Fibre digestion and utilization in goats

Abstract

Dietary fibre contributes significantly to the balancing of nutrient requirements in goats. Dietary fibre also plays a pivotal role in goat production through its influence in and interaction with the intake and digestion of nutrients. Physiological regulation (feedback from metabolic factors) of intake is dominant in goats fed high concentrate diets, while physical fill is the predominant factor in the regulation of intake when goats were fed high-forage diets. Mediated through salivation and buffering capacity, dietary fibre intake influences mastication and rumen fermentation. In growing goats, dietary metabolizable energy density above 2.78 Mcal/kg depresses intake and reduces growth rate in goats. Adequate dietary fibre is essential in producing leaner carcasses in growing goats. In high producing lactating dairy goats, dietary fibre intake plays a role in the prevention of milk fat depression. The effect is mediated through the maintenance of favorable acetate to propionate ratio in the rumen liquor, as acetate is the major precursor of milk fat. It appears that 18–20% ADF or 41% NDF is nutritionally adequate for high producing lactating dairy goats. For growing goats between 4 and 8 months of age, 23% ADF is recommended. Relationship between chewing time and dietary fibre can be defined by the equation: total chewing time (min/day) = 33.11 + 30.13 ADF intake (%). Milk fat yield can be predicted from dietary fibre intake: milk fat yield (g/day) = 115.78 − 0.128 × ADF intake (g/day) + 0.00021 × (ADF intake, g/day) 2.