Abstract

In New Zealand, seasonal calving has created marked variations in the volume and composition of milk supplied to processors across the season. As a consequence, there are also seasonal variations in the manufacturing properties of the milk (Kefford et al.1995). In particular, milk from later in the season can have manufacturing properties which are different from those of early and mid-season milk. Milk from this time typically has elevated concentrations of blood proteins, low casein:whey ratios and an altered min-eral balance (Lucey, 1996). The 2 major factors attributed to causing this phenomenon are the stage of lactation (SOL) of the cows, and seasonal influences which affect both pasture and cows. In a seasonally-calving dairy sys-tem, the precise contributions of these factors to the re-ported changes in milk composition are difficult to define because of the confounding influences of other factors. The aim of the investigation presented here was to separate the respective effects of season and SOL on milk composition.

MJ, Auldist, BJ Walsh, and NA Thomson

Proceedings of the New Zealand Society of Animal Production, Volume 57, , 205-206, 1997