Comparison of calf morbidity, mortality, and future performance across categories of passive immunity: A retrospective cohort study in a dairy herd

Angel Abuelo, Patrick Crannell

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Abstract

Four categories of transfer of passive immunity (TPI) were recently proposed in response to the widespread high preweaning morbidity and mortality risks in calves with adequate TPI when a dichotomous classification was used. However, the risks of preweaned morbidity and mortality and future performance among these TPI categories have not been compared to date. Thus, the objective of this retrospective cohort study was to compare dairy calf morbidity, mortality, growth until weaning, and reproductive efficiency until first calving among the categories of poor (6.2 g/dL) TPI. For this, the records from 4,336 dairy calves (2,272 female, 2,064 male) born January 2014 – April 2017 on a commercial dairy farm in Michigan were analyzed. These calves had been randomly selected for weekly serum total protein determination on 2 to 7 d old calves. Data from both sexes were used to evaluate preweaned health and mortality whereas only the female’s data were used to investigate average daily gain (ADG), reproductive performance, and first lactation milk yield. For each calf, data regarding disease status, growth, and reproductive parameters were obtained from the farm’s software database. Associations of TPI categories with disease events (diarrhea and/or pneumonia), reproduction indices (age at first insemination, successful insemination, and calving; and number of inseminations), first lactation milk yield and ADG at weaning were evaluated by survival analysis and mixed models. Compared to calves with excellent TPI, calves in the inferior TPI categories showed increased risk of diarrhea: poor (Hazard Ratio (HR) = 1.49; 95%CI: 1.22-1.82), fair (HR =1.32; 1.16-1.51), good (HR = 1.14; 1.02-1.29). However, the risk of pneumonia differed only between the calves in the poor and excellent TPI groups (HR = 1.39; 1.05-1.84). The preweaned mortality risk was also higher in calves with poor TPI (HR = 4.29; 1.98-9.27) compared to excellent TPI. However, mortality risks were not statistically different between calves with fair or good TPI and those with excellent TPI. Similarly, calves with poor TPI had a 64%, 55%, and 24% lower risk of reaching first insemination, successful insemination, or first calving, respectively. However, there were no differences in ADG, number of inseminations, or first lactation 305-d mature equivalent (305ME) milk production across TPI groups. Our results confirm the positive effects of optimal TPI in calves’ preweaned health and post-weaning reproductive efficiency. The 4 proposed categories of TPI can assist in decreasing the incidence of diseases that occur in the first weeks of life (i.e., diarrhea), but their impact on other diseases or future performance might be more limited. Although conducted in one herd, this study can be used to illustrate the impact of TPI on future calf performance.
Original languageEnglish
Number of pages10
JournalJournal of Dairy Science
DOIs
Publication statusPublished - Feb 2023

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