The aim of this study was to determine the effect of the supplementation of an organic acid (citric acid), antibiotic growth promoter (avilamycin), a

Tiamulin hydrogen fumarate is a semisynthetic derivative of the diterpene antibiotic pleuromutilin used in poultry medicine to treat mainly Mycoplasm

Organic acids and their salts have been approved by European legislation as an alternate source of antibiotic growth promoter in diets, because antibiotics are associated with problems due to potential residual effects via food animals developing resistant strains of pathogens. Citric acid (CA) is a weak organic acid which is a natural preservative and can add an acidic or sour taste to foods and soft drinks. It exists in small amounts in a variety of fruits and vegetables, most notably citrus. Penicillium mould and Aspergillus niger could be efficient CA producers on a commercial basis. Its inclusion in animal diets has been reported to decrease colonisation of pathogens and limit then production of toxic metabolites, improve availability of protein, Ca, P, Mg and Zn as well as serve as a substrate in intermediary metabolism. Its addition in drinking water is not promising for performance, but lower doses would be useful for sanitary aspects and gut health. Its inclusion at 0.5% in the diet improves performance and non-specific immunity of broilers. It also enhanced specific immunity against new castle disease in vaccinated broilers. Current data supports a recommendation in the broiler diet up to 0.75% in pelleted feed and 0.5% in mash diets, with a safety margin of 6.0%. Additional research is needed to determine the feasibility of its use in low nutrient density broiler diets.

Lutein is an essential dietary carotenoid with health benefits and is inter alia responsible for the colouration of egg yolk. The relationship between lutein accumulation and egg yolk colouration was therefore studied in more detail. After feeding a low-luteine diet for 21 days, 14 birds (Lohmann brown hens aged 20 weeks) were fed a diet containing marigold (80 mg lutein/kg feed) and 14 other birds were fed a diet containing oleoresin (45 mg lutein/kg feed) for 21 days; for both groups of birds, this feeding period was followed by withdrawal for 21 days. The Roche Yolk Colour Fan (RYCF) score (0 to 15, where higher values denote greater colour intensity; R2=0.87; P0.05) and yellowness (R2=0.12; P>0.05) of the yolk. It may be concluded that increased lutein is potentially responsible for an increased RYCF score and redness (a*), but decreased yellowness (b*) and lightness (L*), of egg yolk.