The live-weight gain and dry-matter and water intakes of calves offered milk substitute diets at high concentrations

Abstract

Thirty-two British Friesian calves were individually offered milk substitutes ad libitum twice daily for 12 weeks. The milks were reconstituted to contain 170, 200, 230 or 260 g dry matter (DM) per kg, using spray-dried skim milk powder and homogenized fat-filled powder containing 500 g fat per kg. Drinking water was available ad libitum at all times. The last two blocks of four calves were used to measure the digestibility, absorption and retention of the constituents of the diets at 2, 6 and 11 weeks of age.The DM intakes of the calves given the four diets were variable but generally increased with increasing DM concentration, mean values being 61·5, 59·5, 66·0 and 73·3 g DM per kg M0.75. As the calves increased in age, their intakes decreased from 67·3 g DM per kg M0.75 at 2 weeks of age to 61·1 g DM per kg M0.75 at 8 weeks of age.The higher DM concentrations and intakes were associated with the higher rates of weight gain; the mean live weights at 12 weeks of age being 121·8, 123·9, 135·3 and 141·6 kg for the calves offered milks reconstituted at 170, 200, 230 and 260 g DM per kg respectively.The concentration of the DM had no effect upon the coefficients of digestion or absorption nor on the retention of energy, protein, calcium or phosphorus. The digestibility of protein increased, whilst the absorption and retention of Ca and P declined with age.Intake of drinking water did not change with age, but was higher for calves given the milk containing 260 g DM per kg than for those given the other three concentrations. The total water intakes were similar for the calves given milks containing 200, 230 and 260 g DM per kg.The linear relationship of DM intake to DM concentration of the milk substitute suggested a lower level of intake in the present experiment, than was observed in a previous experiment (Ternouth, Stobo, Roy and Beattie, 1985b) when the milk concentrations were lower and drinking water was not available. When the concentrations of the DM were re-calculated to take into account the quantity of drinking water consumed, the relationships between DM intake and adjusted DM concentration for the two experiments were similar.