Effects of concentrate‐to‐forage ratios and 2‐methylbutyrate supplementation on ruminal fermentation,bacteria abundance and urinary excretion of purine derivatives in Chinese Simmental steers

This study evaluated the effects of dietary concentrate levels and 2‐methylbutyrate (2MB ) supplementation on performance, ruminal fermentation, bacteria abundance, microbial enzyme activity and urinary excretion of purine derivatives (PD ) in steers. Eight ruminally cannulated Simmental steers (12 months of age; 389 ± 3.7 kg of body weight) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement. Moderate‐concentrate (400 g/kg diet [MC ]) or high‐concentrate (600 g/kg diet [HC ]) diets were fed with or without 2MB (0 g/day [2MB ?] or 15.0 g/day [2MB +]). Dry matter intake and average daily gain increased, but feed conversion ratio decreased with the HC diet or 2MB supplementation. Ruminal pH decreased, but total volatile fatty acid increased with the HC diet or 2MB supplementation. Molar proportion of acetate and acetate‐to‐propionate ratio decreased with the HC diet, but increased with 2MB supplementation. Propionate molar proportion and ruminal NH ₃‐N content increased with the HC diet, but decreased with 2MB supplementation. Neutral detergent fibre degradability decreased with the HC diet, but increased with 2MB supplementation. Crude protein degradability increased with the HC diet or 2MB supplementation. Abundance of Ruminococcus albus , Ruminococcus flavefaciens , Fibrobacter succinogenes and Bufyrivibrio fibrisolvens as well as activities of carboxymethyl cellulase, cellobiase, xylanase and pectinase decreased with the HC diet, but increased with 2MB supplementation. However, abundance of Prevotella ruminicola and Ruminobacter amylophilus as well as activities of α‐amylase and protease increased with the HC diet or 2MB supplementation. Total PD excretion also increased with the HC diet or 2MB supplementation. The results suggested that growth performance, ruminal fermentation, CP degradability and total PD excretion increased with increasing dietary concentrate level from 40% to 60% or 2MB supplementation. The observed diet × 2MB interaction indicated that supplementation of 2MB was more efficacious for improving growth performance, ruminal fermentation and total PD excretion with promoted ruminal bacteria abundance and enzyme activity in the MC diet than in the HC diet.     

酪蛋白胶束粉的陶瓷膜分离生产工艺

为尽快建立酪蛋白胶束粉(micellar casein concentrate, MCC)的中试生产线,实现MCC在国内的工业化生产,该研究通过测定牛乳蛋白粒径,选取孔径40和100 nm的中空纤维陶瓷膜进行膜分离效果的对比,并选用膜分离效果较佳的陶瓷膜进行最佳操作参数的确定及稀释过滤工艺的研究,最后将自制MCC和进口MCC进行品质特性对比并分析其工业化生产的可能性。结果表明：孔径40 nm中空纤维陶瓷膜与孔径100 nm中空纤维陶瓷膜相比,渗透液中不含酪蛋白,能够减少酪蛋白损失,更适合于酪蛋白和乳清蛋白的分离,孔径40nm中空纤维陶瓷膜的最佳操作参数为操作压力2×105 Pa,料液温度50℃;采用四段式的连续稀释过滤工艺,可使料液中酪蛋白占真蛋白的比例从69.39%提升至93.34%,真蛋白占干物质的比例从38.45%提升至88.15%;稀释过滤完毕后膜的纯水通量衰减了39.98%,经生物酶清洗液清洗后膜的纯水通量恢复至初始的98.02%;自制MCC在成分组成上与加拿大Proteinco公司生产的MCC相比差异不显著（p < 0.05）,但在溶解度和粉粒的微观形态上优于Proteinco MCC;生产1 kg MCC需要原料乳46.24 L,成本为244.58元,可实现其国内工业化生产。研究结果为实现MCC在国内工业化生产及其应用性研究提供参考。     

利用大豆浓缩蛋白乳清制备水苏糖的发酵条件

利用酵母对大豆浓缩蛋白乳清进行发酵处理制备水苏糖.在确定最佳起始发酵液的糖度为31.8Brix后,对温度、pH、接种量、装液量等工艺条件进行了单因素试验及正交试验,结果表明最佳发酵条件为:温度32°C,pH5.5,接种量8%,在此发酵条件下利用酵母对大豆浓缩蛋白乳清进行发酵处理48 h,水苏糖的纯度达到了90%,保留率为68%.     

高精料条件下延胡索酸对山羊瘤胃微生物体外发酵的影响

通过山羊瘤胃液的体外批次培养,研究延胡索酸对瘤胃混合细菌体外发酵的影响。瘤胃液在含底物(玉米粉、豆粕和黑麦草)和延胡索酸(0、4、8和12 mmol.L-1)条件下发酵24 h。结果表明,在整个发酵期内,不同浓度的延胡索酸均显著提高了累积产气量,同时显著影响总挥发性脂肪酸(TVFA)浓度及其组成,降低乙酸的浓度及比例,增加丙酸的浓度及比例。其中4 mmol.L-1延胡索酸在12~24 h提高了TVFA浓度和丙酸浓度(P<0.05),8 mmol.L-1组和12 mmol.L-1组的TVFA浓度和丙酸浓度在16 h和24 h也有显著提高(P<0.05)。在12、16、20和24 h时,3个添加组乙酸比例均显著低于对照组(P<0.05),而丙酸比例则明显提高(P<0.01),乙酸和丙酸的比值显著降低(P<0.05)。4 mmol.L-1延胡索酸添加组的乳酸浓度在12、16、20和24 h均极显著低于对照组(P<0.01)。结果提示,延胡索酸能显著提高瘤胃微生物体外发酵液中TVFA及丙酸比例,其中4 mmol.L-1延胡索酸对于调控瘤胃微生物体外发酵效果最佳。     

430g/L戊唑醇水悬浮剂的研制

戊唑醇是一种广谱内吸型杀菌剂,对多种作物的病害有较好防治效果。本文介绍了农药悬浮剂发展、加工及实验理论依据,并采用优化组合法对表面活性剂进行了筛选。试验结果表明:该产品悬浮率90%以上,热贮(54℃±2℃,14d)分解率<5%,产品各项指标符合悬浮剂的要求。     

28%多·井悬浮剂防治水稻纹枯病田间药效评价

为明确28%多.井悬浮剂对水稻纹枯病的防治效果,进行田间药效试验。结果表明：28%多.井悬浮剂对水稻纹枯病有显著的防治效果,按500g/hm^2用量,第三次药后14d对纹枯病的防效为86.13%,与常用药剂5%井冈霉素水剂3.75L/hm^2的防效相当,而且对水稻安全,值得推广应用。     

调环酸钙25%悬浮剂对直播稻抗倒伏和产量性状的影响

为了研究新型植物生长调节剂调环酸钙在直播稻上的应用效果,本研究设计了调环酸钙25%悬浮剂在直播稻武运粳8号上的田间试验,用来了解其对直播稻的抗倒伏性状和产量性状的影响。试验结果表明:在直播稻武运粳8号的分蘖期使用调环酸钙25%悬浮剂12~15g/667m2均能够显著降低水稻的株高,缩短茎基部节间长度,提高水稻的抗倒伏能力,同时也能显著提高水稻产量。     

Effects of Adding Mannan Oligosaccharides to Diets with Different Concentrate to Forage Ratios on Ruminal Fermentation of Sheep in vitro

The test was aimed at determining the effects of adding MOS to diets with different concentrate to forage ratios on ruminal fermentation of sheep in vitro.The 4×6 two-factor experimental design was chosen.There were 4 diets with different concentrate to forage ratios(20:80, 30:70, 40:60 and 50:50) and added to 6 dosages MOS(0, 0.4%, 0.8%, 1.2%, 1.6% and 2.0%), respectively.The method of gas production in vitro was used to measure the total gas and CH₄ production, IVDMD, IVCPD and IVOMD after cultured for 3, 6, 9, 12 and 24 h.The results showed that the gas(except 12 and 24 h) and CH₄ production(except 9 h) were not impacted by the two factors(P>0.05).The IVDMD, IVCPD and IVOMD were significantly affected by concentrate to forage ratios(P<0.05), while the IVCPD at 24 h was significantly affected by MOS(P<0.05).Meanwhile, all the indexes were not influenced by the interaction of two factors(P>0.05).The IVDMD and IVOMD increased with the rising of concentrate approximately, while the IVCPD decreased with the rising of MOS roughly.The biggest associative effect was gained in 30:70 concentrate to forage diet when adding 1.2% MOS.     

Sintering of Magnetite Concentrates Without Carbon

With the goal of the sintering of magnetite concentrates without carbon,the effect of quality,inert atmosphere and Fe_3O_4 addition on microwave sintering of magnetite concentrates is studied.It is shown that: With the same basicity(CaO/SiO_2=2.5) and microwave heating condition(1000W,2.45GHz,20min),the centre temperature decreaseds with a increasing sample mass;There is no great difference between with and without inert atmosphere in microwave sintering of magnetite in a same microwave heating condition.When 100g sample(CaO/SiO_2=2.5) is heated by microwave irradiation(1000W,2.45GHz,20min),the more Fe_3O_4 is added,the less liquid phase is produced,which is bad for microwave sintering of magnetite concentrate.     

汽车悬架主要性能参数的匹配研究

通过对汽车悬架结构的比较,对悬架静挠度和动挠度的匹配和车身侧倾中心高度与悬架侧倾角刚度在车轮的分配问题进行分析,利用生产试验的方法,总结了车辆运动特性要求下的悬架设计规则,为确定汽车悬架系统主要性能参数的设计和初始值提供了依据,进而合理地匹配确定其主要性能指标。