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Heat Detecting Critical to AI
Successfully detecting cows and heifers in heat is key to getting good conception rates in artificial insemination (AI) programs where breeding is timed with signs of estrus.
At estrus, physical changes in the uterus and ovaries set the stage for sperm to effectively fertilize healthy eggs. Depositing semen when the uterine environment is most receptive and when the stage of ovulation is optimal gives the best chance for conception.
“For successful insemination of cattle to occur, animals must be detected in standing heat,” says George Perry, South Dakota State University Extension beef reproductive management specialist. “Detecting standing heat is simply looking for the changes in animal behavior associated with a cow or heifer standing to be mounted by a bull or another female. Heat detection is the single greatest limiting factor in managing an AI program.”
Breeding by AI ideally occurs at a later time than bull breeding in order to more closely coordinate semen placement with time of ovulation. This is necessary because of the smaller volume of semen relative to fresh semen.
“To get maximum conception, the best rule of thumb is to AI 12 hours after onset of standing estrus,” says Perry.
Checking cows as often as possible throughout the day gives the best chance of detecting standing heat.
Danny Schiefelbein, a partner in the family-run Schiefelbein Angus of Kimball, Minnesota, checks for heat three times daily, ultimately detecting standing heat in 90% of 1,000 females. He checks at about 7:30 a.m., 1:30 p.m., and 8 p.m.
A heat-detecting aid, a patch that glues on the animal’s tail head, alerts Schiefelbein to cows presently in standing heat or the ones that came into standing heat in the night or between checking times. The patch darkens in color as the number of ridings by other animals increases.
Tail paint is another heat-detecting aid as is the more expensive computerized system using a radio transmitter inserted into a tail head patch.
To estimate onset of estrus as effectively as possible, Schiefelbein watches closely for females showing the earliest signs of coming into heat.
“I write down the cows that I think are coming into heat, marking the numbers with a question mark,” he says. “If I see them in standing heat the next time I check, I have a better idea of when they came in.”
Weather plays a role in successful heat detecting, with both extreme cold and extreme heat altering the extent to which females show signs of estrus.
“During hot weather, cattle won’t show much evidence of standing heat during the middle of the day; they show more signs in mornings and evenings,” explains Perry.
When accurate detection of heat permits optimal breeding times, conception can potentially average 70%. The heat-detection rate then determines end pregnancy rates.
“With a 95% estrus-detection rate and a 70% conception rate, 67% of the animals will be pregnant,” says Perry. “By comparison, only a 39% pregnancy rate will occur with a 55% estrus-detection rate.”
If you want to learn more, contact George Perry at 605/688-5456.