Vet Advice

Dr. J.D. Long

One U.S. study noted on average fewer than 35 per cent of cow-calf producers pregnancy test, but herd size was a factor showing a dramatic increase from 26 per cent for herds less than 50 animals up to 86 per cent in herds of 300 or more. No matter how many head you manage, preg checking should be an annual ritual for your herd. Some choose not to use it on grounds of cost; however, the economic benefits of this practice are simple to realize.

The greatest benefit is the identification of non-pregnant animals. For proof, just compare the average cost of a pregnancy exam to the cost of feeding an open cow for the winter, which can easily run over $200 per head at current prices. Removing these unproductive cows as soon as possible after the breeding season can result in significant cost savings.

An exam can also estimate the age of the fetus. With this information you can calculate your calving date and better supplement your cows through the winter, with the knowledge that nutrient requirements increase as pregnancy progresses.

With a fixed breeding cycle (known bull turnout and removal) one can argue that they know their calving interval and producers with a small herd may feel they can accurately tell which animals are cycling and are therefore open. But some caution is needed. Once cows conceive, most of them will stop cycling for the rest of the pregnancy, but about five per cent of the pregnant ones may still show signs of heat, which can lead to pregnant animals being mistakenly culled. And other, non-pregnant ones may miss being culled because they are not seen cycling. These mistakes cost you money.

Finally, when it comes to culling, various options are available if you know the cow's pregnancy status. If pregnant cows need to be sold, a pregnancy test will appeal to potential buyers who will be looking to purchase animals that will calve in line with the cows already in their herd. As for the non-pregnant animals producers must consider feed availability, current cow prices and their own management when deciding to cull them or not. By pregnancy testing, they are in a position to make the best possible decision. In most situations, that would be to cull the opens as soon as possible.

The cost of owning and maintaining a beef cow for a year is high, so it is important that every cow on the property be fully productive. Even if they have calves at foot, non-pregnant cows are only partially productive. Under certain circumstances it might be better not to cull non-pregnant cows immediately. If feed is plentiful, and if current cow prices are down too much, the best strategy might be to feed non-pregnant cows for sale at a later date. By knowing which animals are not pregnant, they can be fed more cost-effectively, and be ready for market at the most opportune time.

There are two practical methods for pregnancy diagnosis in beef cattle: rectal palpation and transrectal ultrasonography. Rectal palpation is most common and is an accurate form of pregnancy diagnosis that can be performed after six weeks of pregnancy. Most veterinarians are proficient at rectal palpation, and this procedure requires little time in a good facility. A disadvantage of rectal palpation is that it doesn't provide complete information about the health or viability of the fetus. Therefore, females with a nonviable or dying fetus can be diagnosed as pregnant.

Transrectal ultrasonography, commonly called ultrasound, can be used to detect pregnancy as early as 28 days with a high degree of accuracy. This method can be employed just as quickly as rectal palpation in the right facility, and may provide additional information that cannot be determined by rectal palpation. With ultrasound, the fetus is actually visualized, better allowing one to determine the viability of the fetus, and possibly the incidence of twins. It is also possible to determine the sex of the fetus between days 60 and 90 of pregnancy. There will be situations in which ultrasound is a practical method to use in your operation.

It is important to recognize that with rectal palpation and transrectal ultrasonography, a small proportion, approximately five per cent of cows diagnosed pregnant in the first 60 days of gestation, are not yet "safe" in calf. These cows may naturally lose their fetus and turn up as open later.

Pregnancy examination has been found time and again to be one of the most profitable procedures cow-calf producers can perform on their herd. As we come through what has been a tough time in the cow-calf sector, it is a good time to stick with proven methods to improve your herd's profitability.

J.D. Long is a private practitioner with the Deep South Animal Clinic at Ogema, Sask. and is a member of the Western Canadian Association of Bovine Practitioners, which co-ordinates this column. Reprinted from Canadian Cattlemen, November 2008, page 40.

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