Indigestible markers are important in the determination of digestibility values when only a sample of the material may be collected. This situation arises when collecting ileal digesta for determination of ileal digestibilities via a T-piece cannula. Consequently a comparison of indigestible markers was undertaken.

The trial consisted of five treatments: (a) 0.1% Cr2O3, (b) 0.5% Cr2O3, (c) 0.1% TiO2, (d) 0.5% TiO2 and (e) no external marker. Treatment (e) was used for the determination of lignin. 5 cannulated (Landrace x Large White) x Landrace gilts, initially weighing an average of 35 kg, were arranged in a 5 x 5 Latin square. They were placed in metabolism crates, for the collection periods, and housed in a building with a controlled environment. Each of the five periods was preceded by a 9 day acclimatization period. Before period 1 faecal samples had been taken from the 5th to the 9th day after external markers had been included in the diets. These samples were used to determine the quantity of marker excreted in relation to time after inclusion in the diet. Each period consisted of a 5 day marker-to-marker collection of faeces and collection of ileal digesta on the 1st, 3rd and 5th day after the faecal collection. Ileal digesta was collected every 2 hours for 12 hours. Pooled samples of ileal digesta and faeces for each period were used for the determination of nitrogen digestibility.