FIXED-TIME artificial insemination programs are making it easier for beef producers to use some of the highest genetic merit bulls available, and wean heavier calves at the same time.
In the United States, semen sales have increased from 7 per cent to greater than 11pc in the beef cow herd, largely from increased use among commercial breeders.
In Brazil, about 11 million cows are now being artificially inseminated – double those seen just a few years ago – with the increase largely in fixed-time AI programs.
In the past, most AI programs were designed around detecting females in heat before insemination.
This involved much more individual handling of animals compared to fixed-time AI where the entire mob is inseminated at the same time.
Speaking at an ABS Australia and Robertson's AI seminar at Keith last week, University of Florida associate director and Prof Cliff Lamb said fixed-time AI was achieving about 58-60pc pregnancy rates from all animals involved in the synchronisation program.
"To get the same pregnancy rates with heat detection we would need to be detecting 90pc to 100pc of cows on heat so we are seeing a few percent higher rates with fixed time," Prof Lamb said.
The reproductive physiologist with more than 25 years experience said the best practice method of fixed-time AI program involved using gonadotrophin-releasing hormone or Cidirol and at the same time putting a CIDR into each animal to control the oestrus cycle and ovulation.
On day 7, the CIDR is removed from each animal and they are given a shot of prostaglandin. After 60 to 66 hours, they were artificially inseminated and given another GnRH injection at the same time.
The cows do not show physical signs of heat but Prof Lamb said it had the advantage of inducing cows to cycle earlier.
The same program can be used for heifers but they should be artificially inseminated 54 hours after pulling out the CIDR's as they have a shorter oestrus cycle.
Many seedstock producers were also using a slightly different beef synchronization program with Cidirol on day 0 when the CIDR was inserted, then removing the CIDR after day seven and injecting with prostaglandin, another injection of Cidirol on Day 8, and AI on day 9.
Even without considering the value of genetic gain, Prof Lamb said his research had shown up to $49-a-head advantage of fixed-time AI compared to natural mating, resulting in calves born earlier in the season and weaning heavier calves.
This included the extra costs of the drugs and extra handling involved in the program.
"If we can get heifers to breed in the first 21 days of the breeding season, they are also likely to last in the herd longer and they have longer to recover before the next breeding season," Prof Lamb said.
He said producers needed to be mindful of having enough bull power to back up their AI programs, and not running more than 100 cows in a group with two bulls.
*Full report in Stock Journal, April 25 issue, 2013.
