The Digestion of Heather by Red Grouse during the Spring

Abstract

Heather, the main food of red grouse, is of poor quality by agricultural standards, containing much fiber and little N (11 g/kg DM [dry matter]) and P (0.7 g/kg). Wild laying hen grouse ate twice as much heather and retained twice as much ME [metabolizable energy] (1110 kJ/d) as captives (530 kJ/d) eating a pelleted diet. Calculations suggest that wild hens do not actually require all the energy they digest but have to eat large quantities of food in order to attain adequate N (and possibly P) balances. The selection for heather especially rich in N (and P) which is observed is probably also essential for the wild hens to attain the observed N (and possibly P) balances. Free-living wild red grouse digested the heather they ate much more efficiently than captives eating the same food. Wild birds can survive and breed, while captives lose weight, on a heather diet. Wild birds digested more cellulose and lignin than captives on the same diet.