Leng XiangJun

Effect of dietary crystalline or microcapsuled lysine supplementation on growth and plasma total free amino acids of grass carp (Ctenopharyngodon idellus).

At present,more plant protein feedstuffs are used in aquatic feeds for the shortage and the increasing price of fish meal. The deficiencies of some essential amino acids (EAA) in plant protein feedstuffs lead to the addition of some EAA to balance diet composition. However,the effect of supplementing crystalline EAA was not positive for some fishes. As a result,the present experiment was conducted to investigate the effect of crystalline or microcapsuled lysine supplementation into practical diets on growth performance,and the total plasma free amino acids content of grass carp Ctenopharyngodon idellus. Four diets were prepared,which were high soybean meal(SM)diet with 23% SM,low SM diet with 15% SM,low SM diet added with crystalline or microcapsuled lysine,which had the same lysine content as high SM diet respectively. Grass carp (49.0±2.0) g were fed the four diets with triplicate for 8 weeks. Growth rates(GR) of the four groups were 279.3%,239.7%,245.6%,277.5%,feed coefficient(FC) were 1.62,1.88,1.85,1.64,respectively. Compared with low SM group,adding crystalline lysine in diet had no significant effects on growth performance,but the growth rate was improved by 15.8% and FC decreased by 0.24 (P0.05) by adding microcapsuled lysine in diet. Fish fed on low SM added with microcapsuled lysine had the same GR and FC as those of high SM group(P0.05). Plasma total free amino acids(TFAA) concentration at 0,1,2,3,4,5 h after feeding were determined,and the highest concentration of TFAA occurred at 3 h after feeding for high SM diet,low SM diet added without or with microcapsuled lysine,but absorbing peak occurred at 2 h after feeding for low SM diet added with crystalline lysine,which means the absorbing peak was advanced. Leaching loss of crystalline and microcapsuled lysine were 69.82% and 19.81%,which indicated leaching loss of crystalline lysine was significantly decreased by microcapsuling. Results above showed that grass carp fed with diet supplemented with microcapsuled lysine had a slower absorbing peak of serum TFAA than that fed with crystalline lysine. Microcapsuled lysine had a lower leaching loss in water than crystalline lysine. Growth rate of grass carp could be improved,FC decreased by adding microcapsuled lysine in low SM practical diet,but was not affected by crystalline lysine.

Effects of bubbling on growth, use of N and P and biochemical composition of the microalgae Dunaliella salina.

In order to assay the effects of different bubbling modes on microalgae during cultivation,the growth,biochemical composition and utilization on N and P from medium for Dunaliella salina treated with three bubbling modes(shaking flask manually,continuous aeration and CO2 bubbling) respectively were investigated in this paper.The results showed that the biomass(1.62×107 ind/mL) of D.salina treated with continuous aeration was significantly higher than those of the other groups after 5 days.D.salina mainly used the nitrogen stored in cell for growth and reproduction in the first 3 days.Then N in the culture medium was dramatically absorbed by D.salina cell.While the cell of D.salina could rapidly absorb P from the culture medium after inoculation and store P in the cell for the following growth and reproduction.After first three cultured days,N content in the culture medium treated with continuous aeration was significantly lower than those of the other groups.The bubbling mode did not affect the cell of D.salina to absorb P from the culture medium significantly.The contents of total lipid,crude protein and amino acid of D.salina treated with continuous aeration were significantly lower than those of the other groups.The content of PUFAs(poly-unsaturated fatty acids) of the cell treated with continuous aeration was significantly higher than the other groups.It is therefore suggested that the bubbling modes affect growth as well as cell composition of the microalgae D.salina.The growth performance and fatty acid nutritional value of the cell treated with continuous aeration improve while the amino acid nutritional value of the same cell decreases.