奶牛乳脂形成的调控措施及其机理

乳脂是乳中的主要营养成分,也是衡量乳品质优劣的重要指标。乳脂与人类的健康有着密切的关系。文章对乳脂的功能、不同奶畜乳脂含量、乳脂的调控研究、以及不同杀菌强度对乳脂的影响等方面进行综述,对乳脂在未来进一步研究做了展望。     

奶牛瘤胃微生物及其代谢物与乳脂合成关键酶基因对乳脂率的影响

乳脂肪对于人类的健康有着重要的生理作用,乳脂率的高低决定牛乳的品质、风味和营养价值,所以乳脂率对牛乳品质十分关键。奶牛乳脂率的高低受到多种因素的影响,如何提高奶牛乳脂率一直是行业研究的热点。大量研究表明,瘤胃微生物及其代谢产物与乳脂合成关键酶基因对奶牛乳脂率的高低具有重要调控作用。文章就瘤胃微生物及其代谢物与乳脂合成关键酶基因如何影响奶牛乳脂率的研究进行综述,为进一步探索乳脂合成机制,进而改善奶牛乳脂率提供新的思路。     

饲料营养对牛奶乳脂率的影响

<正>乳脂率是衡量乳质优劣的重要指标,牛奶的乳脂率一般为3%～5%。提高乳脂率的主要途径有多种,本文主要介绍饲料营养对牛奶乳脂率的影响。1碳水化合物对乳脂率的影响     

饲喂醋酸钠可提高乳脂率

对高乳脂和低乳脂两组牛进行的试验表明,在10天的基础期中,每头每天喂醋酸钠300克,高脂率牛(乳脂率4.42％)比低乳脂牛(乳脂率3.99％)多产标准奶184.6公斤(乳脂7.386公斤)。即高乳脂牛脂率提高0.63％,而低乳脂率牛提高0.27％。高乳脂牛喂1公斤醋酸钠多产8.79公斤标准乳     

饲料营养对牛奶乳脂率的影响

<正>乳脂率是衡量乳质优劣的重要指标,牛奶的乳脂率一般为3%～5%。提高乳脂率的主要途径有多种,本文主要介绍饲料营养对牛奶乳脂率的影响。1碳水化合物对乳脂率的影响     

中国荷斯坦牛乳脂率变化规律初探

对扬州大学实验农牧场30头成年中国荷斯坦牛乳脂率进行测定，并进行统计分析，结果表明：早班奶乳脂率最低，中班乳脂率最高；在一次挤奶的不同阶段中，前期乳脂率最低，后期乳脂率最高；产奶量高的奶牛乳脂率较低；随泌乳月的延长。乳脂率呈增加趋势，随胎次的增长，乳脂率呈下降趋势。     

奶牛乳脂率下降的原因与对策

乳脂率是衡量奶牛生产性能的一项重要指标,而影响奶牛乳脂率的因素很多.对奶牛养殖者来说,了解影响奶牛乳脂率的各个因素并采取相应的措施避免乳脂率下降,具有非常重要的意义.文章在提示乳脂率下降机理的基础上,分析了导致乳脂率下降的因素,同时提出了提高乳脂率的措施,为促进奶牛养殖业的健康发展和提高奶牛养殖的经济效益提供参考.     

氨基酸影响奶牛乳腺内乳脂合成的机理

乳蛋白前体物主要有游离氨基酸和小肽等。氨基酸不仅能影响乳腺内乳蛋白的合成,而且对乳脂的合成起一定的调控作用。本文主要阐述了氨基酸在乳脂合成过程中的调节作用,并从乳腺对乳脂前体物的摄取规律、乳脂合成相关基因表达、哺乳动物雷帕霉素靶蛋白和腺苷酸活化蛋白激酶信号通路的角度综述了氨基酸对乳脂合成的可能机理,为进一步研究乳脂合成机理及改进牛奶营养品质提供理论依据。     

乳脂品质及其通过饲粮措施进行优化的研究进展

乳脂是乳的重要营养指标之一,其含量和组成与乳品质和人体健康密切相关。针对乳脂的组成特点和人体健康需求,降低其中对健康不利的饱和脂肪酸含量而增加对健康有益的功能性成分含量,可以优化乳脂品质,提高乳和乳制品的质量并增加乳品附加值。改变饲养方式或饲粮组成可以方便有效地实现乳脂优化,其中以放牧或饲喂新鲜牧草最为安全有效。本文在阐述乳脂中主要功能性脂质的基础上综述了乳脂优化的目标、方式及国内外优化乳脂的主要饲粮措施,以期为国内乳脂优化或乳品质提高相关研究和生产提供参考。     

短链脂肪酸调控奶牛乳腺乳脂合成作用机制的研究进展

短链脂肪酸是胃肠道微生物发酵的主要产物,不仅作为乳脂合成前体物直接参与乳腺内脂肪酸的从头合成,还作为信号分子调节乳腺脂肪酸代谢,进而调控乳脂的合成.本文从短链脂肪酸对乳脂合成的影响以及短链脂肪酸调控乳腺乳脂合成的分子机制2方面,综述了短链脂肪酸调控奶牛乳腺乳脂合成的作用机制,为奶牛乳脂合成机制的相关研究提供理论依据.     

商会自治的基石——商会自治规范研究

在现代法律秩序中,商会自治规范是制定法的基础和必要的补充,甚至在某些方面替代了制定法;商会自治规范主要包括商会组织规范、行为规范、惩罚规范以及争端解决规范等;其效力仅及于其内部成员;商会自治规范和制定法之间存在冲突,但也存在整合的基础。     

癸氧喹酯干混悬剂含量测定的改进

采用高效液相色谱法测定癸氧喹酯干混悬剂的含量,在2-250μg/mL范围内,峰面积的常用对数与进样量浓度的常用对数呈良好的线性关系,R^2=1(n=5),平均回收率为99.24%~99.51%,RSD在0.05%~0.28%。此方法分析时间短,样品前处理简便、定量结果准确,重现性好,结果满意,为其质量控制提供了依据。     

猪毛色遗传的研究进展

本文概述了猪的毛色类型、猪的毛色遗传模式,着重综述了猪毛色基因分子基础的研究进展,指出存在问题并就未来发展方向做了思考。     

Comparison of 2 methods of centesis of the bursa of the biceps brachii tendon of horses

REASONS FOR PERFORMING STUDY: Centesis of the bicipital bursa using an 8.9 cm long spinal needle has been reported but the alternative of employing a 3.8 cm long hypodermic needle requires validation. OBJECTIVE: To compare the efficacy of 2 different methods of centesis of the bicipital bursa and to evaluate the usefulness of ultrasonographic imaging to determine the location of solution administered when centesis of the bursa is attempted. METHODS: For Trial 1, 6 clinicians, who had no previous experience of centesis of the bicipital bursa, attempted to inject a solution composed of an aqueous radiopaque contrast medium and physiological saline solution (PSS) into the bicipital bursae of 2/12 horses using the previously described distal approach to inject one bursa and a proximal approach to inject the contralateral bursa. The bicipital tendon and bursa were examined ultrasonographically before and after injection; and both shoulders were examined radiographically to identify the location of the medium. In Trial 2, another 6 clinicians, also with no previous experience of centesis, repeated Trial 1, using 6 horses, but the radiopaque contrast medium was mixed with air instead of PSS. RESULTS: Accuracy of centesis using the proximal approach was 39% and that of the distal approach 28%. Ultrasonographic examination of the shoulder allowed the location of solution and air to be accurately predicted in all 12 shoulders examined. CONCLUSIONS: Clinicians who have had no previous experience performing centesis of the bicipital bursa are unlikely to be successful in centesis using either approach. Radiographic examination after injecting a radiopaque contrast medium may be necessary to assess the success of centesis especially if bursal fluid is not obtained during centesis. Injecting air along with the radiopaque contrast medium provides more accurate ultrasonographic confirmation of centesis and better radiographic definition than does injection without air.     

不同样本商品蜂蜜中硒含量的测定

用硝酸和高氯酸消化蜂蜜,使硒游离出来,在微酸性环境下,硒和2,3-二氨基萘(DAN)生成有较强荧光的物质,用环己烷萃取,在激发波长378nm,荧光波长518nm处测定其荧光强度。蜂蜜中硒含量范围:0.10～0.82μg/g。表明:蜂蜜应视为天然富硒营养品。     

乳酸杆菌益生作用机制的研究进展

乳酸杆菌作为益生菌广泛用于人和动物。本文综述了乳酸杆菌改善宿主健康的机制。乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道。文章重点讨论了乳酸杆菌表面成分（表面蛋白、脂磷壁酸和肽聚糖）与肠道受体（Ｃ型凝集素受体、Ｔｏｌｌ样受体和 Ｎｏｄ样受体）,阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制。     

中华人民共和国农业部公告 第267号

为贯彻落实《兽药生产质量管理规范》(简称《兽药GMP》),进一步推动兽药GMP实施进程,我部制定了《兽药生产质量管理规范检查验收办法》,现予公告。本公告自2003年6月1日起施行。附件:兽药生产质量管理规范检查验收办法二○○三年四月十日第一章 总则 第一条 为推动《兽药生产质量管理规范》(以下简称兽药GMP)的实施,规范兽药GMP检查验收工作,制定本办法。 第二条 农业部负责全国兽药GMP管理和检查验收工作;负责制修订兽药GMP检查验收管理规定;负责兽药GMP检查员队伍建设和监督管理工作,负责国际兽药贸易中GMP互认工作。 …     

鸡败血支原体垂直传播模式及其阻断方法

以国际标准强毒Ｒ株人工感染非免疫产蛋鸡,定时扑杀,分别从鼻窦、眶下孔、气管、肺、气囊、卵巢和输卵管分离ＭＧ,并收集感染鸡所产蛋分离ＭＧ。结果表明,人工感染４８小时后上、下呼吸道及肺已被全面感染,９６小时气囊已被感染,１２０小时输卵管已能分离到ＭＧ,卵巢始终分离不到ＭＧ。人工感染鸡自１４４小时便能在其所产蛋中分离出ＭＧ。药物治疗能在７２小时内消除感染,油乳剂苗则需２４天后逐渐降低蛋内ＭＧ分离率,药物卵内注射、种蛋药浴、高温处理均能杀死卵内ＭＧ,但以研制的种蛋浸泡剂药浴效果为最好。     

Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF

Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo.