# Effects of Guanidinoacetic Acid and Metabolizable Energy Levels on Performance and Nutrient Metabolism in Broilers

## TL;DR

This study shows that adding guanidinoacetic acid (GAA) to standard-energy diets improves broiler performance and energy use, especially in the early growth phase.

## Contribution

The novel finding is that GAA improves feed conversion and energy utilization in standard-energy diets but cannot fully compensate for energy reductions.

## Key findings

- GAA improved feed conversion and energy utilization in standard-energy diets during the starter phase.
- GAA did not fully compensate for energy reductions in diets with 50 or 100 kcal/kg less energy.
- GAA increased apparent metabolizable energy but had minimal effects on protein or mineral digestion.

## Abstract

This study evaluated how different metabolizable energy levels in diets and the addition of guanidinoacetic acid (GAA) affect the performance and nutrient utilization of broiler chickens. Diets with standard energy, reduced by 50 kcal/kg, and reduced by 100 kcal/kg were tested with or without GAA. The results showed that GAA improved feed conversion and energy utilization in diets with standard energy, especially in the starter phase (1 to 21 days). However, GAA did not fully compensate for the energy reduction in diets with reduced 50 kcal/kg or 100 kcal/kg calories. Digestibility analyses showed greater apparent metabolizable energy (AME and AMEn) in broilers that received GAA in normal diets, but there were no major effects on protein or mineral digestion. The inclusion of GAA may improve the performance and energy efficiency of broilers in the starter phase, mainly when used in diets with adequate energy, helping to improve nutrient use.

The effects of three metabolizable energy (ME) levels and the use of guanidinoacetic acid (GAA) were evaluated on broiler performance and nutrient digestibility from 1 to 35 d of age. In total, 1944-d-old Ross AP95 male broilers were randomly distributed to six treatments (12 replicates/treatment). Diets were formulated to contain three ME levels (standard energy [SE], −50 kcal/kg reduced energy [−50 RE] and −100 kcal/kg reduced energy [−100 RE]) in all feeding phases with or without GAA inclusion. For the nutrient-metabolizable analysis, 960-day-old male broilers were separately raised in floor pens until 14 d of age and randomly distributed to six treatments (16 replicates/treatment). Data were analyzed with ANOVA and Tukey’s test at p ≤ 0.05. There was a significant interaction for the feed conversion ratio (FCR) at 21 days, in which the PC diet showed better FCR when GAA was included. In the evaluation of the main effects, an effect of metabolizable energy (ME) was observed on body condition score (BCS) at 7 and 21 days, feed intake (FI) at 21 and 35 days, and feed conversion ratio (FCR) at 21 days, with the PC diet showing better FCR and lower FI. An effect of GAA was observed on feed conversion ratio at 21 days, with the inclusion of GAA in the diet showing better FCR. In conclusion, broilers fed SE diets with GAA, beyond better performance, had improved AME and AMEn compared to broilers fed RE diets without GAA in starter diets.