The influence of yeast supplementation on the digestibility of fibre in horse rations. (Abstract)

Pagan (1989) suggested that the digestion of ligno cellulose was improved by the inclusion of yeast extract in the diet of horses containing 50% of timothy hay. Since Australian horses are typically fed lucerne rather than timothy hay, yeast supplement was provided in lucerne based horse rations to determine if any improvement in nutritional value was obtained. Six thoroughbred horses (540 kg SEM 14) were fed a 50% lucerne hay and 50% cereal grain diet. A reversal trial involving two, four week periods of feeding 9.30 kg DM/day was used with three horses per group. Each horse in the supplemented group had included in its daily ration 10 grammes of yeast extract (Saccharomyces cerevisiae). total faecal collections were made in the last week of each period. Details of the diet composition and digestibility are shown in Table 1. There was no significant difference in ADF digestibility of the two diets (see Table 1) and the very low digestibility reported here confinns the findings of Jorgenson (197 1) that the ligno cellulose fraction has very low nutritional availability to non ruminants. Despite the lack of demonstrated improvement in the ADF digestibility of diets supplemented with yeast, the high digestibility of energy (12 MJ/kg) and nitrogen (0.8 g/g) demonstrated the high nutritional value of lucerne and cereal diets when compared with estimates of digestible energy (8.9 MJ/kg) and digestible nitrogen (0.59 g/g) for spring pasture grazed by mares (Gallagher and McMeniman, 1988).