Duodenal rapeseed oil infusion in early and midlactation cows. 1. Intestinal apparent digestibility of fatty acids and lipids.

Rapeseed oil was infused continuously into the duodenum of lactating dairy cows. Five separate trials were conducted with differences in amount of oil infused (1.0 to 1.5 kg/d), in lactation stage (early to late), and in basal diet (corn or grass silages). The effects of lecithin addition (9 g/d) also were studied. Oil infusion did not affect the apparent digestibility of defatted organic matter. Fatty acid, ether extract, and total lipid digestibilities in control cows were 62 to 82%, 72 to 76%, and 59 to 73%, respectively. Intestinal apparent digestibilities of oil fatty acid and ether extract fractions were estimated to be 63 to 74% and 67 to 81%, respectively. Intestinal apparent digestibility of oil total lipids was only 20 to 57% due to a significant increase in nonfatty acid lipid excretion (160 to 750 g/d above control cows), which sharply decreased the energy value of the infused oil. Lecithin did not modify apparent digestibility in oil-infused cows.