Evaluation of inert markers for the determination of ileal and faecal apparent digestibility values in the pig

A series of experiments was designed to evaluate inert markers employed in studies of ileal and faecal apparent digestibilities of nitrogen and amino acids in pigs fitted with simple ‘T’ piece cannulas. Trial 1 assessed the palatability of diets containing (a) 5 g chromic oxide/kg, (b) 1 and (c) 5 g titanium dioxide/kg at two levels of feeding. The results indicated that there were slight problems in terms of period of feed consumption associated with diets (a) and (c), but that these effects were transitory and disappeared following acclimatization, although higher levels of feeding may compound the problem. Trial 2 estimated N balance, faecal apparent digestibility of amino acids as determined by both total collection and ratio of markers, ileal apparent digestibility of amino acids and recovery of markers using diets containing (a) 1 and (b) 5 g Cr2O3/kg, (c) 1 and (d) 5 g TiO2/kg. An additional assessment of acid-insoluble lignin present within the diet was also undertaken. Cr2O3 was associated with the lowest recovery, whilst calculations based on TiO2 gave lower standard errors. Trial 3 examined diurnal variation in digesta sampling and its effect on faecal apparent digestibility of N and amino acids. There were no evident effects. In general, it was concluded that the most appropriate marker to use in studies of this nature was TiO2 at a rate of 1 g/kg.