奶牛热应激研究进展

当前以源自北欧的不耐热品种荷斯坦牛作为我国主要的奶用品种遍布全国各地,随着其生产性能的不断提高其热应激的表现也越来越严重。特别是在南方农区热应激造成的经济损失十分明显。因此,研究采取有效的预防措施,消除热应激对奶牛的影响,对保证奶牛高产稳产具有重要的经济意义。     

奶牛热应激饲料添加剂研究

奶牛热应激饲料添加剂一号、二号属纯中药制剂，适口性好，饲喂方便。泌乳牛在超过临界温度日均气温２４℃的环境中，加喂一号添加剂１５０克／日、头，可减少泌乳损失近２０％；加喂二号添加剂１９０克／日、头，可减少泌乳损失２０％以上，投入产出比分别为１：４．９７和１：３．０３。试验表明，加强对本添加剂开发性研究的投入，将对缓解武汉市夏季鲜奶供求矛盾，稳定和发展奶牛生产具有重要的经济意义。     

中药防治奶牛热应激研究进展

奶牛是一种耐寒怕热的动物,尤其是产奶期体内产热量大,且奶牛调节体温的能力有限,因此在众多的应激因素中,高温环境对奶牛的应激影响尤为突出。实践证明,适宜奶牛生活的温度范围在10-21℃之间,超过适宜温度时,奶牛体温开始上升,容易引起热应激。在我国,在饲料中添加中草药添加剂来防治热应激的研究颇多,本文对近年来使用中草药防治奶牛热应激的研究进行综述,以供参考。     

用石灰浆喷涂舍顶及外壁可减缓热应激对泌乳奶牛的影响

夏季热应激对泌乳奶牛造成的危害极大 ,当舍内相对湿度较高时 ,若舍内温度超过 2 8℃以上时 ,不仅导致泌乳奶牛采食量减少 ,而且使产乳量出现明显下降和饲养经济效益的降低。因此 ,在夏季搞好牛舍的的防暑降温工作 ,是保证泌乳奶牛发挥正常生产性能的一条有效措施。但从目前国内养牛专业户采取的常规防暑降温措施来看 ,一般大都采用舍内安装吊扇或经常向地面用水冲洗 ,这样一旦遇到停水、停电 ,舍温就难以控制。为此 ,我们根据不同颜色的物体对吸收光的强弱存有差异的特性 ,我们采取了用石灰浆喷涂牛舍舍顶及外壁的方法以减缓热应激对泌乳奶…     

奶牛热应激

本文综述了热应激对奶牛采食量、生理生化指标、生产性能、繁殖性能及机体免疫机能的影响，并提出了加强环境控制、饲养管理、营养调控等抗热应激措施。     

奶牛热应激研究进展

奶牛热应激是奶牛对不利于生理活动的高温环境产生的一种非特异性应答反应,也是影响奶牛夏季生产与繁殖的一种重要应激性的疾病。国内外学者对此病进行过广泛的研究,文章综述了奶牛热应激的发病原因、生理机制、诊断及综合防治措施等,为进一步研究提供参考。     

奶牛热应激研究进展

摘要：我国所饲养的奶牛以荷斯坦牛品系为主,属于怕热耐寒的品种,在夏季高温季节极易发生热应激,不仅造成牛奶产量下降,而且对其繁殖性能也造成非常坏的影响。应从日常的饲养管理方面入手,增加日粮中的营养成分,适当增加饲料中的脂肪含量,适当添加微量元素,搞好疾病防治工作,以降低热应激的发病率。主要综述了奶牛热应激的发病原因、对奶牛的影响、防治措施等,以期为进一步研究提供参考。     

奶牛热应激的发生机制及其预防研究进展

为预防热应激对奶牛生产的影响,文章对奶牛热应激的发生机理、危害及其预防措施进行了综述。     

热应激对奶牛产奶性能和泌乳相关激素影响

热应激导致奶牛食欲减退,采食量下降,乳中的乳脂率、乳蛋白率、乳糖率及非脂乳固体因高温而下降,牛奶质量降低。同时影响催乳素、生长激素、瘦素、胰岛素样生长因子的降低和糖皮质激素的升高。本文就国内外热应激对奶牛产奶性能和泌乳相关激素影响的研究进展进行综述。     

宁夏利通区产奶期奶牛铜盈缺状况调查

对宁夏吴忠市利通区4个奶牛场和10户农户进行奶牛产奶期铜营养状况进行了调查,分别测定了奶牛盛乳期、产奶中期、产奶后期血清和毛铜的含量和血清中铜蓝蛋白、SOD的活性.结果表明:在盛乳期、产奶后期,散户(产奶后期)、中户奶牛血液铜、毛铜含量偏低,但未出现明显缺乏症状,处于亚临床缺乏状态;产奶中期各户奶牛各项指标均在正常范围之内,混合料中的铜符合标准.各期小户奶牛各项指标基本正常,饲喂状况良好.产奶各期血液铜蓝蛋白、SOD的活性变化范围较小,处于正常范围之内.     

Dairy cow reproduction under the influence of heat stress

Dairy farming is vulnerable to global warming and climate change. Improving and maintaining conception rates (CRs) have a paramount importance for the profitability of any dairy enterprise. There is an antagonistic relationship between fertility and milk yield, and intensive selection for milk yield has severely deteriorated reproductive efficiency. Irrespective of geography and husbandry, modern dairy cows experience heat stress (HS) effects leading to fertility declines, but it worsens in tropical climates. The threshold of HS experience among modern dairy cow has lowered, leading to decreased thermal comfort zone. Studies show that this threshold is lower for fertility than for lactation. HS abatement and robustness response to lactation yield lead to negative energy balance, and cow's reproductive requirements remain unfulfilled. The adverse effects of HS commence from developing oocyte throughout later stages and its fertilization competence; the oestrus cycle and oestrus behaviour; the embryo development and implantation; on uterine environment; and even extend towards foetal calf. Even cows can become acyclic under the influence of HS. These harmful effects of HS arise due to hyperthermia, oxidative stress and physiological modifications in the body of dairy cows. Proper assessment of HS and efficient cooling of dairy animals irrespective of their stage of life at farm is the immediate strategy to reduce fertility declines. Other long- and short-term mitigation strategies to reduce fertility declines during HS include feeding care, reducing disease and mastitis rates, using semen from cooled bulls, timed artificial inseminations (AI), allied hormonal interventions and use of embryo transfer technology. Ultimate long-term solution should be well-planned breeding for fertility improvement and HS tolerance.     

Effects of cooled floor pads combined with chilled drinking water on behavior and performance of lactating sows under heat stress

This study was conducted to evaluate whether cooled floor pads combined with chilled drinking water could alleviate negative impacts of heat stress on lactating sows. Thirty sows (Landrace × Yorkshire, Parity = 1 to 6) were housed in individual farrowing stalls in two rooms with temperatures being controlled at 29.4°C (0700–1900 hours) and 23.9°C (1900–0700 hours). Sows in one room (Cool), but not in the other room (Control) were provided cooled floor pads (21–22°C) and chilled drinking water (13–15°C). Behavior of sows (15 sows/treatment) was video recorded during farrowing, and days 1, 3, 7, 14, and 21 after farrowing. Videos were viewed continuously to register the birth time of each piglet, from which total farrowing duration and birth intervals were calculated. The number of drinking bouts and the duration of each drinking bout were registered for each sow through viewing videos continuously for 2 h (1530–1730 hours) each video-recording day. Postures (lying laterally, lying ventrally, sitting, and standing) were recorded by scanning video recordings at 5-min intervals for 24 h each video-recording day, and time budget for each posture was calculated. Rectal temperature and respiration rate were measured for all sows the day before and after farrowing, and then once weekly. Sow and litter performance was recorded. Data were analyzed using the Glimmix procedure of SAS. The cooling treatment did not affect sow behavior or litter performance. Sows in the Cool room had lower rectal temperature (P = 0.03) and lower respiration rate (P < 0.001), consumed more feed (P = 0.03), tended to have reduced weight loss (P = 0.07), and backfat loss (P = 0.07) during lactation than sows in the Control room. As lactation progressed, sows increased drinking frequency (P < 0.001) and time spent lying ventrally (P < 0.0001), standing (P < 0.001), and sitting (P < 0.0001), and decreased time spent lying laterally (P < 0.0001) in both Cool and Control rooms. While cooled floor pads combined with chilled drinking water did not affect sow behavior, they did alleviate heat stress partially, as indicated by decreased rectal temperature, respiration rate, weight, and backfat loss, and increased feed intake in lactating sows.     

家兔热应激研究进展

夏季高温高湿的气候极易引起家兔的热应激反应,导致生长性能、繁殖性能和抗氧化能力降低,阻碍兔产业的健康发展.文章综述热应激对家兔行为及生理生化指标、生产性能、繁殖性能等方面的影响,家兔热应激期的分子调控机制,以及热应激的营养调控措施,旨在为制定家兔热应激调控策略提供参考.     

清热解暑中药验方对热应激奶牛采食行为及产奶性能的影响

本试验探讨3种清热解暑中药验方对热应激奶牛采食行为及产奶性能的影响.40头泌乳末期的中国荷斯坦奶牛随机分为4组,分别接受4种处理,即对照组、清热健胃组、清暑组和加减白虎汤组.所有试验牛饲喂相同的全混合日粮,3个处理组分别补饲清热健胃散、清暑散和加减白虎汤散剂,用量为每日每头150 g.结果发现,全天采食量和牛舍各时点的温度和温湿指数极显著负相关.在奶牛处于轻度热应激时添加清热解暑中药对采食行为影响不显著,仅在第1天早饲时略影响采食速度.清暑组干物质采食量较高,产奶量下降较少,表明清暑散具有缓解热应激、促进食欲的作用.     

夏季奶牛血液中热休克蛋白的表达量

选择40头体质健康的中国荷斯坦奶牛,根据胎次和泌乳天数,按照随机区组试验设计分为Ⅰ组（30kg/d）、Ⅱ组（30～35kg/d）、Ⅲ组（35～40kg/d）和Ⅳ组（40kg/d）。热应激前、热应激前期、热应激中期、热应激后期和热应激后分别于尾静脉采血,用ELISA试剂盒测定热休克蛋白（HSP）27,70,90的表达量。结果显示,Ⅳ组HSP27表达量最高,Ⅱ组表达量最低,Ⅳ组、Ⅲ组和Ⅰ组均显著高于Ⅱ组（P〈0.05）。HSP70表达量各组间没有明显差异,但随产奶量呈线性增加（P〈0.05）。HSP90的表达量,Ⅳ组和Ⅲ组明显高于Ⅱ组（P〈0.05）。HSP27的表达量热应激后差异较大;HSP70的表达量各组整个过程差异较大;HSP90的表达量在热应激前、热应激前期和热应激后差异较大。总之,在热应激过程,高产奶牛血清中热应激蛋白的表达量较高,HSP70表达量随产奶量呈线性增加,而不同热应激蛋白的变化规律差异较大。     

S441分子标记对奶牛抗热应激水平的影响

为了进一步验证S441分子标记对奶牛抗热应激的影响,挑选有、无S441标记的中国荷斯坦奶牛各9头分别作为试验A组和试验B组,对2组奶牛在不同热应激状态下的生理生化指标变化进行了测定和分析。结果表明：（1）在生理指标测定中,产奶量随热应激增强而降低,直肠温度随热应激增强而升高,白细胞总数（WBC）、淋巴细胞数（LYM）和单核细胞数（MXD）随热应激增强而下降,但A组变化辐度较B组低,并在一定的热应激期间达到显著性差异（P〈0.05）。（2）在生化指标测定中,随着热应激的增强,2组奶牛的Se、谷胱甘肽过氧化物酶（GSH-Px）、三碘甲腺原氨酸（T3）、四碘甲腺原氨酸（T4）和皮质醇（Cort）的总体均值呈逐渐下降趋势,促肾上腺皮质激素（ACTH）的总体均值呈逐渐升高趋势,但试验A组奶牛较试验B组变化幅度低;其中Se和GSH-Px总体均值在严重热应激期间达到显著性差异（P〈0.05）;试验A、B组奶牛的红细胞钾含量均不随热应激条件的变化,且试验A组的含量极显著低于试验B组。S441分子标记与抗热应激能力相关的各项生理生化指标均具有较强的相关性,可以作为一种奶牛抗热应激分子标记应用于品种选育和生产中。     

奶牛抗热应激添加剂的应用

本文综述了奶牛抗热应激添加剂的作用机理、应用效果,提出了其在奶牛生产上应用的研究方向。     

添加丙酸铬对热应激期间泌乳牛生产性能的影响

为了研究丙酸铬对热应激期间泌乳牛生产性能的影响,选择54头泌乳天数、产奶量、胎次相近的泌乳牛,随机分为3组,每组18头,对照组饲喂基础日粮,试验Ⅰ组、Ⅱ组分别在基础日粮中添加10和20 g/d丙酸铬。结果:添加丙酸铬可以显著降低乳中体细胞数(P<0.05),试验Ⅰ组和Ⅱ组产奶量比对照组分别提高2.60和1.32 kg/d,但差异不显著(P>0.05),乳脂、乳蛋白、尿素氮均无显著差异(P>0.05)。试验表明,夏季热应激期间,在日粮中添加丙酸铬有提高产奶量的趋势,有助于减少乳房炎的发病率、降低乳中体细胞数、改善乳房健康状况。     

苜蓿黄酮对热应激下体外培养奶牛乳腺上皮细胞凋亡的影响

本实验旨在研究苜蓿黄酮对热应激下体外培养奶牛乳腺上皮细胞的影响。将乳腺上皮细胞分成5组,每组培养基中分别含有0,25,50,75和100 μg/mL苜蓿黄酮,同时置于细胞培养箱37℃,5%CO₂培养72 h,再在 42℃恒温水浴锅中热应激1 h后返回细胞培养箱培养12 h,检测细胞活性、抗氧化指标和相关基因的表达。结果显示:1)添加25 μg/mL组的细胞活性显著高于0和50 μg/mL组(P<0.05),其他各组之间差异不显著。2)相对于0 μg/mL组,50~100 μg/mL组细胞的GSH-Px活性升高(P<0.01),LDH和MDA含量降低(P<0.01或P<0.05),而CAT活性无显著性差异。3)相对于0 μg/mL组,50和75 μg/mL组Caspase3和Socs3基因表达降低(P<0.01),25 μg/mL组P53、Stat1和Socs1基因表达升高(P<0.01或P<0.05),而Bcl-2和Fas基因表达无显著差异。综上所述,在热应激下,苜蓿黄酮能够提高体外培养奶牛乳腺上皮细胞的活性,改善抗氧化能力和抑制细胞凋亡,其中添加75 μg/mL效果较好。