VARIATION IN MENHADEN FISH-MEAL CHARACTERISTICS AND THEIR EFFECTS ON RUMINAL PROTEIN-DEGRADATION AS ASSESSED BY VARIOUS TECHNIQUES

Menhaden fish meal (FM) samples (n = 17) from five processing plants w ere used to evaluate effects of preparation on ruminal degradation of FM protein. The ability of routine industry measurements to predict ru minal protein degradation was also assessed. Industry measurements inc luded fish quality (total volatile nitrogen, TVN), soluble addback (SO LADD), pepsin degradability and drying temperature (DRYT). Crude prote in (CP) and fat contents of FM samples ranged from 65.0 to 75.4% and 9 .1 to 12.7% of dry matter, respectively. Ruminal degradation of FM pro tein was determined by the in situ bag technique (BAGDEG, range of 27. 4 to 56.4%). The ficin enzyme technique provided estimates of ruminal solubility (range of 6.0 to 33.9%) and ruminal degradation (range of 2 8.6 to 57.0%) of FM protein. Pearson correlation coefficients and prob abilities for comparisons of BAGDEG with other estimates of degradabil ity and FM preparation characteristics were determined. Equations to p redict BAGDEG from routine industry measurements and from other estima tes of degradation were developed. The amount of SOLADD explained 75% of the variation in BAGDEG and up to 81% of the variation was explaine d by including DRYT and CP. Prediction equations were evaluated using 10 additional menhaden FM samples. Coefficients of determination for c omparisons of determined BAGDEG with predicted values from models cont aining up to 5 independent components ranged from 0.76 to 0.81 (P < 0. 001). Results confirm that preparation methods alter ruminal degradati on of FM protein. Data demonstrate a one variable model using SOLADD p rovides a simple, rapid and inexpensive way to predict ruminal degrada tion (BAGDEG) of menhaden FM protein and suggest measurements of rumin al solubility are the most closely correlated predictors of ruminal de gradation for FM protein.