The effect of milk substitute concentration upon the intake, digestion and growth of calves

Abstract

ABSTRACTA total of 40 individually-penned British Friesian male calves were offered milk substitutes ad libitum from 2 days until 12 weeks of age. Ten milks were reconstitued from either liquid or spray-dried skim milk and a fat-filled (500 g fat per kg) powder and contained 80, 110, 140, 170 or 200 g dry matter (DM) per kg liquid. A further six calves were used in a randomized-block experiment to measure the digestibility, absorption and retention of the diets containing 80, 140 and 200 g DM per kg.There are no significant differences in the intake, growth rate, digestibility, absorption or retention between calves given milk substitutes reconstituted from liquid or spray-dried skim milk.At all ages, as the DM concentration of the milks increased, liquid intake decreased but DM intake and live-weight gain increased. The mean live-weight gain was 0·99, 1·13, 1·16, 1·28 and 1·27 kg/day for calves given the milk substitute diet at concentrations of 80, 110, 140, 170 and 200 g DM per kg, respectively. The DM intake to live-weight ratios were constant at all ages when live weight was expressed to the power of 0·61.No significant adverse effect of the diets was evident from the fortnightly monitoring of jugular blood samples for packed cell volume and concentrations of glucose, urea-N, Na, total protein, albumin, globulin and haemoglobin; nor from faecal consistency, rectal temperature, heart rate and respiration rate.There was no indication that age affected digestibility, except that digestive efficiency was reduced in calves with diarrhoea, particularly at 2 to 4 weeks of age; nor that dietary concentration influenced digestion or absorption. The true absorption of N, Ca and P from the milk diets was high with mean coefficients of 0·99, 1·01 and 0·95 respectively. The main endogenous losses of N and P occurred through the urine and of Ca through the faeces.