Effects of time of calving on the productivity of pasture‐based dairy systems: A review

Abstract

Effects of season of calving, date of calving within season, and pattern of calving on different components of pasture‐based systems of dairying and on the system as a whole are reviewed. Season and pattern of calving can influence the shape of the lactation curve (by influencing the level of yield at peak of lactation, the rate of decline after the peak, or the total days in milk), the annual milk yield and milk composition, the herd's reproductive performance, and animal health. For systems in which the cows calve in spring, an earlier study reported small advantages from later calving, whereas more recent studies have shown advantages from earlier calving. These latter advantages resulted from extra days in milk, provided that sufficient feed was available for the herd in early lactation. A combination of early calving and extra feed in early lactation may achieve the benefits and avoid the disadvantages of early calving. Comparisons between autumn and spring calving systems showed that autumn‐calved cows require more supplements during early lactation (winter) and usually have lower daily milk yields at peak lactation than spring‐calved cows. However, autumn‐calved cows can have higher annual yields of milk and milksolids than spring‐calved cows, mainly as a consequence of both longer lactations and higher daily milk yields during late lactation. Time of calving is a key element in construction of the farming system, which can be integrated with stocking rate, pasture supply, and availability of supplementary feed.