Dietary guanidinoacetic acid supplementation favourably modulates energy dynamics and nitrogen balance in broilers

Abstract

The arginine-sparing potential of guanidinoacetic acid (GAA) has been well documented; however, information regarding its effects on energy dynamics and nitrogen balance in broilers is limited. This study evaluated the effects of dietary GAA supplementation on heat increment, net energy, efficiency of energy utilization, and nitrogen and energy balance in broilers using closed-circuit calorimetry chambers. One-d-old Ross 308 male broilers (39 ± 1 g, n = 80) were fed common starter and grower diets until 18 d of age. From d 19, birds continued to receive the grower diet supplemented with 0, 0.03%, 0.06%, or 0.09% GAA. Following an acclimation period in chambers (d 22–25), indirect calorimetry measurements were conducted from d 25 to 28. Each dietary treatment consisted of eight replicate chambers with 2 birds per chamber divided across two consecutive experimental runs. In each run, there were four replicate chambers per treatment. The efficacy of GAA on growth performance was evidenced by a linear improvement in feed conversion ratio (FCR; P = 0.022), along with a tendency for quadratic responses in body weight gain (WG; P = 0.057) and feed intake (P = 0.080) as GAA levels increased. Dietary GAA did not affect (P > 0.05) apparent metabolizable energy (AME) or nitrogen-corrected AME (AMEn) of the feed. However, dietary net energy (NE) tended to increase linearly (P = 0.063) with increasing GAA inclusion. The efficiency of AME utilization for NE, expressed as NE/AME and NE/AMEn, was affected by GAA supplementation, with a linear increase in NE/AMEn (P = 0.017) and a tendency for a linear increase in NE/AME (P = 0.062). Dietary GAA linearly decreased (P = 0.031) AME intake per unit of body WG while it had no impact (P > 0.05) on NE intake. Increasing dietary GAA levels increased nitrogen (N) retention in a quadratic manner (P = 0.017) and linearly improved N utilization efficiency (P = 0.002). Heat production decreased linearly (P = 0.015) with increasing GAA concentration. The RE as protein increased quadratically (P = 0.022) and RE as fat tended to decrease linearly (P = 0.090) with increasing GAA levels. In conclusion, dietary GAA reduced heat production and the efficiency of AME utilization for NE, and favourably modulated body energy partitioning by enhancing energy retention as protein, thereby improving feed efficiency in broilers.