Milk fatty acid and protein profiles of late-lactation dairy cows as affected by time of allocation of a fresh strip of ryegrass-based pasture

Abstract

Abstract Eighty late-lactation dairy cows were used to examine the effects of allocating a new strip of a perennial ryegrass-based sward in the morning (AM) or in the afternoon (PM) on milk fatty acid (FA) and protein profiles. Milk total polyunsaturated FA (PUFA) were greater from cows on AM herbage, whereas total saturated and monounsaturated FA (MUFA) were similar. Time of allocation only affected the milk protein α-casein, which was greater in milk from cows on PM herbage, in turn affecting the casein:whey ratio. Under the current conditions, timing of allocation altered the herbage nutrient supply to cows; a greater concentration of precursor FA in AM herbage resulted in a greater concentration of beneficial FA in milk compared with cows on PM herbage. Quantifying the composition of FA in herbage could potentially aid in the design of grazing strategies to increase precursors of beneficial FA in dairy products. Keywords: fatty acids, milk proteins, herbage composition, time of allocation