FEED ADDITIVES ▶▶▶
Use of natural extracts as feed additives
The regulatory removal of AGP in Europe has prompted many new additives to appear in nutrition technology, or the reshaping of old additives for new applications. One of the most important segments of newer additives in animal nutrition are plant extracts.
U BY JUAN JAVIERRE, NUTRITION SCIENTIST LAYN
nder this category, both essential oils and non-aro- matic plant extracts are grouped together. Often both kinds of ingredients are used as combined additives, as there are claims that their association
may have additive or synergistic effects. In this article we will focus on polyphenols.
Benefits of tea polyphenols For the last 10 years, numerous papers on the use of polyphenols in animal nutrition and health have been pub- lished. Reviewing them, a summary of potential benefits can be made. Tea polyphenols, a mixture of phenolic compounds found in the tea plant (Camellia sinensis), are mainly com- posed of (–)-epicatechin (EC), (–)-epigallocatechin (EGC), (–)-epicatechin gallate (ECG) and (–)-epigallocatechin gallate (EGCG). These polyphenols have been recognised as potent antioxidants to scavenge cytotoxic ROS and protect normal cells. In a trial using diquat-challenged pigs (Deng, Q J et al.,) tea polyphenols administered through the diet at 500 mg/ kg, partially reversed the decreased feed intake, growth rate and improved FCR (Fludarabine, Cyclophosphamide and Rituximab). Idiquat injection caused inflammatory interleu- kins to increase, while the tea polyphenols treatment re- duced interleukin secretion, thus demonstrating its effect on controlling inflammation.Tea polyphenols were also shown to reduce the amount of liver lipids and abdominal fat mass, due to enhanced activity of AMP-activated protein kinase that stimulates fat oxidation and reduces lipid synthesis.
Polyphenols tested in pigs Three commercial products containing polyphenols of differ- ent origins were tested in a pathogenic E. coli assay with new- ly weaned piglets. Animals were orally challenged with the
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bacterium and assigned to groups. The polyphenol group animals received the products through their diet. Two of the polyphenols controlled diarrhoea and E. coli excretion through faeces.
Resveratrol Resveratrol assays in chickens caused a quadratical response improving average daily gain, antibody titres against New- castle disease virus, and insulin-like growth factor-1 expres- sion (Zhang, C et al.,). Resveratrol supplementation delayed cell proliferation and reduced apoptosis in immunocytes. Di- etary resveratrol supplementation improved growth, pro- tected immunocytes against antigen-induced apoptosis, and upregulated immune response in chickens that received con- ventional vaccinations.
Sweet chestnut The effect of sweet chestnut tannins on several aspects of animal rearing have been reported. Tests with commercial sweet chestnut extract (Schiavone, A. et al.,) showed im- proved chicken performance at low and medium dose, and especially in the first phase of rearing. The higher dose demonstrated negative effects. No improvement on nutrient digestibility was observed at any dose.Sweet chestnut tan- nins showed high inhibitory activity upon Chlostridium per- fringens. Other tannins from chestnut, sumach, tara and quebracho were tested against Salmonella,a bacterium re- sponsible for food intoxications. Gallotannins from sumach and tara, and ellagitannins from chestnut wood showed inhibitory activity in vitro. In pigs, the effect of sweet chestnut tannins caused lower oxi- dation in the meat after slaughter, with no impact on growth or performance.
Grape skins and seeds Grape skins and seeds are a rich source of flavonoids and stud- ies have shown flavonoids act as powerful antioxidants by scavenging free radicals and terminating oxidative reactions. When applied to poultry diets, together with vitamin E, there was no effect on growth rate or performance, but liver tocoph- erol increased and meat oxidation after slaughter decreased. Grape polyphenols can constitute a novel source of antioxi- dant for poultry, reducing lipid oxidation of meat. Grape seed
PHOTO: LAYN
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