On the ability of calves to digest hay

Three experiments have been carried out with altogether 16 Ayrshire calves in order to determine the digestibility of timothy hay cured at the early flowering stage and containing some red clover. The ages of the calves varied from 2 ½ to 9 months. Hay was given either totally or almost ad lib. Lignin was used as tracer. In experiment 1 the ages of the six experimental calves varied from 3 to 9 months. The calves aged 5—9 months digested hay equally efficiently when com-pared with each other. The youngest calf aged 3 months digested hay less efficiently (Table 1). In Experiment 2 the ages of the six experimental calves varied from 10 to 22 weeks. In the trial two control cows were also included. The calves aged 10—12 weeks digested hay less efficiently and the calves aged 4—5 months almost as efficiently as the control cows (Table 2). The ability of calves of the same age to digest hay was quite variable. Experiment 3 was carried out with four 7 months old calves. At the end of the trial the calves were slaughtered and the contents of the different parts of the digestive tract were weighed and sampled. On the ground of the analyses of the hay, the contents of the abomasum and the faeces, the digestibilities of N-free organic matter and N-free non-lignin organic matter in the proventriculi and in the whole digestive tract were esimated. The share of the proventriculi in the total digestibility of the said substances was 82—88 per cent (Table 3). The contents of the reticulo-rumen of the calves in Experiment 3 as well as those of younger calves aged 3 ½—4 months were weighed in connection with the slaughtering. The quantity of the contents in calves of 7 months was 30—40 kg and that in calves aged 3 ½—4 months 12—15 kg.