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An AI Cowculator

An AI Cowculator

Dr. Cliff Lamb, University of Florida, launched his AI Cowculator app as a free download from iTunes or Google Play last August and an online version this March. There’s also a Facebook page to get answers to questions as you work through the “what ifs” when comparing the impact of fixed-time artificial insemination versus buying bulls.

Lamb braved the cold to speak to Saskatchewan producers this past winter about his seven-day co-synch protocol for fixed-time AI.

His seven-day protocol has become popular in the U.S. and even in Brazil where the cows are anything but tame. In all it requires three trips through the chute and is, he says, somewhat foolproof.

The average pregnancy rate across the 18,000 cows he has data for is 58 per cent. He considers this impressive because in temperate regions only 30 to 70 per cent of cows will be cycling naturally at the start of the breeding season. Pregnancy rate (per cent pregnant compared to total number synchronized), however, is the true measure of an AI program’s success.

Lamb says there are lots of pat reasons for using fixed-time AI, but the main one to his mind is overcoming postpartum anestrus, which is greatly influenced by the condition of the cow at calving.


Late-calving cows can take seven years to catch up and that’s if everything goes right from then on. Later cows wean smaller calves and that has implications for your bottom line.

Six years ago, he says, the calving interval on females bred by bulls in the university herd was 120 days. Fixed time AI was implemented in 2008 and by 2012 the calving interval was down to 70 days. That added another $124 to the average calf value in this herd just by shifting the calving date with fixed-time AI.

After Lamb’s session in Saskatoon some producers in the audience were curious about how he manages the females that don’t catch, and whether they came back into heat 21 days later.

Lamb says the first natural heat on the open females generally occurs 17 to 23 days after the entire group is inseminated, and potentially 40 per cent of these non-pregnant females could cycle on the same day. That works out to 15 to 20 cows on a 100-head AI program so two bulls would likely be able to handle it.

Beyond that, you’ll need extra bull power but he says throwing all the bulls into one cleanup pasture won’t work. They’ll all be trying to breed all of the cows in heat and fighting will only add to the ruckus. Instead, Lamb suggests dividing the herd into smaller groups and using a normal bull-to-cow ratio.

So why not AI the open cows instead of turning them out with bulls? The problem is that 21 days post-AI is too early to be able to identify those not in calf. One strategy to consider involves placing a CIDR in all of the cows 12 to 13 days after AI and then on day 20 after AI, pull the CIDRs and put a heat detection patch on each animal to aid visual detection. Within 2.5 days, approximately 75 per cent of the non-pregnant cows will come into heat.

For more information contact Lamb at [email protected], or visit to view his presentation. The Excel version of the AI Cowculator can be found at this link.

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