engleski

Concentrations of calcium, phosphorus, carboxy-terminal telopeptides of type I collagen and 1.25 dihydroxy vitamin D3 and activity of bone specific alkaline phosphatase in blood serum of periparturient dairy cows

In the present study, influence of lactation on bone metabolism parameters in dairy cows was investigated. Concentrations of calcium (Ca), phosphorus (P), carboxy-terminal telopeptides of type I collagen (CTX) 1.25 dihydroxy vitamin D3 (1.25 (OH)2 D3) and activity of bone alkaline phosphatase (BALP) were measured in blood serum of periparturient dairy cows, to investigate of bone metabolism in the beginning of lactation. The research was carried out on dairy Holstein cows and heifers between 2 and 7 years of age. Samples were taken from heifers (n=6) and cows in three experimental periods: 14 days before calving (n=24), 10th day (n=24) and 30th day (n=24) after calving. For determination of 1.25 (OH)2 D3, n were 6 (heifers), 10 (14 days before), 10 (10th day after) and 8 (30th day after calving). The investigated biochemical parameters were measured by standard methods and commercial kits. Significance of differences was tested by paired T-test and for heifers by independent T-test. A significant increase of CTX (p < 0.0001) concentrations was found on the 10th and CTX and 1.25 (OH)2 D3 (p < 0.0001 and p<0.05) on the 30th day after calving, as compared to the 14th day before calving. In heifers, significantly higher concentrations/ activities of P (p<0.01 to p<0.0001) and BALP (p<0.0001) considering all three experimental periods in cows, were determined ; concentration of CTX was significantly higher considering the cows 14 days before calving (p<0.0001) ; concentration of 1.25 (OH)2 D3 was equivalent to the period around the 14th day before calving in cows and significantly lower considering the group of cows on the 30th day after calving (p<0.05). The results indicate high rate of bone resorption in the beginning of lactation, as a source of calcium and phosphorus for compensation of these minerals lost by milk. Increase of 1.25 (OH)2 D3 to 30th day after calving could implicate to gradual adaptation of calcium absorption from the digestive tract. Higher concentrations/ activities of CTX, P and BALP in heifers confirm the high rate of bone remodelling during growth and formation of skeleton.

dairy cows; lactation; bone metabolism

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