Enteritis induction by soybean meal in Totoaba macdonaldi diets: Effects on growth performance, digestive capacity, immune response and distal intestine integrity

The aim of the present study was to investigate the effects of increasing levels of dietary soybean meal (SBM) with constant taurine supply in the induction of enteritis in juvenile Totoaba macdonaldi. Four isoproteic (48.5%) and isolipidic (8.6%) diets were formulated to include increasing levels of a mixture of soybean meals (SBM); (soy protein concentrate and soybean meal at a ratio of 1:4) at 0%, 22%, 44% and 64% replacing fishmeal in a diet containing 1% taurine. Upon completion of the 56-day feeding trial, SBM caused marked dose-dependent responses in growth performance and digestive physiology processes. Severe enteritis symptoms in the distal intestine and liver were found when SBM was included above 22%. SBM dose-dependent impairments in digestive functions were found in digestive enzyme activity for trypsin, chymotrypsin, L-aminopeptidase, total alkaline proteases, and amylase. Interleukin (il-8) expression patterns showed an inflammatory response during the first four weeks in the presence of the higher levels of SBM (44% and 64%) suggesting an impaired immunological response. However, after 8 weeks no immunological inflammatory response was observed, but a severe atrophy of the intestine could still be revealed. Results indicate a detrimental status of the digestive physiology of totoaba fed SBM-based diets at inclusion levels above 22%. Thus, suggesting that SBM should be cautiously used in totoaba feed formulations.