Problems With Overfit Breeding Cattle – for Sep. 9, 2010

Any good purebred producer will tell you that in order to win at shows cattle need lots of condition. It goes against their better judgment, but their show cattle are definitely fed differently.

While we all know cattle in good condition (body condition 2.5-3.5 on a five-point system) for calving and rebreeding are ideal, show cattle typically are in the four-plus range. It is too bad that we consistently take the genetically superior cattle and then overfit them as it definitely hurts them both in reproduction and longevity.

Although better-conditioned cattle appear to “look better,” all cattle judges are experienced enough to know when it goes overboard. Most are exper ienced stockmen themselves so know all the negative attributes with too much fat or from overfeeding over a short period. A show steer, which is going to market where carcass characteristics such as marbling and back fat are paramount, is quite different from a show heifer where future breeding and milking ability is key to her productive life.

The female’s condition is critical at breeding. The old adage is that in order to breed, females must be on a rising plane of nutrition. If cattle are fat already, they must get fatter in order to conceive. Dieting if necessary needs to happen long before the breeding season in order to not affect breeding. Many female show-class winners don’t make it back the next year or breed late because of these very phenomena.

With females with extreme growth there is also the worry of higher-than-normal

male hormones. While this enhances growth, being a little too masculine may affect fertility. The extreme of this is the freemartin heifer which can look like the growthiest heifer (if we can call her that) in the pen because of the circulating male hormones.

As a further note, if implanting these freemartins it is more advantageous to use the steer implants on them. Also some implants are approved once early in a heifer’s life and will not affect fertility. With replacement heifers I don’t personally recommend it. The extra 25 pounds you get

at weaning really will have no bearing the following year.

The overfit female deposits fat in numerous locations, both externally and internally. Fat in and around the pelvis decreases the pelvic opening, which makes calving that much harder. Fat around the developing udder definitely gets deposited in the mammary tissue and future milk production is greatly reduced. There are also the problems with laminitis or related foot problems. Cattle who walk more are fitter and leaner, plus there is the added benefit of keeping their feet and legs in better condition.

A not overfat, in-shape heifer is more likely to cycle, breed, conceive, deliver a calf and produce enough milk to raise that calf and rebreed the following year. With overfat heifers at calving, the fat in the pelvis can ball up ahead of the calf in the birth canal and burst out through the wall of the vagina. This is called prolapse of perivaginal fat and often must be attended to by your veterinarian. Otherwise this mass of fat becomes infected and causes straining and rebreeding issues.

SHOW BULLS

Young bulls are the other side of the equation. In show bulls, a fact of life is they must be very fit almost overfit to do well in the show ring. This again hurts them later reproductively. Too much fat in the scrotum interferes with temperature regulation. This extra insulation keeps the internal temperature too high, which in turn damages the sperm.

Bulls need to be able to move and breed, an athletic feat. Fatter bulls do not move over pasture well, looking for cows in heat. The extra non-muscle weight makes them unathletic and prone to injury and breakdowns with their feet and legs.

The back feet and legs are especially critical and need to be functional in order to have successful breeding. If out of shape it will take them several weeks of weight loss in order to reach the desired fitness so they don’t tire after one or two breedings and look for the nearest shade tree. The breeding season is short and intense so you can ill afford to have freeloading bulls. On large pastures they must cover lots of acreage seeking cows in heat.

If possible, during the off season it is best to house bulls in large pens where they can get lots of exercise to keep them in good shape. As with cows they are better on a rising plane of nutrition just before breeding season. With today’s high grain prices, bulls winter very well on forage and producers may substitute a little grain just before the breeding season.

Make sure to have them semen evaluated just before the breeding season. As mentioned, semen quality is poorer in fat bulls and I believe they have higher incidences of testicular degeneration as well.

We need cattle fit but not overfit in order to maintain good reproductive performance in our herds both on the female and male side of the equation.

Roy Lewis is a large-animal veterinarian practising at the

Westlock Veterinary Centre in Westlock, Alberta.

His main interests are bovine reproduction and herd health.

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roy lewis

dvm

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Althoughbetter-conditionedcattleappearto lookbetter,”allcattlejudgesareexperienced enoughtoknowwhenitgoesoverboard.

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