Rates of passage of solutes, microbes and particulate matter through the gastro-intestinal tract of ewes fed at a constant rate throughout gestation

Abstract

The rates of passage of solutes, microbes and particulate matter were measured at different stages of gestation in multiparous Corriedale ewes. The mean retention times (MRT) of each of these constituents in the rumen decreased as gestation progressed. There was an increase in the MRT of digesta distal to the stomach which was sufficient to compensate for the decrease in solute MRT in the rumen. Thus, for the whole tract, only the MRT of particulate matter decreased during gestation. There were good relationships between the rate of passage from the rumen of microbes and of particulate matter and that of water, reflecting the importance of water as the vehicle for passage from the rumen. The fractional outflow rate of the particle-associated marker 103Ru-phen was greater than the net value for microbes, but was similar to the calculated value for non-microbial, non-ammonia nitrogen. The proportion of the rumen microbial population that was free-floating declined to a minimum of 0.18 as the fractional outflow rate of water increased. A peristaltic activity index showed a tendency to decline, particularly in the duodenum, as gestation progressed.