Blood mineral, hormone, and osteocalcin responses of multiparous Jersey cows to an oral dose of 25-hydroxyvitamin D3 or vitamin D3 before parturition.
Twenty-seven multiparous Jersey cows were randomly assigned to receive an oral bolus containing corn starch (control, CON), corn starch plus 15 mg of 25-hydroxyvitamin D(3) (25-OH), or 15 mg of cholecalciferol (D(3)) at 6 d before expected parturition. Cows were maintained in individual box stalls from 20 d before expected parturition and fed a common diet. Jugular blood samples were collected at -14, -13, -5, -4, -3, -2, -1 d before expected calving, at calving, and at 1, 3, 5, 7, 9, 11, 13, 28, 56, and 84 d postcalving. After calving, cows were housed in 1 pen in a free-stall barn and consumed a common diet. Colorimetric assays were used to analyze Ca, P, and Mg concentrations in serum. Serum concentrations of osteocalcin (OC), an indicator of bone formation, serum 25-hydroxyvitamin D(3), and parathyroid hormone (PTH) were determined in samples obtained from d -5 through d 13. The 9 control multiparous cows and 5 untreated primiparous cows were used to evaluate the effect of parity on the variables that were measured. There was no effect of parity on Ca, PTH, or 25-OH concentration. Compared with second-lactation cows and older cows (>2 lactations), first-lactation cows had greater serum OC (22.3, 32.0, and 48.3 ng/mL, respectively), indicating that younger animals were forming more bone. Blood Ca, P, and Mg decreased near the time of calving and then increased over time. Serum 25-hydroxyvitamin D(3) was greater for cows dosed with 25-OH (119.0 ng/mL) compared with those dosed with D(3) (77.5 ng/mL) or CON (69.3 ng/mL). Cows dosed with 25-OH tended to have lower serum PTH concentration, but treatments did not affect serum Ca, P, or Mg. Serum OC was greater in second-lactation cows compared with cows entering their third or fourth lactation but OC was unaffected by treatment. Although results indicated a 60% increase in serum 25-hydroxyvitamin D(3) due to a single oral dose of 25-OH before calving, the amount administered in this study apparently was not sufficient for initiation of any improvement in Ca homeostasis at parturition.
Taylor
M S
MS
Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315, USA.
Knowlton
K F
KF
McGilliard
M L
ML
Seymour
W M
WM
Herbein
J H
JH
D000375:Aging / Q000378:metabolism / Q000502:physiology; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D002112:Calcifediol / Q000008:administration & dosage*; D002118:Calcium / Q000097:blood; D002417:Cattle / Q000378:metabolism* / Q000502:physiology; D002418:Cattle Diseases / Q000517:prevention & control; D002762:Cholecalciferol / Q000008:administration & dosage*; D005260:Female; D008274:Magnesium / Q000097:blood; D008903:Minerals / Q000097:blood*; D009751:Nutritional Requirements; D015675:Osteocalcin / Q000097:blood*; D010281:Parathyroid Hormone / Q000097:blood*; D010298:Parity; D036801:Parturition / Q000502:physiology; D010758:Phosphorus / Q000097:blood; D049590:Postpartum Period; D011247:Pregnancy; D011897:Random Allocation
D008903:Minerals; D010281:Parathyroid Hormone; D015675:Osteocalcin; D002762:Cholecalciferol; D010758:Phosphorus; D008274:Magnesium; D002112:Calcifediol; D002118:Calcium