Physical processing of barley and its effects on intra-caecal fermentation parameters in ponies

Intra-caecal fermentation parameters in caecally-fistulated ponies offered barley based diets in which the barley had been physically processed by either rolling (RB), micronising (MB) or extruding (EB). Three ponies were offered 4 kg dry matter (DM) per day of either 100% hay cubes (HC), or one of three diets consisting of a 50:50 barley:HC mix. Due to small refusals of HC, the actual DM intakes (kg per day) were 3.74, 3.67, 3.57 and 3.52 (S.E.D. 0.18) for the HC, RB:HC, MB:HC and EB:HC diets, respectively. With the exception of butyrate, all intra-caecal fermentation parameters 4–8 h post feeding in ponies given diet RB:HC were significantly (P<0.05) different from those observed in ponies fed diet HC. Thus, in ponies fed diet RB:HC, intra-caecal pH and acetate molar proportions were reduced whilst lactate concentration and propionate molar proportions were increased (P<0.05) compared with values recorded in ponies fed diet HC. By contrast, intra-caecal total VFA, lactate and pH levels of ponies fed diets MB:HC or EB:HC were similar to those in ponies fed HC at all time points measured, although acetate and propionate molar proportions were lower and higher, respectively, in ponies fed diets EB:HC and MB:HC compared with those fed HC. These results suggest that micronisation or extrusion of barley offer advantages over rolling barley in that the values for the intra-caecal fermentation parameters in ponies fed MB:HC or EB:HC were largely similar to those of ponies fed the HC forage diet. Where equines are to be given substantial quantities of cereals in their diet then use of micronised or extruded products may be beneficial in minimising hindgut dysfunction.