APPARENT PROTEIN DIGESTIBILITY AND MINERAL AVAILABILITIES IN VARIOUS FEED INGREDIENTS FOR SALMONID FEEDS

Apparent digestibility of protein and availability of minerals (Ca, K, P, Mg, Na, Cu, Fe, Mn, Sr, Zn) in various feed ingredients were deter mined for coho salmon and rainbow trout using yttrium oxide (Y2O3) as the inert marker and passive feces collection tanks. The feed ingredie nts were herring meal, menhaden meal, anchovy meal, deboned whitefish meal, poultry by-product meal, feather meal, soybean meal, corn gluten meal, wheat gluten meal, wheat middling and wheat flour. Apparent dig estibility (%) of protein and availability (%) of minerals were determ ined as a fractional net absorption of nutrients from diets. Apparent digestibility of protein and availability of K was high (> 80%) in all feed ingredients, whereas digestibility of dry matter and availabilit y of Ca, Cu, Fe, Mg, Mn, Na, P, Sr and Zn were variable among ingredie nts. Apparent availability (%) of mineral elements was not significant ly correlated to the amount of nutrient intake (mu g nutrient g(-1) BW day(-1)) in any test diet. Net nutrient absorption (mu g g(-1) BW day (-1)) was positively correlated (P < 0.05) to the nutrient intake exce pt for Mn, Fe and Ca. Fecal nutrient losses (mu g g(-1) BW day(-1)) we re positively correlated (P < 0.05) to nutrient intake except for prot ein, Na, K and Zn. (C) 1998 Elsevier Science B.V.