S.J. Wells

Factors associated with mortality to 21 days of life in dairy heifers in the United States

Abstract Results from the first national study of US dairy heifer health indicated that factors associated with mortality in the first 21 days of life included first colostrum-feeding method, timing, and volume; time of separation from dam; calving ease; and twin birth. Population attributable fraction estimates; demonstrated the importance of these factors in preventing early calfhood mortality. This analysis indicated that up to 31% of dairy heifer mortality during the first 21 days of life could be prevented by changes in first colostrum feeding method, timing, and volume. Similar analyses for time of separation from dam, calving ease, and twin birth indicated that 16%, 12%, and 3%, respectively, of mortality in the first 21 days of life could be prevented.

Factors associated with the presence of Escherichia coli O157 in feces of feedlot cattle

Fecal samples were collected from pens of cattle in a total of 100 feedlots in 13 states. Fecal samples were cultured for Escherichia coli O157. E. coli O157 isolates were probed for the genetic coding for verotoxin production. At the time of sample collection, data were collected on the type of cattle present in the pen, as well as the length of time these cattle were in the feedlot, ingredients for the current ration, and cattle health history since arriving in the feedlot. Factors associated with increased likelihood of a pen being positive (one or more samples probe-positive for E. coli O157) included feeding of barley (odds ratio [OR] = 2.75) and cattle being on feed less than 20 days (OR = 3.39). Factors associated with a reduced likelihood of a pen being positive included feeding soy meal (OR = 0.50), a cattle entry weight of at least 700 lb (ca. 317.5 kg) (OR = 0.54), and at least 85% of the cattle in the pen being beef-type heifers (OR = .33).

Individual cow risk factors for clinical lameness in lactating dairy cows

Abstract A case-control study investigating relationships between clinical lameness and individual-cow (within herd) risk factors was performed in 17 Minnesota and Wisconsin dairy herds. Cases were defined as lactating cows found lame by either of two observers during farm visits in the summer of 1989 and spring of 1990 using a uniform scoring system. A single control cow (matched by herd, season, parity, and stage of lactation) was selected for each case at each visit. Assessments of body weight, body condition, dorsal claw angles, and limb lesions were made for each case and control animal. Conditional logistic regression analysis revealed positive associations between prevalent clinical lameness and heavier body weight, lower body condition score, and shallower slope of rear lateral claw angle. Lesions associated with clinical lameness included non-tarsal rear limb superficial swellings, abnormal hoof overgrowth (including corkscrew claw), and limb lacerations. Superficial tarsal swellings, intra-synovial tarsal swellings, and carpal swellings were not associated with clinical lameness.

Health status of preweaned dairy heifers in the United States

The first national estimates of mortality and morbidity for preweaned dairy heifers in the US were generated from monitoring heifers from 906 operations in 28 states prospectively using a daily diary card system. Results indicated that the cumulative mortality incidence risk from birth to 8 weeks of life was 6.3% with a peak of 1.9% during the first week of life. Season of birth was significantly associated with cumulative mortality incidence risk, and mortality risk was highest in the periods January to March and October to December. Cumulative incidence risk of diarrhea to 8 weeks of age was 24.6% with a peak of 15.4% during the second week of life. Diarrhea incidence risk varied by region, with the West having the highest incidence risk (30.5%) and the Northeast the lowest (19.2%), as well as by herd size, with the smallest herd size having the lowest reported incidence risk of diarrhea to 8 weeks of age (18.8%). Other reported 8 week cumulative disease incidence risks included listlessness, 10.0%; respiratory disease, 8.4%; dehydration, 4.1%; lameness or joint problems, 1.1%.

Prevalence of bovine viral diarrhea antibodies in 256 U.S. cow-calf operations: A survey

Outbreaks of acute bovine viral diarrhea (BVD) characterized by high morbidity and mortality in cattle of all ages have been reported in eastern Canada and several areas in the United States. Because of the severity of the outbreaks the US Department of Agriculture, Animal and Plant Health Inspection Services, Veterinary Services (USDA:APHIS:VS), with the cooperation of several other agencies, institutions and individuals has taken several steps to monitor the disease and compile and disseminate information regarding BVD to all concerned parties. Toward that end an analysis was made of the vaccination practices and of the prevalence of BVD antibodies in US beef cow calf operations. The results of the analysis of data obtained from the Cow-calf Health and Productivity Audit (CHAPA) suggest that more than 90% of US beef cow/calf operations and more than 68% of animals have been exposed to BVD virus either through vaccination or natural exposure. Those herds and animals that have not been previously exposed may be at high risk should a virulent strain of BVD be introduced.

FACTORS IN THE EMERGENCE OF FOOD BORNE DISEASES

Food borne diseases are an important public health problem. Over the past two decades, the epidemiology of food borne diseases has changed rapidly as a consequence of changes in the social environment and the ability of pathogens to adapt to new niches. Several newly recognized pathogens have emerged and well-recognized pathogens have increased in prevalence or become associated with new food vehicles. Several factors have contributed to the changing patterns of food borne diseases, and addressing food borne diseases will require rapid surveillance and effective prevention strategies. This article examines these factors and briefly addresses prevention and control of food borne diseases.