Risk factors associated with animal mortality in pasture-based, seasonal-calving dairy and beef herds1

Abstract

Animal mortality is indicative of animal health and welfare standards, which are of growing concern to the agricultural industry. The objective of the present study was to ascertain risk factors associated with mortality at multiple life stages in pasture-based, seasonal-calving dairy and beef herds. Males and females were stratified into seven life stages based on age (0 to 2 d, 3 to 7 d, 8 to 30 d, 31 to 182 d, 183 to 365 d, 366 to 730 d, and 731 to 1,095 d) whereas females with ≥1 calving event were further stratified into five life stages based on cow parity number (1, 2, 3, 4, and 5). Mortality was defined as whether an animal died during each life stage; only animals that either survived the entire duration or died during a life stage were considered. The data, following edits, consisted of 4,404,122 records from 1,358,712 animals. Multivariable logistic regression was used to estimate the logit of the probability of mortality in each life stage separately. The odds of a young animal (i.e., aged ≤ 1,095 d) dying was generally greater if veterinary assistance was required at their birth relative to no assistance (odds ratio [OR]: 3.10 to 31.85), if the animal was a twin relative to a singleton (OR: 1.46 to 2.31) or if the animal was male relative to female (OR: 1.14 to 6.15). Moreover, the odds of a cow (i.e., females with ≥1 calving event) dying were greater when she required veterinary assistance at calving (OR: 2.69 to 7.55) compared with a cow that did not require any assistance, if she produced twin relative to singleton progeny (OR: 1.59 to 2.03) or male relative to female progeny (OR: 1.09 to 1.20). Additionally, the odds of a first or second parity cow dying when she herself had received veterinary assistance at birth were only 0.63 to 0.66 times that of a cow that was provided no assistance at birth. For both young animals and cows, the odds of dying generally increased with herd size, whereas animals residing in expanding herds had lower odds of dying. Results from the present study indicate that the risk factors associated with mortality in pasture-based, seasonal-calving herds are similar to those reported in literature in confinement, nonseasonal-calving herds. Moreover, the present study identifies that these risk factors are similar in both dairy and beef herds, yet the magnitude of the association often differs and also changes with life stage.

Dressing percentage and the differential between live weight and carcass weight in cattle are influenced by both genetic and non-genetic factors1

“…Furthermore, only bulls slaughtered between 14 and 24 mo of age, and steers and heifers slaughtered between 14 and 36 mo of age were retained. Animals were classified as either born in a dairy or beef herd based on the breed composition of their dam (Ring et al, 2018). The parity of each dam was categorized as 1, 2, 3, 4, and 5+.…”

Associations between colostrum management, passive immunity, calf-related hygiene practices, and rates of mortality in preweaning dairy calves

“…Preweaning calves are particularly vulnerable to health issues such as enteritis and this is generally the age group in which bovine mortality rates are greatest (Murray et al, 2016;Ring et al, 2018). Colostrum quality and management, as well as calf-related hygiene practices (e.g., cleaning routine for feeding equipment, calving pens, group calf pens), can have a pronounced effect on dairy calf health and mortality (Godden, 2008;Uetake, 2013;Renaud et al, 2018).…”

Genetic and nongenetic factors associated with lactation length in seasonal-calving, pasture-based dairy cows

“…Herd size was categorized into 5 groups, in intervals of 50 cows, from ≤50 cows calving in a given year to >250 cows calving in a given year. Heterosis and recombination loss coefficients were calculated for each cow as described by Ring et al (2018). Heterosis was divided into 12 classes (0%, >0% and ≤10%, >10% and ≤20%, >20% and ≤30%, >30% and ≤40%, >40% and ≤50%, >50% and ≤60%, >60% and ≤70%, >70% and ≤80%, >80% and ≤90%, >90% and ≤99%, and >99%).…”