Dietary protein-oil supplements for alteration of chemical composition of goat milk and physical characteristics of milk fat

Protein-oil supplements (POS) containing ascorbyl palmitate (AP), high oleic acid sunflower oil (HOSO), and defatted soy flour mixed either with casein or solubilized chicken feathers were treated by a safe chemical agent to form gels. Part of the ground casein gel (WC) was dried to form DC, and ground feather gel was dried to form OF. In each of four 11-day feeding periods (one rep), each of 3 lactating goats was fed daily basal diet (BO) for 7-days followed by 4-days feeding BO + WC, DC, OF, or AP (VC). Blood and milk samples were taken from each goat at 7 and 11 days of each period. Two reps were run.

WC, DC, and OF had, respectively, 55.9, 9.8, and 19.8% moisture; 15.4, 29.2, and 23.6% protein; and 15.5, 29.2, and 23.6% fat; fat had 85.4% oleic acid (C18:1). BD had 4.3% fat with 23.5% C18:1. Compared with BO, WC, DC, and OF, but not VC, increased (P < 0.05) vitamin C levels (VITC) in blood serum, and WC and DC increased VITC in milk. DC doubled (P < 0.05) the C18:1 level in BO-fed goats milk from 12.5 to 25.2%, and WC and OF increased (P < 0.05) C18:1 level to 19.2 and 19.0%, respectively. The increase in C18:1 levels decreased levels of saturated fatty acids (SFA) with 6 to 16 carbons and elaidic acid (C18:1t). Similar but smaller differences (P < 0.05) in levels of C18:1, SFA, and C18:1t were found in serum.

The most abundant triacylglycerols (TG) in milk fat were those containing 42, 44, and 46 total carbons in their 3 fatty acids. Feeding POS increased the levels of TG with 46 and 50 carbons while decreasing levels of TG with 26 to 32 carbons. At 10°C, DC lowered (P < 0.05) the 34.8% solid fat content (SFC) of milk fat from BO-fed goats to 23.0%, and WC and OF decreased the SFC to 26.5 and 29.6%, respectively. Feeding DC produced goat milk fat spreadable at < 10°c while feeding BD did not. Feeding DC to dairy cows also might produce naturally "healthier" butter spreadable at refrigerator temperatures (5-6°C).