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季节性繁殖是指动物在长期的进化过程中,为了适应生活环境而形成的只在特定季节才出现繁殖的现象.国内外学者研究表明,绵羊的性腺在日照逐渐缩短的秋冬之际开始活动,主要受外界环境中光照周期的调控[1-2].其作用机制为:光照作用于视网膜,通过复杂的神经通路传递到松果腺,黑暗时交感神经兴奋,分泌的去甲肾上腺素(NE)增多,促进松果体分泌褪黑激素(Melatonin,MLT);而光照则抑制交感神经,减少松果体分泌MLT,血液中MLT浓度的变化规律,就反映出昼夜的变化节律. 相似文献
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动物体外传播(Epizoochorous dispersal)是植物种子实现远距离传播的一种重要方式,尤其在放牧生态系统中,这种现象更为普遍。为探究放牧季节(暖季和冷季)及种子性状(质量、形状和附属结构)对高寒草甸牦牛皮毛种子库的大小及组成特征的调控作用,分别在2019年暖季(8月下旬)和冷季(10月中旬),模拟收集了牦牛皮毛附着的种子,并对皮毛种子库大小和组成及种子形态学特征(质量和形状)进行了统计。结果表明:暖季皮毛种子库大小(585.27±23.56粒/m 2)显著高于冷季(218.18±22.67粒/m 2)(P<0.05),并且暖季皮毛种子库物种丰富度(16)和多样性指数(1.85±0.19)均高于冷季(4和0.66±0.11)。暖季皮毛种子库主要由多年生植物构成(87.50%),冷季时只包括多年生植物。皮毛种子库主要由中等质量(1~10mg)、形状不规则(形状指数>0.01)的种子构成,并且附着的种子中有75%存在附属结构(芒、冠毛、翅和距)。在高寒草甸放牧生态系统中,植物种子可以通过牦牛进行体外传播,这是草-畜互作的一种表现形式,也是动物-植物共同进化的结果。 相似文献
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本试验探讨了高海拔地区进行冷季补饲对母牦牛繁殖性能的影响,对妊娠后期母牦牛每日用母牛专用浓缩饲料0.30kg/头补饲150d。结果表明:补饲期内补饲组母牦牛掉膘减重12.3kg,显著低于对照组减重30.2kg(P0.05);试验组母牦牛平均减重82g/d,显著低于对照组的201.3g/d(P0.05);暖季体重恢复期,补饲组母牦牛平均增重30.4kg,显著高于对照组25.2kg(P0.05);试验组母牦牛平均日增重253g,显著高于对照组的208.3g(P0.05);补饲组公、母牦牛犊初生重分别为15.1kg,14.3kg。对照组公、母牦牛犊初生重分别为11.9kg,10.3kg。补饲组公、母牦牛犊初生重分别比对照组提高了26.9%和38.8%,差异均极显著(P0.01);补饲组母牦牛发情率和连产率分别为44.7%和34.0%,比对照组提高了32.9%和22.2%,差异极显著(P0.01)。冷季对妊娠母牦牛进行补饲,可防止母牦牛掉膘减重,增加犊牦牛初生重,促进暖季带犊母牦牛体重增加、体能恢复,提高母牦牛发情率和连产率。 相似文献
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冷季母牦牛采用补饲+保温措施能起到减损保膘、降低成畜死亡率、提高繁殖成活率、所产犊牛6月龄日增重快的效果,试验确定了不同补饲量.结果表明:冷季母牦牛日补饲青干草1.5 kg、精料0.25 kg以上组在减损保膘、成畜死亡率、繁殖成活率、犊牛初生重、6月龄体重、日增重等方面比补草组Ⅲ组和不补饲组Ⅳ组均有极显著提高.效益分析:总效益Ⅰ组比Ⅱ组、Ⅲ组、Ⅳ组分别高2 580元、11 055元、17 822元,头均增效益Ⅰ组比Ⅱ组、Ⅲ组、Ⅳ组分别高129.0元、553.1元、891.1元,差异均极显著(P<0.01). 相似文献
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396头适繁母牦牛和226头围产期牦牛按体况评分方法进行体况评分,并在发情季节进行了发情率的跟踪观察;对446头围产期牦牛按体况评分2.0组和2.0以下组在进行不同量补饲对比试验,旨在探讨体况基础上的营养调控繁殖研究。结果表明:发情牦牛的体况评分为4.16±0.44,未发情牦牛的体况评分为3.49±0.45,差异极显著;妊娠母牦牛产前体况评分在2.63,产后体况评分下降到0.34的母牦牛产后发情率达到45.46%,而产前体况低于2.0,产后体况下降0.5以上的母牦牛产后发情周期不能恢复;围产期牦牛体况评分低于2.0,补饲1kg/d,围产期体况高于2.0,补饲0.5kg/d,能使17%～30%的产后母牦牛当年进入发情配种状态。 相似文献
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对1 049头3岁以上青海环湖母牦牛进行了繁殖状况的调查,结果发现,环湖母牦牛繁殖率为54.3%,繁活率为43.4%,自然双犊率为0.35%;母牦牛初产年龄3岁以上,其中90%的环湖母牦牛在4~6岁初产;成年适龄母牦牛一年一胎占9.89%,两年一胎占82.34%,三年一胎占7.77%,平均产犊间隔时间为722.3d;母牦牛年均产犊0.5胎,在5~14岁繁殖性能较稳定。 相似文献
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对牦牛三元杂交又一个组合(西×黄)♂×牦牛♀研究结果表明,含1/2西门塔尔牛血缘的西黄杂种公牛从半农半牧区引入川西北高寒牧区有良好的适应性,与牦牛自然交配,繁殖成活率达43.85%,比用"冻配"技术生产犏牛提高20.15个百分点.繁殖的F1代犏牛杂种优势明显,初生重大,公、母分别为(21.74±2.49)kg、 (20.83±3.62)kg,分别比牦牛高7.07 kg和7.88 kg(P＜0.01);生长发育快,2.5岁时,公、母体重分别为(326.75±13.61)kg、 (321.29±15.3)kg,分别比同龄牦牛相应重142.45 kg和165.43kg(P＜0.01),杂种优势率高达40.42%;母犏牛2～3岁可初配,比母牦牛提前1～2岁投入生产,第一胎产奶量704.55kg,为同胎次母牦牛的2.8倍(P＜0.01).建议在牦牛改良中推广(西×黄)♂×牦牛♀和(荷斯坦×黄)♂×牦牛♀两个牦牛三元杂交组合. 相似文献
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文章采用体外细胞培养和放射免疫测定(RIA)等方法,研究了褪黑素(MLT)对季节性繁殖的蒙古母羊垂体细胞分泌促卵泡素(FSH)、促黄体素(LH)和促乳素(PRL)的作用。结果表明:当单独用递增的MLT(0、10、100、1000pg/ml)处理原代垂体细胞时,伴随时间的延长FSH的分泌量极显著下降(P<0·01),但对LH的基础分泌没有影响;用10IU/ml hCG单独刺激或用不同剂量MLT与10IU/ml hCG共同刺激垂体细胞,FSH和LH的分泌都极显著高于对照组(P<0·01),但与MLT的剂量没有关系。MLT能改变抑制垂体细胞PRL的分泌,用10IU/ml HCG单独作用使垂体细胞PRL分泌减少,但这种作用可被MLT呈剂量依赖性抑制。本研究表明MLT可作用于季节性繁殖蒙古绵羊的垂体细胞并影响其促性腺激素的分泌。 相似文献
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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
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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
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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
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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
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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