Synergies Investigated Between Feeding Whole Wheat and Essential Oils

In the UK in recent years, there has been increasing interest in the use of whole grain wheat in broiler diets as well as essential oils as an alternative to antimicrobial growth promoters, explained Lorraine Salmon¹ of Danisco Animal Nutrition. The objective of the trial she reported was to investigate whether there were any synergistic effects between whole wheat and essential oils on performance, nutrient utilisation and the development of the digestive tract.

Weight gain of the broilers of the 35-day experimental period was not affected by the form of the wheat (whole versus ground) although feed conversion was numerically better with the whole wheat. All diets were pelleted.

Essential oils improved weight gain with both wheat forms but particularly ground wheat.

There were interactions between the wheat form and the oils in their effects on gizzard and caecal weights. Essential oil supplementation increased relative gizzard weight in birds fed the ground wheat diet, but not with whole wheat. The effect of the caecum was less clear.

Both whole wheat inclusion and the essential oils improved apparent ileal nitrogen digestibility but had no effect on apparent ileal energy digestibility.

Dr Salmon said, in summary, that the dietary addition of essential oils could significantly improve broiler weight gain and nitrogen digestibility in diets based on whole wheat or ground wheat, but that the magnitude of this response was greater when the diet contained whole wheat.

She added the observation that whole wheat increased the size and volume of the gizzard but not its weight in this trial, which is contrary to previous research.

Peas and Beans for Broiler Feeding

The UK poultry feed industry is becoming increasingly reliant on imported soybeans whose high prices – partly driven by EU legislation on the use of genetically modified ingredients – is prompting investigations into the use of home-grown alternatives, explained Dr Helen Masey-O'Neill⁴ of the University of Nottingham.

She added that environmental concerns also drive this research because increasing the digestibility of crude protein and amino acids reduces nitrogen output from the production system. She reported an experiment investigating the variation in co-efficient of apparent ileal digestibility (AID) of crude protein and amino acids in UK-grown pea and bean varieties.

From the results, it appears that peas of low trypsin inhibitor activity may be more valuable in poultry diets than beans. Furthermore, there was little variation between the different varieties of peas or beans in terms of AID of crude protein or amino acids. Dr Masey-O'Neill also remarked that, contrary to other reports, the tannin level in beans did not appear to affect AID in broilers.

Using Feed Enzymes to Improve Utilisation of Full-Fat Rapeseed by Broilers

Full-fat rapeseed is a valuable source of energy, protein and omega-3 fatty acids for broilers but incomplete rupturing of the seeds during feed processing can reduce its feeding value, said Damian Józefiak⁵ of the University of Life Sciences in Poznan, Poland, in the introduction to his paper. He reported work using a combination of carbohydrase and phytase enzymes supplemented to diets containing full-fat rapeseed and their effects on broiler performance and fat utilisation.

Phytase alone or with carbohydrase increased bodyweight gain over the period 0 to 9 days although the difference was not statistically significant for the full experimental period of 42 days. The enzyme combination improved feed conversion efficiency at each stage of the trial and overall. The enzymes had no significant effect on blood insulin concentration but phytase alone and in combination with carbohydrase increase the percentage of insulin receptors in the liver.

He concluded that full-fat rapeseed can be used effectively in broiler diets, and that its feeding value can be enhanced by using a combination of carbohydrase and phytase.

Role of Trypsin Inhibitor in Causing Wet Litter Problems

Dr Emily Clarke² of Nottingham Trent University explained that wet litter is a major concern in broiler production because of its negative impacts on bird health, welfare, performance and carcass characteristics.

Recent anecdotal reports, she said, had indicated a possible link between the level of trypsin inhibitor – an anti-nutritive factor in soybeans – on digesta viscosity and excreta moisture in broilers.

From the results, Dr Clarke concluded that, whilst trypsin inhibitor activity levels in both full-fat soybean mean and solvent-extracted soybean meal did cause variation in digesta viscosity, the effects were considerably lower than those usually associated with poor litter quality or a deterioration in gut health. Excreta moisture was not associated with trypsin activity level in these trials so trypsin inhibitors do not appear to have a direct, negative impact on litter quality.

Investigating the Effect of Tannins on Nutrient Absorption

Dietary tannins are known to have a negative effect on many nutrients by reducing digestibility but the mechanism is not known, reported Dr B. Mansoori³ of the University of Tehran in Iran in his paper to the WPSA Meeting. Tannins are known to increase endogenous losses, he said, but he has investigated whether they also reduce absorption capacity from the intestine.

Previous work had shown that polyethylene glycol (PEG) forms a complex with tannic acid in the gut, alleviating many of the negative effects of tannins in terms of the reduced absorption of D-xylose.

By varying the ratio of PEG to tannic acid, Dr Mansoori was able to show that the two compounds disrupt the trans-cellular and/or para cellular mechanisms involved in the absorption of simple sugars such as xylose. He and his colleagues were thus able to shed light on the way in which tannins interfere with nutrient absorption.

References

All papers were presented at the World's Poultry Science Association (UK Branch) Annual Meeting in Belfast in April 2010.

1. Amerah, A. M. et al., 2010. Influence of whole wheat inclusion and essential oils supplementation on the performance, nutrient utilisation and digestive tract development of broilers.
2. Clarke, E. et al. The effects of dietary trypsin inhibitor content on digesta viscosity and excreta moisture in broilers
3. Mansoori B. et al. The importance of tannic acid/polyethylene glycol ratio on the absorption capacity of chicken intestine for D-xylose.
4. Masey-O'Neill H.V. et al. Crude protein and amino acid distensibility of 13 varieties of UK-grown peas and beans for broilers
5. Józefiak D. et al. Multicarbohydrase and phytase supplementation improves growth performance and liver insulin receptors sensitivity in chickens fed diets containing full-fat rapeseed.

July 2010