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Abstract
This article focuses on the most important diseases of dairy calves and heifers and presents clinical approaches that can improve detection, diagnosis, and treatment of herd-based problems. A systematic herd investigation strategy is pivotal to define the problems, understand important risk factors, develop a plan, and make recommendations for disease management accurately. A review of records, colostrum and feeding routines, housing and bedding management, routine procedures, vaccination, and treatment protocols begins the investigation and determines which diagnostic procedures and testing strategies are most useful. Disease management is most effective when the problem source is well defined and the exposure can be limited, calf immunity can be enhanced, or a combination of both. Screening examinations performed regularly or done at strategic time points improves detection of disease, can be used to monitor treatment outcomes, and can avoid disease outbreaks.
Relationships between air quality, a variety of environmental risk factors, and calf respiratory health were studied in 13 naturally ventilated calf barns during winter. A minimum of 12 preweaned calves were randomly selected and scored for the presence of respiratory disease in each barn. An air sampling device was used to determine airborne bacteria colony-forming units per cubic meter (cfu/m3) of air in calf pens and central alleys within the barns. Airborne bacteria samples were collected on sheep blood agar (BAP) and eosin methylene blue (EMB) agar plates. Temperature and relative humidity were recorded in each calf pen, the barn alley, and outside the barn. Samples of bedding were collected in each pen and DM was measured. Pen bedding type and a calf nesting score (degree to which the calves could nestle into the bedding) was assigned to each barn. Calf numbers, barn and pen dimensions, ridge, eave, and curtain openings, and exterior wind speed and direction were determined and used to estimate building ventilation rates. Factors that were significantly associated with a reduced prevalence of respiratory disease were reduced pen bacterial counts (log10 cfu/m3) on BAP, presence of a solid barrier between each calf pen, and increased ability to nest. Individual calf pen bacterial counts were significantly different from barn alley bacterial counts on both BAP and EMB. Significant factors associated with reduced calf pen bacterial counts on BAP were increasing pen area, increasing number of open planes of the calf pen, decreasing pen temperature, and wood-particle bedding. Significant factors associated with reduced alley bacterial counts on BAP were increased ventilation changes per hour, increased barn volume per kilogram of calf, reduced pen bacterial counts, and barn type.
The mortality of 8,964 heifer calves born in 122 dairy herds in southwest Sweden in 1998 to 2000 was monitored from January 1998 until December 2000. Farmers were requested to send carcasses for necropsy from animals that died from 1 d of age to first calving. Age and seasonal patterns of mortality were investigated using Kaplan-Meier curves. The median herd-level mortality risk was 2.1%. In total, 3.1% of the animals died before 90 d of age, 0.9% between d 91 and 210, and 2.2% between d 211 and first calving or d 810 (27 mo of age). The median age at death was 50 d and the risk of dying was highest during the first week of life. Of the 421 dead animals, 236 (56%) were subjected to either postmortem examination or were diagnosed as having died from trauma based on information from the farmers. In total, pneumonia was the most common cause of death (27%). However, in calves less than 31 d old, enteritis was the most common cause of death; in young stock 211 to 450 d old, trauma dominated; and in young stock more than 450 d old, trauma and calving-related diseases accounted for a majority of the mortality. The largest proportion of deaths was observed from January to March, and in June. Kaplan-Meier curves suggested that housing in small-group pens was associated with the lowest mortality (other housing systems were single pens and large-group pens with automatic milk feeders), but the association was not significant.
Background Concerns on human and environmental safety and label claims of many microbicides point to the need for safer, faster acting, and broad-spectrum substitutes. ACCEL TB, a 0.5% accelerated H2O2 (AHP)-based disinfectant described here, is a potential candidate. Methods ACCEL TB was tested for its broad-spectrum microbicidal activity, safety and materials compatibility using internationally accepted protocols. Activity against bacteria (Staphylococcus aureus, Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa, vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, and Salmonella choleraesuis) was tested with the AOAC use-dilution method and the first tier of a quantitative carrier test (QCT-1). Mycobactericidal activity was tested against Mycobacterium bovis and Mycobacterium terrae using a quantitative suspension test (QST) and QCT-1, respectively. Fungicidal activity (Trichophyton mentagrophytes) was determined with the AOAC test and QCT-1. Activity against several enveloped and nonenveloped viruses was evaluated using the American Society for Testing and Materials (ASTM) method No. E-1053. Sanitizing action was tested against 7 types of vegetative bacteria with method No. DIS/TSS-10. All microbicidal tests contained an added soil load; in all AOAC tests, it was 5% fetal bovine serum, and, in QCT-1, a mixture of 3 types of proteins in phosphate buffer was used instead. The methods to test for acute oral, dermal, inhalation toxicities, and dermal and eye irritation as well as skin sensitization complied with the requirements of the Organization for Economic Cooperation and Development and the US Environmental Protection Agency (OPPTS 870). Standard methods were also used to test compatibility with metals and plastics. Results At 20°C, the full-strength product was bactericidal and virucidal in 1 minute and mycobactericidal and fungicidal in 5 minutes. It was nonirritating to skin and eyes. The acute oral LD50 (lethal dose 50%) was >5000 mg/kg. It was compatible with 12 types of plastic and 3 out of 4 metals. Conclusion The tested formulation showed a high safety and materials compatibility profile in addition to being a fast acting, intermediate-level disinfectant.
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