CALCIUM-RELEASE FROM VARIOUS ROUGHAGES AND INFLUENCE OF CA ON DRY-MATTER DEGRADABILITY OF ROUGHAGES IN THE RUMEN AND APPARENT DIGESTIBILITYOF RATION

Three series of experiments were carried out to determine the Careleas e from various roughages in the rumen of sheep and goats, to measure t he Ca solubilization under low pH conditions and to investigate the in fluence of various Ca-levels of rations on in sacco dry matter degrada bility (DMD) in the rumen of small ruminants and apparent digestibilit y of total ration. Nylon bag method was used in all experiments. Sampl es were incubated for 6, 12, 24, 48 and 72 hours in the rumen. In expe riment 1 of experimental series I, three rumen fistulated sheep each w ere fed on rations rich or poor in roughages. DMD and Ca-release were determined from ryegrass, untreated and ammonia treated wheat straw. I n experiment 2 of this series, DMD and Ca-release from ryegrass, alfal fa and wheat straw were measured in sheep and goats fed on a ration ri ch in concentrate. Incubation time and type of feed influenced DMD and Ca-release significantly. Type of feeding and animal species had a lo wer influence. Ca inflow into straw containing bags was sometimes larg er than its release. In experimental series II alfalfa and straw were incubated into the rumen of four sheep for 48 h. Afterwards residues w ere soaked in HCl solution of pH 2. Ca-concentration of alfalfa and st raw residues decreased from 11.0 and 6.7 to 1.8 and 1.1 g per kg DM re spectively. Ca absorption by ruminants seems largely independent of di etary characteristics. In experimental series III three sheep and goat s each were fed on rations containing 0.8 or 5 g Ca per animal per day . Alfalfa and wheat straw were incubated in the rumen. Apparent digest ibility of total ration was determined. Lower Ca-content of ration dec reased DMD of straw and lowered fibre digestibility. It is concluded t hat the calcium content of some feeds is sometimes below animal requir ements.