Short communication: Influence of dietary tallow and fish oil on milk fat composition

Four midlactation Holstein cows in a 4 x 4 Latin square design were fed one of four diets that contained 3% added fat (dry matter basis) as 100:0, 67: 33, 50:50, or 33:67 tallow:fish oil. Feed intake and yield and composition of milk were not affected by treatment. The proportion of fatty acids 18:0 and cis-18:1 decreased and trans-18:1, conjugated linoleic acid, 18:3, 20:4 , and 20:5 increased in milk fat with increasing fish oil. The efficiency o f transferring dietary 20:5 and 22:6 to milk fat was < 7%.