title: Kinetics of phosphate absorption in lactating dairy cows after enteral administration of sodium phosphate or calcium phosphate salts.
abstract: Hypophosphataemia is frequently encountered in dairy cows during early lactation. Although supplementation of P is generally recommended, controversy exists over the suitability of oral P supplementation in animals with decreased or absent rumen motility. Since the effects of transruminal P absorption and the reticular groove reflex on the absorption kinetics of P are not well understood, it is unclear in how far treatment efficacy of oral P supplementation is affected by decreased rumen motility. Phosphate absorption was studied in six phosphate-depleted dairy cows fitted with rumen cannulas and treated with test solutions containing either NaH2PO4 or CaHPO4 with acetaminophen. Each animal was treated orally, intraruminally and intra-abomasally in randomised order. Absorption kinetics of P were studied and compared with the absorption kinetics of acetaminophen, a marker substance only absorbed from the small intestine. Intra-abomasal treatment with NaH2PO4 resulted in the most rapid and highest peaks in plasma inorganic P (Pi) concentration. Oral and intraruminal administration of NaH2PO4 resulted in similar increases in plasma Pi concentration from 4 to 7 h in both groups. Treatment with NaH2PO4 caused more pronounced peaks in plasma Pi concentration compared with CaHPO4. Neither transruminal P absorption nor the reticular groove reflex affected P absorption kinetics as determined by comparing plasma concentration–time curves of P and acetaminophen after administration of 1M-phosphate salt solutions. It is concluded that oral treatment with NaH2PO4 but not CaHPO4 is effective in supplementing P in hypophosphataemic cows with adequate rumen motility. Decreased rumen motility is likely to hamper the efficacy of oral phosphate treatment.
authors.affiliation: Department of Farm Animal Health, Utrecht University, Utrecht, The Netherlands.
authors.forename: Walter
authors.initials: W
authors.lastname: Grünberg
authors.forename: Paul
authors.initials: P
authors.lastname: Dobbelaar
authors.forename: Gerhard
authors.initials: G
authors.lastname: Breves
mesh_terms: D015502:Absorptiometry, Photon; D000042:Absorption; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D019540:Area Under Curve; D002130:Calcium Phosphates / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002417:Cattle / Q000502:physiology*; D018592:Cross-Over Studies; D003612:Dairying; D004032:Diet; D004750:Enteral Nutrition; D005260:Female; D006706:Homeostasis; D007774:Lactation; D010710:Phosphates / Q000008:administration & dosage / Q000097:blood* / Q000378:metabolism / Q000493:pharmacokinetics; D012159:Reticulum / Q000378:metabolism; D012417:Rumen / Q000378:metabolism
chemical_list: D002130:Calcium Phosphates; D010710:Phosphates; C020243:calcium phosphate; C018279:sodium phosphate