Effect of intraruminal infusions of volatile fatty acids on the intake of a low-digestibility straw by sheep

Extract

The voluntary intake of roughage diets by ruminants is related to their degradation characteristics (Hovell et al., 1986). Furthermore, as forage quality is improved the outflow of undegraded particles is increased. Previous studies have shown that differences between forages in outflow from the rumen were mainly associated with the outflow of liquid from the rumen. In this context there could be chemical factors arising from the rapid fermentation of the more degradable forages that could stimulate salivary flow or movement of water across the rumen wall, increasing liquid outflow from the rumen, and thus washing undegraded residues from the rumen and enabling the animal to eat more. One possible signal is rumen volatile fatty acids (VFA) levels since YFA production and concentration are significantly greater with roughages that support greater intakes and rumen outflows. Intraruminal infusions of VFA have been shown to depress feed intake in ruminants (Baile & Forbes, 1974). However, most of the infusion studies have been conducted with animals fed diets containing concentrates or high-quality forages, and most of them examined short-term intake responses to intraruminal infusions of, probably, supraphysiological levels of VFA (Dejong, 1986). The aim of this experiment was to examine whether the voluntary intake of a low quality roughage by sheep could be affected by the infusion of VFA at different doses into the rumen.