The Influences Of Stocking Density And Grape Proanthocyanidins On Growth Physiology And Biochemistry Of Red Tilapia

Stocking density is one of the important contents of aquatic population ecology research.This paper explored the respiratory characteristics of physiology, besides that different stocking densities and GPC supplementation was conducted to evaluate the effects of growth, digestive enzymes and immune-related implications in Red Tilapia to summarize the law of physiological effects in the fish, so that it can provide a scientific basis for the future health of farmed fish. The main research includes three aspects as following:1. Effects of body weight and temperature on oxygen consumption rate, ammonia excretion rate and asphyxiation point of Red Tilapia.The effects of temperature and body weight on oxygen consumption rate(OCR), ammonia excretion rate(AER) and asphyxiation point(AP) of Red Tilapia had already been studied with ecological methods in laboratory. The results showed that temperature and weight had significant effects on oxygen consumption rate, ammonia excretion rate and asphyxiation point. From 15 ℃to 35 ℃, the oxygen consumption rate, ammonia excretion rate and asphyxiation point of Red Tilapia showed an increasing trend as the temperature increasing, and the rate values become obviously different from each other in the range(P<0.05). The regressive equation of OCR, AER and the water temperature could be expressed as RO= 0.0664 T + 0.0086(R2 = 0.9693) and RA =3.8494 t +3.9275(R2=0.9168). The body weight from 27.5 g to 201.87 g, the oxygen consumption rate and ammonia excretion rate showed a decreasing trend with the body weight increasing, however, the asphyxiation point was increasing as the increasing level of individual body weight and the difference was significant(P<0.05). The regressive equation of OCR, AER and the body weight could be expressed as Ro= ﹣0. 0422 W + 0.312(R2 = 0. 9896)and RA = ﹣4.2818 W + 26.4(R2 = 0.9884).2. Effects of stocking density on growth, digestive enzyme activity, muscle RNA/DNA ratio, immune responses and antioxidant indices in Red Tilapia.Red Tilapia were fed for 30 days under five different stocking densities with 4.07 kg/m3,9.89 kg/m3, 13.89 kg/m3, 18.14 kg/m3, 25.29 kg/m3. The results showed that the SR, SGR, WG and muscle RNA/DNA ratio was firstly increased and then decreased with the increasing level of stocking density, and the lowest value appeared in 4.07 kg/m3 group while the highest value appeared in 9.89 kg/m3 group with significant difference(P<0.05). At different stocking density levels of Red Tilapia, there were significantly differences(P<0.05) in the protease, amylase andlipase activity of hepatopancreas, intestine and stomach. The RNA/DNA ratio was showed a gradual increasing trend in the breeding density from 4.07 to 9.89 kg/m3(P<0.05), and was decreasing between 9.89 to 25.29 kg/m3(P <0. 05).Stocking density of Red Tilapia affected the immune and antioxidant capacity markedly.With the increasing level of stocking density, the activities of ACP, AKP, SOD, CAT, POD,GSH-Px, GR and GST were showed an increasing trend. The peak value of T-AOC was in 25.29kg/m3 group while LZM activities decreased at 10 d as the difference was significant(P<0.05). In addition, at 30 d, the activities of ACP, AKP, SOD, CAT, POD, GSH-Px, GR and GST were appeared a decreasing trend, and they were difference significantly(P<0.05). Antioxidant enzymes and immune indicators remained stable in 4.07~9.89 kg/m3 groups while decreased significantly in 13.89~25.29 kg/m3 groups as the time passed.3. Effects of GPC supplementation on growth, digestive enzyme activity, immune and antioxidant indicators of Red Tilapia.Under the condition of breeding density of 9.68 kg/m3, Red Tilapia were fed for basal diets supplemented with 0(control group), 200, 400, 600, 800, 1000, 1200 mg/kg GPC respectively.Compared to the control group, the WGR, SGR and DGW in all GPC supplemental groups was significantly difference(P<0.05), and fatness, liver count system and survival rate was no significant difference(P<0.05). In the hepatopancreas and intestine, the levels of protease,amylase and lipase activity in all GPC supplemental groups were significantly higher than those in control group(P<0.05). In the stomach, the levels of protease and lipase activity in all GPC supplemental groups were significantly higher than that of the control group(P<0.05), but there were no significantly difference from each other(P>0.05). In addition, the levels of stomach starch enzyme activity in all GPC supplemental groups were not significantly different(P>0.05).The activities of ACP, AKP, LZM, SOD, CAT, POD, GSH-Px, GR, GST and T-AOC in all GPC supplemental groups were significantly higher than that of the control group(P<0.05), in which the activities of ACP, AKP, LZM, CAT, GST, T-AOC appeared an increasing trend; MDA in serum was significantly lower than that in the control group(P<0.05) and there was no significantly difference among all experimental groups. The results indicated that a suitable supplemental level of GPC in diets could effectively promote the growth performance and feed conversion ratio, regulate digestive enzyme activity and significantly improve the immune and antioxidant capacity of Red Tilapia.