Addition of sorbitol to a milk substitute for veal calves. II. Effects on plasma, liver and muscle lipids

Lipoprotein metabolism in the preruminant calf: effect of a high fat diet supplemented with L-methionine

The effects of dietary lipid and L-Met supplementation on plasma lipids and lipoproteins were investigated in 16-wk-old preruminant calves. Four calves received the basal milk diet (2.0 g of lipid/kg of BW per meal) for 8 d followed by the same diet supplemented with L-Met (2.6 g/kg of dietary DM) for 5 d. Similarly, seven calves received successively the basal diet supplemented with cream (2.7 g of lipid/kg of BW per meal) and the same diet supplemented with L-Met. The diet with cream induced higher triglyceridemia than the basal diet because of a marked increase in chylomicra and in very low density lipoproteins, which suggested stimulation of intestinal lipoprotein secretion. Moreover, this lipid-enriched diet stimulated the formation of very light high density lipoproteins to the detriment of heavy high density lipoproteins. These particles, the bovine counterpart of mammalian high density lipoproteins of type 1, were distributed within the density range of low density lipoproteins. Addition of L-Met in the diets increased plasma concentrations of chylomicra and very low density lipoproteins, suggesting direct stimulation of the intestinal secretion of both of these lipoproteins and of the hepatic very low density lipoproteins. No effect of L-Met was observed on the concentrations and the physicochemical properties of low and light high density lipoproteins.

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.

Lipid metabolism of liquid-associated and solid-adherent bacteria in rumen contents of dairy cows offered lipid-supplemented diets

The lipid distribution and fatty acid (FA) composition of total lipids, polar lipids and free fatty acids (FFA) were determined in liquid-associated bacteria (LAB) and solid-adherent bacteria (SAB) isolated from the rumen contents of seven dairy cows fitted with rumen fistulas. Two experiments, arranged according to a 4 x 4 and 3 x 3 Latin Square design, were performed using two basal diets consisting of one part hay and one part barley-based concentrate, and five lipid-supplemented diets consisting of the basal diet plus (g/kg dry matter):53 or 94 rapeseed oil, 98 tallow, 87 soya-bean oil or 94 palmitostearin. For all diets used, total lipids were 1.7-2.2 times higher in SAB than in LAB (P less than 0.05); this probably resulted from a preferential incorporation of dietary FA absorbed onto food particles. Addition of oil or fat to the diets did not modify the polar lipid content but increased the FFA content of SAB and LAB by 150%. Lipid droplets were observed in the cytoplasm in SAB and LAB using transmission electron microscopy, which suggested that part of the additional FFA was really incorporated into the intracellular FFA rather than associated with the cell envelope by physical adsorption. Linoleic acid was specifically incorporated into the FFA of SAB, which emphasized the specific role of this bacterial compartment in the protection of this acid against rumen biohydrogenation.