Comparing growth and condition in post-release juvenile common pheasants on different diets.

Abstract

We studied juvenile common pheasants Phasianus colchicus in 10 large open-topped release pens in woodlands on a shooting estate in southern England in 1998. In six pens the pheasants were fed a pelleted high-protein feed from 6 to 16 wk of age; in the four other pens they were fed the diet from 6 to 10 wk and then wheat grain only from 10 to 16 wk. Natural plant and animal food was also available to the birds in and around the release pens. When a sample of previously tagged, numbered, and weighed birds was caught from each pen and reweighed at 16 wk of age, we noted that birds from pens that remained on the high-protein feed had gained more weight than those from pens in which the diet was switched to grain only (P < 0.05). Of approximately 500 tagged birds collected during shooting days between 5 and 15 wk later, differences in body mass gain between groups were still significant (P < 0.05). A subsample, 50 males and 50 females aged 22 to 24 wk, of tagged birds that were shot were kept for post-mortem examination. From this smaller sample, the differences in body mass were not significant (P > 0.05). Breast muscle mass and tarsal length did not differ between treatments. However cloacal fat was higher in the birds fed a high-protein diet (P < 0.05), suggesting that the results relating to body mass were due to differences in fat accumulation. Most pheasants examined postmortem contained the gut nematode Heterakis gallinarum with an average burden of 118 ± 14 worms per bird. Although the abundance of these worms was not related to diet, it was negatively correlated with body mass, breast muscle mass, and cloacal fat (P < 0.05).