“Fixed Time AI” – an interesting proposition

I am one of the few who believe that it is better to AI your cattle, than to run a bull naturally. The reason is that statistically the progeny will be better cattle, genetically, and my unscientific guess is that the increased profit from the better progeny cover any costs.

In saying that, I do have a Piedmontese bull running with girls whose genetic potential is not good enough to breed replacements. Also – they say that you still need a bull to cover any girls who do not get in calf from their AI.

Apart from the cost of AI (cost of semen and cost of actual insemination), there are a number of issues which farmers don’t like (and significant reasons why they don’t do it):

  • Its difficult to detect estrus (cycling) accurately.  You need to check your girls at least three times a day, and have good detection pads/paint etc) to find those who have cycled during the night.  Every time you miss a cow cycling you put her calving back another 21 days. That does not even cover the girls who had a false cycle (or you detected it incorrectly, and waste the AI cost).
  • Getting cows in small numbers into the yards, and call the AI technician (5% of your ready cattle will cycle every day) is labour intensive and, frankly, a “pain in the arse”.  Its a lot easier for dairy cows, who are coming into the shed every day to be milked.
I have read articles in American journals about “Fixed Time AI” – and have discussed this with my vet and others.  This is a protocol of synchronising cows, and AIing them in a batch.  My vet (and most of the others I have spoken to)  only really understand “Timed AI” and not “Fixed Time AI”.   They still say you should try to detect estrus, and AI them accordingly.  Whilst most of your cows will cycle over a few days (a much tighter period) there is still the same issues of calling AI technicians, and detecting estrus.
Over the weekend, I did some more research, and finally came up with the correct protocols for Fixed Time AI. Its a simply process:-
  1. Day 1: Insert CIDR into cow – to add progesterone and hold any estrus. Give injection of GnRH to set follicular wave to start.
  2. Day 7: Remove CIDR and give the cow a PG injection to force estrus
  3. 60-66 hours after PG injection perform the AI (52-54 hours for heifers).  At the same time give another injection of GnRH to force ovulation.
Its that simple, and you can program all your ready cows to be AIed at the same time.  Its only a 10  day period (not 21 days as in natural cycling). There is no estrus detection (in fact they discourage detection, least you start changing the rules, thinking you are dong some good, and improving the percentages).
This process removes both of the AIing issues as mentioned above.  Statistically the conception rate is as good as traditional AI (65-70%). It does, however, increase the costs of AI – which is a big factor!
The are some other significant advantages:
  • Any cows that did not hold can be programmed again – so that four AIs can be done in 65 days.  Traditionally you can only do three is this period.
  • You will do a better job than your bull at covering all your cows.  Your statistic of pregnant cows in the earliest time will be better.
  • You can bring your calving forward (the earlier the calves are born the better – so long as they are not all born when there is no feed for the cows).
  • Some cows who are not ready to cycle naturally will cycle with the injections.  You must give a reasonable time, though, for the cow to recover from calving.  Allow cows 45 days after calving – and make sure they are in good condition.
In essence, in my view – this is a “no brainer” !! Whilst I need to study the cost/return ratio, if the goals are to have efficient insemination and to continually improve the genetic performance of your herd, this seems to be easily the best process.
So – I am going to experiment later this week with 6-7 cows, and see if the protocol works as well as stated.  If they do, I will be elated, and will allow me to carry no bull next season.  I only have one question on the protocol – and have emailed the overseas experts for their advice.  To date I have not had a response, and will wait until I do (or ring them if need be).  The question I have relate to the last GnRH injection.  It takes 16-20 hours for this injection to work, so why not give the injection 16-20 hours earlier?).  There must be a logical explanation.

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