The influence of herbage water consumption on the nutritive value of Persian clover for dairy cows and sheep

Abstract

Three experiments were done with lactating dairy cows and one with wether sheep to study the effects of adding water to, or removing water from, fresh Persian clover on its apparent digestion and utilization in ruminants. In these experiments, the dry matter content of freshly harvested herbage averaged 10%; this was extended by wilting herbage for 12-24 h, adding a small amount of dry feed to the diet or loading the rumen with additional water. This resulted in mean water consumption ranging from 62 to 173 L/day in lactating cows. Water consumption per se appeared to have no effect on apparent digestibility coefficients in the total gastrointestinal tract or milk production (P > 0.05) at either low or high levels of feeding. However, digestibility coefficients were significantly lower (P < 0.05) when wilted Persian clover herbage was fed to animals, with concomitant reductions in milk yield; most of this reduction was due to herbage respiration and enzymatic losses probably associated with the breakdown of non-structural carbohydrates. It has been suggested that digestibility coefficients may be reduced with forages of very high water content due to reduced mean retention times of digesta in the rumen. Chromium dilution rates in rumen fluid were fast and there was a tendency for these to be positively related to water consumption. Therefore, while there may have been reduced digestion of nutrients in the rumen with higher flow rates, this must have been countered-balanced by greater digestion in the intestines.