# Zootechnical Additives Associated with Antimicrobials: Effects on Immune Response and Intestinal Histomorphometry in Broiler Chickens

## TL;DR

This study explores how combining antibiotics with additives like probiotics and essential oils affects chicken growth and gut health.

## Contribution

The study identifies that combining AGPs with zootechnical additives improves performance but may negatively impact gut structure.

## Key findings

- Zootechnical additives combined with AGPs improved growth performance compared to AGPs alone.
- Essential oils were particularly effective in supporting growth and immune function.
- Some combinations negatively affected gut structure and intestinal histomorphometry.

## Abstract

Antibiotic growth promoters (AGPs) are commonly used in poultry farming to enhance growth and health, but concerns about antibiotic resistance have driven the search for alternatives. This study investigated the effects of combining AGPs with different zootechnical additives, including prebiotics, probiotics, essential oils, and organic acids, on broiler chicken performance, immune response, and gut health. A total of 1400 chicks were divided into seven feeding groups, and their growth, feed efficiency, immune activity, and intestinal structure were evaluated. The results showed that zootechnical additives combined with AGPs improved the broiler chickens’ growth performance compared to AGPs alone, but some combinations negatively affected their gut structure. Essential oils were particularly effective, supporting both their growth and immune function. These findings provide valuable insights for poultry producers seeking to optimize feed strategies while reducing the reliance on antibiotics.

This study evaluated the effects of zootechnical additives in combination with antibiotic growth promoters (AGPs) on broiler performance, leukocyte differential activity, phagocytic activity, intestinal histomorphometry, and the inside index. A total of 1400 one-day-old Cobb 500 male chicks were assigned to a completely randomized design with seven treatments and eight replicates of 25 birds per unit. The treatments included a basal diet without AGPs, a basal diet with AGPs, and AGPs combined with different zootechnical additives: prebiotics (fructooligosaccharides, galactooligosaccharides, beta-glucans, and mannan-oligosaccharides), probiotics (Bacillus subtilis LFU160), essential oils (cashew nut shell liquid), and organic acids (butyric acid glycerides). The results showed the treatments combining AGPs and zootechnical additives had better effects (p < 0.05) on weight gain, feed intake, the feed conversion ratio, and the productive efficiency index. The phagocytic activity was worse in birds without AGPs and with AGPs but without additives. However, birds that received AGPs in combination with zootechnical additives exhibited a poorer intestinal histomorphometry and lower inside index compared to those fed only AGPs or diets without AGPs. In conclusion, zootechnical additives can be used alongside AGPs to enhance broiler performance and immune function, particularly during early growth stages, with essential oils showing the most promising results.