Abstract
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.
Highlights
Inert markers are routinely used in nutrient digestibility studies to eliminate the need of total collection of the excreta produced (Sales and Janssens, 2003a)
Two assays recommended for the determination of Acid insoluble ash (AIA) in animal digestibility studies are those reported by Vogtmann et al (1975) and Van Keulen and Young (1977)
The diets were based on cereals and soy Abbreviations used: AIA; apparent metabolisable energy nitrogen-corrected (AMEn); CV; dry matter (DM); GA (González-Alvarado et al [2007) technique]; N; organic matter (OM); tract apparent retention (TTAR); VK (Van Keulen and Young [1977] technique); VO (Vogtmann et al [1975] technique)
Summary
Inert markers are routinely used in nutrient digestibility studies to eliminate the need of total collection of the excreta produced (Sales and Janssens, 2003a). Yin et al (2000) reported that the recovery of titanium in pigs fed diets high in fibre was very low, ranging between 60.6 and 67.8%, a variability which was probably related to segregation of the marker. Acid insoluble ash occurs naturally in feed ingredients (McCarthy et al, 1974) but the amount of AIA in the final feed is usually low, which makes convenient the inclusion of extra amounts of the marker in the diet to increase the accuracy of the chemical analysis (van Leeuwen et al, 1996; Gracia et al, 2003). Two assays recommended for the determination of AIA in animal digestibility studies are those reported by Vogtmann et al (1975) and Van Keulen and Young (1977). This research was conducted to compare two techniques used in research to estimate AIA content of diets and excretas and nutrient retention in broiler fed diets varying widely in ingredient composition
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