Content and apparent ileal digestibility of protein and amino acids in diets fed to parent stock of farm-raised polar foxes (Alopex lagopus L.)

This study aimed to compare content and apparent ileal digestibility of protein and amino acids in diets used over 1 year (4 feeding periods) on 2 farms of reproductive polar foxes (A and B). Two diets (1 from farm A, 1 from farm B) from the same feeding period were tested in succession (4 eight-day digestibility experiments) on 5 polar foxes with 'end-to-end' ileorectal anastomosis. The main protein sources were poultry, fish, and beef offal in diets A and beef offal in diets B. In diets A, considerably higher content of protein and total essential and nonessential amino acids was found. In each feeding period, diets B had higher (P < 0.05) digestibility of protein and amino acids including sulfur-containing amino acids. Methionine was the amino acid of the highest digestibility in diets A and arginine in diets B. In the diets from both farms, high digestibility was noted for histidine, lysine, phenylalanine, glutamic acid, and proline. The lowest digestibility was recorded for cystine. Too high a content of ash in diets A reduced (P < 0.05) digestibility of protein and amino acids. Diversified composition of feeds for polar foxes provides a definitely higher supply of digestible protein and amino acids.