Effect Of Different Lipid Diets On The Growth,Reproduction And Predation Of Propylea Japonica (Thunberg)

By the method of nutrition and biochemistry, an attempt was made to study the effect of different lipid artificial diets on the Propylea japonica, including growth, fecundity, nutritional indices, body composition, activity of digestive enzyme in midgut and the functional response to cotton aphid. The purpose is to provide reference for optimum lipid of artificial diets. The results are as follows:1, Effect of different lipid diets on the growth of P. japonica1.1 Effect of different lipid diets on the developmental period and weight gainrate of P. japonicaP. japonica was fed containing liver, honey and sucrose, adding in different lipid to investigate the effect on the developmental period and weight gain rate, using the ladybird fed on cotton aphid as control. The results implied that the developmental period became longer significantly when the larval fed with diet containing different lipid diets, there was on difference among the treatments that fed on different artificial diets in pupal period (P>0. 05), the survival rate of larvae fed with olive oil increased remarkably; the weight of ladybird increased rapidly at the initial days after eclosion, and then the increase rate decreased gradually; the dietary bean oil or corn oil could increase the weight gain rate of female , male P. japonica significantly.1.2 Effect of different lipid diets on the feeding amount of P. japonicaThis park investigates the effect of different lipid diets on the feeding amount , approximate digestibility and feed conversion rate of P. japonica, using the ladybird fed on cotton aphid as control. The results indicated that the feeding amount of ladybird increased sharply at the initial days after eclosion, and then decreased gradually. The feeding amount and the approximate digestibility of the beetles fed on cotton aphid were higher than that of the beetles fed with artificial diets. While the efficiency of conversion of ingested food and the efficiency of conversion of digested food in the control were significant higher than that in beetles fed with artificial diets, which was probably the strategy of the insects whose food intake was low to survive. The results indicated that the dietary colza oil could reduce the feeding amount, approximate digestibility and feed conversion rate; the dietary olive oil could improve the approximate digestibility of the artificial diets; the dietary bean oil or corn oil could improve the feed conversion rate.1.3 Effect of different lipid diets on the body composition of P. japonicaUsing the ladybird fed on cotton aphid as control, this park investigates the effect of different lipid diets on the moisture, crude protein and crude fat of P. japonica. The results suggested that the moisture and crude protein of P. japonica were higher than the ladybird fed on artificial diets (P<0.05), the crude fat was lower than that (P<0.05); there was no difference among different treatments (P>0.05), supplementing olive oil in diet could remarkably increase the crude fat content; as compared with the control, the ladybird fed on the artificial diets has a higher unsaturated fatty acid content and a lower saturated fatty acid; the dietary olive oil could significantly increase the content of monounsaturated fatty acids, while the dietary bean oil or corn oil could significantly increase the content of monounsaturated fatty acids.1.4 Effect of different lipid diets on the activity of digestive enzyme of P. japonicaThis park uses the ladybird fed on cotton aphid as control, investigates the effect of different lipid diets on the activity of digestive enzyme in midgut of P. japonica. The results suggested that the activities of tryptase and lipase became higher, and reached the peak at 20^th and 10^th day respectively with the growth of the adult beetles; the activities of the amylase sharply decreased after eclosion. Supplementing olive oil in diets could increase the tryptase activity in the midgut; there was no difference among all treatments, the amylase activities of all groups were lower than the control. 2, Effect of different lipid diets on the propagation of P. japonicaTo investigate effects of artificial diets on the propagation of Propylea japonica, the results suggest that pre-ovipositional periond of the control and the ladybird fed on olive oil was shorter than the beetle fed with corn oile, bean oil and colza oil. The female fed on cotton aphid had a long peak of oviposition; the beetles fed with artificial diets supplementing corn oil did not have a long peak of oviposition, while the ladybirds fed with diets supplemented with olive oik corn oil and colza oil had a long peak of oviposition. The control's quantity of the oviposition was higher than the beetles fed on the artificial diets, supplementing olive oil in diets could increase the quantity of the oviposition remarkably. 3, Effect of different lipid diets on the predation of P. japonicaThe investigation of the predation effect of P. japonica showed that fed with artificial diets or cotton aphid ,the functional response of P. japonica to cotton aphid was fitted to Holling II model. The control's handing time was the shortest; the daily maximum number was the highest. Between the four artificial diets, the handing time and the daily maximum number of the beetles fed with diet supplemented corn oil was higher than that of beetles fed with other artificial diets, it indicated the ladybird had stronger capability to control the cotton aphid than others when it fed with the diet supplemented with corn oil.The results of studies completely showed that the ladybird could improve the feed conversion rate to have a high weight gain rate when fed on diets supplemented corn oil or bean oil; while the beetles fed on diets supplemented olive oil, it could improve the feeding amount and change the body composition to have higher quantity of the oviposition. So, we suggested that we could supplement the survival rate of larvae and the quantity of the oviposition by adding olive oil in artificial diets; while adding bean oil or corn oil in diets to improve the weight gain rate.