Abstract
A study to determine whether calcium intake and the type of dietary protein would show an interaction with regard to macronutrient digestibility in veal calves was carried out. Eighty four male calves, about 8 weeks of age, were fed four experimental milk replacers in a 2 x 2 factorial design. The diets contained either dairy protein as a sole source of protein or whey protein (76% of total protein) plus soya protein concentrate (24% of total protein) and either a low or high concentration of calcium. Calcium was added to the high-calcium diets in the form of calcium formiate. The concentration of calcium was on average 0.64% of air-dry matter in the low-calcium rations 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 average 5.5 kg) in the calves that had been fed on the diets containing soya protein concentrate and whey protein. Calcium intake did not significantly influence weight gain. In the calves that were fed soya proteins, digestibility of protein and carbohydrates was significantly lower than in those fed dairy protein only, but fat digestion was unaffected. High calcium intake significantly reduced the digestibility of protein, fat and carbohydrates. With 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 soya protein instead of dairy protein only.