The digestibility by sheep and goats of five roughages offered alone or with concentrates

Abstract

SUMMARYThe digestive efficiency, rumen fermentation pattern, nitrogen balance, water intake and urine excretion were compared using four mature vasectomized Chios rams and four Damascus goats for each of five roughages (barley, lucerne or sudax hay, barley straw and leaves and twigs of acacia) offered alone or with concentrates (1:1 ratio), at approximately the maintenance energy level.There were no species differences in the apparent digestibility of nutrients when the roughages were offered alone except for the significantly higher digestibility of dry matter, organic matter (OM), and gross energy (GE) of straw by goats. Sheep exceeded goats significantly in the digestibility of D.M., OM, GE and crude protein (CP) of lucerne hay plus concentrate and of CP when barley hay or sudax hay were supplemented with concentrate.Compared with sheep, goats tended to consume more D.M. per kg W0·75 and drink less water and excrete less urine, but significant differences for water were obtained only with barley straw plus concentrate and for urine with barley hay and acacia.Daily protein retention (g/kg W0·75) was consistently lower in goats than sheep but significant difference was obtained with acacia and with lucerne hay or straw plus concentrate. These results would suggest that Damascus goats require more protein for maintenance than sheep.Compared with sheep, goats had significantly higher rumen NH3·N concentration with both acacia diets but lower with lucerne hay.Total VFA concentration tended to be higher in sheep with all diets, but significance was observed only with barley hay although rumen pH was lower (acacia diets) or similar compared with goats. The molar proportion of acetic was significantly higher in sheep than goats with barley hay plus concentrate. Goats exceeded sheep significantly in the proportion of propionic with straw, of butyric with both barley hay and sudax hay plus concentrate diets, and of isobutyric with barley hay or acacia plus concentrate; with the other diets goats tended to have higher proportions of butyric and isobutyric.