Pre-breeding evaluation of heifers – reproductive tracts
For producers who develop replacement heifers, your veterinarian can perform reproductive tract evaluations on each heifer approximately four to six weeks prior to the start of the breeding season. The veterinarian will palpate the uterine horns and ovaries to assign the tract a score on a scale of 1 to 5. This score is based on development of the uterine horns and structures present on the ovaries, such as a dominant follicle or a corpus luteum. Heifers with a score of 4 or 5 are considered pubertal heifers, with the only difference being the stage of the cycle: Tract score 4 heifers have a large dominant follicle on an ovary, and tract score 5 heifers have a corpus luteum on an ovary. Heifers with a score of 2 or 3 are considered peripubertal. Tract score 2 heifers are generally estimated to be over 30 days from reaching puberty, whereas tract score 3 heifers are estimated to be within 30 days from reaching puberty.
Your veterinarian can also identify heifers with a tract score of 1 and will recommend these be removed from the breeding program. Tract score 1 heifers have an infantile reproductive tract and are extremely poor candidates for becoming pregnant. Along with identifying the heifers that may have trouble conceiving during the breeding season, your veterinarian can also identify other problems: freemartin heifers, heifers with cystic ovaries and even heifers that may already be pregnant.
So what can you do with this information? Heifers that have no chance of becoming pregnant during the breeding season (freemartins, tract score 1 heifers, etc.) can be removed from the breeding program. This will save you money on the cost of continued development of these heifers until pregnancy diagnosis is performed. With heifers that were assigned a tract score of 2 or 3, you have the option of managing these heifers a little differently for the next few weeks leading up to the start of the breeding season. Increasing the plane of nutrition of these heifers will help them reach puberty sooner and afford them a greater chance of becoming pregnant early in the breeding season or to artificial insemination.
Pre-breeding evaluation of heifers – pelvic measurements
Another reproductive management service your veterinarian can provide is pelvic measurements of heifers. Using a tool known as a pelvimeter, your veterinarian can take a horizontal and vertical measurement of the pelvic canal. This measurement can be used as a screening tool for producers to make culling decisions on heifers that might have a harder time calving. When this measurement is taken at the time of reproductive tract scoring, heifers with a concerningly small pelvic area can also be removed from the breeding program. Culling a heifer that may have trouble calving gives you a greater chance of avoiding the emergency dystocia call or the potential loss of the heifer or calf.
Pregnancy diagnosis
Your veterinarian can provide you with a tremendous amount of information about the calves you will have the next calving season by performing pregnancy diagnosis or preg checking your cows. Through either the use of an ultrasound or palpation, your veterinarian can evaluate the size of the developing calf and determine when the cow conceived. If you used timed artificial insemination or embryo transfer and want your veterinarian to distinguish those pregnancies from those that resulted from natural service, wait approximately 14 days before turning bulls out after the timed breeding event.
If a veterinarian uses an ultrasound, he or she can determine fetal sex of the calf. The ultrasound image also allows the veterinarian to identify cows carrying twin pregnancies, calves with abnormalities and cows that are aborting their pregnancy. The crucial thing to remember about acquiring all of this information is when the pregnancy diagnosis is performed. Scheduling your veterinarian to perform pregnancy diagnosis no later than approximately 90 days after the start of the breeding season allows him or her to differentiate between A.I. or ET calves and determine fetal sex, before the calf becomes too deep to palpate or see on the ultrasound screen.
You might ask, why have your veterinarian perform pregnancy diagnosis when you could just as easily turn cows out to pasture? Is the cost and the additional trip through the chute really necessary? Instead of thinking about the cost, think about the return: The information your veterinarian will provide you with can be profitable. Cows that turn up open at the end of your breeding season won’t have to be maintained on the farm for additional months, incurring feed and other expenses. If you are trying to market bred animals, knowing the sire of the unborn calves, expected calving date and potentially even the sex of the expected calf will allow you to provide more information to your potential customers.
What about the bulls?
Knowing the pregnancy diagnosis of your cows at the end of breeding season can also alert you if your clean-up bulls are not performing as they should be. That being said, it is helpful to have your veterinarian complete breeding soundness exams on your bulls before the start of the breeding season. If a problem is detected in your bull prior to the time you turn them out, you can find a replacement before the problem becomes detrimental to your pregnancy rate.
It makes dollars and sense
Reproductive success plays a major role in the profitability of an operation. The number one reason cows are culled is failure to become pregnant. Why not take advantage of the reproductive management tools your veterinarian can provide? The information you receive can help you cut unnecessary costs and add profit to your operation. 
Rachael Bonacker is a DVM/Master of Science student at the University of Missouri – Division of Animal Sciences.
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Jordan Thomas
- Assistant Extension Professor and State Beef Reproduction Specialist
- University of Missouri – Division of Animal Sciences
