Calcium salts of CLA improve availability of dietary CLA

Six sheep, fitted with ruminal and duodenal cannulae, were assigned by weight to two replications of a 3 × 3 Latin square design to compare the effects of dietary sources of conjugated linoleic acid (CLA) on availability of CLA and other long-chain fatty acids for absorption from the intestine. The control diet contained 45% alfalfa hay, 50% cracked corn, and 5% soybean meal. The CLA-supplemented diets were identical to the control diet, except they were either supplemented with 1% CLA as the free acid or with 1% CLA as the calcium salt. Each period lasted 3 weeks. Feed, rumen, duodenal, and fecal samples were collected during the final week of each period to determine apparent digestibility of dietary components, biohydrogenation of CLA in the rumen, and intestinal absorption of CLA and other long-chain fatty acids. Dietary supplementation of CLA did not affect digestibility of dry matter and crude protein, but CLA supplementation did increase lipid digestibility. Dietary CLA did not affect ruminal VFA distribution. Availability of CLA for intestinal absorption and the efficiency of intestinal absorption of CLA were increased by supplementing the diet with CLA. Ninety-seven percent of CLA fed as the free acid was biohydrogenated in the rumen, whereas 90% of CLA fed as the calcium salt was biohydrogenated in the rumen. Thus, although feeding the calcium salt of CLA approximately doubled the availability of CLA for intestinal absorption compared with feeding the free acid of CLA, in absolute terms, the increase was still only 0.66 g/day.