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Cited by 35Animal health and immunologyAnimal Behavior and Welfare StudiesEffects of Environmental Stressors on Livestock

Risk factors for bobby calf mortality across the New Zealand dairy supply chain

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Boulton, Alana C., Kells, Nikki J, Cogger, Naomi, Johnson, Craig B., O’Connor, Cheryl, Webster, Jim, Palmer, Anna, Beausoleil, Ngaio J.·2020·Preventive Veterinary Medicine
DOI 10.1016/j.prevetmed.2019.104836PMC PMC7127677
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Abstract

The objective of this study was to identify risk factors for morbidity and mortality of bobby calves across the whole dairy supply chain in New Zealand. A case-control study was carried out in the 2016 spring calving season. A total of 194 bobby calves, comprising 38 cases (calves that died or were condemned for health or welfare reasons before the point of slaughter) and 156 controls (calves deemed acceptable and presented for slaughter) were included in the study. Case and control calves were selected by veterinarians located at 29 processing premises across New Zealand. Information regarding management of selected calves on-farm, during transport and at the processor was obtained retrospectively via questionnaires administered to supplying farmers, transport operators and processing premises personnel. Associations between management variables and calf mortality (death or condemnation) were examined using multivariable logistic regression models. Factors associated with an increased risk of calf mortality included time in the farm of origin's calving season, duration of travel from farm to the processor and processing slaughter schedule (same day or next day). Every additional week into the farm's calving season increased the odds of mortality by a factor of 1.2 (95%CI 1.06, 1.35). Similarly, each additional hour of travel time increased the odds of mortality by a factor of 1.45 (95% CI 1.18, 1.76). Risk of mortality was significantly greater for calves processed at premises with a next day slaughter schedule than those processed at premises with a same day slaughter schedule (OR 3.82, 95% CI 1.51, 9.67). However, when the data set was limited to those cases that died or were condemned in the yards (i.e. excluding calves that were dead or condemned on arrival) the effect of same day slaughter was not significant. In order to reduce bobby calf mortality and morbidity, transport duration should be kept as short as possible and a same day slaughter schedule applied. While these factors can be regulated, New Zealand's pastoral dairy system means that calves will inevitably be transported for slaughter across several months each spring. Although farm management factors did not apparently influence the risk of mortality in this study, the effect of time in farm's calving season suggests there may be farm-management related factors that change over the season. This requires further investigation.

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  • Increased duration of transport has been shown to increase mortality rates during transport in young calves (approximately four to seven days of age) transported to slaughterhouses in Australia and New Zealand.

    “Furthermore, an increased duration of transport has been shown to increase mortality rates during transport in young calves (approximately four to seven days of age) transported to slaughterhouses in Australia and New Zealand [16, 17].”

    From Observational study: effect of varying transport durations and feed withdrawal on the physiological status and health of dairy calves (2025) · cites this paper as [17]

    The Introduction describes New Zealand bobby calves as approximately four to seven days old, and the Discussion’s “Travel time” section reports higher death or condemnation risk with longer transport duration. But those outcomes were recorded on arrival or in the yards, not solely during transport. The Australian study discussed in that section measured transport distance, not duration. (LLM, conf=0.88)

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Authors
Boulton, A. C., Kells, N. J., Cogger, N., Johnson, C. B., O’Connor, C., Webster, J., Palmer, A., & Beausoleil, N. J.
Affiliations
  • Massey University (NZ)
  • AgResearch (NZ)
Corresponding author
Kells, Nikki J
ORCID
Venue
Preventive Veterinary Medicine
Publisher
Elsevier BV
Published
2020-01
Volume
174
Pages
104836
ISSN
0167-5877 (ISSN-L)
DOI
10.1016/j.prevetmed.2019.104836
PMC
PMC7127677
OpenAlex
W2986666586
Cited by
34
References
23
Citations by year
2026: 2 · 2025: 4 · 2024: 5 · 2023: 8 · 2022: 4 · 2021: 10 · 2020: 1
FWCI
4.94
Type
journal article
Language
en
Open access
Licence
Locations
  • Preventive Veterinary Medicine (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Figshare (submittedVersion, cc-by)
Funders
Ministry for Primary Industries
Topics
  • Health Sciences › Veterinary › Small Animals › Animal health and immunology
  • Health Sciences › Veterinary › Small Animals › Animal Behavior and Welfare Studies
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Effects of Environmental Stressors on Livestock
Keywords
calf mortality, dairy supply chain, calving season, calf morbidity, dairy cattle
MeSH terms
Animals, Cattle, Cattle Diseases, Dairying, Morbidity, Mortality, New Zealand, Risk Factors, Case-Control Studies

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