The effect of a dacitic (rhyolitic) tuff breccia (Azomite®) in corn, soybean, and DDGS based diets that vary in inorganic phosphate source on pellet mill energy use, 0 to 21-day broiler performance, and apparent ileal amino acid digestibility

Abstract

Past research has shown that Azomite ( AZM ) can increase pellet mill production rate in diets that include inorganic phosphate sources ( IPS ) of dicalcium phosphate ( DCP ) or tricalcium phosphate ( TCP ). The authors hypothesized that if production rate were held constant then pellet mill energy consumption would decrease for diets that contained AZM. The objective was to determine the effect of AZM (0.25%) in diets with DCP and TCP on pellet mill energy consumption, subsequent live bird performance, and apparent ileal amino acid digestibility ( AIAAD ) when fed to broiler chicks for 21 d. Feed was manufactured in a 2 (IPS) × 2 (AZM inclusion) factorial across 4 days in a Latin Square Design. Post manufacture, 320 one-day-old Ross 708 males were allocated to 8 replicate pens, 10 chicks per pen, in a randomized complete block design. Dietary treatments were arranged in a 2 (DCP or TCP) × 2 (AZM or no AZM) factorial. On d 21 ileal contents were collected for amino acid and titanium dioxide analysis. Pellet mill motor load decreased by 5% in diets containing TCP compared to DCP ( P < 0.001), and 1% when AZM was included ( P < 0.001). Pellet durability was increased in diets containing DCP when AZM was included, while TCP diets were unaffected ( P < 0.001). Hot pellet temperature increased for TCP diets with AZM, whereas DCP diets did not change ( P < 0.05). AIAAD of cysteine increased for DCP diets with AZM, but not TCP diets ( P < 0.05). Similar trends were observed for lysine, isoleucine, and valine ( P < 0.10). An increase in FCR by 0.02 was observed in DCP diets with AZM (1.283 vs. 1.309, P < 0.05), while TCP diets were unaffected (1.294 vs. 1.287, P > 0.05). Decreased pellet mill motor load that resulted from AZM inclusion suggests that feed was subjected to less frictional heat and/or pressure within the pellet die. This reduction in frictional heat and pressure likely preserved amino acid conformation, but the improvement was not translated to growth efficiency.