title: The effect of high ambient temperature on Ca, P and Mg balance and bone turnover in high-yielding dairy cows.
abstract: We investigated the effect of heat stress on Ca, P and Mg balance and bone turnover in lactating cows. In a 2 x 2 crossover design, four multiparous lactating Holstein cows were kept in a chamber and subjected to a constant moderate (18 degrees C) ambient temperature (MT) or high (28 degrees C) ambient temperature (HT). The cows were fed total mixed ration (Ca, 0.7%; P, 0.4%; Mg, 0.2%) ad libitum. The milk yield under HT (35.4 kg/day) tended to be lower (P < 0.10) than that under MT (43.2 kg/day). The concentrations of milk P (P < 0.05) and Mg (P < 0.01) were significantly lower under HT than MT. The Ca, P and Mg intake (P < 0.10); Ca (P < 0.10), P, and Mg (P < 0.05) secretion into milk; and Ca (P < 0.05), P (P < 0.01), and Mg (P < 0.05) absorption in the intestine were lower under HT than MT. The plasma osteocalcin, a marker of bone turnover, was significantly lower (P < 0.05) under HT than MT. Heat stress did not affect plasma C-telopeptide of collagen type I, a bone resorption marker, and plasma parathyroid hormone concentration.
authors.affiliation: National Agricultural Research Center, Koshi,Kumamoto, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Kamiya
authors.forename: Masahito
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D016723:Bone Remodeling / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002417:Cattle / Q000502:physiology*; D004781:Environmental Exposure; D005260:Female; D006358:Hot Temperature; D008274:Magnesium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D013312:Stress, Physiological / Q000502:physiology
chemical_list: D008274:Magnesium; D011188:Potassium; D002118:Calcium