Effects of intraruminal and intra-abomasal additions of cod-liver oil on milk fat production in the cow.

Four Holstein cows were used in a modified switchback design to show the effect on milk-fat synthesis of (1) control diet, (2) 29.23, 3.92, 6.48, 30.65, 3.44 control diet plus 255 g/day of cod-liver oil in rumen, and (3) control diet plus 225 g/day of cod-liver oil in abomasum. Mean milk yield (kg/day), fat production (kg/day), and milk-fat percentage were (1) 21.87, .79, 3.63; (2) 22.99, .70, 3.05; and (3) 23.02, .75, 3.28. Compared to the post-treatment control period, only one cow decreased in milk-fat percentage on 3 while all cows decreased in milk-fat percentage on 2. Proportions of carbons 16:0, 16:1, 18:0, 18:1, 18:2, and trans-monoene fatty acids of the milk fat were (1) 30.31, 3.24, 10.15, 30.48, 2.59, 7.91; (2) 26.37; and (3) 26.30, 3.72, 10.56, 30.10, 2.96, 9.84. Proportions of rumen volatile fatty acids were not significantly affected by treatment. Proportions of carbons 16:0, 18:0, 18:1, 18:2, and 18:3 fatty acids in the rumen ingesta were (1) 17.28, 47.92, 21.71, 10.59, 2.46; (2) 19.55, 25.90, 37.21, 11.97, 5.39; and (3) 16.90, 50.80, 19.66, 9.11, and 3.23. Fatty acid composition of blood-serum phospholipids were affected by treatment.