The Impact of Seasonality in Pasture-Based Production Systems on Milk Composition and Functionality

Abstract

Seasonal calving, pasture-based dairy systems are widely practiced in countries with a temperate climate and plentiful rainfall such as Ireland and New Zealand. This approach maximizes milk production from pasture and, consequently, is a low-cost, low-input dairy production system. On the other hand, the majority of global milk supply is derived from high input indoor total mixed ration systems where seasonal calving is not practiced due to the dependence on ensiled silages, grains and concentrated feeds, which are available year-round. Synchronous changes in the macro and micronutrients in milk are much more noticeable as lactation progresses through early, mid and late stages in seasonal systems compared to non-seasonal systems-which can have implications on the processability and functionality of milk.

Keywords: composition; dairy; functionality; milk; pasture; seasonal; total mixed ration.

Figure 1

Daily milk yield (a), adapted from McAuliffe et al. [4], average % fat (b) and % crude protein (c), adapted with permission from O’Callaghan et al. [5], copyright 2021 Elsevier, on a weekly basis produced by seasonal calving herds consuming perennial ryegrass, perennial ryegrass with white clover, and total mixed ration (TMR) diets throughout lactation.

Figure 2

Depiction of the average Irish dairy cows’ feed budget and milk production over a 12-month period, updated from that previously reported by Dillon [21].

Figure 3

Depiction of seasonal variation in the average proportion of fat in milk produced by dairy cows in Ireland between January and December in the years 2017, 2018 and 2019, adapted from CSO data [44].

Figure 4

Depiction of the average protein concentration in milk produced by Irish cows between January and December in the years 2017, 2018 and 2019, adapted from CSO data [44].