Volatile fatty acids and metabolizable energy derived from cecal fermentation in the willow ptarmigan

Abstract

Abstract 1. Volatile fatty acid (VFA) production in the cecum, cecum size and fill, type of food and chemical composition of food were determined for willow ptarmigan shot during April in interior Alaska. 2. Willow buds and twigs comprised 93% of the crop contents; willow buds were the most nutritious item in the crop based on chemical qualities. 3. The cecum averaged 100 and 107 cm in females and males, respectively, and total cecum weight was 5·7% of body weight for both sexes. 4. The average production of acetate, propionate and butyrate was 0·66, 0·47 and 0·36 μM/g per min, respectively, while the relative rates of absorption of these acids were butyrate > propionate > acetate. VFA production for a 24 hr period averaged 16·9 mM which was equivalent to 5·7 kcal metabolizable energy (ME). 5. The % of standard metabolism, existence and free living energy requirements supplied by the ME of VFA were estimated to be 11, 4·8 and 3·8%, respectively. 6. A comparison of cecal fermentation rates and cecum size suggested avian species have a more efficient cecum than mammals.