Effects Of Lysine Methyl Ester On Growth Performance And Feed Utilization In Grass Carp And Approaching To Its Mechanism

This research was conducted to evaluate the effects of lysine methyl ester on growth performance,feed utilization,body figure,serum and muscle amino acids,serum biochemical parameters,nutrition of whole fish and its muscle, and approaching to the mechanism by feeding experiment, dissection experiment and lab analysis of related samples.A total of 360 healthy juvenile grass carp were divided into four groups, each of which included 3 replicates of 30 individuals with initial weight 8.34±0.02g.The control group were fed basal diet which was short of lysine (contain 1.25% lysine).The 3 experimental groups were supplemented with lysine of 0.375% (in the form of lysine·HCl),0.25% and 0.375% (in the form of lysine methyl ester·HCl)respectively. The feeding experiment was done in tanks (300L) under the conditions of circulaton,filtration,temperature 24-30℃, dissolved oxygen 9.71±0.5mg/L,pH 7.2～7.4, NH4+<0.5 mg/L.The fish were restrictly fed twice per day, total feed weight per day was 2-5%(wet weight basis) of fish biomass.Fish was weighed biweekly and the daily ration was adjusted accordingly. Fecal matter and uneaten diets were collected by siphoning from the tank after feeding for 40 minutes. The experiment lasted for 56 days while the preparing experiment was 14 days.During the experimental period,fish activity, feed intake and feces conditions were observed every day, feed intake and weight of the dead fish were recorded. At the end of rearing, the grass carp were fasting for 24 hours.Then,the fish were weighed,and weight gain,feed intake and feed conversation ratio were caculated.Nine grass carp with the same size in each replicates were fetched to determine the length and weight, then,the serum was collected and the fish were dissected. Liver and muscle were collectedThe fish left were fed again as usual,on 1, 3,5,7 hours after fed,three fish per replicate were chosen and the serum was collected.Besides, three fish were collected per replicate before and after the experiment as whole fish samples.All samples were snap-frozen in liquid nitrogen for analysis.The main results were as follows:(1)Supplementation with lysine methyl ester-HCl in the feed improved weight gain rate,specific growth rate,feed conversion ratio and protein convertion ratio of grass carp compared with the control group (P<0.05),while lysine HCI had no significant effect(P>0.05).(2) Lysine methyl ester·HCl increased coefficient of fatness and deinternal organ ratio(P<0.05),decreased internal organ ratio and liver ratio (P<0.05), while lysine·HCl had no significant effect on figure and internal organ ratio of grass carp (P>0.05)(3) Lysine methyl ester-HCI enhanced protein sediment rate,whole body protein content and amino acid level of grass carp muscle(P<0.05), and decreased fat content, mesenterium fat ratio and liver fat ratio(P<0.05),while lysine·HCl had no significant effect(P>0.05).(4) Lysine·HCl and lysine methyl ester·HCl had no significant effect on the activity of GOT and GPT in the liver (P>0.05).(5) Compared with control group,lysine methyl ester·HCl increased total serum protein and albumin as(P<0.05) while decresed the contents of SUN, Ca and P (P<0.05),lysine·HCl improved contents of Ca and P (P<0.05) but had no significant effect on other parameters.(6) The results of serum free amino acid level of grass carp at various time intervals after feeding showed that addition of lysine methyl ester·HCl achieved pinnacle of EAA individuals after feeding on about 3 hours,while control group and supplementation with lysine·HCl achieved pinnacle on about 1 hour.These results implicated that:(1)Adding lysine methyl ester·HCl to the feed which is short of lysine could improve weight gain rate and feed conversion ratio of grass carp,so as had a better effect than ordinary lysine·HCl.(2) Supplementation with methyl ester lysine·HCl could improve protein sediment rate,whole body protein content and most of amino acid contents in muscle of grass carp,and decrease fat content, mesenterium fat ratio and liver fat ratio,so as increase coefficient of fatness and improve edible ratio of the fish.(3) Lysine maybe released slowly with lysine methyl ester·HCl under the effect of lipase,then digested,absorbed and utilized with protein-combined amino acid at the same time, so as induce serum essential amino acids reaching pinnacle later. As a result, tissue amino acids could be utilized and protein synthesis improved effectively.