EFFECT OF MILLET AND SOYBEAN HULLS ON NUT RIENT AND ENERGY-UTILIZATION IN GROWING PIGS .1. CHARACTERIZATION OF DIETS, GROWTH-PERFORMANCE AND NUTRIENT UTILIZATION

An experiment with growing pigs was conducted to examine the effects o f various sources of dietary fibre in comparison to starch on growth p erformance and energy utilization. Twenty percent of a control diet (K O) was either replaced with wheat starch (20%STA), millet hulls (20%HI ) or soybean hulls (20%SO). Sixteen male Large White castrates were ho used in individual pens from 20.0 kg live weight (LW). The animals wer e fed a restricted diet. Just after slaughter at 95.3 kg LW, digesta s amples were taken from different parts of the digestive tract. In comp arison to diet KO, no differences could be seen in intake of digestibl e energy (DE) by the addition of wheat starch, whereas daily weight ga in was lowered by 6%. No significant differences in growth parameters and DE content (average: 15.8 MJ/kg DM) were observed between diets KO and 20%SO. In diet 20%HI, DE content was lowered by 14% and DE intake also decreased. This resulted in a reduced daily weight gain and an i mpaired feed-conversion rate. Precaecal energy digestibility [d(E)] wa s significantly lowered by the content of total dietary fibre, whereas faecal excretion d(E) was influenced by the content of dietary fibre and its composition. The main fibre constituents influencing faecal ex cretion d(E) were insoluble hemicelluloses and lignin. It was conclude d that differences in fibre utilization are mainly influenced by the p rocesses in the digestive tract (mainly large intestine). Furthermore, pigs would be able to meet an important part of their energy requirem ents from microbial degradation of precaecally non-degradable nutrient s in the large intestine, if lignin incrustation of insoluble hemicell uloses were not a limiting factor.