Systems of Winter Milk Production based on all Autumn Calving Cows

Abstract

A supply of winter milk is needed by certain milk processors for the production of high value dairy products with a short shelf life to balance the high level of commodity based products which are mainly manufactured from seasonal milk produced from spring calving herds. Winter milk is generally produced by suppliers with split calving herds. A proportion of the cows (30-50%) calve in Autumn (September-December) to supply winter milk for which they receive a winter bonus for a contracted supply for the months of October to February. The remainder of the herd calve in Spring (Feb-April) and produce milk mainly off grass for which no bonus is paid. This system evens out the supply of milk throughout the year but complicates management, as it involves running two herds on the farm, with two calving seasons, two breeding seasons and two sets of replacement heifers to be reared. Also there is no break from milking. A system of winter milk production based on calving all of the cows in Autumn would be simpler, as it would involve only one herd, with a break from milking in late Summer and would appeal to many winter milk producers. In this study the feasibility of operating an all Autumn calving herd was examined, in terms of management, calving, winter feeding, reproduction and summer grazing. The herd was located in the Ballyderown farm attached to the Moorepark Research Centre. Alternative winter feeding systems were put in place over a three year period to compare the feed requirements and milk production of each system. A control system based on grass silage as the sole forage was compared with one where grass silage was supplemented with extended grazing of grass in late Autumn and early Spring or with a system based on a mixed forage diet based on grass silage, maize silage, brewers grains or a brewers grains/beet pulp mix. Grass silage and maize silage was produced within each system and the cows on each system were grazed separately within their own farmlets. The overall stocking rate for each system was 2.7 cows/ha using 350 kg N fertiliser/ha in addition to cattle slurry. Cows were dried off in mid-late July and were grazed tightly until calving down. The calving season extended from early September to early December. Most cows calved down outdoors at pasture or in a calving paddock without assistance. Cows were housed from early November to late March and were allocated to their respective diets in batches according to milk yield, lactation number and calving date. The cows given access to winter grass were given a daily allocation of grass (6-8 kg DM/cow) and grazed between morning and evening milking.