Effects of a supplemental calcareous marine algae bolus on blood calcium concentration in dairy heifers

Oral calcium (Ca) supplementation is common in dairy farms. The source and physical form of Ca greatly influence gastrointestinal absorption and consequently blood Ca responses. The aim of this study was to compare the effects of calcareous marine algae (CMA), calcium carbonate (CC) and calcium propionate (CP) on blood total Ca (tCa) and biologically active ionized form (Ca2+) concentrations in dairy heifers. Holstein Friesian heifers (n = 6), 14.8 ± 0.75-month-old, were used in a 3 × 3 repeated Latin square design of treatments. For each treatment, a daily oral bolus was administered for 7 days by balling gun, and serial blood samples were obtained on days 1 and 7. Serum tCa at day 1 was higher for CMA (2.41 mmol/l) in comparison to CC (2.38 mmol/l) and tended to be higher in comparison to CP (2.39 mmol/l). In addition, the area under the curve in the first 60 min (AUCab0-60) was increased by CMA as compared to both CP and CC, without any difference between the other two sources. Oral Ca bolus supplementation did not improve plasma Ca2+ concentration. Effects on mean blood tCa concentration and AUCab0-60 highlight the potential use of CMA as an oral Ca supplementation to promote a faster peak of blood tCa concentration than CC and CP.