It may seem like the Cadillac approach to cattle breeding, but researchers say estrus synchronization combined with artificial insemination can be affordable and practical for beef producers.
It is difficult to estimate how many commercial cattle producers are using that approach, but researchers believe interest has waned on the Prairies because of BSE and the resulting efforts by producers to cut costs during a time of market uncertainty.
However, producers who review the costs of estrus synchronization and AI, which is also known as fixed-time AI, may find that the costs are comparable to breeding with live bulls and that the benefits could be considerable.
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“There’s plenty of research to prove that artificial insemination is a way to improve profits and efficiencies of the herd, and to respond quickly to market demands,” said Julie Small, a research scientist specializing in beef cattle reproductive management at the Agriculture Canada Brandon Research Centre.
“What’s limited its growth is good estrus detection, even though we know that with good estrus detection you’ll get good conception rates.”
Estrus is the period of time when cows and heifers are sexually receptive and signal that an egg, ready to be fertilized, is about to be released. It normally occurs every 18 to 24 days.
Estrus detection can discourage commercial cattle producers from embracing AI because good detection is time consuming.
However, advancements in estrus synchronization can alleviate the workload and improve overall pregnancy rates with AI.
An estrus synchronization program developed at the Brandon research centre has become a standard in the cattle industry, although research continues on how to improve it. Small described the centre’s method as a three-step program: a modified CO-Synch protocol for cattle.
“The lowest cost is the three-step, and whenever you add anything else to it, you’re increasing the cost,” she said.
The program enables producers to schedule when they want their cows bred and eliminates the need to study the herd each day for signs of heat.
Small said the cost of the fixed-time AI program can be competitive with using live bulls for breeding, but the benefits can be greater.
AI can speed the enhancement of herd uniformity and calving ease. As well, it can tighten the window in which cows are bred. Small said grouping births toward the start of calving season means potentially more weight at weaning time.
The three-step program begins with an injection of GnRH, or gonadotropin releasing hormone, which can be given at any stage of the estrus cycle. GnRH causes either luteinization or ovulation of the dominant follicle and prevents estrus until after the prostaglandin injection is given.
The prostaglandin is given seven days after the GnRH injection and another injection of GnRH is given 66 hours later. Artificial insemination is done at the same time.
Pregnancy rates typically average about 50 percent, although rates have varied as low as 33 percent and as high as 60 percent. With that approach, there is ample time to synchronize the animals that didn’t catch and to do another round of AI breeding.
“By starting the breeding season off with a fixed-time AI program, you’re giving the cows two to three chances to get pregnant within 45 days,” Small said. “We end up with close to 90 percent consistently pregnant within 40 days.”
Reuben Mapletoft of the Western College of Veterinary Medicine in Saskatoon said AI advancements should make it more appealing to commercial cattle producers. The accuracy of information on expected progeny differences enables producers to target for desired traits from AI sires without worrying about the disappointments they might have experienced 25 years ago.
“I don’t think synchronized breeding is used even as much in Canada as it is in countries like Argentina, for example,” Mapletoft said.
“I’ve seen herds there where they will artificially inseminate two to three thousand animals.”
The use of a CIDR to enhance fixed-time AI protocols is one of the advancements that Mapletoft has worked on. The CIDR is a vaginal insert that releases natural progesterone. It has been approved in Canada for estrus synchronization in beef cattle.
In literature that he provided, Mapletoft noted that the use of a CIDR in a seven-day GnRH-based program improved pregnancy rates from 39 percent in GnRH-treated controls to 68 percent in heifers treated with GnRH and the CIDR.
Both Mapletoft and Small emphasized the importance of cattle being in good condition in order for fixed-time AI to be successful.
“Several years ago we did a study with embryo transfer and we body condition scored every animal that we put an embryo into,” Mapletoft said.
“Our pregnancy rate in those body condition scored three was significantly higher than anything below that.”
The scoring in that study was done with a scale of one to five. For producers doing body condition scoring on a scale of one to nine, a score of 51Ú2 to six would be ideal for fixed-time AI, Mapletoft said. Small favoured a score of 41Ú2 to six.
