The variations in milk yields caused by season of the year, service, age, and dry period, and their elimination: Part IV. Dry period, and standardisation of yields

Abstract

This paper describes a statistical analysis of the records collected by the Norfolk Milk Recording Society (3918 lactations), comparing the results with those obtained from the records of the Penrith M.R.S. (already published).As in the case of Penrith, autumn calvers were found to average more milk in a lactation than spring calvers, but the best months of calving were two months later—i.e. October to February instead of August to December; this is because in the case of Norfolk, yields are maintained well throughout the winter, whereas they fall off very rapidly in the Penrith district from February to April, and if this bad period comes early in the lactation a low yield results. The yield falls off, in both districts, very rapidly during summer (after the flush of grass in spring) and particularly during the two periods June-July and September-October; the average rates at which the yield declines during different calendar months, appears to provide the explanation of the variation in yield according to the month of calving. Seasonal variations appear to be nutritional, rather than meteorological, in nature, and it seems probable that with more knowledge of feeding and management they should be largely eliminated; the greatest scope for improvement lies in summer, when it is suggested arrangements should be made for a supply of catch-crops for feeding green, and this supplementing of the grass should begin much earlier in the year—i.e. beginning of June in normal seasons—than is generally believed.