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%.