In situ studies on the time-dependent degradation of recombinant corn DNA and protein in the bovine rumen

An in situ technique was adopted to investigate the time-dependent ruminal degradation of chloroplast compared with recombinant DNA of Bt176 corn using conventional and quantitative PCR assays. In parallel, the Cry1Ab protein content and fragment sizes were determined by ELISA and immunoblotting techniques. Triplicate nylon bags filled with 5 g of each substrate (whole-plant isogenic, whole-plant transgenic, ensiled isogenic, and ensiled transgenic corn) were positioned within the rumen of 5 rumen-cannulated, nonlactating cows and incubated for 2, 4, 8, 16, 24, and 48 h. To investigate the DNA degradation process, PCR assays were developed to detect fragments of the endogenous highly abundant rubisco gene (173, 896, 1,197, and 1,753 bp) and of the recombinant cry1Ab gene (211, 420, 727, and 1,423 bp). Short fragments of rubisco (<431 bp) and cry1Ab DNA (211 bp) were amplifiable in whole-plant and ensiled corn samples incubated in the rumen for 48 h, whereas the traceability of larger fragments depended on previous processing of the sample (whole-plant or ensiled corn), the length of the target sequence, and concomitantly on the length of time incubated in the rumen. Quantification of rubisco and cry1Ab gene fragments applying real-time PCR assays revealed degradation to <20% of initial 0-h values within 2 h and <0.5% after 48 h of ruminal incubation. Analysis of Cry1Ab protein in whole-plant corn using the ELISA technique revealed a decrease to 28.0% of the initial value within 2 h and to 2.6% within 48 h. The concentration of Cry1Ab protein of ensiled corn was only 10% that of whole-plant corn. Ensiled corn Cry1Ab protein decreased to 10% of initial values after 48 h of ruminal incubation. Using an immunoblotting technique, the full-size Cry1Ab protein was only detectable up to 8 h; thereafter, only fragments of approximately 17 and 34 kDa size were found. In conclusion, ruminal digestion decreased the presence of functional cry1Ab gene fragments. It is unlikely that full-size, functional Cry1Ab protein will be present after 8 h of incubation in the rumen. Therefore, results based on ELISA measurements should be interpreted carefully and verified by another detection method that discriminates between the full-size and fragmented Cry1Ab protein.     

Detection of corn intrinsic and recombinant DNA fragments and Cry1Ab protein in the gastrointestinal contents of pigs fed genetically modified corn Bt11

Genetically modified corn has been approved as an animal feed in several countries, but information about the fate of genetically modified DNA and protein in vivo is insufficient. Genetically modified corn Bt11 is developed by inserting a recombinant DNA sequence encoding insecticidal Cry1Ab protein from Bacillus thuringiensis subsp. kurstaki. We examined the presence of corn intrinsic and recombinant cry1Ab gene by PCR, and the Cry1Ab protein by immunological tests in the gastrointestinal contents of five genetically modified corn Bt11-fed and five nongenetically modified corn-fed pigs. Fragments of corn zein (242 bp), invertase (226 bp) and of ribulose-1,5-bisphosphate carboxylase/ oxygenase genes (1,028 bp) were detected in the gastrointestinal contents of both Bt11 and nongenetically modified corn-fed pigs. Fragments of recombinant cry1Ab gene (110 bp and 437 bp) were detected in the gastrointestinal contents of the Bt11-fed pigs but not in the control pigs. Neither corn intrinsic nor cry1Ab gene fragments were detected in the peripheral blood by PCR. The gastrointestinal contents were positive for Cry1Ab protein by ELISA, immunochromatography, and immunoblot; however, these methods did not work for blood and precluded conclusions about any potential absorption of the protein. These results suggest that ingested corn DNA and Cry1Ab protein were not totally degraded in the gastrointestinal tract, as shown by their presence in a form detectable by PCR or immunological tests.     

砂仁精油对紫花苜蓿青贮品质的影响

为了研究砂仁精油(Amomum villosum Lour. essential oil,AVEO)对紫花苜蓿(Medicago sativa L.)青贮发酵品质和营养品质的影响,本试验分别在紫花苜蓿中添加了0.5% AVEO和1% AVEO进行青贮,以添加等量蒸馏水的紫花苜蓿为对照组(CK),在15 d和30 d开袋取样,并对青贮的发酵参数和营养成分进行分析。结果表明,AVEO显著降低了紫花苜蓿青贮的pH值(P<0.01),提高了干物质含量、干物质回收率和真蛋白含量(P<0.01)。此外,在青贮第15 d,1% AVEO显著减少了紫花苜蓿青贮中的大肠杆菌的数量(P<0.05);在青贮第30 d,1% AVEO显著提高了紫花苜蓿青贮的乳酸的含量(P<0.05)。因此,添加AVEO对紫花苜蓿进行青贮有利于改善紫花苜蓿青贮的发酵品质和营养品质。     

Fermentation characteristics and microorganism composition of total mixed ration silage with local food by‐products in different seasons

Total mixed ration (TMR) silage in different seasons was prepared with apple refuse, orchardgrass hay, orchardgrass silage, corn silage and a commercial compound feed in Tohoku, Japan, and with tofu cake, brewers' grains, tall fescue hay, Sudangrass hay, timothy hay, alfalfa hay and a commercial compound feed in Shikoku, Japan, respectively, and their fermentation quality and microorganism composition were evaluated. In Tohoku, the TMR silage in spring, autumn and winter displayed poor quality, with pH value above 4.7, and the harmful microorganisms such as escherichia, yeasts and molds were detected even after 60 days of ensiling; but the TMR silage in summer was well preserved and the escherichia were too few to count after 7 days of ensiling. In Shikoku, the TMR silage in all seasons was well preserved, with low pH, high lactic acid contents, and escherichia, yeasts and molds were consistently at or below the detectable numbers after 7 days of ensiling. The results showed that the TMR silage could not produce sufficient lactic acid to improve silage quality under low‐temperature conditions. Therefore, it is necessary to develop preparation techniques of promoting the lactic acid fermentation for TMR silage in cold seasons.     

添加乙醇对象草青贮发酵品质的影响

本试验研究了不同添加水平的乙醇对象草青贮发酵品质的影响。乙醇的添加比例分别为0,1.5%,2.5%,3.5%和4.5%(占鲜重的比例)。在青贮后的第1,3,5,7,14和30天打开青贮罐,测定青贮饲料发酵品质的动态变化。试验结果表明,乙醇抑制了好氧性微生物对蛋白质的分解,在青贮过程中,各添加处理青贮饲料的氨态氮/总氮低于(P>0.05)或显著低于(P<0.05)对照处理。最初3 d乙醇处理的pH值下降速度较对照慢,3 d后pH值下降幅度较大。随着青贮发酵的进行青贮饲料的乳酸含量呈增加趋势,第7天左右达到最大值,而且30 d后乙醇处理的乳酸含量均高于对照。在发酵的开始阶段,青贮饲料的水溶性碳水化合物含量下降较快,添加乙醇后青贮饲料的水溶性碳水化合物利用效率比对照高,发酵30 d后各添加处理的水溶性碳水化合物含量均高于对照。在第1和14天乙醇添加处理的青贮饲料乙酸含量显著(P<0.05)低于对照,但各处理间含量差异不显著 (P>0.05)。在象草青贮中添加乙醇能抑制发酵初期好氧性微生物对蛋白质和水溶性碳水化合物的利用,减少发酵过程中的损失,为乳酸菌发酵提供更多的发酵底物,产生更多的乳酸,从而提高象草的青贮发酵品质。     

青贮密度和青贮时间对紫花苜蓿发酵品质及营养成分的影响

为研究不同青贮密度和青贮时间对紫花苜蓿（Medicago sativa L.）发酵品质及营养成分的影响，本试验以第二茬初花期（10%植株开花）刈割的紫花苜蓿为原料，采用双因素试验设计，分别设计青贮密度550，600和650 kg·m^-3以及时间30，60和120 d，对不同处理青贮料的发酵品质和营养成分进行分析。结果表明：除乙酸和粗蛋白（Crude protein，CP）含量外，青贮密度和时间的交互作用显著影响了苜蓿的发酵品质和营养成分（P<0.05）；与密度为650 kg·m^-3的处理组相比，密度为600 kg·m^-3的处理组青贮30和60 d后，乳酸和干物质（Dry matter，DM）含量增加，酸性洗涤纤维（Acid detergent fiber，ADF）和可溶性碳水化合物（Water soluble carbohydrate，WSC）含量减少；在密度为600 kg·m^-3下，与青贮30 d相比，青贮60 d的样品中乳酸、乙酸、DM，CP和粗脂肪（Ether extract，EE）含量增加。综上，苜蓿在青贮密度600 kg·m^-3、时间60 d条件下，青贮效果最佳。     

Assessing the fate of recombinant plant DNA in rabbit’s tissues fed genetically modified cotton

Various feeding studies have been conducted with the different species of animals to evaluate the possible transfer of transgenic DNA (tDNA) from genetically modified (GM) feed into the animal tissues. However, the conclusions drawn from most of such studies are sometimes controversial. Thus, in the present study, an attempt has been made to evaluate the fate of tDNA in rabbits raised on GM cotton-based diet through PCR analysis of the DNA extracted specifically from blood, liver, kidney, heart and intestine (jejunum). A total of 48 rabbits were fed a mixed diet consisting variable proportions of transgenic cottonseeds meal (i.e. 0% w/w, 20% w/w, 30% w/w and 40% w/w) for 180 days. The presence of transgenic DNA fragments (Cry1Ac, Cry2A and CP4 EPSPS) or plant endogenous gene (Sad1) was traced in those specific tissues and organs. The presence of β-actin (ACTB) was also monitored as an internal control. Neither the transgenic fragments (459 bp of Cry1Ac gene, 167 bp of Cry2A gene and111 bp of CP4 EPSPS gene) nor cotton endogenous reference gene (155 bp of Sad1) could be detected in any of the DNA samples extracted from the rabbit's tissues in both control and transgenic groups. However, 155 bp fragment of the rabbit's reference gene (ACTB) was recovered in all the DNA samples extracted from rabbit tissues. The results obtained from this study revealed that both plant endogenous and transgenic DNA fragments have same fate in rabbit's tissues and were efficiently degraded in the gastrointestinal tract (GIT).     

瘤胃纤维素降解菌系对灭菌水稻秸秆结构性碳水化合物降解的影响

为了提高水稻秸秆的青贮发酵品质,本研究旨在从黑白花奶牛瘤胃中筛选出具有降解纤维素能力的兼性厌氧复合菌系,探讨其对水稻秸秆青贮过程中结构性碳水化合物降解及发酵品质的影响。试验采集了黑白花奶牛瘤胃内容物,经富集培养、刚果红染色初筛,耐酸诱导,滤纸降解复筛,酶活力测定,获得高效兼性厌氧纤维素降解复合菌系M6。试验设4个处理组：1）水稻秸秆直接自然青贮（CK）组;2）灭菌后水稻秸秆青贮（IRR）组;3）灭菌水稻秸秆接种复合乳酸菌（CLAB）青贮组;4）灭菌水稻秸秆接种复合菌系（M6）青贮组,分别于青贮3、6、15、45、60和90 d后开窖取样分析。结果表明,青贮3 d后,M6处理组pH始终低于其他各组,青贮第60天达到最低值（4.62）。青贮45 d后,M6处理组乳酸含量始终显著高于其他各组（P<0.05）,且在青贮90 d达到最高值（23.90 g·kg^-1 DM）。青贮15 d后,中性洗涤纤维、酸性洗涤纤维和纤维素含量在M6组均显著低于其他各组（P<0.05）,且在第90天达到最低值。青贮60 d后,IRR和M6组保持较高水平的水溶性碳水化合物含量,其次为CLAB组。综上所述,复合菌系M6在水稻秸秆青贮过程中具有降解粗纤维和促进乳酸发酵的作用,添加纤维素降解复合菌系可有效改善水稻秸秆青贮发酵品质,为青贮添加剂的研发与应用提供了理论依据。     

ORIGINAL ARTICLE: Effects of long‐term feeding of genetically modified corn (event MON810) on the performance of lactating dairy cows

A long‐term study over 25 months was conducted to evaluate the effects of genetically modified corn on performance of lactating dairy cows. Thirty‐six dairy cows were assigned to two feeding groups and fed with diets based on whole‐crop silage, kernels and whole‐crop cobs from Bt‐corn (Bt‐MON810) or its isogenic not genetically modified counterpart (CON) as main components. The study included two consecutive lactations. There were no differences in the chemical composition and estimated net energy content of Bt‐MON810 and CON corn components and diets. CON feed samples were negative for the presence of Cry1Ab protein, while in Bt‐MON810 feed samples the Cry1Ab protein was detected. Cows fed Bt‐MON810 corn had a daily Cry1Ab protein intake of 6.0 mg in the first lactation and 6.1 mg in the second lactation of the trial. Dry matter intake (DMI) was 18.8 and 20.7 kg/cow per day in the first and the second lactation of the trial, with no treatment differences. Similarly, milk yield (23.8 and 29.0 kg/cow per day in the first and the second lactation of the trial) was not affected by dietary treatment. There were no consistent effects of feeding MON810 or its isogenic CON on milk composition or body condition. Thus, the present long‐term study demonstrated the compositional and nutritional equivalence of Bt‐MON810 and its isogenic CON.     

晾晒时间和青贮时间对青贮玉米发酵品质的影响

目的 探究不同晾晒时间和青贮时间对全株青贮玉米发酵品质的影响。方法 以玉米（Zea mays L.）青贮品种“曲辰9号”为试验材料,将乳熟末期的青贮玉米全株收获粉碎后,在阴凉处分别晾晒0（对照,CK）、1、2、3、4 d,然后在塑料桶（5 L）中分别进行青贮,待青贮60、90、120 d时进行发酵品质的评定。结果 青贮玉米的含水量随着晾晒时间的增加而降低,在晾晒2、3、4 d后含水量显著（P<0.05）低于CK;用晾晒2、3、4 d的全株青贮玉米原料进行青贮,pH值显著（P<0.05）高于CK,晾晒2 d青贮120 d处理除外。晾晒时间对乳酸、丁酸、中性洗涤纤维（NDF）和酸性洗涤纤维（ADF）含量均产生显著（P<0.05）影响,青贮时间仅对乳酸、丁酸产生显著（P<0.05）影响,其中,乳酸含量随着青贮时间的延长而增加,丁酸含量在原料晾晒之后明显增加。CK处理中,青贮90、120 d的NDF含量显著（P<0.05）高于青贮60 d处理。利用氨态氮、乙酸、丙酸、丁酸开展V-Score分析,晾晒导致青贮玉米发酵品质降低,试验中品质较优的青贮为原料粉碎后未经晾晒的处理（CK）。结论 在未经晾晒处理下进行青贮60 d的青贮玉米,综合品质较高。在青贮玉米原料含水量为74%时,不建议粉碎之后通过晾晒降低含水量再青贮。     

甲酸添加剂及青贮时间对紫花苜蓿青贮品质的影响

以第2茬初花期(10%植株开花)刈割的紫花苜蓿为原料进行青贮,针对甲酸添加剂和青贮时间设计两因素试验,甲酸添加剂浓度为3(A₁)、6(A₂)和9 mL·kg^-1(A₃),以不添加作为对照(CK),分别在发酵30、60和120 d开袋分析。结果表明,适量的甲酸添加剂和适当的青贮时间能够改善青贮品质,甲酸添加剂能够显著降低青贮的pH、氨态氮/总氮及酸性洗涤纤维(ADF)值(P<0.05);除粗蛋白(CP)外,青贮时间对青贮原料的其他营养品质均有显著影响(P<0.05),在所有处理中,甲酸添加剂浓度6 mL·kg^-1(A₂),青贮时间60 d,苜蓿青贮效果最佳;甲酸添加剂和青贮时间的交互作用显著影响了干物质(DM)、中性洗涤纤维(NDF)和粗脂肪(EE)含量(P<0.05),对其他成分无显著影响(P>0.05)。     

Influence of transgenic corn (CBH 351, named Starlink) on health condition of dairy cows and transfer of Cry9C protein and cry9C gene to milk, blood, liver and muscle

The influence of transgenic event CBH 351 (Starlink)-derived hybrid corn (SL) on the health condition, physiological function and lactational performance of dairy cows as well as the transfer of the cry9C gene and Cry9C protein present in SL to milk, blood, liver and muscles was examined, and compared with a diet containing non-transgenic (isogenic) control corn (non-SL). After adapting to a diet containing non-SL for 2 weeks, four Holstein cows were assigned to each of the non-SL and SL groups and were fed diets containing non-SL or SL, respectively, for 5 weeks. There were no significant influences on the physiological condition, milk yield or serum biochemical and hematological values after feeding with SL. There was also no influence on pH value, cell density of protozoa, or volatile fatty acid concentration and composition of rumen fluids. In addition, no significant differences were observed on histopathological examination of the major organs and tissues between the SL and non-SL groups. Moreover, the cry9C gene and Cry9C protein were not detected by the polymerase chain reaction method and ELISA in the milk, blood, liver and muscles of the cows at the end of the experiment.     

复合乳酸菌对全株玉米青贮及有氧暴露后微生物及饲料品质的影响

为探讨不同复合乳酸菌对全株玉米青贮及有氧暴露后青贮饲料中微生物数量及其发酵品质的影响,进一步筛选出可提高青贮饲料品质和有氧稳定性的复合乳酸菌接种剂,共设置3个不同组合乳酸菌分别添加全株玉米进行青贮,并设空白对照,测定青贮3、7、15和30 d,开袋有氧暴露1、3、7、15和30 d时微生物数量、发酵品质和营养成分的变化情况。结果表明,分别添加异型乳酸菌组合(Hetero)、同型乳酸菌组合(Homo)和同型+异型乳酸菌组合(Homo+Hetero)的各处理组均能有效地增加青贮过程和有氧暴露后饲料中乳酸菌的数量、乳酸(LA)和乙酸(AA)的含量,减少好氧细菌、酵母菌和霉菌数量,降低pH和氨态氮(NH₃-N)含量,减少粗蛋白(CP)损失,显著改善青贮饲料发酵品质,抑制青贮饲料有氧暴露后的二次发酵,其中Homo+Hetero效果最好,Homo处理组好于Hetero处理组。     

多菌灵在果园白三叶青贮中的降解及其对微生物群落的影响

为了解白三叶青贮后不同浓度多菌灵农药的降解情况和果园喷施多菌灵对白三叶青贮过程中细菌多样性的影响，扩大具有农药残留的果园覆盖植物利用途径，在喷施不同浓度［2.0 （RU^-），2.5 （RU），3.0 g·L^-1 （RU⁺）］的多菌灵后进行白三叶青贮，以喷水为对照，发酵60 d。采用Miseq高通量测序技术，分别在青贮开始前、青贮第3和60天取样，对白三叶中细菌群落多样性进行研究。结果表明，青贮后多菌灵降解率达到59.6%以上，喷施量越高，降解率越高；多菌灵处理显著（P<0.05）增加了白三叶青贮发酵的乳酸、乙酸、丙酸含量，乳酸在多菌灵RU^-、RU、RU⁺浓度下分别增加了47.55%、63.24%、71.08%，乙酸分别增加了24.49%、44.90%、46.94%，丙酸分别增加了66.67%、187.50%、250.00%，有利于白三叶青贮饲料营养成分的保留；多菌灵喷施显著（P<0.05）改变了白三叶青贮菌群群落构成，增加了青贮的菌群丰度、多样性；多菌灵处理中乳球菌属、魏斯氏菌属、泛菌属、Rosenbergiella、假单胞菌属、寡养单胞菌属、肠杆菌属、芽孢杆菌属菌群丰度增加，不利于青贮发酵，但随着青贮时间的推移，寡养单胞菌属、肠杆菌属、芽孢杆菌属等菌群丰度减少。喷施多菌灵后有利于青贮发酵微生物菌群的丰度增加，对青贮发酵有害菌、多菌灵降解菌群丰度及青贮微生物多样性产生影响，青贮后多菌灵残留高于欧洲食品安全局规定的作物类动物饲料中农药最大残留量，达不到饲用标准。研究结果可为具有农药残留的白三叶青贮饲料的饲用安全性和果园覆盖植物资源的开发利用提供理论依据。     

Effects of stage of maturity on ensiling characteristics and ruminal nutrient degradability of oat silage.

A study was conducted to determine the effects of stage of maturity on ensiling characteristics and ruminal nutrient degradability of oat silage. Oat was field grown and forage was harvested at the boot or soft dough stage and ensiled in mini-silos for 0, 2, 4, 8, 16 and 45 days. Two lactating Holstein cows fitted with ruminal fistulas were used determine ruminal nutrient degradability. Regardless of the stage of maturity, ensiled forages went through a rapid fermentation with a sharp decline in pH during the first 2 days of ensiling. Extensive proteolysis took place between 0 and 2 days as indicated by a reduction in true protein and neutral detergent insoluble protein (NDICP) and an increase in non-protein nitrogen (NPN). Chemical analysis of the 45 days silage showed that stage of maturity had no effect on neutral detergent fibre (NDF) and acid detergent fibre (ADF) of oat silage. However, oat harvested at the boot stage contained more crude protein (CP) and less starch than that harvested at the soft dough stage. Distribution of protein fractions showed that oat harvested at the boot stage contained lower NPN, NDICP and acid detergent insoluble protein than oat harvested at the soft dough stage. Results of the in situ incubation experiment indicated that oat harvested at the soft dough stage had lower ruminal dry matter (60.6 vs. 66.4%). CP (81.3 vs. 88.7%) and NDF (35.4 vs. 42.2%) degradabilities than oat harvested at the boot stage. It was concluded that chemical composition and ruminal nutrient degradability of oat silage are significantly influenced by stage of maturity.     

白花草木樨与燕麦混合青贮的研究

试验设置了单贮白花草木樨(Melilotus albus)、单贮燕麦(Avena sativa)、70%白花草木樨和30%燕麦混贮、50%白花草木樨和50%燕麦混贮与30%白花草木樨和70%燕麦混贮5个处理组,贮后分别测定其发酵品质和化学成分,由此找出白花草木樨和燕麦混合青贮的最佳比例.结果表明,单贮白花草木樨的pH值...     

Evaluation of transgenic event CBH 351 (StarLink) corn in broiler chicks

The influence of transgenic event CBH 351 (StarLink; SL)-derived hybrid corn on the growth performance, health condition and physiological function in broiler chicks, as well as the possible transfer of the cry9C gene and Cry9C protein to blood, liver and muscle were examined in comparison with chicks fed on a diet with non-transgenic corn (SL-F). Bodyweight gain and feed conversion ratio in the chicks fed on a diet with SL were significantly greater than in chicks fed on a diet with SL-F during the starter phase (0–3 weeks of age), but this significant difference disappeared during the finisher phase (4–7 weeks of age). No abnormalities in health condition in either SL or SL-F groups were observed, and livability did not differ significantly between SL and SL-F groups. Moreover, no significant differences in serum biochemical and hematological values, histopathological observation and necropsy findings were observed between SL and SL-F groups at the end of the experiment. The cry9C gene and Cry9C protein were not detected in blood, liver and muscle of chicks at 3, 5 or 7 weeks of age. The results indicate that feeding SL does not influence growth performance, health condition or physiological function in broiler chicks, and the cry9C gene and Cry9C protein are not transferred to the blood, liver and muscles of broilers.     

Tevaluation of transgenic event CBH 351 (StarLink) corn in pig

This study examined the influence of transgenic event CBH (StarLink™; SL)-derived hybrid corn on growth, health and physiological functions of pigs, as well as the possibility of transferring the cry9C gene or Cry9C protein to the blood, liver or muscles, in comparison with pigs fed a diet with non-transgenic (isogenic) corn (non-SL). The diet for the SL group was composed of 70% SL corn, and the diet for the non-SL group was composed of 70% non-SL corn. Forty pigs approximately 3 months in age were used in the current experiment. After the pigs were acclimatized to their environment for 7 days, they were fed piglet diets for 7 weeks, and afterwards fed growing-finishing diets until the end of the experiment. There were no significant differences in bodyweight gain, feed intake or feed conversion ratio between the pigs fed SL diet and those of non-SL diet. No abnormalities were observed in the health conditions of either the SL or the non-SL group. Moreover, no significant differences were observed between the two groups in hematological values, histopathological examination and necropsy findings. Although the serum biochemical values within each group were normal, the blood urea nitrogen values of the SL group showed a tendency to be slightly higher than those of the non-SL group. Also, the blood glucose values of the SL group were significantly lower than those of the non-SL group. However, the cause of the significant differences in the blood glucose values between the two groups is unknown. The PCR and ELISA did not detect the cry9C gene and Cry9C protein in the blood, liver or muscles of the pigs at the end of the experiment.     

青贮发酵对玉米秸秆品质及菌群构成的影响

本研究旨在探讨青贮发酵对玉米秸秆感官指标、发酵品质、营养成分以及门、纲、目、科和属5个水平细菌群落构成及丰度的影响。将去穗后仍青绿的蜡熟期玉米秸秆切短揉搓至1~2 cm,将水分调节至65%~70%后,取青贮前样品(3个重复)和青贮后样品(3个重复)使用聚乙烯袋真空包装,室温贮藏45 d后开启取样,运用实验室检测手段及Mi Seq高通量测序技术分析青贮前后玉米秸秆品质及菌群结构的变化。结果表明:1)青贮发酵45 d后的玉米秸秆青贮饲料呈黄绿色,质地较好,呈酸香味。青贮发酵作用能够使玉米秸秆p H迅速降低(P0.05),乳酸含量显著增加(P0.05),中性洗涤纤维(NDF)及酸性洗涤纤维(ADF)含量有下降趋势(P0.05)。2)玉米秸秆经过青贮发酵后,变形菌门(Proteobacteria)、γ-变形菌纲(Gammaproteobacteria)、肠杆菌目(Enterobacteriales)、肠杆菌科(Enterobacteriaceae)和魏斯氏菌属(Weissella)菌群数量显著降低(P0.05);青贮发酵能够显著增加厚壁菌门(Firmicutes)、芽孢杆菌纲(Bacilli)、乳杆菌目(Lactobacillales)、乳杆菌科(Lactobacillaceae)、片球菌属(Pediococcus)和乳杆菌属(Lactobacillus)菌群数量(P0.05)。综上,青贮发酵改善玉米秸秆感官指标、发酵品质以及营养成分的同时,可以有效降低有害细菌的数量,增加有益菌的数量,从而可以降低致病菌对家畜健康存在的潜在风险。通过实验室检测手段及Miseq高通量测序技术相结合,能够在分析青贮品质的同时,提供青贮前后整个菌落构成及丰度变化的信息,进而为发酵过程的调控提供依据。     

Effects of Bacillus thuringiensis Cry1Ab toxin on mammalian cells

The Cry proteins produced by Bacillus thuringiensis are considered to be highly specific insecticidal proteins. Judged to be safe for humans and farm animals due to their insect-oriented selective toxicity, the proteins have been utilized as a biological pesticide and introduced into genetically modified plants. However, some critical fundamental characters of the Cry proteins remain unclear, and the direct effects of activated Cry proteins on mammalian cells have not yet been fully confirmed. Therefore, in this study we employed primary cultured bovine hapatocytes as a model system to determine if Cry1Ab, a Cry protein, affects mammalian cells. There were no significant changes in the secretion of albumin or the morphology of the Cry1Ab-treated cells. The LDH release showed a tendency to increase after the administration of Cry1Ab, but not significantly. Taking these results on bovine hepatocytes into consideration, Cry1Ab has little acute toxicity on mammalian cells.