Apparent Metabolizability of Alfalfa Components by Yearling Pacific Black Brant

We determined apparent metabolizability (AM) of organic matter, nitrogen (N), phosphorus, neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, lignin, and energy for black brant (Branta bernicla nigricans) fed a pelleted alfalfa diet. Brant retained 26% of the organic portion of the diet including 16% of the NDF. Acid detergent fiber, cellulose, and lignin were not metabolized although negative estimates for the apparent metabolizability of the lignin fraction suggest interference by unknown compounds in the analysis of fecal samples. Brant were in positive nitrogen and phosphorus balance, and apparent metabolizability of these fractions of the diet increased steadily from midwinter through spring. There was also a tendency for total food consumption to increase during the same period which is consistent with our understanding of hormonally mediated changes in behavior and physiology that precede and coincide with spring migration.