S.W. Martin

Dairy calf management, morbidity and mortality in Ontario Holstein herds. III. Association of management with morbidity

Abstract Associations between heifer calf management and morbidity, particularly scours and pneumonia, were studied on 104 randomly selected Holstein dairy farms in southwestern Ontario between October 1980 and July 1983. At the farm level, data were stratified by season, with two six-month seasons (winter and summer) per year. The odds of farms with particular management strategies having above median morbidity were calculated. At the individual calf level, the odds of a calf being treated, controlling for farm of origin and month of birth, were calculated for different management practices. Farm size, and policies related to anti-scour vaccination, offering free-choice water and minerals to calves, methods of feeding, and the use of medicated feeds significantly altered the odds of a farm experiencing above-median pneumonia rates. Farm policies with regard to anti-scour vaccination, offering free-choice salt to calves, age at teat removal, type of calf housing, and use of preventive antimicrobials significantly altered the odds of a farm experiencing above-median scours rates. Scours and pneumonia were significantly associated with each other at both the farm and the calf level. No significant associations were found between individual calf management practices and the odds of being treated for scours. Sire used, method of first colostrum feeding, navel treatment, use of anti-scour vaccine in the dam, and the administration of preventive antimicrobials significantly altered the odds of a calf being treated for pneumonia.

Dairy calf management, morbidity and mortality in Ontario Holstein herds. I. The data

Abstract Heifer calf management practices and clinical outcomes were studied on 104 randomly selected Holstein dairy farms in southwestern Ontario between October 1980 and July 1983. Data were collected at both the farm level (all farms) and the individual calf level (1968 calves, 35 farms). Farm-level management data were collected by means of questionnaires and farm visits. Calf-level management data were recorded by farmers on forms provided. Treatments for disease and mortality data were recorded by the farmers on the calves up to the age of weaning, the age at which calves were no longer fed milk or milk substitutes on a regular basis. Farm size ranged from 23 to 154 calvings per year. Farm-level mortality rates per six-month season (winter/summer) were skewed, with a mean of about 6%, a median of zero, and a range of 67%. Morbidity rates were similarly skewed. Four percent of liveborn heifer calves died, 20% were treated for scours, and 15% were treated for pneumonia before the age of weaning. Stated farm policies on calf rearing were implemented to varying degrees on different farms, as estimated from individual calf data. This posed particular problems for interpreting farm-level data, since the danger of committing an ecologic fallacy was high. The data set described in this paper formed the basis for an observational study of the interlationships of heifer calf management and clinical outcomes.

Dairy calf management, morbidity and mortality in Ontario Holstein herds. II. Age and seasonal patterns

Abstract Heifer calf management practices and clinical outcomes were studied on 104 randomly selected Holstein dairy farms in southwestern Ontario between October 1980 and July 1983. Data were collected at both the farm level (all farms) and the individual calf level (1968 calves, 35 farms). Age at death, and at first treatment for disease, during the first 20 weeks of life were described by life table methods and depicted graphically. Variations over calendar time in morbidity and mortality were described graphically. The percentage of calves at risk first treated for scours peaked during the second week of life, at 8.1% per week, then declined sharply, approaching zero by about six weeks. Pneumonia treatment rates peaked at about the sixth week of life, at 2.3% per week, but were more persistent than the rates for scours. Calves were at greater risk of dying during the first week of life than at any time thereafter; however, calf mortality in this population never exceeded 4% of the total. Treatment rates for scours and pneumonia were generally lower in spring and summer than during the autumn and winter. The mortality rates remained at

Path analysis of peripartum and postpartum events, rectal palpation findings, endometrial biopsy results and reproductive performance in Holstein-Friesian dairy cows

Peripartum events, rectal palpation findings, histological and bacteriological results of endometrial biopsy, and postpartum disease variables were included in a path analysis of reproductive performance for 55 Holstein-Friesian cows from one herd. Both logistic and least squares regression were used. Based on this model, dystocia had both direct and indirect sparing associations on poor reproductive performance. A larger corpus luteum on the ovary ipsilateral to the previously non-gravid horn at Day 26 postpartum indirectly was associated with a decreased likelihood of poor reproductive performance through reduced isolation of Actinomyces pyogenes from the uterus and reduced inflammation in the stratum compactum. In the model, A. pyogenes indirectly increased poor reproductive performance through reduced number of lymphocytic foci and increased inflammation in the stratum compactum at Day 26. Increased numbers of lymphocytic foci had a direct sparing effect on poor reproduction. Stratum compactum inflammation was associated with a direct and indirect increase in the likelihood that a cow would experience poor reproductive performance via increased occurrence of cystic ovarian disease. Presence of a larger follicle on the ovary ipsilateral to the previously gravid horn had a direct beneficial effect on reproductive performance.

Analysis of early calfhood health status and subsequent dairy herd survivorship and productivity

Abstract Heifer calves contracting a navel-joint illness within their first 4 months of life exhibited a significantly poorer survival distribution pattern than their other 4 cohort groups in a study of 460 calves born into 2 institutional dairy herds from January 1, 1971 to December 1, 1978 inclusive. The cohorts of calves identified as having either respiratory, gastrointestinal, septicemia, or ‘other’ diseases did not have a survival function significantly different from each other, or from the control group. Also, on a per lactation basis, all 4 disease cohorts did not have a significantly different milk production or reproductive performance than the control group. These observations suggest that a selective culling program can maintain similar productivity and breeding performances on a lactation basis regardless of early calfhood health status. However, heifer calves contracting a navel-joint illness cannot survive as well as other calves under such a management program and hence, from a biological point of view, may warrant culling immediately upon diagnosis.

Calf health in cow-calf herds in Switzerland

In 1993, an observational study was initiated to provide general information on animal health in extensive beef farms, to estimate disease frequency and the economic impact of calf diseases and to identify risk factors related to health and weight gain. The longitudinal study was conducted from fall 1993 until winter 94/95 and included 100 farms in western Switzerland. The basic concept was to follow one generation of calves on these farms and record all events concerning animal health from birth to weaning. The study population included 1270 calves (most were Angus crossbreds). Farm-management data were collected with a questionnaire conducted on the farm. Birth and weaning weights were obtained from the beef cattle breeding association. Clinical diagnoses and treatment costs were provided by the farm veterinarians. Two thirds of the dead calves were submitted to a complete postmortem examination. Fifty-three percent of the farms in the study were primary type income farms while 47% were secondary type income farms. Thirty-eight percent of the farms were situated in the lower areas of Switzerland, 14% in the prealpine foothills, the remaining 48% were located in mountain areas. Preweaning calf mortality was 5%. The main causes of calf deaths were respiratory diseases and digestive disorders. Twenty-two percent of the calves were treated at least once by a veterinarian; 36% of the treatments administered by the veterinarian were applied because of diarrhea, 27% because of respiratory diseases. Disease incidence was highest during the months of November, December and January. The association of disease and potential farm-level risk factors was analysed using chi 2-statistics and multivariable regression methods including generalized estimating equations to adjusted for herd effects. Specific risk factors for disease were not identified. Treatment for disease was not associated with 250-day standardized weight gain.

Undifferentiated bovine respiratory disease (shipping fever): Is it communicable?

Abstract A study was conducted on 6–8-month old calves entering 2-research facility feedlots in 1983–1985, to examine if the occurrence of undifferentiated bovine respiratory disease (BRD) clustered within pens. For the purposes of analysis, 12 different groups of cattle were formed based on the source of cattle within year and/or year of arrival. The morbidity rates of BRD ranged from 5.7 to 64% and varied significantly from group to group (i.e., source to source) within year and from year to year. In all groups except one, the secondary attack (morbidity) rates were lower than the morbidity rates. An algorithm to examine for extra-binomial variation was used to formally examine for pen effects (clustering of disease within pen). In all models, a simple binomial model was sufficient to describe the data, i.e., the usual binomial parameter was estimated to describe the mean level of BRD by group, no additional parameter estimates were required to describe pen effects within group. Thus, although BRD has important pathogens as part of its sufficient causes, there is no evidence that clinical disease in one individual increases the risk of disease for other cattle in the same pen.

A prevalence study of bovine tuberculosis and brucellosis in Malawi

Abstract A study was performed in 1986 to identify the prevalence and distribution of tuberculosis and brucellosis infections in cattle in Malawi. The cattle were obtained through multistage random sample consisting of administrative districts, dip tanks and/or dairy cooperative bulking groups within district, and then farm and/or animal sampling within group. The single intradermal comparative cervical (SIDCC) tuberculin test was used to assess tuberculosis status, and the rose bengal test followed by the tube agglutination test for brucellosis status. Data on each sampled animal included age, breed, sex, owner, dip tank or bulking-group identification, and district, as well as the outcomes for tuberculosis and brucellosis. The study included 2032 cattle selected from dip tanks and 1449 dairy cattle from bulking groups; all of these were tested for tuberculosis, and 2017 of them were tested for brucellosis. Overall, the prevalence of tuberculosis reactions was 3.85%. The prevalence varied by district, by group (dip tank cattle had a higher prevalence than cattle from bulking groups), breed and sex (males higher than females). Age was not related to prevalence. The change in skin thickness on the SIDCC test was influenced by original skin thickness, those with thicker skin tending to give a larger response. Most of the differences in prevalence by district were explained by differences in breed and sex. The overall prevalence of brucellosis was 0.3%. Sixteen animals were rose bengal test positive and six of these were slide agglutination test positive. Only two reactors came from the same herd.

Air emissions from sour-gas processing plants and dairy-cattle reproduction in Alberta, Canada

The dispersion of air pollutants from all 231 licensed sour-gas processing plants in Alberta, Canada, was modeled on a monthly basis over a 10-year period (1985-1994). Exposure estimates for sulfur dioxide (SO(2)-used as a surrogate for exposure to combusted emissions) then were assigned to 1382 provincial dairy farms using a geographical-information system. Individual average and peak exposure for periods prior to each of 15 months of age and conception (four exposure-averaging periods for each of two dispersion models) were estimated for 163,988 primiparous female dairy-cattle between 1986 and 1994. Monthly or annual average farm-site exposure estimates likewise were assigned to associated herd-level data sets for the biologically relevant period of interest for each of three additional reproductive outcomes: monthly herd-average calving interval, stillbirth risk, and twinning risk. In one of the main-effects models, the maximum (i.e., peak) monthly sour-gas exposure experienced by individual-animals from birth to conception was associated with an increased time to first-calving in the very-highest exposure category (hazard ratio=0.86, 95% CI=0.80, 0.92). This equates to a decreased hazard (lambda) of calving (in each month subsequent to 22 months of age) for the highest-exposure animals (lambda=0.170) versus the zero-exposure animals (lambda=0.198) in a model with referent values for agro-ecological region and season of birth. The dose-response was not consistent across the full range of exposure categories. There was significant (P=0.003) interaction of emissions with agro-ecological region. After accounting for the interaction, a more-consistent dose-response was evident for some (but not all) agro-ecological regions. This suggests that any effect of emissions on dairy-heifer reproduction is subject to modification by features of soil type, vegetative cover, and/or climate. The increase in monthly herd-average calving interval on farms exposed to the very-highest levels of emissions appeared quite small and of limited practical importance within the range of expected exposures. There was no association between exposure and the risk for twinning. Herds exposed to higher emissions exhibited a slight decrease in risk for stillbirth.

Lack of associations between air emissions from sour-gas processing plants and beef cow–calf herd health and productivity in Alberta, Canada

This paper describes a large-scale investigation into the effects of licensed air emissions from sour-gas processing plants on the health and productivity of beef cow-calf herds in the province of Alberta, Canada. In conjunction with a geographical information system, two atmospheric-dispersion models were used to assess historical exposures at 5726 beef cow-calf farm-sites from 1987 to 1990. We did secondary analyses of health, productivity, and management data, from a government-extension survey previously administered to beef cow-calf producers across the province. Statistical models (adjusted for potential confounding and clustering within herd and over time) were used to determine associations with estimates of sour-gas emission exposure. All analyses were conducted at the herd-level. There were no significant (P>0.05) detrimental associations of exposure and the annual herd risk for culling, calf-crop delivered, calf-crop season profile, stillbirth and twinning, calfhood mortality, or calf-crop weaned.