Đánh giá việc bổ sung khoáng hữu cơ lên tỷ lệ sống và hiệu quả sử dụng thức ăn trong ương giống cá tra (Pangasianodon hypophthalmus)

Abstract

Microminerals of Zn, Se, Cu, Fe, Mn and Cr were supplemented in the feed either in inorganic minerals (sulfate salt) or organic minerals (Methionine-mineral) at various concentrations over an 8-week period. Catfish fry (15-day old) were fed the experimental diets for 8 weeks. At the end of the feeding trial, fish were challenged by immersion in a solution of Edwardsiella ictaluri bacteria. The mortality was monitored for 14 days. The results showed that the survival rates of fish fed the organic mineral-supplemented diets were higher than those fed the inorganic mineral-supplemented diets. Treatment 7 supplemented with organic minerals of 60.0 mg/kg Zn, 0.40 mg/kg Se and 0.40 mg/kg Cr had the highest weight gain and survival rates and the lowest FCR, there were significant differences in those parameters between treatment 7 and the control diet supplemented with inorganic minerals. The variation in fish weight and length of treatment 7 was also lowest and significantly different (P < 0.05) from that of the control treatment. After 14 days of bacteria challenge, the cumulative mortality of fish in the control treatment was highest (67.86%) and the cumulative mortality of fish in treatment 7 was lowest (34.82%), and the cumulative mortality rates of fish in these two treatments were significantly different (P < 0.05) from those of the others. The cumulative mortalities of fish in organic minerals treatments were lower than those of fish in inorganic mineral treatments. The study indicated that the dietary supplementation of organic minerals of zinc (Zn), selenium (Se) and chromium (Cr) would improve growth, survival rate and disease resistance to E.ictaluri bacteria in Pangasius catfish nursing (from 15 to 75 days old).