奶牛热应激的危害及预防

夏季热应激对泌乳奶牛造成的危害极大，发生热应激时，奶牛为了减少体热会减少采食量。据测定，气温在22～25℃时，采食量开始下降；超过30℃，采食量下降10％以上；40℃以上时采食量下降50％以上，个别奶牛将停止采食。采食量的下降造成奶牛营养不良。研究表明，在21℃以上时，气温升高会引起体温上升，体温每升高0．6℃，采食量下降1．4kg，产奶量下降1．8kg，     

南方地区夏季奶牛热应激的预防措施

南方地区夏季高温时间较长，热应激对泌乳奶牛造成极大的危害。有研究表明，在21℃以上时，当气温升高引起体温上升，每升高0．6℃，采食量下降1．4kg，产乳量下降1．8kg。采食量的下降造成钙摄入量不足，血钙浓度下降，易导致产后瘫痪等缺钙症。同时由于采食量的减少，热应激还可以使母牛发情时间缩短，发情周期延长，发情不明显或乏情，从而影响适时配种，使受胎率、妊娠率下降，早期胚胎死亡率、流产率上升。     

炎夏减轻热应激对奶牛危害的几项有效措施

炎夏热应激是导致奶牛夏季产奶量和繁殖力下降的最重要的原因之一。热应激由此造成的损失也是十分明显的，如产奶量下降，空胎期拉长，繁殖力下降。为缓解和减少热应激对奶牛的危害，主要应从环境和营养两方面加大饲养管理力度。     

夏季奶牛热应激的防治

热应激可使泌乳牛产奶量降低,乳脂率、乳糖、乳蛋白比率下降,从而降低了乳汁的营养价值;还可使母牛发情时间缩短,发情周期延长,发情表现不明显,影响适时配种,而且母牛受胎率降低,分娩母牛易发生流产,不育公牛增多.热应激还使奶牛乳房炎、胎衣不下、子宫内膜炎、腐蹄病等发病率升高.热应激防治如下:     

夏季奶牛热应激的预防措施

奶牛要求最适宜的外界环境温度为 8～ 16℃ ,高于或低于这个临界温度 ,将会对奶牛产生一系列应激反应。在炎热的夏季 ,外界气温在 30℃以上的时间长达 3个月之久。在这种高温的环境下 ,奶牛表现呼吸加快 ,体温升高 ,散热量减少 ,食欲下降 ,产奶量降低 ,生理代谢紊乱 ,给生产带来很大损失。据研究 ,当气温从 2 5 9℃上升到 2 8 6℃时 ,奶牛标准奶产量下降 2 5 4%。因此 ,采取有效措施 ,消除夏季热应激对奶牛的影响 ,对保证奶牛高产、稳产具有重要经济意义。1　植树绿化夏天奶牛在运动场活动时间较长 ,搞好环境绿化 ,有助于改善牛场内部小…     

热应激条件下复合添加剂对奶牛生产性能和生理指标的影响

试验选择22头处于泌乳中期的荷斯坦奶牛,随机分为对照组和试验组,对照组饲喂常规日粮,试验组日粮中添加复合添加剂。结果表明:复合添加剂对奶牛干物质采食量没有影响;试验组奶牛产奶量比对照组提高了1.52%(P0.05),对照组奶牛产奶量比试验前下降了16.36%,而试验组提高了1.45%;复合添加剂除可明显降低乳脂率外(P0.05),对其他乳成分基本没有影响;与对照组比较,试验组的直肠温度显著降低(P0.05),呼吸频率显著升高(P0.05)。     

夏季奶牛热应激反应的预防措施

在炎热的夏季，当气温超过30℃时，奶牛即呈现热应激反应，采食量和泌乳量下降，尤其产乳高峰期热应激反应更明显。产乳量下降的原因主要有两个：一时以蒸发为主要散热方式增加了维持需要的能量，例如体重635kg日产乳27kg的奶牛在35℃时维持需要的能量比在20℃时约高20％；二是奶牛的采食量下降，摄入的营养物质不能满足产乳的需要。为预防奶牛热应激反应，维持高水平的产乳量，应采取相应的措施。     

奶牛热应激的监控方案

奶牛热应激是指奶牛对于不利于其生理的环境高温产生的非特异性应答反应的总和,它通过改变奶牛的各种生理生化反应,降低奶牛的采食量、生产繁殖性能和免疫力,给奶牛生产造成严重的危害。长期以来,热应激是影响我国夏季奶牛饲养的普遍性问题,严重影响了我国乳业的发展,造成了巨     

奶牛夏季科学喂养

夏季由于热应激效应,奶牛生理机能发生变化,产奶性能和繁殖力下降。因此,夏季奶牛的饲养,首要问题就是尽量减少热应激对奶牛的影响,充分发挥其生产潜力。除了在管理方面要求牛舍通风、凉爽、运动场必设凉棚外,饲养方面应采取以下几项措施。1　增进食欲奶牛夏季产奶量下降的一个重要原因是食欲不振。因此,增进奶牛食欲是夏季喂养的重要措施。除了尽量提高饲料的适口性,少喂勤添,保证新鲜外,在干草饲料中添加少量苏打(碳酸氢钠),是增进奶牛食欲的有效方法。国内外很多研究证实,对产奶母牛,每日在干草饲料中添加50～200ｇ苏打,可使日采食量增加…     

热应激对奶牛生产力的影响及预防措施

应激是动物机体对外界或内部的各种刺激所产生的非特异性应答反应的总和。应激的目的是为了克服应激源 (Stressor)的危害 ,以保持体内平衡 ,所以这是一种适应性的非特异性防御反应。但如果刺激强度过大或作用时间过长 ,机体就会逐渐失去应答能力 ,出现病理状态 ,表现出衰竭现象。温度变化可产生冷热应激 ,而热应激更为重要 ,也最为常见。热应激往往导致动物体内平衡破坏 ,出现疾病 ,甚至死亡。例如新疆呼图壁种牛场一分场 1994年 6月 3 0日由于持续高温天气使 6头成母牛发生中暑 (热射病 ) ,死亡 1头。1　热应激的概念热应激即指处于极端高…     

Thermoregulatory response of dairy cows fed ergotized barley during summer heat stress.

Claviceps purpurea infects the seed heads of cereal grains and grasses and produces ergopeptine alkaloids that cause hyperthermia and agalactia in cattle during periods of heat stress. A field experiment was undertaken to examine the effects of ergopeptine alkaloids found in barley on thermal status of dairy cattle during periods of heat stress. Production end points were also measured to identify the effect of the change in thermal status. Contaminated barley screenings containing known levels of ergopeptine alkaloids were fed to lactating Holstein cattle (10 microg total ergopeptine alkaloids/kg BW/day) for 10 days during summer heat stress. Air temperature increased 14.4 C during the first 8 days of treatment and then declined the same during the last 2 days. Extreme daily values for rectal temperature and respiration rate, using averages of all animals, showed maximum increases of 2.3 C and 56.8 breaths/minute, respectively, during this period. Group afternoon milk production decreased 2 kg/day during the heat stress period, with no measurable change in feed intake. A greater level of hyperthermia occurred in cattle consuming the diet with ergopeptine alkaloids, with only marginal symptoms of ergot toxicosis reflected in feed intake and milk production. Therefore, the ergopeptine alkaloid dose used in this study represents a level for minimal induction of the ergot toxicity response.     

夏季奶牛的保健措施

夏季天气炎热多雨，气温过高，极易造成奶牛热应激，严重影响奶牛生产性能。炎夏，奶牛饲养管理的原则应以防暑降温为主，具体措施如下：     

夏季肉种鸡防止热应激方法

随着夏季的来临,防暑降温又被各种鸡场提上工作日程,如何采取有效的措施防暑降温,以帮助肉种鸡安全稳定的度过炎热的夏季,也就是如何预防肉种鸡免遭热应激的伤害,是一个值得讨论的现实问题。     

预防炎热季节的家禽热应激

高温会使家禽产生热应激,热带和亚热带地区国家的家禽总是处于较高的热应激危险之中。然而,采取适当的预防措施可以将由此带来的不良影响降至最低限度。     

鸡热应激的危害及防治措施

我国大部分地区夏季炎热期达3个月之久，长江以南地区高温持续时间更长，严重影响鸡群的生长和生产性能，导致鸡群采食量减少，体重下降，肉仔鸡生长缓慢，蛋鸡产蛋率下降，给养鸡业带来重大经济损失。因此，在夏季必须重视鸡舍的防暑降温，加强饲养管理，并通过某些营养素的调节来改善热应激造成的鸡群生产性能的下降，确保鸡群能安全渡夏，从而提高鸡群在热应激状态下的经济效益。     

A study on stress response and fertility parameters in phenotypically thermotolerant and thermosensitive dairy cows during summer heat stress

It is well documented that heat stress (HS) causes subfertility in dairy cows. However, during the last ten years we have been observing that, under high temperature–humidity index (THI ≥ 75), despite the overall reduced fertility, some cows conceive at the first artificial insemination (AI). Here, we examined distinctive features of cows with conserved fertility under severe HS. From the databases of three herds, 167 lactating Holstein cows were selected; group TT cows (n = 57) conceived in the previous summer (THI ≥ 75) at the 1st AI, and group TS (n = 110) failed to conceive at the same period after at least 2 consecutive AIs. The animals calved in spring, and in August, blood samples were collected during a hot day (THI ≥ 81) for the determination of cortisol and HSP70 concentrations. In one farm, the validity of fertility data of the previous year was re-examined. In 28 cows from group TT and in 39 cows from group TS, the conception rate was examined during July and August. In 6 cows from each group (TT and TS) the oestrous cycles were synchronized, ovulation was induced with GnRH (THI = 80), and the concentration of the pre-ovulatory LH surge was determined in 9 blood samples. The progesterone concentration in the ensuing cycle was determined in blood samples collected every other day. Overall, cortisol and HSP70 were significantly lower in TT group compared to TS. More (p < .05) animals from group TT conceived at the first AI compared with those from group TS. The induced pre-ovulatory LH surge peaked at higher level (p < .002) in group TT than in group TS, while no difference was recorded among groups either in mean progesterone concentrations or in the duration of the ensuing oestrous cycle. These results are highly suggestive that thermotolerance in some dairy cows is an inherent characteristic, warranting further genetic investigation.     

Effect of feeding slowly fermentable grains on productive variables and amelioration of heat stress in lactating dairy cows in a sub-tropical summer

Feeding low-fiber and high-energy diets to dairy cows is one approach to ameliorate heat stress (HS) by reducing heat increment (HI) during digestion. However, rapidly and slowly fermentable cereal grains differ in their HI. The aim of this experiment was to quantify if feeding slowly fermentable grains ameliorated the physiological responses to HS and improved milk production (MP) in dairy cows. Holstein-Friesian lactating dairy cows were housed in shaded pens and were fed either a total mixed ration (TMR) plus wheat (TMRW), a TMR plus wheat treated with 2% of a commercial starch-binding agent (TMRB), or a TMR plus corn (TMRC) (n?=?8 cows per diet) during summer in Queensland, Australia. Respiration rate (RR) and panting score (PS) were measured four times a day; rumen temperature (RuT) was recorded every 20 min, and rectal temperature (RT) and milk samples were obtained every 4 days. Cows fed slowly fermentable grains had higher milk production (MP) than cows fed TMRW, and cows fed TMRC had lower RT than those fed TMRW and TMRB (P?<?0.001). Rumen temperature was positively correlated with temperature-humidity index and negatively correlated with MP (P?<?0.05). In summary, feeding TMRC ameliorated HS as indicated by lower RT and improved MP in dairy cows. Milk production was improved with starch-binding agents; however, this was not associated with efficient thermoregulatory responses. Furthermore, determination of RuT enabled the prediction of changes in physiological variables and productive responses due to HS in lactating dairy cows.