Effect of dietary methionine hydroxy analogue-free acid (MHA-FA) supplementation levels on growth performance, blood metabolites and immune responses in broiler chickens

Abstract

Background: Broiler diets are commonly supplemented by liquid methionine hydroxy analogue-free acid (MHA-FA) containing as product with 88% of active substance to meet sulphur amino acid (SAA) requirements. Objectives: Two experiments were conducted to assess the effects of different dietary MHA-FA levels on growth performance, blood metabolites and immune responses in broilers. Methods: In experiments 1 and 2, 432 and 360 male broilers were fed either a basal corn–soya bean meal diet that met the energy and nutrient requirements with the exception of SAAs or the basal diet supplemented with 5 graded levels of MHA-FA (+0.9 and +0.8 g/kg), for 1–11 and 11–24-day ages, respectively. Chicks were vaccinated with inactivated H9N2/Newcastle disease (ND) and live-ND on days 5 and 11, respectively. Results: Responses in both experiments had similar tendency at corresponding dietary MHA-FA levels. By increasing dietary MHA-FA level, weight gain (WG), feed efficiency (FE), relative breast weight (RBW) and immunity against ND and avian influenza virus inoculation improved with quadratic trend. Blood serum triglyceride, low-density lipoprotein, alanine aminotransferase and alkaline phosphatase concentration were affected in response to dietary MHA-FA levels with quadratic trends. By using broken-line regression analysis, the optimum dietary MHA-FA levels for optimized WG, FE and RBW during 1–10-day age were obtained at 2.20, 3.31 and 3.33 g/kg, respectively; based on MHA-FA content of Met equivalent, the digestible SAA requirements were estimated 0.81%, 0.91% and 0.92%, respectively. Similarly, for the 11–24-day age period, the optimum dietary MHA-FA supplementation levels were obtained 1.79, 2.21, 2.41 and 2.53 g/kg, with the digestible SAA requirements estimated 0.75%, 0.79%, 0.80% and 0.81% for optimized WG, FE, RBW and immune responses, respectively. Conclusions: Supplemental levels of MHA-FA that optimize performance, breast meat and immunity in broilers fed corn–soya bean meal diet, varied from 0.18% to 0.33%, correspond to age and what traits are considered for optimization.