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Long winters: a tipping point in calf health

This year’s winter will go into the record books as one of the longest and coldest.

The Accumulated Winter Season Severity Index based on daily temperatures, snowfall, and snow depths show the season’s severity exceeded cumulative totals for the last 50 years in many areas of Western Canada.

The harsh winter took its toll on livestock. Feed supplies reached critically low levels on many farms and ranches. Most significantly, lingering cold and borderline energy and protein intake by brood cows through the last trimester of pregnancy precipitated a significant weight loss by cows through a critical time of fetal development. The result of cold and weak calves produced one of the worst calving seasons experienced by many livestock producers.

Weight loss by brood cows since the new year was insidious and caught many off guard. Body condition scoring of pregnant animals 90 days before calving would have signalled the weight loss and could have provided time for fortifying rations with additional protein and energy.

Calf health suffers when moms are losing condition. The inherent disease-fighting ability of an immune system primed by high-quality colostrum is compromised. Cold and wet calving grounds on top of a handicapped immune system establishes an ideal environment for disease-causing organisms to multiply. Scours and a variety of other intestinal conditions, respiratory disease, and navel infections can decimate a calf crop.

Recently I was talking to a Cochrane-area rancher over coffee. Through the lament and stress of his worst calving season ever was the regret he expressed over losing 20 of his best calves from what had tentatively been diagnosed as enterotoxemia. The cause: Clostridium perfringens. The precise “type” amongst the four or five associated with the bacteria had not yet been determined. Calves were either found dead, or appeared slightly depressed one day and died within 24 hours despite treatment with antibiotics.

In 2008, an article published in scientific literature raised the question about Clostridium perfringens Type A’s emergence as a serious problem in calves. At the time it had been identified as an agent associated with severe inflammation of the abomasum (true, or fourth stomach of cattle) with fatality rates of five to 50 per cent.

In describing the disease, veterinarians discovered as many questions as there were answers.

In cases of abomasal inflammation caused by C. perfringens Type A, gas accumulates rapidly. Clinical signs often include rapid progressive bloat and shock, colic, excessive salivation. Not infrequently, calves are found dead and bloat is assumed to be something that occurs in most ruminants after death. Animals that appear normal in the morning can be found dead by evening. Enterotoxemia typically occurs in calves less than two weeks of age. In beef herds, it is not uncommon to see calves up to six weeks old affected.

Clostridium perfringens are spore-forming bacteria commonly found in many environments, including soil, water, feed, contaminated colostrum or milk, calving areas, and the normal bovine intestinal tract. They are divided into “types” based on the toxin they produce. A number of C. perfringens types affect calves. Sudden deaths and a range of gut problems are characteristic of them all. Type C is one of the more commonly encountered types of C. perfringens. It is especially virulent in calves less than 10 days old. Enterotoxemia due to C. perfringens Type C may result in severe bloody diarrhea, although calves often die before diarrhea develops.

In small numbers, C. perfringens bacteria are generally harmless in the intestine, but under the right conditions they grow and proliferate. As C. perfringens proliferates in the gut, toxins are produced that damage the gut lining locally and enter the bloodstream to cause inflammation, shock, and cardiac arrest.

Because of the widespread nature of the organism, calves are readily exposed to C. perfringens in the environment. Damp calving grounds pockmarked with contaminated run-off promote the multiplication and ingestion of bacteria. Among factors that contribute to rapid proliferation of ingested bacteria are abrupt changes in feeding patterns, physical or environmental stress, nutritional deficiencies, and conditions that impair movement of the intestine (such as diarrhea due to other causes). C. perfringens is not spread from calf to calf, but it is not uncommon for groups to be affected at the same time.

Diagnosis of C. perfringens can be difficult. It should be one of the conditions ruled out when young calves die suddenly. Tissue samples from calves suspected of having clostridial enterotoxemia need to be collected soon after death and kept well preserved. Cases of C. perfringens Types C and E, will sometimes reveal severe tissue damage and hemorrhage in the small intestine. Calves affected with Type A will often show inflammation, ulceration, and hemorrhage of the lining of the rumen and abomasum. Because C. perfringens is often found in the intestine of normal calves, culture results need to be considered along with clinical signs, lesions observed at necropsy, and, in some cases, toxin identification, to reach an accurate diagnosis.

Because clinical signs are usually a result of the toxin, not the bacteria itself, treatment of C. perfringens is usually unsuccessful.

Prevention of enterotoxemia due to C. perfringens in beef herds requires attention to two main areas: minimizing exposure to bacteria, and enhancing immunity in the young calf. Producers concerned about enterotoxemia should consult their veterinarian.

Careful attention must be paid to sanitation of calving areas, which may include moving groups that calve on range onto new ground. Ensuring cows are properly vaccinated is of utmost importance in the resistance of calves to C. perfringens enterotoxemia. Antibodies in colostrum consumed by the newborn become the primary barrier of defence.

National Weather Service meteorologists showed the winter of 2014 was one of the most miserable on record. C. perfringens added to the misery index for a number of ranchers.

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen [email protected] or WCABP [email protected].

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Dr. Ron Clarke

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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