The aim of this study was to examine the effects of calcium supplementation during the first trimester of lactation on the variations of serum phosphatases activity and mechanisms of calcium homeostasis. Twelve Holstein-Friesian cows with average daily production of 35 kg of milk were fed complete daily ration (hay, grass silage, maize silage and concentrates). This diet led to severe deficiency in calcium supply (-17.1±15.2 g of calcium day-1) and mild excess of phosphorus (4.7±5.6 g of phosphorus day-1). Two oral supplementation with 50 g of calcium-formiate were performed successively in 72 hour intervals. As the biochemical indicators of bone turnover the following parameters were measured before and 4 days after the calcium supplementation: serum calcium (Ca), inorganic phosphorus (iP), magnesium (Mg) concentrations, total alkaline phosphatase (ALP), bone alkaline phosphatase (bALP) and acide phosphatase (ACP) activity. A slight increase in Ca serum levels (2.09±0.11 mmol/L vs. 2.20±0.19 mmol/L; P=0.064) and decrease in iP (1.73±0.26 mmol/L vs. 1.66±0.24 mmol/L; P=0.373) and Mg (1.26±0.10 mmol/L vs. 1.16±0.11 mmol/L; P=0.058) was recorded. There was a rapid drop in mean bALP (-22.7%) but not in ALP (+1.4%) and ACP (+17.6%) activity, suggesting diminished osteoblastic mobilisation after the calcium supplementation. In contrast, osteoclastic resorption remained unchanged. The findings confirm the capacity of calcium supplementation on bone metabolism and the usefulness of bone ALP as biochemical indicator of bone turnover.
Agricultura 1: 24-27 (2002)

Key words: dairy cows; early lactation; calcium supplementation; serum phosphatase activity

1. Bigras-Poulin M, Tremblay A. An epidemiological study of calcium metabolism in non-paretic postparturient Holstein cows. Prev. Vet. Med. 1998;35:195-207.

2. Collignon H, Davicco MJ. Barlet JP. Metacarpal growth and systemic markers of bone metabolism in the ovine fetus. Reprod. Fertil. Dev. 1996;8:287-95.

3. Dhiman TR, Sasidharan V. Effectiveness of calcium chloride in increasing blood calcium concentrations of periparturient dairy cows. J. Anim. Sci. 1999;77: 1597-1605.

4. DLG. Futterwerttabelen für Wiederkäuer. DLG Verlag,Frankfurt, 1991.

5. Eyre DR. Bone biomarkers as tools in osteoporosis management. Spine 1997;22 Suppl S:17S-24S.

6. Fürl M, Schäfer M, Dabbagh MN. Auswirkungen dreiwochiger Buttersäurebalastung auf den Mineralstoffwechsel und das Skelettsystem bei Rindern. Berl. Münch. Tierärztl. Wschr. 1993;106:370-7

7. Hartigan P. Treatment of milk fever: the early history. Irish. Vet. J. 1999;52:443-8.

8. Jemtland R, Lee K, Segre G. Heterogenity among cells that express osteoclastassociated genes in developing bone. Endocrinology 1998;139:340-9.

9. Jonsson NN, Pepper PM, Daniel RCW, McGowan MR, Fulkerson W. Association between non-parturient post-partum hypocalcaemia and the interval from calving to first ovulation in Holstein-Friesian cows. Anim. Sci. 1999;68:377-83.

10. Kenward MG. Analysis of repeated measurements. University press, Oxford, 2000.

11. Lappetelainen R, Lappetelainen E, Hassinen T, Hahl M, Pirskanen A, Maenpaa PH. Biochemical indicators of bone metabolic activity in bovine peripartum hypocalcemia. J. Vet. Med. 1993;A40:67-72.

12. Mosel van M, Wouterse HS, Klooster van AT. Effects of reducing dietary (Na+K) - (Cl+SO4) on bone in dairy cows at parturition. Res. Vet. Sci. 1994;56:270-6.

13. Moss DW, Whitby LG. A simplified heat-inactivation method for investigating alkaline phosphatase isoenzymes in serum. Clin. Chim. Acta 1975;61:63-71.

14. Philipov JP. Changes in some biochemical indicators of bone turnover after ultraviolet irradiation of dairy cows. Res. Vet. Sci. 1992;53:397-8

15. Philipov JP. Comparative investigation of blood biochemical parameters in metabolic and inflamatory bone diseases of cows. Vet. arhiv 1996;66:123-7.

16. Rosol TJ, Capen CC. Calcium regulating hormones and diseases of abnormal mineral (calcium, phosphorus, magnesium) metabolism. In: Kaneko JJ, Harvey JW, Bruss ML. (eds) Clinical biochemistry of domestic animals. Academic Press, San Diego, 1990; 619-702.