共查询到20条相似文献，搜索用时 62 毫秒
1.
《中国畜牧杂志》2017,(12)
本文以30个省(市、自治区)猪肉月度价格数据作为研究对象,运用TGARCH模型对中国各地区猪肉价格波动的非对称性特征及其成因进行实证研究。结果表明:仅有8个地区的猪肉价格存在非对称波动,表明中国猪肉价格非对称性波动不是普遍规律,而是个体特征;中国猪肉价格波动的非对称性特征存在着区域差异,山西省、吉林省和天津市的猪肉价格存在负的非对称波动,黑龙江省、甘肃省、安徽省、云南省以及浙江省的猪肉价格则存在着正的非对称波动;疫病、自然灾害、政策和技术等不规则因素的变动是引发猪肉价格非对称性波动的主要原因。有鉴于此,生猪饲养者应区别对待具有不同非对称性特征地区的猪肉价格变化信息,提高对波动的预判能力;政府部门相关政策的制定也应因地制宜,实现对猪肉价格波动的有效调控。 相似文献
2.
3.
4.
5.
近年来,由于原料成本上涨、市场价格波动加剧、疾病防控和食品质量安全压力增大等原因,农村散户以及一些中小型猪场大量退出养猪行业。而与此同时,规模养殖企业比重增加,逐渐占据市场的主导地位,养猪产业结构调整步伐加快,行业资源整合力度不断加大,中国生猪养殖产业正朝着规模化、集约化、标准化的方向快速发展。相信未来5~10年将是中国规模化养猪业发展的黄金期。然而,养猪业仍然面临着诸多的风险和挑战,如养猪观念落后,专业人 相似文献
6.
7.
随着中国经济的高速发展,社会生产的分工进一步细化,养猪业正快速向专业化、规模化、集约化的方向发展,令人遗憾的是大部分的投资者、行业人士似乎并没有做好充分的准备来迎接这种挑战.当前中国的养猪业正经历着一次前所未有的市场价格高峰,这将吸引大量其他社会资金进入这个行业,将有更多新的规模化猪场投入建设. 相似文献
8.
9.
10.
集约化和规模化是国际养猪业发展的趋势,美国、英国等世界发达的养猪国家都实现了养猪产业结构的调整,猪场数目减少,单个猪场的规模扩大,集约化和规模化程度提高。我国养猪业目前仍以农户散养为主,集约化和规模化的程度相当低,规模化猪场只占猪场 (户)总数的0．27％,其出栏量只占总出栏量的1/5。集约化和规模化能大大提高生产效率,对保持猪肉供需平衡和价格稳定具有积极意义。 相似文献
11.
12.
13.
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。 相似文献
14.
魏静 《四川畜牧兽医学院学报》2009,(4):28-32
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。 相似文献
15.
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. 相似文献
16.
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. 相似文献
17.
18.
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。 相似文献
19.
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. 相似文献