Butter composition and texture from cows with different milk fatty acid compositions fed fish oil or roasted soybeans.

Changing the milk fatty acid composition can improve the nutritional and physical properties of dairy products and their acceptability to consumers. A more healthful milk fatty acid composition can be achieved by altering the cow's diet, for example, by feeding supplemental fish oil (FO) or roasted soybeans (RSB), or by selecting cows with a more unsaturated milk fatty acid composition. We examined whether feeding supplemental FO or RSB to cows that had a more unsaturated milk fatty acid composition acted additively to produce butter with improved fatty acid composition and texture. Using a 3 x 3 Latin square design with 2 replications, we fed diets to multiparous Holstein cows (60 to 200 DIM) chosen for producing either more or less unsaturated milk fatty acid composition (n = 6 for each group) for three 3-wk periods. The control diet contained 3.7% crude fat and the 2 experimental diets contained, on a dry matter basis, 0.8% of additional lipids in the form of 0.9% of FO or 5% of RSB. The milk, collected in the third week of feeding, was used to make butter, which was analyzed for its fatty acid composition and physical properties. Dry matter intake, milk yield, and milk composition were not significantly affected by cow diet or by cow selection. Cows that produced a more unsaturated and healthful milk fat prior to the feeding study, according to a "health-promoting index" [HPI = (sum of % of unsaturated fatty acids)/ (%12:0 + 4 x %14:0 + %16:0)], maintained a higher HPI in their butter during the feeding study than did cows with a low HPI. Milk from cows fed supplemental FO or RSB yielded more unsaturated butters with a higher HPI. This butter also was softer when the cows were fed RSB. Feeding RSB to cows chosen for their high milk HPI yielded the most unsaturated butter with the highest HPI and softest texture. Thus, selecting cows with a more health-promoting milk fatty acid composition and feeding supplemental RSB can be used in combination to produce butter that has a consumer-friendly texture and a healthful fatty acid profile.

Postprandial lipoprotein composition in pigs fed diets differing in type and amount of dietary fat.

To determine the effects of diet on postprandial lipoprotein composition, growing pigs were fed diets containing 20 or 40% of energy as soybean oil, tallow or a 50:50 blend of soybean oil and tallow. At the end of wk 6, a blood sample was drawn from pigs fasted for 12 h. Pigs were then fed, and blood samples were drawn 1 and 4 h later. In LDL, concentrations of free and total cholesterol were greater in pigs fed 40% of energy as fat than in pigs fed 20% of energy as fat (P less than 0.02). Pigs fasted for 12 h had lesser concentrations of triacylglycerol and greater concentrations of phospholipid in LDL and HDL than did pigs fasted for 1 and 4 h (P less than 0.05). In HDL, total cholesterol and phospholipid concentrations were greater in pigs fed 40% of energy as fat than in pigs fed 20% of energy as fat (P less than 0.01). A greater concentration of triacylglycerol was found in VLDL of pigs fed 40% of energy as fat than in pigs fed 20% of energy as fat (P less than 0.01). Amount of dietary fat had a greater effect than did type of dietary fat on composition of lipoproteins from postprandial pigs.

A surgical model for studying biliary bile acid and cholesterol metabolism in swine.

Techniques were developed in young growing pigs to simultaneously collect and reinfuse bile. Silastic cannulae were designed and surgically implanted in the common bile duct and the duodenum. Direct sampling of the hepatic bile was achieved by bypassing the gallbladder. The techniques allowed for steady-state studies of hepatic function to be conducted in conscious swine in two different studies. Pigs, thus surgically modified, can serve as an appropriate model for physiologic, pharmacologic, and nutritional research that involves bile sampling.

Effect of dietary fat source on lipoprotein composition and plasma lipid concentrations in pigs.

Most studies of the effects of dietary fat sources on plasma lipid components have used diets with extreme fat compositions; the current study was designed to more nearly mimic human dietary fat intake. Young growing pigs were fed diets containing either 20 or 40% of energy as soy oil, beef tallow or a 50/50 blend of soy oil and tallow. Different dietary fats did not affect concentrations of cholesterol, triacylglycerol or protein in plasma or major lipoprotein fractions. The concentration of phospholipid was less in plasma and in very low density lipoproteins with soy oil feeding than with tallow feeding. The weight percentage of cholesteryl ester in the low density lipoprotein fraction tended to be greater with 40% than with 20% tallow and tended to be less with 40% than with 20% soy oil. Phospholipid as a weight percentage of low density lipoprotein was least in pigs fed soy oil. Tallow feeding increased the percentage of myristic, palmitic, palmitoleic and oleic acids in plasma, relative to both other groups. Soy oil feeding increased the percentage of linoleic and linolenic acids. These moderate diets were not hypercholesterolemic, but they did alter plasma fatty acid composition and phospholipid concentrations in plasma and very low density lipoprotein.

The effect of feeding lovastatin and colestipol on production and cholesterol content of eggs.

The purpose of the present study was to determine whether feeding lovastatin or colestipol, or both, to laying hens would decrease the concentration of cholesterol in eggs. Forty-eight White Leghorn hens (69 wk of age) were allocated randomly to one of four groups. For 5 wk, the birds were fed: 1) a control diet; 2) diets supplemented with 35 mg of lovastatin per kg of feed; 3) 11.7 g of colestipol per kg of feed; or 4) both 35 mg of lovastatin and 11.7 g of colestipol per kg of feed. Drug feeding did not affect egg production or the concentration of cholesterol in the yolk, muscle, or liver. Lovastatin residue was found in liver samples from hens receiving lovastatin, but no lovastatin residue was found in the muscle, egg-white, or egg-yolk samples from hens on any treatment. These findings suggest that lovastatin or colestipol, or both, fed at relatively low amounts do not decrease the concentration of cholesterol in egg yolk and do not depress egg production.

Simple enzymatic assay for determining cholesterol concentrations in bile.

We use bilirubin oxidase (EC 1.3.3.5) to remove interference by bilirubin in the assay of cholesterol concentration in bile by standard enzymatic methods. Samples are treated for 10 min with nonlimiting amounts of bilirubin oxidase to form biliverdin from bilirubin before the reagent for cholesterol is added. The relatively small interference by biliverdin is easily eliminated by use of sample blanks. The method is simple, convenient, and not hampered by the "chromogen oxidase" activity (the inherent ability of bilirubin oxidase to oxidize some chromogens) that plagues other assays of this type. Using this assay, we have accurately and precisely determined the concentration of cholesterol in bile. Such elimination of bilirubin will also be useful in assays of other biliary constituents or constituents of urine or icteric plasma.

Influence of dietary calcium and cholecalciferol on composition of plasma lipids in young pigs.

Young growing pigs were fed diets containing either 1 or 3 times the daily requirement of calcium and 1, 5 or 25 times the daily requirement of vitamin D (as cholecalciferol) in a completely randomized design with treatments in a 2 X 3 factorial arrangement. Excess dietary calcium increased the phospholipid concentration in the plasma, but not its partitioning among plasma lipoproteins. The level of dietary calcium had no effect on cholesterol, triacylglycerol or protein concentrations in plasma or their partitioning among plasma lipoproteins. Excess dietary calcium decreased body weight gains of pigs. The level of dietary cholecalciferol had no effect on body weight gain or on the concentrations of cholesterol, phospholipid, triacylglycerol or protein in plasma, or on their partitioning among plasma lipoproteins. Increased vitamin D intake resulted in increased plasma 25-hydroxycholecalciferol, whereas high dietary calcium decreased concentrations of 1,25-dihydroxy-vitamin D. Increased dietary calcium also increased plasma calcium concentrations of only plasma phospholipids and decreased growth rate, whereas excess dietary vitamin D had no effect on growth or lipid composition of plasma in growing pigs.