Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2439959 | Journal of Dairy Science | 2008 | 9 Pages |
Abstract
Twenty-seven multiparous Jersey cows were randomly assigned to receive an oral bolus containing corn starch (control, CON), corn starch plus 15Â mg of 25-hydroxyvitamin D3 (25-OH), or 15Â mg of cholecalciferol (D3) 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 â14, â13, â5, â4, â3, â2, â1 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 D3, and parathyroid hormone (PTH) were determined in samples obtained from d â5 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 48.3Â 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 D3 was greater for cows dosed with 25-OH (119.0Â ng/mL) compared with those dosed with D3 (77.5Â ng/mL) or CON (69.3Â 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 D3 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.
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Authors
M.S. Taylor, K.F. Knowlton, M.L. McGilliard, W.M. Seymour, J.H. Herbein,