Chromic oxide and acid-insoluble ash as faecal markers in digestibility studies with young growing pigs

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Abstract
In two separate conventional metabolism trials, each involving eight 13 kg liveweight pigs given a barley-based diet, mean faecal recoveries (±SD) of chromic oxide added to the diet and naturally occurring acid-insoluble ash of 85.3 (±6.19) and 98.2 (±4.03) % respectively, were obtained. Total faeces collection gave significantly (P < 0.05) higher apparent digestibility coefficients than those calculated by reference to chromic oxide for diet dry matter, organic matter, and gross energy, but there were no differences (P > 0.05) in nutrient digestibility for total collection compared with acid-insoluble ash. There were only very small differences in nutrient digestibilities calculated by reference to the concentration of each respective marker in aliquots of the total faeces excreted and composite 6-day grab samples of faeces. Based on the correlation between organic matter digestibility determined by reference to the chromium content of cumulatively bulked daily grab samples of faeces, it was deemed necessary to collect daily grab samples of faeces for at least 5 consecutive days to form a suitable composite grab sample. The natural marker, acid-insoluble ash shows promise for use in digestibility studies with young pigs.