Factors limiting the intake of feed by sheep. III. The mean retention time of feed particles in sections of the alimentary tract

Abstract

The mean retention time of feed particles in the alimentary tract of sheep was measured by means of a stained-particle technique, when lucerne hay or a diet of wheaten straw + wheaten hay (1 : 1) was offered ad libitum. The levels of intake of the straw diet and lucerne hay were equivalent to 11.8 and 25.8 g organic matter/day/kg body weight. The mean retention time of particles in the entire alimentary tract when the straw diet was offered was 57.5 hr, this consisting of 36.3 hr in the rumen + omasum and 21.2 hr in the abomasum + intestines. The retention time in the rumen + omasum was calculated to consist of (a) 19.7 hr during which the particles were being degraded to a size at which transfer from the rumen could be readily effected, and (b) 16.6 hr of residence in the rumen + omasum as small particles. With lucerne hay, the retention times were shorter: small particles spent 10.8 hr in the rumen + omasum and retention time in the abomasum + intestines was 16.1 hr. It was calculated that only a small proportion of the difference between the straw diet and lucerne hay in organic matter intake could be attributable to differences between the diets in the rate of removal of finely divided particles of organic matter from the rumen.