Effect of the incorporation level of dehulled soybean meal into test diet on apparent digestibility coefficients for protein and energy by juvenile haddock, Melanogrammus aeglefinus L.

Abstract

The apparent digestibility coefficients (ADCs) for protein and energy of dehulled soybean meal were calculated in relation to the incorporation levels in a test diet using two different published equations [Cho, C.Y., Slinger, S.J., Bailey, H.S., 1982. Bioenergetics of salmonid species: energy intake, expenditure and productivity. Comp. Biochem. Physiol. 73B, 25–41; Forster, I., 1999. A note on the method of calculating digestibility coefficients of nutrients provided by single ingredients to feeds of aquatic animals. Aqua. Nutr. 5, 143–145]. Soybean meal was incorporated at levels of 10, 20, 30 and 40% to 90, 80, 70 and 60% (w/w basis) of the basal diet, respectively. Haddock with mean initial body weight of 49 g were randomly distributed among 5 tanks (40 fish/tank) equipped with fecal collection columns. Reference and test diets were fed to fish to apparent satiation three times daily week days and twice daily on weekends and fecal samples collected. ADC values were calculated based on actual mixing levels of feed ingredient (i) and basal diet (100 − i), taking into account the dry matter content of soybean meal (89.1%) and basal diet (91.7%), and relative contributions to total protein or energy content from the basal diet and the test feed ingredient. ADCs for protein and energy of the reference diet were 94.8 and 86.1%, respectively. Increasing the incorporation level of soybean meal from 10 to 40% into the test diet had no significant effect on protein digestibility. The method of ADC calculation also had no significant effect on the value obtained for protein digestibility with the Cho et al. [Cho, C.Y., Slinger, S.J., Bailey, H.S., 1982. Bioenergetics of salmonid species: energy intake, expenditure and productivity. Comp. Biochem. Physiol. 73B, 25–41] method giving an average of 96.1% (range, 95.0–96.9%) and Forster [Forster, I., 1999. A note on the method of calculating digestibility coefficients of nutrients provided by single ingredients to feeds of aquatic animals. Aqua. Nutr. 5, 143–145] giving 96.1% (range, 95.0–96.8%). The same was true for energy digestibility, which averaged 87.9% (range, 86.5–88.9%) according to Cho et al. [Cho, C.Y., Slinger, S.J., Bailey, H.S., 1982. Bioenergetics of salmonid species: energy intake, expenditure and productivity. Comp. Biochem. Physiol. 73B, 25–41] and 88.1% (range, 86.5–89.2%) according to Forster [Forster, I., 1999. A note on the method of calculating digestibility coefficients of nutrients provided by single ingredients to feeds of aquatic animals. Aqua. Nutr. 5, 143–145].