Antibiotics are added to poultry feed at sub-therapeutic doses to improve growth and feed conversion efficiency to prevent infections. However, there are concerns about the increase in resistance to antimicrobial compounds, which is a potential threat to human health. The European Union banned the use of antibiotics as growth promoters from 1 January 2006 for precautionary reasons. Therefore, it is practically inevitable to limit the use of antibiotics due to market and export restrictions. Therefore, in recent years, finding alternatives has received more attention.
Types of alternatives:
These alternatives should have all the characteristics of growth promoter antibiotics. Considering the mechanism of action of growth promoter antibiotics (microbiome and immune system-related activities), there will be practical alternatives to them. These alternatives should also have a positive effect on feed conversion/growth. A variety of alternatives have been proposed and tested. Which include probiotics, prebiotics, symbiotics, organic acids, enzymes, phytogenic substances and metals.
Enzymes:
Enzymes are actually biologically active proteins that facilitate the chemical breakdown of nutrients into smaller components for further digestion and absorption. Various enzymes derived from microbes during the fermentation process (bacteria and fungi) have been used in poultry nutrition in recent years and their value in promoting growth and feed efficiency has been well documented. Types of enzymes used include phytase, carbohydrase (xylanase, cellulase, alpha-galactosidase, beta-mannanase, alpha-amylase and pectinase) and protease. The effect of various enzyme-additives in feed on improving growth and feed efficiency in poultry has been well documented and reviewed.
It is now accepted to use enzymes of exogenous origin that act on anti-nutritional factors present in plant-based foods such as phytic acid, NSP, and cell wall complex carbohydrates. The improved performance resulting from enzyme supplementation is associated with an increase in overall digestibility and availability of nutrients for absorption.
Mechanism of action of enzymes added to feed:
Includes:
Increase the digestibility of nutrients that cannot be degraded by host enzymes (e.g. phytic acid).
Relieve the effects of nutrient entrapment by polysaccharide cell walls and increase the availability of starch, amino acids and minerals.
Inactivate anti-nutritional factors (e.g. phytic acid or soluble NSPs) and reduce intestinal viscosity.
Increase the solubility of insoluble NSPs and stimulate cecal fermentation.
Supplement the activity of endogenous enzymes that are insufficient, especially in young animals whose digestive systems are not fully developed.
In addition to the effects that enzymes have on nutrient digestibility, they also appear to affect the microbial composition of the digestive system.
The microbial changes induced by the enzyme are indirect and appear to be mediated by two mechanisms:
Reduction of indigestible substrates
Generation of short-chain oligosaccharides from the NSP cell wall with potential prebiotic effects
These mechanisms affect nutrient reserves and the intestinal environment, thus altering the selective pressure on a variety of bacterial species.
Experiments and results:
The potential for using feed-added enzymes as alternatives to antibiotics to improve performance in poultry is very significant. Several meta-analyses have been conducted to investigate the association of these beneficial effects in broilers with enzyme supplementation. In one meta-analysis, the addition of a multi-enzyme to a diet containing phytase and NSP enzymes to the diet improved final weight gain by 3.7% and reduced FCR by 2.64%. Another meta-analysis also examined the positive effects of combining xylanase, amylase, and protease. According to this review, it was shown that the combination of specific enzymes increased the digestibility of undigested crude protein, starch, and fat by 22.7, 88.9, and 33.4%, respectively.
Source:
Alternatives to antibiotics for maximizing growth performance and feed effiency in poultry
(https://www.cambridge.org/core/journals/animal-health-research-reviews/article/alternatives-to-antibiotics-for-maximizing-growth-performance-and-feed-efficiency-in-poultry-a-review/834725E86141F209DDDE7BBA11A98635)
