Efficiency of transfer of polyunsaturated fats into milk

Polyunsaturated milk has been produced by feeding cows safflower oil enclosed in a casein coat protected with formaldehyde (SOC‐F) or formaldehyde‐treated soybean (SB) preparations. The efficiency of transfer of dietary 18∶2 ranged from 17 to 42% for various lots of SOC‐F and was only 2–8% for SB (per cent transfer=18.2 in milk fat per dietary 18∶2×100). The 18∶2 content of the milk fat increased from basal levels of 2–3% of total fatty acids to 35% with certain SOC‐F levels and 7% with SB. Major compensatory changes were noted in 14∶0 and 16∶0 fatty acids. Blood cholesterol, triglycerides and nonesterified fatty acids all increased markedly as cows were fed increasing amounts of SOC‐F. There was no increase in cholesterol in the milk.