Fertilizer calcium as a factor affecting the voluntary intake, digestibility and retention time of pangola grass (Digitaria decumbens) by sheep

1. Pangola grass (Digitaria decumbens) grown with and without calcium fertilizer was cut at three stages of regrowth to measure voluntary intake of dry matter (DM) and digestibility of various components of the dried-grass diet by sheep kept in metabolism crates. To determine the extent of a simple Ca deficiency half the sheep on each diet were supplemented with 1·4g Ca/d. Retention times of the various dietary components in the reticulo-rumen were also determined. 2. Feeding a Ca supplement had no effect on voluntary intake or digestibility. 3. Ca fertilizer increased the Ca content of the grass from 2·2 to 3·8 g/kg DM and DM digestibility from 0·455 to 0·476 (P < 0·01) due to an increase in the digestibility of the hemicellulose. 4. Voluntary intake was increased from 38·8 to 43·2 g/kg body-weight0·75 per d by Ca fertilizer due to an 18% reduction in the period of time the DM was retained in the reticulo-rumen. 5. Regressions relating voluntary intake to DM digestibility for the Ca-fertilized and control grass were significantly different (P < 0·01). When compared at the same DM digestibility the voluntary intake of the Ca-fertilized grass was 2·6 g/kg body-weight0·75 per d higher than that of the control. 6. It was concluded that Ca fertilizer increased both DM digestibility and voluntary intake as a result of changes in the structural composition of the grass and not by a simple increase in the Ca content of the diet.