Effects of Dietary Protein Levels on Body Weight, Food Consumption, and Nitrogen Balance in Ruffed Grouse

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Abstract
The effects of 5 dietary protein levels on the body condition of captive female ruffed grouse (B. umbellus) were studied throughout the breeding cycle at Guelph, Ontario [Canada]. Isocaloric rations containing protein levels (% dry matter) of 7.6, 11.5, 13.6, 17.0 and 20.1 were supplied to 5 test groups in late Feb. 1979. Before egg-laying, test groups had similar body weight and food consumption (P > 0.05). While birds grew heavier, the daily values for N balance increased linearly as the level of dietary protein (%) increased (P < 0.01). Over the laying period, an increase in dietary protein (%) was associated with greater food consumption, and for a 2-day period at least, higher N balance values (P < 0.01). During egg-laying, test groups receiving higher protein (%) rations generally lost less weight than groups receiving lower protein rations. After egg-laying, test groups had similar food consumption and began new primary feather growth at about the same date (P > 0.05). A significant positive quadratic trend in body weight, but no significant trend in N balance, was evident among test groups about 4 wk after egg-laying.