An update on ascorbic acid in poultry

Abstract

This paper provides a review of research on ascorbic acid as a nutrient in poultry published subsequent to a major review in this journal in 1986. Further experiments have confirmed the effects of a nutritional supply of AA in limiting the metabolic signs of stress and alleviation of the physiological consequences of stress is manifest in the performance, immunological competence and behaviour of birds. Birds under stress can recognise the stress-relieving properties of a diet containing AA and increase their intake of it, though they require a colour association to make the correct diet selection. Practical studies have generally confirmed the experimental findings, though the responses have been more variable, perhaps because of the greater difficulty in establishing the degree of stress experienced by birds under practical conditions. Optimum responses in growth, feed efficiency and/or liveability in broilers under heat stress seem to occur with supplements of about 250 mg AA/kg. Laying hens under stress, particularly climatic stress, have also shown responses to supplemental AA. This has resulted in improvements in liveability, food intake, egg production and egg quality with dietary AA concentrations in the range 250–400 mg/kg. AA can be beneficial in countering the adverse effects on shell quality of drinking water containing a high concentration of salts. The AA concentrations that have been found to be effective lie in the range 1–2 g AA/kg feed or /I drinking water, though it is possible that breed differences or additional stress factors might affect the response. Studies on the role of AA in the growth of poultry bone and connective tissues have suggested possible benefits of dietary supplementation in some stress or disease situations. AA has also been shown to interact with a number of other vitamins and minerals.

Keywords::

• ascorbic acid
• stress
• immunity
• behaviour
• antioxidant
• bone