Effect Of Storage Duration On Rice Straw Quality In Southern Environment

With the development of beef cattle industry in China,the demand for feed is increasing.Rice straw is a common roughage for beef cattle in southern China,and its demand is also increasing every year.However,in the southern environment,mildew often occurs in the storage process of rice straw due to high temperature and high humidity,but there is a lack of systematic research on the law of this mildew and its impact on rice straw.In this experiment,dry rice straw was stored in a closed room according to the conventional storage method.Samples were collected every 22 days,and the test cycle was 374 days;The changes of conventional nutrients,mycotoxins,microstructure and rumen degradation rate of rice straw with the increase of storage time and the change of temperature and humidity in the experimental environment were studied by means of conventional feed analysis,enzyme-linked immunosorbent assay and scanning electron microscope.Experiment 1 Effect of storage duration on rice straw quality in southern environment1.Variation law of storage ambient temperature and humidity:during the storage period of 374 days,the variation range of ambient humidity is 37%～93%,more than 70%has 194days,and its variation is not regular.The temperature variation range is-1.5℃～37.3℃,which changes regularly.There are 171 days above 20℃.The temperature is low in winter(44 days～110 days)and gradually increases in spring and summer(132 days～330 days).There is no correlation between the temperature and humidity of the storage environment in this test(r=-0.174,P=0.503>0.05).The variation range of temperature and humidity index(THI)is 45.93～88.93,and the variation trend is similar to that of temperature.THI is low in winter and gradually increases in spring and summer,with large fluctuations.2.Change law of routine nutrients:with the increase of storage duration,the contents of dry matter(DM),crude protein(CP)and crude fat(EE)in rice straw changed significantly(P<0.05),and showed significant linear and secondary effects(P<0.05).The content of DM increased first and then decreased;The content of CP increased from 66 to 88 days,and then remained stable;The content of EE decreased gradually.The contents of ASH,NDF,ADF,CF,Ca,P and GE did not change significantly(P>0.05).3.Change law of mycotoxin:with the extension of storage time,the contents of aflatoxin(AFT)and fumonisin(FB)increased significantly(P<0.05),showing significant linear and secondary effects(P<0.05),but did not exceed the limit standard of mycotoxin content in feed hygiene standard.When THI is 70～80,the growth is the highest.According to the calculation of the fitting curve,when the rice straw is stored for 618 days and 1385days,the AFT and FB will exceed the standard one after another.4.The change law of crystallinity(Crl)and microstructure:during the whole storage period,the Crl of rice straw decreased significantly at 22,154 and 242 days compared with 0days(P<0.05),but there was no obvious regular change(R~2=0.1578).The microstructure showed obvious changes with the increase of storage time.The surface structure of rice straw gradually became rough and irregular,the number of surface fungi gradually increased,and fungal characteristic structures such as hyphae and spores appeared.Part of the surface waxy film fell off and some mastoid structures were destroyed,but the whole structure was well preserved.Summary of Experiment 1:during the 374 day storage period of rice straw,DM content first increased and then decreased,CP content first increased and then remained stable,EE content gradually decreased,and ASH,NDF,ADF,CF,Ca,P and GE had no significant changes(P>0.05).The content of aft and FB in rice straw increases with the increase of storage time,but it is lower than the limit standard of mycotoxin in feed hygiene standard.Ignoring the influence of other factors,it can be estimated that when rice straw is stored for618 days and 1385 days,aft and FB will exceed the standard one after another.With the increase of storage time,the damage degree of rice straw surface structure becomes greater,but the overall fiber structure is well preserved.Experiment 2 Effect of storage duration on rumen degradation rate of rice straw in southern environmentThe degradation rates of DM,CP,NDF and ADF of rice straw were determined by nylon bag method with 0,2,4,8,12,24,48 and 72 h as degradation time.1.With the increase of storage duration,the rumen degradation rate of rice straw DM decreased significantly only at 72 h(P<0.05),and showed significant linear and secondary effects(P<0.05),but there was no significant difference at other time points(P>0.05).2.With the increase of storage duration,the rumen degradation rate of straw CP decreased significantly at 8 h and 48 h(P<0.05),and showed significant linear and secondary effects(P<0.05),but there was no significant difference at other time points(P>0.05).3.With the increase of storage duration,the rumen degradation rate of rice straw NDF decreased significantly at 8 h,12 h and 72 h(P<0.05),and showed significant linear and secondary effects(P<0.05),but there was no significant difference at other time points(P>0.05).4.With the increase of storage duration,the rumen degradation rate of rice straw ADF decreased significantly at 4h and 72h(P<0.05),showing significant linear and secondary effects(P<0.05),and there was no significant difference at other time points(P>0.05).Summary of Experiment 2:after 264 days of storage,the degradation rates of DM,NDF and ADF decreased significantly,showing significant linear and secondary effects(P<0.05),but the degradation rate of CP was not significant.Therefore,the storage duration of dry straw treated by drying and baling in a closed environment should not exceed 264 days.Therefore,in the southern environment,the pollution of mycotoxin can be effectively prevented by drying and dehydrating the rice straw and storing it in a closed and dry room.However,the quality of rice straw still decreases with the increase of storage duration.The storage duration should not exceed 264 days.After 264 days,the available value of rice straw as roughage begins to decline.