The development of rumen function in the lamb.

Abstract

A series of experiments is presented, describing the development of the rumen function in grazing lambs and the effects of' diet on the rumen development of artificially reared lambs. In grazing lambs the volume of the abomasum contents showed little change with age. The volume of the rumen contents increased with age, and the rate of' this increase was most marked from 3 weeks of age onwards. The volume of the rumen contents, relative to both the liveweight and the volume of the abomasum contents, was constant from 8 weeks of age onwards. The rumen volatile fatty acids (V.F.A.) concentrations in grazing lambs increased from birth and reached adult levels at 8 weeks of age. The total quantity of V.F.A. present in the rumen at a given time, relative to liveweight, increased up to 8 weeks of age but from this age onwards was approximately constant. The rumen ammonia nitrogen (N) concentrations in grazing lambs were high for the first few weeks after birth, but showed a continuous fall, reaching adult levels at 5 weeks of age. The quantity of ammonia N present in the rumen at a given time, relative to liveweight, increased up to 8 weeks of age and then remained approximately constant. The rumen volumes, V.F.A., and ammonia N concentrations were normal only in lambs that had been fed roughage. When lucerne chaff was fed to young lambs, the digestibilities of the dry matter, crude protein, and crude fibre were high, irrespective of whether the previous diet had been milk or chaff. The ad libitum dry matter intake from roughage, relative to the liveweight, increased up to 8 weeks of age and then remained approximately constant. When roughage was fed to lambs which had been reared on 'milk' (a preparation from dried cows' milk) only from birth to 9 weeks of age, the rumen V.F.A. concentrations rose immediately and levelled off at adult levels within 1 week.