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Mapping Disease Trends In Cattle Herds

Numbers by themselves have little purpose until they are arranged and presented in a way so they tell a story that means something to the reader.

The Alberta Veterinary Surveillance Network (AVSN) is a case in point. The Veterinary Practice Surveillance (VPS) component of AVSN gathers animal health data every day over a secure website from beef and dairy veterinary practitioners in Alberta. No reference is made to either the herd or the owner’s name. This is just raw data but when summarized it provides a pretty accurate daily snapshot of the overall health and existing disease trends in Alberta’s cattle herd.

Colleagues south of the border have counted on USDA’s National Animal Health Monitoring System (NAHMS) since 1983 to provide much the same service across the United States.

While very different in scope and method of reporting, information generated by the two systems provides interesting comparisons between Canadian and U.S. cattle industries. In 2007, about one in every three of the 2.08 million farms and ranches in the United States had beef cows. The average herd size back then was 42. In the same year Statistics Canada reported a similar breakdown — 27 per cent of Canadian farms had beef cattle but the average herd size at that time was 61 head. In Alberta, 53 per cent of farms have cattle and the average herd size is 189 head.

Information sources

In the U.S., veterinarians were identified by the highest percentage of operations as an important source of information (54 per cent) followed by other producers (25 per cent), extension specialists (22 per cent) and producer associations (16 per cent). Published material like beef magazines and agriculture journals were considered important sources of information for 18 per cent of cattle operations surveyed; 13 per cent favoured information from company salespersons.

Overall reproductive performance

Depending on which data set is used, the number of North American beef cows and heifers exposed to bulls or artificially inseminated that actually wean a calf may be as low as 71 per cent (17.4 per cent open at the end of breeding season, 2.3 per cent lost during gestation, 6.4 per cent lost near birth, 2.9 per cent lost between birth and two weeks). These figures suggest that the economic engine of the beef industry is wavering right off the starting line.

Death losses

Two-thirds of calf losses occur between birth and 500 pounds with about one-third of the losses happening beyond that point. Overall, 1.7 per cent of the U.S. beef cattle inventory is lost to non-predator causes annually. Operations with one to 49 cattle lose a higher percentage than operations with 500 or more cows.

Clinical conditions observed and reported by Alberta practitioners through VPS are categorized into “syndromes.” Between Jan. 1, 2006 and Dec. 31, 2009, there were 2,810 reports posted from cow-calf operations for neonatal calves less than six weeks old. To no one’s surprise, gastrointestinal syndromes topped the list of neonatal diseases. The top six neonatal disease syndromes included: gastrointestinal disease, lameness, miscellaneous swelling and edema, respiratory, neurological/recumbent and sudden death. These six represent over 90 per cent of conditions observed in young calves presented to clinics or observed during farm visits.

Within the gastrointestinal syndromes, the common infectious diseases represented a significant proportion of conditions reported by practitioners. Based on clinical signs and history the causes of intestinal infections were most often attributed to bacteria likeE. coliand other infectious agents like rotavirus, coccidia, cryptosporidia, coronavirus and clostridia. Intestinal accidents, abomasal ulcers and rectal prolapses were also commonly reported.

Of the lameness cases, 75 per cent were related to trauma, another 14 per cent to arthritis and joint infections.

Omphalophlebitis (navel infection), hernias and abscesses were major entries under among miscellaneous swellings and edema syndromes.

Common causes of respiratory disease included bovine respiratory disease complex (BRD), necrotic laryngitis, aspiration pneumonia with a significant number categorized as simply a respiratory condition.

Within the group of neurological/ recumbent syndromes reported by practitioners, bacteremia/septicemia (generalized infections), meningitis, trauma and vitamin/selenium deficiency were clinical conditions noted most frequently. A number of others were lumped under neurological signs or inability to stand.

While many of the sudden and unexplained deaths in calves remain undiagnosed, bacteremia/septicemia, peritonitis (infection involving the lin- ing of the abdominal cavity), abomasal ulcers and heart failure were the most probable diagnoses made during service calls to cow-calf clients.

U.S. survey numbers provide several interesting comparisons. Under NAHMS, the six leading causes of death losses in calves from birth to weaning included: respiratory problems (31.8 per cent), digestive problems (21.2 per cent), problems related to calving (17.7 per cent), unknown (11.5 per cent), weather related (7.6 per cent) and other causes, which included lameness and injury (3.5 per cent).

Calving difficulty, technically dystocia, remains a major cause of death loss in cow-calf herds everywhere. Some authors suggest it could be responsible for up to 33 per cent of all calf losses either as a result of calves born dead or dying of injuries suffered during birth and that over 15 per cent of long-term breeding problems is induced because of difficult calving. A sound management program to reduce dystocia and rapidly identify cattle experiencing dystocia is critical to cattle welfare and farm profitability.

High “undifferentiated,” “unknown” and “other” numbers in most disease-based surveillance systems reflects the economic reality associated with routinely ordering lab tests in a clinical practice, and the general lack of access to diagnostic services, even in Canada’s biggest livestock-producing province.

Dr.RonClarke

About the author

Columnist

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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