# Optimizing Low Crude Protein Diets with Coated Cysteamine Hydrochloride and Exogenous Alkaline Protease Supplementation in Broiler Chickens

## TL;DR

This study shows that combining coated cysteamine hydrochloride and exogenous alkaline protease in low-protein diets improves broiler chicken growth and health while reducing environmental impact.

## Contribution

The study is the first to demonstrate the synergistic effects of CSH and EAP in low-protein diets for broiler performance and intestinal health.

## Key findings

- Combining CSH and EAP improved body weight gain, feed conversion ratio, and carcass characteristics in broilers.
- The additives enhanced gut morphology, nutrient digestibility, and immune response in low-protein diets.
- A 10% reduction in crude protein was achieved without compromising performance when using the additive combination.

## Abstract

Feeding broilers with low crude protein (CP) diets can negatively affect growth performance, but at the same time, it lowers nitrogen excretion to the environment. Feed additives like coated cysteamine hydrochloride (CSH) and exogenous alkaline protease (EAP) improved protein utilization and gut health when fed separately to broilers. These two additives improve metabolism and digestibility, but their combined effects in low CP diets remain untested. This study examines the collaborative impact of CSH and EAP on broiler performance and physiological parameters. In total, 600 one-day-old broiler chicks were divided into four treatments. Two inclusion levels of coated CSH (0.2 and 0.4 g/kg with or without EAP (0 and 0.2 g/kg) were tested in reduced CP diets. A significant interaction between CSH and EAP was detected in body weight gain, feed conversion ratio, carcass characteristics, and gut histology in the study. Nutrient digestibility and immune response were improved when CSH and EAP were combined. It was concluded that the synergistic use of coated CSH with EAP in lower CP broiler diets can enhance broilers’ performance and intestinal health.

Decreasing crude protein (CP) in broiler diets can improve sustainability but may compromise growth performance. Feed additives like coated cysteamine hydrochloride (CSH) and exogenous alkaline protease (EAP) can enhance protein utilization and promote gut health. While CSH modulates metabolism, EAP improves digestibility, but their combined effects in low CP diets remain unclear. This study examines the synergistic impact of CSH and EAP on broiler growth, gut histology, carcass traits, immune response, and nutrient digestibility, aiming to optimize performance while reducing environmental impact. Six-hundred, 1-day-old broiler Ross-308 chicks (male) were allotted to four treatments, each consisting of six replicates of twenty-five birds, in a factorial arrangement using a completely randomized design. The treatments comprised two inclusion levels of coated CSH (0.2 and 0.4 g/kg with or without EAP (0 and 0.2 g/kg) in reduced CP diets. A ten percent reduction in CP from the standard requirements of Ross-308 (20.7% vs. 23% in the starter, 19.35% vs. 21.5% in the grower, and 17.55% vs. 19.5% in the finisher phase) was made in all the dietary treatments. A notable interaction (p ≤ 0.05) between CSH and EAP was detected in body weight gain (BWG), feed conversion ratio (FCR), carcass characteristics, and gut morphology during the whole study duration. Similarly, nutrient digestibility and immune response were also influenced by the combined use of CSH and EAP. The synergistic use of coated CSH at 0.2 g/kg or 0.4 g/kg with EAP in reduced CP broiler diets can enhance performance, intestinal health, carcass characteristics, immune response, and nutrient digestibility. Implications of these findings in commercial feeding practices could substantially improve the efficiency and sustainability of broiler production systems.