Influence of pasture allowance on the composition and cheese-yielding potential of milk.

Abstract

Effects of pasture allowance on the yield, composition and cheese-yielding potential of milk were investigated using 48 Friesian cows in crossover experiments during spring (~60 days after calving) and summer (~180 days after calving). All cows were subjected to two nutritional treatments: ad lib. grazing (pasture allowance >45 kg DM/cow/day) and restricted grazing (16-18 kg DM/cow/day). Milk samples were collected from each cow on the final day of each treatment period and analysed for a range of components. Pasture dry matter intakes (DMI) during treatment periods were determined using the n-alkane technique. Increasing pasture allowance resulted in increased DMI. Cows grazing ad lib. had higher milk yields, concentrations of protein (spring only), casein, whey protein (spring only), casein:whey protein ratio (summer only), α-casein, β-casein and urea, but lower concentrations of serum albumin and immunoglobulin, than cows grazing a restricted pasture allowance. Nutritional effects on milk composition were greatest in spring, at which time theoretical Cheddar cheese yields were greater for milk from cows grazing ad lib. than restricted cows. Concentrations of some milk components were correlated with DMI of cows. These results provide evidence that on-farm management practices can affect milk composition and the potential yield of dairy products. Maintaining an adequate pasture allowance for dairy cows is important not only to maximise milk production, but also to optimise the manufacturing potential of milk. Keywords: casein, cheese, milk, pasture allowance, protein