putting her back with the rest of the cows till all her riding activity has stopped.
  • Stray electricity. Check any troughs near your yards for stray voltage.
  • There are cases of low conception rates when cows have drunk from troughs soon after insemination that were found to carry stray voltage from poorly-earthed fences.
Keep the records safe
  • File the insemination certificates in a safe place.
  • Mark on the calendar or wall chart the date 21 days after insemination, to watch to see if the cow returns to heat and needs a repeat insemination.
  • But always watch out for short returns and file these records with the first insemination record as you'll have to work out the calf's correct sire when it is born in relation to the insemination date.
  • Remember gestation in the cow is 283 days with a spread and 14 days either side of that is accepted as normal variation.

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