title: Site of mineral absorption in lactating cows fed high-fat diets.
abstract: Five lactating Holstein cows with ruminal and duodenal cannulas were used in a 5 x 5 Latin square to determine the site of mineral absorption and effects of sources and amount of dietary fat on apparent absorption. Cows were fed (DM, 17.4 +/- .8 kg/d) chopped alfalfa hay, alfalfa haylage, corn silage, and concentrate at 1:1:1:2 (DM) at 12-h intervals. Calcium salts of palm fatty acid distillate (CS) or animal-vegetable (AV) fat were 0% (control), 2.5% (low, L), or 5.0% (high, H) of the diet DM. After 2 wk of adaptation, duodenal and fecal grab samples were collected at 7-h intervals for 5 d and composited by animal. Calcium intake increased (P < .05) with high-fat diets (195 vs 170 g/d), whereas Mg intake remained unchanged (54.3 +/- 9.0 g/d). Apparent absorption, estimated by Cr2O3, was regressed on Ca or Mg intake (grams/day) and fatty acid (FA) intake (grams/day). Total absorption of Ca (grams/day) = -37.4 + .264 Ca (P = .07, R2 = .14). Ruminal absorption of Mg was independent of FA intake, and magnesium was secreted posterior to the duodenum. Total tract Mg absorption (grams/day) was described by -7.685 + .464 Mg -.0044 FA (P < .0005, R2 = .46). Fat intake decreased (P < .05) total tract Mg absorption, and Ca absorption was decreased by high fat compared with low fat intake (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Dairy Science, Ohio State University, Wooster 44691.
authors.forename: S
authors.initials: S
authors.lastname: Rahnema
authors.forename: Z
authors.initials: Z
authors.lastname: Wu
authors.forename: O A
authors.initials: OA
authors.lastname: Ohajuruka
authors.forename: W P
authors.initials: WP
authors.lastname: Weiss
authors.forename: D L
authors.initials: DL
authors.lastname: Palmquist
mesh_terms: D000042:Absorption; D000821:Animal Feed; D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics; D002417:Cattle / Q000378:metabolism*; D004041:Dietary Fats / Q000008:administration & dosage*; D004064:Digestive System / Q000378:metabolism*; D005227:Fatty Acids / Q000008:administration & dosage; D005260:Female; D007774:Lactation / Q000378:metabolism*; D008274:Magnesium / Q000008:administration & dosage / Q000493:pharmacokinetics; D008903:Minerals / Q000008:administration & dosage / Q000493:pharmacokinetics*; D016226:Phosphorus, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics; D017419:Potassium, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics; D012044:Regression Analysis; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D002136:Calcium, Dietary; D004041:Dietary Fats; D005227:Fatty Acids; D008903:Minerals; D016226:Phosphorus, Dietary; D017419:Potassium, Dietary; D012982:Sodium, Dietary; D008274:Magnesium