Study On Pretreatment Method Of Silkworm Excrement Feed And Its Nitrite Degradation Measures

Silkworm excrement contains rich nutrients and a variety of biological active component.Using it to develop animal feed can make not only increasing the value of silkworm production output,but also avoiding the serious environmental environmental pollution caused by the abandonment.But Silkworm excrement hasn’t been one of feed ingredients.The experiment collected fresh silkworm excrement from different sources,and used natural drying,hot air drying,heat pump drying,microwave drying,and fermentationdrying to study the effect of pre-processing methods on the nutrient composition and health safety of fresh silkworm excrement.The new silkworm excrement collecting models,like shoot rearing on the ground+bentonite mode,shoot rearing on the ground+zeolite powder mode,shoot rearing on the net mode,are designend to explore the effect of the new models on the reduction of nitrate content in fresh silkworm excrement and its effect on sericulture performance.At the same time,the silkworm excrement of different silkworm excrement collecting models are used to study on nitrite degradation of silkworm excrement in different sericulture modes by fermentation.The main experiment results are as follows:1、There were significant differences in the contents of crude protein,crude fiber and other nutrient indicators of fresh silkworm from different sources(p<0.05).The number of microbial contaminants(bacteria,mold,salmonella)and nitrite content exceeded the limits set by the feed hygiene standards.Inorganic pollutants(fluorine,mercury,arsenic,chromium,lead,cadmium),pesticides(carbendazim,dichlorvos,dimethoate,trichlorfon,methomyl)and chloramphenicol residues all met the feed hygiene standards.The nutritional value and safety of silkworm excrement in the Guangdong Wengyuan are high.2、After the fresh silkworm excrement from different sources were dried,the crude protein content decreased.The performance was as follows: fresh silkworm excrement> microwave drying> hot air drying> heat pump drying> drying naturally;the crude fiber content was elevated: natural drying Dry> heat pump drying> hot air drying> microwave drying> fresh silkworm excrement.There was no significant difference in crude fat,crude ash,Ca and P contents(p>0.05).In addition,drying effectively reduced the number of microbial contaminants to feed hygiene standards,but nitrite content increased slightly.Through the response surface analysis test,the silkworm excrement fermentation process was as follows: inoculation amount 10%,fermentation moisture 45%,fermentation temperature 33 °C,fermentation time 64 h.Before and after fermentation,there was significant difference in crude protein,crude fiber,crude fat,and crude ash content(p<0.05).The maximum crude protein was increased by 3.62% and the maximum degradable material was 1.66% crude fiber.There was no significant difference in the content of Ca and P between fermentation materials(p>0.05).Before and after fermentation,the content of nitrite was significant(p<0.05),and the degradation rate of nitrite by fermentation was up to 91.06%.3、Compared with fresh silkworm excrement of shoot rearing on the ground mode,the using of bentonite,zeolite powder,the net can make the nitrite reduction rates up to 37.90%,25.01%,and 15.82% respectively.However,the content of nitrite in fresh silkworms of the four silkworm excrement collecting models still exceeds the feed hygiene standards.The new models can significantly increase silkworm infant rate and worm rate.(p<0.05).4、The content of nitrite in the fermentation process of fresh silkworm excrement and corn,soybean meal and wheat bran increased first and then decreased under the action of organic acids and nitrite reductase.After 32 hours of fermentation,the nitrite content of the material was lower than 15 mg/kg.After 40 hours of fermentation,no nitrite was detected in the materials of each group.Fermentation can effectively solve the problem of excessive nitrite content in silkworm excrement,and the fermentation time is suitable between 32 and 40 hours.The above result explains that the quantity of microbiological contaminants and nitrite content in fresh silkworm excrement exceed the feed hygiene standards and should not be fed directly.In terms of production,it is possible to collect the fresh silkworm excrement of the traditional shoot rearing on the ground model from the economic point of view,to improve the quality of the silkworm excrement by fermentation and then drying.This can scientifically develop silkworm excrement feed.