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The Cow-Calf Manager

Livestock Update, January 2005

John B. Hall, Extension Animal Scientist, Beef, VA Tech

Beef Cow Reproductive Problems in 2004?
Part 2: Spring calving herds

Last month's column focused on reported reproductive problems and the possible solutions in fall calving herds. This month the focus is on spring calving herds.

What types of problems are being seen? In spring calving herds, the reports indicate greater numbers of open cows. Since not all producers pregnancy check cows, producers with spring calving herds may not realize a problem exists until next spring. Overall these reports appear to be scattered, but they may represent a trend that is being picked-up by better managers. In addition, these problems are of great concern and impact on the affected operations.

If your herd has been pregnancy checked and there were too many open cows, you should review the options in this article and make changes accordingly. If you didn't preg check your cows, then compare your normal management to the suggestions in this article.

Spring Calving Problem - Too many open cows
Possible causes: 1) Last year's poor hay, 2) Too much clover, 3) That darn fescue, 4) Lepto, 5) Da bull.

Last year's poor hay: Certainly last year's hay had the poorest nutrient content of any hay we made in the last 10 years, but there was a lot of it. Spring calving cows fed only first cutting hay during the last trimester and early lactation were in very poor body condition (< BCS 4) at breeding time. As a result, fewer cows were cycling at the beginning of the breeding season. This caused more cows to breed later in the breeding season, and some failed to breed at all.

As a manager, this is the first cause I would consider. Overall possibility = high. Reproductive solution: Test hay and design proper nutrition program for cows in late gestation and early lactation. Skimping on nutrition during this critical time period is just asking for trouble.

Too much clover: Certain plants like clover and alfalfa contain phytoestrogens which can affect reproduction. However in the US, the types of clover we use have lower phytoestrogen levels than clovers in Australia and New Zealand. The impact on reproduction by phytoestrogens from clover is remote.

Also, high levels of rumen degradable protein have been linked to reproductive problems in cattle especially dairy cows and heifers that don't receive enough energy. This problem is rarely seen in beef cattle on our normal mixed grass clover pastures, but the possibility (although not great) cannot be ruled out.

As a manager, I would not rule out too much protein or too high phytoestrogen levels from clover, but I wouldn't lose sleep over it. Overall possibility = low. Reproductive solution: Focus on keeping cows in good body condition and supply them with enough energy. Avoid grazing pastures that contain greater that 60% legumes early in the breeding season. Do not plant subterranean type clovers from Australia or New Zealand.

That darn fescue: Without a doubt, research indicates that cows grazing endophyte infected fescue have lower reproductive rates. The effect is most dramatic when the breeding season is during the hot months. Increased body temperatures associated with fescue toxicosis increases early embryonic mortality. A few studies indicated that luteal (CL) function may also be impaired. In Virginia, we see a 5 to 10% increase in pregnancy rates in fall calving compared to spring calving herds on the same farm. At least part of the increased pregnancy rates in fall calvers can be attributed to breeding during the colder months.

If your breeding season started in June and lasted through the summer, it is highly possible that fescue toxicity could account for some of the reduction in pregnancy rates. Overall possibility = Moderate to moderately high. Reproductive solution: Beef operations that are east of the Blue Ridge Mountains should seriously consider moving the calving season to fall. For spring calving herds, moving the start of the breeding season back to May should help. Breeding pastures for spring calving herds should have a good mix of forage species in addition to fescue.

Leptospirosis (Lepto) and other reproductive diseases: The principal reproductive diseases of cattle in Virginia are Leptospirosis, IBR and BVD. Abortions and decreased pregnancy rates can be a result of these diseases, but often the causes are hard to pinpoint without extensive testing. Samples from aborted fetuses, cow blood samples, and sometimes DNA samples need to be provided to the diagnostic laboratory. Producers are disappointed if inconclusive results are returned from the laboratory, but this should not prevent producers and their veterinarian from using this diagnostic tool.

Leptospirosis is the most common reproductive disease and is prevalent throughout Virginia. It causes abortions in the middle and last trimesters of gestation. The disease can be water borne, and it is spread by the urine of infected animals (cows, deer, dogs, raccoons) contaminating water or feed. In addition, the immunity provided by vaccination is not long lived, so cows need to be revaccinated every 6 months. Recently, a new serovar called Lepto hardjo-bovis appears to be causing problems in some dairy and beef herds.

In addition to abortions, IBR and BVD can produce weak calves or calves that die soon after birth. Vaccinations against these viruses are ideally given as modified live virus vaccines to open (recently calved) cows before the breeding season.

Managers should not ignore these preventable diseases as possible causes for abortions. However, you should not jump to the conclusion as these are the only cause. Overall possibility = Moderately high in unvaccinated herds. Reproductive solution: Review your herd vaccination program with your veterinarian. Call your veterinarian after appearance of the second aborted calf.

Bulls: Failure of the bull to settle cows may be a failure in management. Bulls young and old need to be examined by a veterinarian for breeding soundness before the breeding season. Producers need to watch bulls to make sure they are breeding cows and have not suffered an injury during the breeding season. Bull management is a subject for a later column as well.

Managers often overlook bulls, especially mature proven bulls, as a factor until it is too late. Overall possibility = moderate to high. Reproductive solution: All bulls need a breeding soundness exam every year. Check bulls at least weekly for body condition, injuries, and libido.

Determining the cause of reproductive problems is difficult. Producers that believe that their herd is having problems need to consult their veterinarian, Extension agent, and nutritionist. Multiple perspectives are often needed to identify areas for improved management.

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