Chemical Composition and Processability of Milks from Herds with Different Calving Patterns.

Abstract

The primary objective of this project was to research the detailed composition and processability of milk produced by spring calving, autumn calving and combined herds. This information is required as it may influence the future value of milk and allow informed decisions to be made by the dairy industry regarding diversification of the present product range. Specific issues to be established included (i) the processing characteristics of late lactation milk from well managed spring and autumn-calved herds and the lactation stage cutoff point for product manufacture from such milks, based on quality and functionality, (ii) the processing characteristics of mid and early lactation milk from well managed spring and autumn-calved herds, respectively, (iii) the volume of early lactation milk required to mix with late lactation milk in order to maintain milk processing quality and (iv) the difference (if any) in processing characteristics of bulk spring/autumn milks mixed at the farm or the processing plant. By maintaining spring-calved cows on a good plane of nutrition in late lactation, milk yield, composition and processing characteristics and quality of Mozzarella cheese can be sustained until late November/early December (~275 DIM [days in milk]). In general there were no notable adverse effects of stage of lactation on the composition or processing characteristics of late lactation autumn milk or on the quality and functionality of Mozzarella cheese made from it, during the lactation period 240-330 DIM (up to mid/late August). Early lactation autumn and mid lactation spring milks generally had better processing characteristics than late lactation spring and autumn milks, respectively. Combining early lactation milk with late lactation milk improved the processing characteristics of the late lactation milk and overcame any processing problems associated with it. Approximately 70 % of autumn milk is required in a spring/autumn bulk milk to maintain processability and to improve the milk sufficiently for cheesemaking from 275 DIM of the spring lactation. Mixing of late lactation spring milk with early lactation autumn milk at the factory from separate herds would result in similar processing characteristics to milk from a mixed spring and autumn calving herd. In conclusion, the manufacturing period for spring milk in late autumn/winter may be extended by good herd management practices on-farm. In addition, the production of autumn milk in combination with this allows a further extension of the manufacturing period. Alternatively, autumn milk may be used exclusively for short shelf-life products. This information suggests that it is possible to overcome the traditional milk processing problems experienced due to the seasonal pattern of milk production in Ireland.