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Vet’s Voice: Low conception rates in heifers

For the September 24, 2011 edition of Tri-State Livestock News.

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Finally the cool days of fall have arrived after one of the hottest, driest summers I can remember. In our area we didn’t receive much rain since the first of July and the pastures are “toast.” Many producers are worrying about feeding their cows soon, adding expense to the ranch. Hopefully primary vaccinations are complete and the calves are weaned and on feed. Now is a good time to pregnancy check the cowherd to determine this summer’s reproductive success.

We have been pregnancy testing via ultasounding for several months and are finding low conception rates in our area. In heifers we are seeing only 40-50 percent conception rates for producers using a timed artificial insemination (AI) programs. Producers using heat observation have between 81-89 percent conception. In timed AI programs, even after cleanup bulls have been turned out for 45 days there are still 10-40 percent of these animals open!

In my work at the salebarn there was one group of 50-plus freeze-branded heifers chalked as open that came through. A buyer from Nebraska told me he synchronized 450 heifers for AI and only got 52 percent AI-bred at pregnancy testing. All of these numbers are way below the 65 percent conception rate expected. Our average is 10.57 percent open after a 45-day breeding season, which gives us a reproductive rate of 90 percent.



We set our benchmark at 95 percent for reproductive percentage. Reproduction rate is the most important factor in herd profitability. Harlan Hughes states in graphs seen in BEEF magazine (September 2011) that it costs $600 per year to run a mama cow here in the high plains. The lower the reproductive rates and weaning rates, the more it costs to run that cow. Profits are directly proportional to efficiency.

Why the low conception rates on heifers this year? Think about conditions this spring and summer. Dr. George Perry, South Dakota State University reproductive specialist, has studied heifers and reproductive rates in South Dakota for several years. He found that heifers losing weight at breeding time and in subsequent months had lower conception rates than counterparts that maintained or gained weight. Although fleshy heifers are more likely to be sexually mature and cycling at breeding, they had a lower overall conception rate than their thinner counterparts at pregnancy checking time.



Many heifers we’ve seen were backgrounded in the feedyard at approximately 2 pounds per day average daily gain. The mud and rains at breeding time may have greatly reduced this figure. Couple that with the fact that many of these fragile girls were moved to grass, a total feed change, at breeding or shortly thereafter. It is probably a much better scenario to have the heifers on grass before breeding for optimum results. This may be a reason cows, which are usually bred later and on grass, are closer to expected reproduction levels for times AI. The extreme heat may have also caused some infertility and decreased libido in bulls. Some of the females may have suffered embryonic death of the fetus and subsequent sloughing.

With feed on short supply this would be a good year to conduct an early pregnancy diagnosis on your herd. You will be able to better utilize feedstuffs for the pregnant cows as well as understand how many replacements will be needed to maintain herd size. Now appears to be a good time to replace open and lower producing cows. Visit with your veterinarian, nutritionist or extension specialist and plan your winter feeding and spring calving strategy.

Finally the cool days of fall have arrived after one of the hottest, driest summers I can remember. In our area we didn’t receive much rain since the first of July and the pastures are “toast.” Many producers are worrying about feeding their cows soon, adding expense to the ranch. Hopefully primary vaccinations are complete and the calves are weaned and on feed. Now is a good time to pregnancy check the cowherd to determine this summer’s reproductive success.

We have been pregnancy testing via ultasounding for several months and are finding low conception rates in our area. In heifers we are seeing only 40-50 percent conception rates for producers using a timed artificial insemination (AI) programs. Producers using heat observation have between 81-89 percent conception. In timed AI programs, even after cleanup bulls have been turned out for 45 days there are still 10-40 percent of these animals open!

In my work at the salebarn there was one group of 50-plus freeze-branded heifers chalked as open that came through. A buyer from Nebraska told me he synchronized 450 heifers for AI and only got 52 percent AI-bred at pregnancy testing. All of these numbers are way below the 65 percent conception rate expected. Our average is 10.57 percent open after a 45-day breeding season, which gives us a reproductive rate of 90 percent.

We set our benchmark at 95 percent for reproductive percentage. Reproduction rate is the most important factor in herd profitability. Harlan Hughes states in graphs seen in BEEF magazine (September 2011) that it costs $600 per year to run a mama cow here in the high plains. The lower the reproductive rates and weaning rates, the more it costs to run that cow. Profits are directly proportional to efficiency.

Why the low conception rates on heifers this year? Think about conditions this spring and summer. Dr. George Perry, South Dakota State University reproductive specialist, has studied heifers and reproductive rates in South Dakota for several years. He found that heifers losing weight at breeding time and in subsequent months had lower conception rates than counterparts that maintained or gained weight. Although fleshy heifers are more likely to be sexually mature and cycling at breeding, they had a lower overall conception rate than their thinner counterparts at pregnancy checking time.

Many heifers we’ve seen were backgrounded in the feedyard at approximately 2 pounds per day average daily gain. The mud and rains at breeding time may have greatly reduced this figure. Couple that with the fact that many of these fragile girls were moved to grass, a total feed change, at breeding or shortly thereafter. It is probably a much better scenario to have the heifers on grass before breeding for optimum results. This may be a reason cows, which are usually bred later and on grass, are closer to expected reproduction levels for times AI. The extreme heat may have also caused some infertility and decreased libido in bulls. Some of the females may have suffered embryonic death of the fetus and subsequent sloughing.

With feed on short supply this would be a good year to conduct an early pregnancy diagnosis on your herd. You will be able to better utilize feedstuffs for the pregnant cows as well as understand how many replacements will be needed to maintain herd size. Now appears to be a good time to replace open and lower producing cows. Visit with your veterinarian, nutritionist or extension specialist and plan your winter feeding and spring calving strategy.


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