Composition of Milk Produced on Pelleted Hay and Heated Corn

Abstract

Eight lactating cows were fed rations of (A) long hay plus heated (flaked) corn, (B) long hay plus ground corn, (C) ground pelleted hay plus heated corn, and (D) ground, pelleted hay plus ground corn in a 4 x 4 Latin square with 5 wk periods. Pelleted hay resulted in an average decrease in milk fat of 33% and an increase in protein of 5%. Milk composition was generally erratic on Rations C and D. Milk production was not influenced by changes in milk fat synthesis. Milk fat depression was accompanied by a relative decrease in rumen acetic and an increase in rumen pro-pionic acid. Milk fat composition was altered by a decrease in saturated acids and an increase in unsaturated acids resulting in iodine values > 60. Increased unsaturation did not influence susceptibility to oxidized flavor.