The effects of Spirulina algae inclusion and conditioning temperature on feed manufacture, pellet quality, and true amino acid digestibility

Diet formulation and manufacturing techniques dictate pellet quality and in turn influence broiler chicken performance; however, the degree of improvement may be dependent on potential changes in nutrient digestibility. For example, high steam conditioning temperature has been shown to increase pellet quality but also decrease amino acid digestibility. Therefore anticipated broiler performance improvement due to increased pellet quality would be diminished. Formulating diets with ingredients that contribute to pellet binding may allow for low temperature conditioning and maintenance of pellet quality. The inclusion of Spirulina algae in broiler diet formulations has been shown to improve pellet quality. The objectives of this study were to describe the manufacture, quality, and true amino acid digestibility (TAAD) of pelleted corn and soybean meal based broiler diets produced with different Spirulina algae inclusions and steam conditioning temperatures. Treatments were arranged as a 5 × 3 factorial that varied in algae inclusion (0, 0.5, 1, 5, and 10%) and steam conditioning temperature (74, 82, and 91 °C). The Spirulina algae was analyzed for mineral content, metabolizable energy, and digestible amino acids to balance treatment formulations. The manufacture of each treatment was replicated three times and blocked by time of manufacture. All treatments were steam conditioned for a 10 s duration and extruded through a 4.7 × 38 mm pellet die. Hot pellet temperature (HPT) and pellet mill motor amperage increased (P < 0.05) with either increased algae inclusion or steam conditioning temperature. However, pellet production rate was not affected by treatment (P > 0.05). Algae inclusion and conditioning temperature interacted to affect pellet durability (P < 0.05). Algae inclusion and conditioning temperature increased pellet durability, with algae inclusion having a greater influence at low conditioning temperature. Single comb white leghorn cockerels were precision fed each dietary treatment to determine TAAD. Conditioning temperature, in general, affected TAAD of multiple tested amino acids (P < 0.02), more specifically leucine, valine, isoleucine, alanine, and aspartic acid decreased in digestibility when conditioned at 91 °C (P < 0.05). Lysine TAAD tended to be similarly effected by conditioning temperature (P = 0.06). Threonine, cystine, proline, and glutamic acid digestibility were affected by the interaction of conditioning temperature and algae inclusion (P < 0.05), demonstrating that TAAD was reduced at either 82 °C or 91 °C depending on the inclusion of algae. The combination of Spirulina algae inclusion and low conditioning temperature may improve pellet quality without detriment to amino acid digestibility.