Effects of season, sex, and dietary nitrogen on muskoxen

Abstract

Growth and survival of muskoxen (Ovibos moschatus) are dependent on forage that varies in quality and quantity. One of the most limiting factors is nitrogen. In chapter 1, I predicted that growth would vary with season, sex and dietary nitrogen. While growth is highly season and results in dimorphism, it is not affected by supplemental nitrogen. In chapter 2, I predicted an inverse relationship between intake and digestibility of diets in adults. Intakes increased dramatically from spring to summer with no impact on digestibility. This resulted in increased body fat from summer to winter with little change in body protein. Cellulose digestibility decreases in winter, suggesting a seasonal regulation of digestive and absorptive systems. High solute loads did not affect plasma osmolality because renal function probably eliminates excess N and K during autumn. Differences in intake and growth patterns are probably the result of sexual and non-sexual hormonal controls.