title: Modulation of intestinal calcium and phosphate transport in young goats fed a nitrogen- and/or calcium-reduced diet.
abstract: Feeding ruminants a reduced N diet is a common approach to reduce N output based on rumino-hepatic circulation. However, a reduction in N intake caused massive changes in Ca and inorganic phosphate (Pi) homoeostasis in goats. Although a single dietary Ca reduction stimulated intestinal Ca absorption in a calcitriol-dependent manner, a concomitant reduction of Ca and N supply led to a decrease in calcitriol, and therefore a modulation of intestinal Ca and Pi absorption. The aim of this study was to examine the potential effects of dietary N or Ca reduction separately on intestinal Ca and Pi transport in young goats. Animals were allocated to a control, N-reduced, Ca-reduced or combined N- and Ca-reduced diet for about 6-8 weeks, whereby N content was reduced by 25 % compared with recommendations. In Ussing chamber experiments, intestinal Ca flux rates significantly decreased in goats fed a reduced N diet, whereas Pi flux rates were unaffected. In contrast, a dietary Ca reduction stimulated Ca flux rates and decreased Pi flux rates. The combined dietary N and Ca reduction withdrew the stimulating effect of dietary Ca reduction on Ca flux rates. The expression of Ca-transporting proteins decreased with a reduced N diet too, whereas Pi-transporting proteins were unaffected. In conclusion, a dietary N reduction decreased intestinal Ca transport by diminishing Ca-transporting proteins, which became clear during simultaneous N and Ca reduction. Therefore, N supply in young ruminant nutrition is of special concern for intestinal Ca transport.
authors.affiliation: Department of Physiology,University of Veterinary Medicine Hannover,D-30173 Hannover,Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Elfers
authors.affiliation: Department of Physiology,University of Veterinary Medicine Hannover,D-30173 Hannover,Germany.
authors.forename: Mirja R
authors.initials: MR
authors.lastname: Wilkens
authors.affiliation: Department of Physiology,University of Veterinary Medicine Hannover,D-30173 Hannover,Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Breves
authors.affiliation: Department of Physiology,University of Veterinary Medicine Hannover,D-30173 Hannover,Germany.
authors.forename: Alexandra S
authors.initials: AS
authors.lastname: Muscher-Banse
mesh_terms: D000821:Animal Feed; D000818:Animals; D002118:Calcium / Q000008:administration & dosage* / Q000378:metabolism*; D004032:Diet; D006041:Goats; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000201:enzymology; D008297:Male; D009584:Nitrogen / Q000008:administration & dosage*; D010710:Phosphates / Q000378:metabolism*
chemical_list: D010710:Phosphates; D009584:Nitrogen; D002118:Calcium
keywords: BBM brush-border membranes; CP crude protein; CaBPD9K
                    
                  Ca-binding protein D9K; CaR
                  Ca-sensing receptor; Flux rates of calcium and phosphate; Goats; IGF1 insulin-like growth factor 1; IGF1-R
                  insulin-like growth factor 1 receptor; Na+-dependent P transporter IIb; NaPiIIb
                  Na+-dependent Pi transporter IIb; PBST PBS containing 0·1 % Tween 20; PMCA
                  plasma membrane Ca2+ ATPase; Pi
                  inorganic phosphate; PiT1
                  Na+-dependent Pi transporter 1; TRPV6
                  transient receptor potential vanilloid channel type 6; Transient receptor potential vanilloid channel type 6; Ussing chambers; VDR vitamin D receptor