Intake, digestibility and rumen characteristics of sheep given grass fertilized with phosphorus

Abstract

Pangola grass (Digitauia decumbens) was grown on an infertile sand and fertilized with low and high levels of phosphorus (P) and adequate levels of other nutrients. Regrowths were cut at 8, 11, 13 and 14 weeks, dried and fed to sheep to measure their voluntary intake and digestibility with and without a P supplement. Retention time of feed in the reticulo-rumen was determined by a total emptying procedure using rumen-fistulated sheep. Fertilizer P increased mean P levels in the grass from 0.16 to 0.26%, but had no significant effect on other elements and carbohydrate fractions. P fertilizer had no significant effect on the intake and digestibility of the dry and organic matter of the unsupplemented grass. However, when the P-fertilized grass was supplemented with P, intake was depressed. This adverse effect on voluntary intake may be attributed to a narrowing of the Ca : P ratio, which was associated with an increase in the time grass was retained in the reticulorumen.