Main content area

Dietary inclusion of hydrolyzed soybean and cottonseed meals influence digestion, metabolic enzymes, and growth-related hormones and growth of juvenile turbot (Scophthalmus maximus)

Song, Zhidong, Li, Peiyu, Wang, Jiying, Sun, Yongzhi, Wang, Chengqiang
Aquaculture international 2018 v.26 no.4 pp. 1017-1033
Scophthalmus maximus, alanine transaminase, aspartate transaminase, blood serum, cottonseed meal, digestibility, digestion, energy, enzyme activity, feed conversion, glucokinase, glucose, growth performance, hydrolysis, insulin, insulin-like growth factor I, juveniles, liver, pepsin, phosphofructokinases, soybeans, tanks, trypsin, turbot, weight gain
To investigate the effects of a mixture of hydrolyzed soybean and cottonseed meals (HSC) on the digestion, metabolic enzymes, growth-related hormones, and growth of turbot (Scophthalmus maximus) (initial weight ca 35 g), six isoenergetic (ca 20 kJ/g) and isoproteic (ca 45%) diets were formulated with 0 (control), 14.7% (HSC14.7), 29.4% (HSC29.4), 44.1% (HSC44.1), 58.8% (HSC58.8) HSC, and 44.1% its native protein (SC44.1). Each diet was assigned to triplicate tanks with 36 fish per tank in a re-circulating system. Fish were fed twice daily. After 54 days, fish were weighed after a 24-h fast, and five digestive tracts were dissected for digestive enzyme analysis. Six blood and liver samples were collected from remaining 31 fish at 5 h post-feeding for metabolic enzymes and hormones analysis. The results showed that fish fed diets containing 14.7–44.1% HSC had higher average weight gain (g) (38.77–41.52 vs 29.74) but lower feed conversion rate (0.83–0.88 vs 1.02) than fish given the control diet. The HSC diets increased apparent digestibility coefficients of dry material, protein, and energy from 73.82% to 80.03%, 87.38% to 93.68%, and 76.13% to 81.46%, respectively. Pepsin and trypsin activities (U mg prot⁻¹) were higher in group HSC14.7 (4.94 vs 4.26, 141.66 vs 115.14) than in the control group. The HSC44.1 and HSC58.8 diets increased the serum insulin level (IU L⁻¹) (5.38, 5.50 vs 4.05), as well as the activities (U g prot⁻¹) of hepatic alanine transaminase (868.42, 938.71 vs 730.82), aspartate transaminase (793.84, 854.64 vs 600.30), and glucokinase (104.76, 109.17 vs 93.90). The HSC diets reduced glucose 6 phosphatase activity (262.27–383.81 vs 537.21, U g prot⁻¹) but increased phosphofructokinase activity (1592.55–1983.71 vs 978.52, U g prot⁻¹). The HSC29.4 diet increased insulin-like growth factor 1 level (187.30 vs 151.17, ng L⁻¹). Fish fed the SC41.1 diet exhibited lower growth performance and diet utilization than those fed the HSC44.1 diet. In conclusion, juvenile turbot can efficiently utilize HSC, and the recommended inclusion level is 27.14–30.70%.