Effect of sodium hydroxide treatment on chemical composition and in vitro and in vivo digestibility of hay

The effect of NaOH spray treatment on hay digestibility was studied by in vitro and in vivo methods. Four hay types were compared: untreated long or shredded hay and shredded hay treated with 3% and 6% NaOH. In vitro digestibility was measured by three methods: the Tilley and Terry procedure, a one-stage nylon bag technique (rumen digestibility only), and a two-stage nylon bag technique (rumen digestion + pepsin - HCl digestion). In vivo digestibility was estimated on eight young bulls given the four hay types at two levels according to a 2 x 2 latin square. In vitro and in vivodigestibilities of dry matter, organic matter and crude fiber were increased by the NaOH treatment. Both in vitro and in vivo techniques revealed the existence of an optimum NaOH concentration which in our experiments was close to the 3% treatment.