Herbs, thyme essential oil and condensed tannin extracts as dietary supplements for broilers, and their effects on performance, digestibility, volatile fatty acids and organoleptic properties

Abstract

1. Herbs, thyme essential oil (EO) and condensed tannin (CT) extracts were compared for their effects, as dietary supplements, on broiler growth performance, nutrient digestibility and volatile fatty acid (VFA) profiles in the gut. Cooked meat from the birds fed on diets with 4 herbs and an EO extract was compared by a taste panel against those fed on the control treatment, for organoleptic properties in the meat.

2. Female broiler chicks were fed on wheat-soybean meal diets from 0–42 d of age. These chicks were given either the basal diet (control), or the basal diet with one of rosemary, garlic or yarrow herbs, mimosa, cranberry or grapeseed CT's, or thyme EO supplements (8 treatments in total). Body weight (BW) and feed consumption (FC) were measured.

3. The garlic supplement tended to improve growth rate over the first 7 d, while mimosa CT and thyme EO supplements reduced weight gains. The mimosa supplement in diets significantly reduced FC to d 21. Meanwhile, the addition of a cranberry supplement reduced the digestibility of DM, OM and N, compared with the controls. Dietary thyme EO, yarrow, rosemary and garlic supplements modified caecal isovaleric and isobutyric acid proportions (presented as ‘Other VFA’; p < 0.05). Dietary herb significantly affected the intensity of meat flavour, and the potential of observing both garlic and abnormal flavours. There were large differences between the consumption of red and white meat samples, while meat temperature affected several flavour attributes.

4. Broiler performance and digestibility for birds given dietary garlic and grapeseed CT supplements were similar to the controls, and these supplements appear suitable for dietary inclusion. Careful choices are necessary when selecting dietary plant extract supplements for broilers, but beneficial effects can be observed.

Acknowledgements

SAC is funded by the Scottish Executive for Environment and Rural Affairs Development Department (SEERAD; NCR 643701). Special thanks to Devenish Nutrition Ltd., Belfast, for funding and provision of herbs, garlic and the emulsifier. Thanks to Ian Nevison of Biostatistics Scotland (BIOSS) for help with statistics, and Ian Mackay (SAC) for help with HPLC analysis. Finally, the authors thank Danisco Animal Nutrition, Marlborough, (Avizyme 1210), Nutriad Ltd., Cheshire (cranberry, grapeseed), and Roy-Wilson-Dickson, Flintshire (mimosa).