 |
||||
|
||||
|
||||
|
Nutrition and Immunity by Dr. David Porter Price For as long as there have been backgrounding yards, we have known that the key to survival with respect to freshly weaned calves is nutrition. If calves eat, they live. If they don't eat, morbidity and death loss will mount. Clearly we have known that immunity is tied to nutrition. Countless research studies have looked at the effect of various individual nutrients such as vitamins and minerals on the ability of calves to respond to infections. Likewise, over 30 years ago it was recognized that stressed calves have a higher protein requirement. The protein is required to form antibodies. Indeed, it was in this context that nutrition was deemed to have its effect. As we discussed last month, however, there has been a revelation in the area of nutritional physiology. It has been discovered that fat cells produce a hormone. Known as "leptin," this hormone apparently triggers estrus. It has also been discovered that this hormone triggers antibody production. Last time, we discussed how leptin is secreted only when fat cells are growing. For estrus, this means that a cow must have enough energy to gain weight before she will breed. For a calf, this means he must also have enough energy to be gaining weight before he can respond to disease infections. Specifically, leptin signals what are known as T-cells to begin producing antibodies. Apparently the body rationalizes that nutrients cannot be spared when the animal doesn't have enough to maintain body weight. Again, while we didn't know the exact mechanism involved, by observation we knew energy was important. Dozens of studies have shown that death loss is reduced when backgrounding rations contain high energy concentrates. Indeed, most commercial backgrounding rations contain 20-40 percent grain and likewise most consulting nutritionists typically formulate calf rations to contain about 40 percent concentrates. Ironically, many, if not most, auction barns still feed nothing but hay (usually grass hay). At the time when calves are at their point of greatest stress, they are deprived of the nutrition they need. This puts added emphasis on the need to get calves to eat when they arrive at the feedyard. Occasionally, however, we see backgrounding yards attempting to receive calves on nothing but hay. The rationale is that calves will readily eat hay, and that if they will eat hay, hay is better than nothing. Certainly calves will eat hay, but any nutritionist worth his salt can formulate receiving rations that calves will readily eat. The key is to formulate specifically for calves, and avoid "starting" rations designed for feedlot yearlings. Chemical inducements In many countries there are drugs available that can be used to stimulate calves to eat. At one time in the U.S. there was a drug known as elfazepam, which was a powerful intake stimulant. Originally slated for FDA clearance, unfortunately at the last moment the parent company chose not to submit it for testing. Chemically very similar to a popular human tranquilizer, it was rumored this had something to do with the decision not to release it for use in cattle. What we can use Even though drugs to specifically stimulate intake are not available (without a prescription) there are still some commonly available products that do in fact cause cattle to eat more -- estrogenic implants. Many backgrounders withhold implanting freshly weaned calves, thinking the stress of implanting should be postponed. Not necessarily so. Estrogens are well known to stimulate intake and there are studies showing implanted calves to have lower morbidity rates than unimplanted calves. Estrogen speeds up the metabolism and whether or not that has any affect on the immune system has not been proved. In calves, expect about a 10 percent increase in consumption. The bottom line is that in order to minimize morbidity, we must maximize intake. To do that we must minimize stress, formulate highly palatable high protein rations that contain at least 20 percent concentrate, and if necessary, bait calves to the ration with hay. And yes, calves should be implanted with an estrogenic product at a dosage suitable for their bodyweight. Dr. Porter Price has several books and a subscription newsletter available by calling Feed*Lot Magazine, Inc. at 800-798-9515. |
||||
|
|
||||
|
||||
|
All information is copywrited by Feed Lot magazine and cannot be printed or re-printed without the publishers express consent. Please contact Feed Lot Magazine for reprint and copy authorization. | ||||