The influence of date of calving on milk production

Abstract The importance of the time of calving, during the spring period, on 200‐day and total lactation milk production, was examined using records from identical twin cattle with widely spaced calving dates. Significant differences in favour of the later calvers were obtained for milk, butterfat, solids‐not‐fat, and total protein yields. Production records from 239 lactations for Jersey cows calving in different months were also compared. Considerable differences in milk and butterfat yields occurred between the mean productions of cows calving in different months, but none of these differences reached significance. These results have been discussed with particular reference to their application to general farm practices.