Abstract:
Eight cows in each of four treatment groups grazed regulated areas of green oats and consumed either 0, 1.3, 2.5 or 3.1 kg of a formaldehyde-treated sunflower seed supplement (FSS) per head per day. The digestible energy content of the rations was balanced with hammer-milled barley. Milk fat percentages and milk fat yields were higher from cows fed on FSS, responses being in proportion to the amount of FSS eaten. Protein percentages were significantly lower in milk from cows fed on FSS. Milk and protein yields did not differ significantly between treatments. The linoleic acid (C18:2) content of milk fat was three to five times as high in cows fed on FSS as in those not fed on FSS. The stability to oxidation and the rennet curd firmness of the milk decreased as the percentage of C18:2 in milk fat increased. Changes in the heat stability of milk were associated with the introduction of FSS feeding. Plasma cholesterol levels increased with increasing intakes of FSS. Milk of high C18:2 content can be produced by dairy cows fed on FSS and grazed on green oats. The milk readily oxidizes and its properties for cheese and skim milk powder manufacture are altered.