Cow-level association between serum 25-hydroxyvitamin D concentration and Mycobacterium avium subspecies paratuberculosis antibody seropositivity: a pilot study.

Vitamin D deficiency has been associated with various human diseases. Therefore, the objective of this study was to evaluate the cow-level association between serum 25-hydroxyvitamin D [25(OH)D] concentration and Mycobacterium avium ssp. paratuberculosis (MAP) seropositivity of dairy cows, adjusting for diet, breed, hair coat color, stage of lactation, reproductive status, and cow age. The sera of 80 MAP antibody ELISA-positive and 80 test-negative herd mates from 5 Minnesota dairy herds were analyzed for 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. The cows' age, production records, and hair coat color were recorded. Additionally, feed samples were obtained and analyzed for vitamin D(2) and vitamin D(3) content. A linear mixed model was used to identify potential predictors for serum 25(OH)D concentration, accounting for herd of origin. The majority of rations analyzed had over 22,000 IU of vitamin D/day (maximum: 52,000 I U/d) and the study cows' average serum 25(OH)D concentration was 62.5 ± 13.8 ng/mL. Serum ELISA-positive cows had, on average, 5.3 ng/mL lower 25(OH)D serum levels than test-negative herd mates. The reproductive status of cows was also associated with the 25(OH)D levels, with fresh cows having the lowest serum concentration. In this cross-sectional study, a temporal or causal association between MAP antibody ELISA status and serum 25(OH)D concentration could not be evaluated. In addition, the high levels of vitamin D in the rations of participating farms and the average 25(OH)D serum concentration suggest that additional supplementation with vitamin D in the ration is likely to be ineffective.

Reduced digestibility of beef tallow and cocoa butter affects bile acid excretion and reduces hepatic esterified cholesterol in rats.

We investigated stearic acid (18:0) digestibility and how it affects bile acid excretion in male Sprague-Dawley rats fed diets containing (g 18:0/ 100 g fatty acids): pork lard (13); beef tallow (19); cocoa butter (35); corn oil (2) or corn oil plus cholestyramine for 25 d. Apparent lipid digestibility was reduced with increased dietary intake of 18:0 as follows: lard (90%), beef tallow (82%), cocoa butter (78%), cholestyramine (87%), and corn oil (94%); P < 0.001, pooled SD = 2. Hepatic concentrations of total and esterified cholesterol were significantly less in cocoa butter-, beef tallow- and cholestyramine-fed groups compared with lard- and corn oil-fed groups. Fecal bile acid excretion was significantly greater in rats fed cocoa butter or cholestyramine compared with those fed corn oil. The half-life of intraperitoneally administered 14C-cholic acid was significantly longer in rats fed cocoa butter (1.36 +/- 0.02 d) compared with cholestyramine (0.98 +/- 0.03 d) and intermediate in those fed corn oil, lard or beef tallow (1.11-1.21 +/- 0.05 d). Fecal excretion of muricholic acids (bile acids) correlated strongly with dietary intake of 18:0 (r2 = 0.98, P < 0.01), whereas excretion of bile acids derived from cholic and chenodeoxycholic acids was similar among groups. In summary, the lower digestibility of cocoa butter is associated with increased fecal bile acid excretion, reduced hepatic concentration of esterified cholesterol, decreased fractional turnover of 14C-cholic acid and increased excretion of muricholic acids in rats. The mechanism by which stearate-rich dietary fats alter bile acid and cholesterol metabolism is, however, uncertain.

Biliary manganese excretion in conscious rats is affected by acute and chronic manganese intake but not by dietary fat.

We hypothesized that biliary excretion of manganese would be sensitive to acute and chronic variations in manganese and fat intakes. In the acute study, we gavaged rats with solutions containing 54Mn with either 0, 0.2, 1 or 10 mg Mn as MnCl2. We collected bile from unanesthesized rats that were simultaneously reinfused with bile acids. Total manganese excretion (from 0.5 to 6.5 h after dosing) was proportional to the acute doses (approximately 3.4% of doses). In the chronic study, weanling rats were fed diets containing 5 or 20 g corn oil/g diet and 0.49 or 72 micrograms Mn/g diet for 8 wk and then deprived of food for 12 h before bile collection. Manganese-deficient animals excreted only 0.7% as much manganese in bile as manganese-replete animals, but this reduction was not sufficient to prevent 50-80% reduction of tissue manganese concentrations. Moreover, biliary manganese excretion (calculated for 24 h) by both manganese-deficient and manganese-replete rats (deprived of food for previous 12 h) accounted for only 1% of their manganese intake on the previous day. Dietary fat and manganese concentrations had few effects on excretion of total or individual bile acids. Ours is the first report of biliary excretion of orally administered manganese by conscious rats.

Bile acid metabolism in rats fed two levels of corn oil and brans of oat, rye and barley and sugar beet fiber.

High concentrations of fecal bile acids are associated with a higher incidence of colon cancer. Dietary changes that alter bile acid metabolism are therefore of interest. Here, we report the effect of feeding diets containing four fiber sources and two fat levels for 7 wk on bile acid excretion and small intestinal bile acids (an index of pool size) in rats. The fiber sources were oat bran, rye bran, barley bran and sugar beet fiber. Fiber-containing diets were 8% dietary fiber and contained either 5 or 20% corn oil. All fiber sources caused significantly greater fecal output compared with the fiber-free basal diet. All fiber sources also resulted in significantly (P less than 0.05) lower fecal bile acid concentration compared with the fiber-free basal diet. Only rye bran resulted in significantly (P less than 0.05) higher total fecal bile acid excretion. Oat bran resulted in a slightly but significantly (P less than 0.05) higher quantity of small intestine bile acids compared with the other diets. Dietary fat level had no significant effect on fecal bile acid concentration or excretion or quantity of small intestinal bile acids. We conclude that all four fiber sources tested resulted in lower fecal bile acid concentration, by effectively causing greater fecal mass. Changes in dietary fat level as corn oil had no effect on fecal bile acids.

Consumption of prunes as a source of dietary fiber in men with mild hypercholesterolemia.

Forty-one free-living adult men with mild hypercholesterolemia (5.2-7.5 mmol/L) voluntarily participated in an 8-wk crossover study designed to determine the effect of prunes as a source of fiber on plasma cholesterol and on fecal output and bile acid concentration. During the prune period, subjects supplemented their usual diets with 12 prunes (100 g; 6 g dietary fiber) daily. Plasma low-density-lipoprotein cholesterol was significantly lower after the prune period (3.9 mmol/L) than after the grape-juice-control period (4.1 mmol/L). Fecal bile acid concentration of lithocholic acid was significantly lower after the prune period (0.95 mg bile acid/g dry wt stool) than after the grape-juice-control period (1.20 mg bile acid/g dry wt stool). Both fecal wet and dry weights were approximately 20% higher after the prune period than after the grape-juice-control period. Total bile acids (mg/72 h) did not significantly differ between experimental periods.

Effects of corn oil and wheat brans on bile acid metabolism in rats.

High concentrations of colonic bile acids may promote tumor formation. Some studies have found that high levels of dietary fat increase fecal bile acid excretion, whereas others report no effect. Wheat bran appears to reduce fecal bile acid concentration. This study was conducted to determine the effect of different dietary fat levels and types of wheat bran on bile acid metabolism. Rats were fed diets containing either no fiber, 2% cholestyramine (CHO) or brans of hard red spring, soft white winter or durum wheat--at both a 5 or 20% fat level. Animals were fed for 7 wk, and feces were collected in the last week. Wheat bran (all types) significantly increased fecal mass approximately fourfold, and CHO significantly increased fecal mass twofold compared to the fiber-free diet. Increasing the fat level did not increase fecal bile acid excretion, nor did the addition of wheat bran. Addition of CHO, however, more than doubled it. CHO increased fecal bile acid concentration, all wheat brans decreased it and fat level had no effect. Bile acid pool size was increased slightly by fat level and cholestyramine feeding but not by wheat brans. These results indicate that fat level slightly alters bile acid metabolism but that wheat brans do not.