Comparative study of two analytical procedures for the determination of acid insoluble ash for evaluation of nutrient retention in broilers

Inert markers are routinely used in research to estimate nutrient retention and apparent metabolisable energy nitrogen-corrected (AMEn) content of poultry diets. Acid insoluble ash (AIA) is used as a marker to substitute metal compounds because of environmental concerns. In the current research, two methodologies recommended for determining AIA content in feeds and excretas for the evaluation of total tract apparent retention (TTAR) of nutrients, were compared in 12 broiler diets. The experimental design was completely randomised with 2 AIA analytical techniques and 12 dietary treatments that resulted from a combination of two cereals (corn and rice), two heat processing of the cereal (raw and cooked) and three fiber sources (control with no added fibre, 3% oat hulls and 3% soybean hulls). All diets included 1% celite (diatomaceous earth) as additional source of AIA. The techniques used for AIA determination were coded as VO and GA, respectively. The TTAR of dry matter and organic matter and the AMEn of the feeds differed (p ≤ 0.001) among diets and were lower when using GA than when using VO (p ≤ 0.05). However, no interaction between diet and methodology was observed. Moreover, the TTAR of nutrients as determined by both techniques, were highly correlated (r > 0.98). We concluded that the GA methodology results in lower retention values than the VO methodology but that both methodologies can be used indistinctly to estimate TTAR of nutrients in broiler feeds.