  BeefTalk:
Are Your Heifers Ready to Breed?
By Kris Ringwall, Extension Beef Specialist,
NDSU Extension Service
For most beef operations, heifers are the first group of females to be bred.
Research shows heifer growth to at least 65 percent of mature body weight and
adequate fleshing is necessary for successful spring breeding. Based on this
data, heifers should be in feeding groups based on weight and target gain by
this time.
At the North Dakota State University Dickinson Research Extension Center, the
benchmark is 70 percent. Our winter feeding regimen was set up so we could
achieve that target weight. Estimated mature weight was determined by measuring
the frame score of the heifer and using an established formula to estimate
mature weight. National Research Council (NRC) guidelines for beef cattle and
actual feed analysis were used to formulate rations to meet the desired targeted
gain levels.
For the center, the replacement heifers weighed 648 pounds on Feb. 6, and as
of April 3 weighed 734 pounds. These heifers had an average frame score of 5.2,
which calculates to an estimated mature weight of 1,188 pounds. The 70 percent
target weight for these heifers is 831 pounds. That means they need to gain an
additional 97 pounds before breeding on May 14. The heifers need to gain 2.3
pounds a day, which is very achievable. (Keep in mind that the steer mates to
these heifers are gaining over 4 pounds a day in the feed lot.)
Ultimately, the nutritional and growth regimens should have an outcome of all
the heifers expressing estrus prior to the scheduled breeding date. Although
heifers may be bred naturally, with no synchronization, we would like to achieve
the maximum number of heifers conceived to the first estrus.
This year, the heifers will be estrus synchronized to facilitate a single
artificial insemination (AI) service followed by a second AI for any return
heats. The method of heifer estrous synchronization the center uses is the MGA/PGF
system. Melengestrol Acetate (MGA) is a feed additive that suppresses estrus.
Once MGA is removed from the diet, heifers exhibit estrous behavior. The heifers
will have MGA added to the ration the morning of April 11 and the last day of
MGA feeding (completing the required 14 days) will be the morning of April 24.
This year the heifers will receive the prostaglandin injection the morning of
May 12. The prostaglandin (PGF) will induce most heifers to express estrus
within 48 to 96 hours. Estrus activity will be monitored and breeding heat
detected with the use of the HeatWatch system. Heifers are artificially
inseminated 12 hours after standing heat is detected. The majority of the
heifers will be bred may 14 and 15. Heifers not responding to estrus
synchronization or not settling to the two AI opportunities will either be
placed in the feed lot and marketed on the rail or exposed to cleanup bulls and
marketed as April calving heifers.
All these heifers are scheduled to be checked by ultrasound for pregnancy on
June 12, which will allow the heifers to be sorted and allotted to summer
pastures.
Stay tuned for updates as the breeding season arrives.
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 BT0034.
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Source: Kris Ringwall, (701) 483-2045, kringwal@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu
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