Dakota State University -- NDSU Agriculture
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BeefTalk: Now Is Time to Check for Breeding Success
By Kris Ringwall, Extension Beef Specialist,
Fundamental to a research extension center is the pursuit of knowledge. The management of the cows at the NDSU Dickinson Research Extension Center revolves around the pregnancy stage of the cows. All cows are grouped according to a simple system and assigned a calving group. Cows are coded N1, N2 or N3 based on anticipated calving cycles. N1 should calve the first 21 days, N2 the next 21 days, N3 the third cycle calves.
Why 21 days? That’s generally the length of a cow’s estrous cycle. In an ideal world if all the cows are cycling they would all conceive next year’s calf crop within 21 days of exposure to a fertile male.
For every group of 100 cows, 4.76 percent should be in heat every day. In cow numbers, four to five cows should be in heat every day during the first 21 days of the breeding season.
On June 28, the center put 88 cows through the chutes. This set of cows were first exposed to the bull on May 16, following a heat synchronization utilizing gonadotrophin releasing hormone and prostaglandin (commonly referred to as Select Sync). Cows could have conceived one day to 42 days prior to the weigh day. Those cows that conceived to the synchronized breeding would have calves old enough to detect by an ultrasound evaluation.
Pregnancies can be detected fairly early with today’s technology. From a practical sense, I prefer to wait four weeks after the bulls are pulled. A 28-day-old calf should be readily detectable.
For this group of cows, 60 cows or 68 percent were identified as pregnant to the first 21 day cycle. Is this good? The rolling five-year average for first 21 day conception rates within the CHAPS program is 58 percent. In other words, the average herd has 58 cows out of 100 bred, 21 days after the bulls were turned out. For the center, the typical first cycle conception rate has been 47 percent, approximately 11 percent below average.
Given the preliminary check of the 88 cows, our conception rate appears to be excellent, increasing the group average by 21 percent and coming in 10 percent better than the rolling CHAPS average. This early evaluation of the 2001 breeding season is good and gives us direction in planning next year’s synchronization programs.
Normally, the cows are evaluated for pregnancy 70 days after the bulls are turned out, thus allowing the identification of all those cows bred for the first cycle (fetus: 51 to 70 days) and the second cycle (fetus: 29 to 50 days of age). Those cows in which pregnancy status is not determined will be rechecked prior to selling cows in the fall. I actually recheck all the cows to identify those cows that aborted the calf early in the cycle, generally less than 1 percent. The cows are also managed, sorted and fed according to the calving cycle (N1, N2, N3 etc.) to allow for more accurate management and rations.
The July calendar gets busy, depending on when different sets of cows are workable. Give your local veterinarian a call for help to evaluate your breeding season. Hopefully good early indications will confirm a good 2002 calf crop.
May you find all your ear tags.
Your comments are always welcome at www.BeefTalk.com For more information, contact the North Dakota Beef Cattle Improvement Association, 1133 State Avenue, Dickinson, ND 58601 or go to www.CHAPS2000.COM on the Internet. In correspondence about this column, refer to BT0046.
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