Kaolin and chromic oxide under different forms of administration in a study of consumption and digestibility

Animal nutrition needs simple methodologies to be applied under field conditions, providing valid estimates of consumption and digestibility that can be used by both farmers and animal input industry. Thus, the search for new substances, provided in a practical way, quantified by simple and low-cost analytical methodologies, replacing external indicators (chromic oxide used as reference) would be well accepted by the scientific community. In this context, the aim of this study was to assess the supply of chorionic oxide by esophageal route or mixed in the diet and the use of kaolin as an indicator, under the same forms of administration, to estimate fecal production and digestibility using four castrated male Holstein cattle. The experimental design was a 4 × 4 Latin square design, with four experimental periods of 12 days and six-day intervals between periods. Treatments consisted of supplying chromic oxide by esophageal route (COer), kaolin by esophageal route (Kaoer), chromic oxide mixed to the diet (COdiet), and kaolin mixed to the diet (Kaodiet). The treatment Kaodiet allowed obtaining estimates of fecal production similar to the treatment COer. The treatment COdiet did not differ from the treatment COer (p > 0.05) considering all the assessed parameters, evidencing that the indicator chromic oxide can be supplied mixed directly in the diet without damaging the estimates of fecal production and digestibility. Under the studied conditions, kaolin was not an effective indicator to obtain accurate estimates of fecal production and further studies are needed to adjust the analytical techniques of aluminum extraction as well as to resolve some doubts regarding its digestion process.