Abstract
Simple SummaryIn this study, we set out to compare the health of contract- vs. conventionally reared replacement dairy heifers. Contract-reared heifers are raised off-farm on another farm by another farmer, for a fee. A total of 120 dairy farmers were enrolled in the study: 55 farmers were rearing their own heifers (control farmers; CFs), and 65 were sending heifers to a contract-rearing farm (source dairy farmers; SDFs). Over two years, we monitored approximately 5500 replacement heifers from these farms to check for signs of ill health using a calf health scoring system that involved individually examining each animal at four farm visits (twice annually). Additionally, faecal and nasal swabs were taken from a proportion of heifers with clinical signs of diarrhoea and respiratory disease. Overall, the results indicated few differences in the health and infectious status of home-reared versus contract-reared heifers. Additionally, the number of source dairy farms represented and mixing of heifers from multiple farms at the rearing unit were not associated with an increased incidence of respiratory disease or diarrhoea among contract-reared heifers. Therefore, it was concluded that contract-rearing did not result in adverse health outcomes for replacement dairy heifers.The aim of this study was to compare the health status of contract- vs. conventionally reared replacement dairy heifers over a 2-year period. A total of 120 dairy farmers were enrolled in the study in spring 2018: 55 farmers were rearing their own heifers (control farmers; CFs), and 65 were sending heifers to a contract-rearing farm (source dairy farmers; SDFs). Between spring 2018 and autumn 2019, approximately 5500 replacement heifers from these farms were monitored for signs of ill health during four farm visits using a modified version of the Wisconsin calf health scoring system. Additionally, faecal and nasal swabs were taken from a proportion of heifers with clinical signs of diarrhoea and respiratory disease to determine the associated aetiological agents. Results indicate few differences in the health status and pathogen exposure status of home-reared versus contract-reared heifers. Additionally, the number of source dairy farms represented and commingling of heifers from multiple origins at the rearing unit were not associated with an increased incidence of respiratory disease or diarrhoea among contract-reared heifers. It was concluded that contract-rearing did not result in adverse health outcomes for replacement dairy heifers. This is the first study to demonstrate this finding in a robust, longitudinal, herd-level population study.
Highlights
Contract-rearing of replacement heifers is proposed as a solution to overcome the challenges associated with land and labour shortages experienced by dairy farmers, those who wish to expand their herd following the abolition of EU milk production
Potential challenges to heifer health associated with contract-rearing include the commingling of cattle of unknown disease status from multiple sources, an important risk factor for several infectious diseases, bovine respiratory disease (BRD) [3,4]
1 A1; autumn 1 sampling period, heifers approximately 8 months old, 2 S2; spring 2 sampling period, heifers approximately 12 months old, 3 A2; autumn 2 sampling period, heifers approximately 20 months old. This was a longitudinal, descriptive study to compare the prevalence of heifer health outcomes on contract- and non-contract-rearing dairy herds
Summary
Contract-rearing of replacement heifers is proposed as a solution to overcome the challenges associated with land and labour shortages experienced by dairy farmers, those who wish to expand their herd following the abolition of EU milk production. Between-herd movement of cattle represents a major transmission route for several infectious diseases [2], and because contract-rearing involves the movement of animals between their source herd and one or more rearing units which, in turn, may be raising heifers for multiple dairy herds, the potential risk of inter-herd disease transmission is high. Potential challenges to heifer health associated with contract-rearing include the commingling of cattle of unknown disease status from multiple sources, an important risk factor for several infectious diseases, bovine respiratory disease (BRD) [3,4]. Suboptimal colostrum feeding practices on dairy farms engaged in contract-rearing [1] can place heifers at risk for failure of the passive transfer of immunoglobulins with resultant increased susceptibility to infection [6]
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