First data-driven approach to using individual cattle weights to estimate mean adult dairy cattle weight in the UK

ABSTRACT Introduction Knowledge of accurate weights of cattle is crucial for effective dosing of individual animals with medicine and for reporting antimicrobial usage metrics, amongst other uses. The most common weight for dairy cattle presented in current literature is 600 kg, but this is not evidenced by data. For the first time, we provide an evidence-based estimate of the average weight of UK dairy cattle to better inform decisions by farmers, veterinarians and the scientific community. Methods We collected data for 2,747 dairy cattle from 20 farms in the UK, 19 using Lely Automatic Milking Systems with weigh floors and 1 using a crush with weigh scales. These data covered farms with different breed types, including Holstein, Friesian, Holstein-Friesian and Jersey, as well as farms with dual purpose breeds and cross-breeds. Data were used to calculate a mean weight for dairy cattle by breed, and a UK-specific mean weight was generated by scaling to UK-specific breed proportions. Trends in weight by lactation number, DIM and production level were also explored using individual cattle-level data. Results Mean weight for adult dairy cattle included in this study was 617 kg (standard deviation (sd) 85.6 kg). Mean weight varied across breeds, with a range of 466 kg (sd=56.0 kg, Jersey) to 636 kg (sd=84.1, Holsteins). When scaled to UK breed proportions, the estimated mean UK dairy cattle weight was 620 kg. Overall, first-lactation heifers weighed 9% less than cows. Mean weight declined for the first 30 days post-calving, before steadily increasing. For cattle at peak production, mean weight increased with production level. Conclusions This study is the first to calculate a mean weight of adult dairy cattle in the UK based on on-farm data. Overall mean weight was higher than that most often proposed in the literature (600 kg). Evidence-informed weights are crucial as the UK works to better monitor and report metrics to monitor antimicrobial use and are useful to farmers and veterinarians to inform dosing decisions.