High intake of calcium formiate depresses macronutrient digestibility in veal calves fed milk replacers containing either dairy proteins or whey protein plus soya protein concentrate

A study to determine whether calcium intake and the type of dietary protein would show an interaction with regard to macronutrient digestibility in ve al calves was carried out. Eighty four male calves, about 8 weeks of age, w ere fed four experimental milk replacers in a 2 x 2 factorial design. The d iets contained either dairy protein as a sole source of protein or whey pro tein (76% of total protein) plus soya protein concentrate (24% of total pro tein) and either a low or high concentration of calcium. Calcium was added to the high-calcium diets in the form of calcium formiate. The concentratio n of calcium was on average 0.64% of air-dry matter in the low-calcium rati ons and 1.25% in the calcium-rich rations. After the experimental diets had been fed for 10 weeks, body-weight gain was significantly lower (on averag e 5.5 kg) in the calves that had been fed on the diets containing soya prot ein concentrate and whey protein. Calcium intake did not significantly infl uence weight gain. In the calves that were fed soya proteins, digestibility of protein and carbohydrates was significantly lower than in those fed dai ry protein only, but fat digestion was unaffected. High calcium intake sign ificantly reduced the digestibility of protein, fat: and carbohydrates. Wit h regard to carbohydrate digestibility there was an interaction between the amount of calcium and type of protein in the diet such that the effect of calcium was greater when the diet contained 24% of protein in the form of s oya protein instead of dairy protein only.