Effects of acid-binding capacity of South African feedstuffs and water pH on the performance of broilers

Abstract

Acid-Binding Capacity (ABC) is measured as the amount of acid required to drop the pH of 1 kg feed to pH 3 and pH 4. Each feed ingredient will therefore contribute to the ABC value of complete feed and has the potential to alter stomach pH by buffering the HCl secreted. Protein digestion begins with pepsin, which is secreted as the enzyme precursor pepsinogen, that requires a low gastric pH to be activated. The pepsin enzyme has been shown to have an optimum pH of 2. Therefore, feed ingredients or diets that raise the pH above a critical threshold have the potential to reduce protein digestibility. This can have a greater effect in young broilers due to their reduced ability to regulate their pH levels with reduced affinity for HCl secretion. This could potentially result in decreased performance and downstream gut health issues. Water alkalinity is essentially the buffering capacity of the water. This could potentially influence the pH of the gastrointestinal tract. The aim of this study is to create a survey for the pH and ABC values of all commonly used feed ingredients, in South Africa for the pH and ABC values. The study had a 2x2x2 factorial arrangement of treatments with two ABC values, two water alkalinity values and two water pHs with the aid of a water acidifier. The lower ABC value significantly (P<0.01) improved the feed conversion ratio (FCR), crude protein (CP) digestibility and dry matter (DM) digestibility. The use of a water acidifier did not have a significant (P<0.05) effect on any of the parameters measured. When birds consumed a diet with high ABC and a high-water alkalinity the CP digestibility in broiler chicks at 7 days of age significantly (P<0.05) decreased compared to birds fed a low ABC and a low alkalinity diet. The CP and DM digestibility was significantly (P<0.01) higher at day 21 compared to day 7. The pH of the gizzard and duodenum significantly (P<0.01) increased from day 7 to 21. The results from this study indicate that a low ABC diet improved performance and nutrient utilisation and should be incorporated into diet formulation and consideration for nutritionists to use in the future.