Seminal changes in boars after heat stress

The object of the present study was to investigate the influence of elevated ambient temperature on sperm production, sperm morphology and composition of seminal plasma in boars. A total of 8 boars were used, 4 of them were exposed to 35°C, in a climate room, during 100 h and 4 served as controls and were kept at 20°C during 100 h in the climate room.Ejaculate volume and total sperm count per ejaculate remained unaltered. An obvious decrease in sperm motility was seen in all heat exposed boars 15–21 days after the exposure. The most consistent increase in sperm abnormalities were proximal cytoplasmic droplets and abnormal sperm heads. The highest levels were found during the 4th week after exposure. All the sperm characteristics assessed had returned to normal levels at the end of the experimental period, which means 7–8 weeks after the end of exposure.Only minor and inconsistent alterations were found in the seminal plasma components analysed and these changes were observed both in control and experimental boars.     

Semen quality and fertility after heat stress in boars

Sperm morphology and the fertilizing capacity of ejaculated spermatozoa were examined in 6 Swedish Landrace boars before and after heat stress. The boars were exposed to 35° C during 100 h in a climatic room. Fertility was measured by insemination of gilts before and at various times after heat stress. Each gilt (n = 44) was inseminated with a total of 5×10⁹ spermatozoa diluted to 10O ml with EDTA-glucose diluent and fertilization was assessed by examining recovered ova 2 days after insemination.Changes in semen quality varied among the boars from a very weak response in 2 boars to pronounced semen alterations occurring 2–6 weeks after heat stress in the other boars. A close relationship was found between seminal changes and fertilization rates, all ejaculates which had high fertilization rates being of the same quality as the pre-exposure ejaculates. The ejaculates that had poor fertility were characterized by lowered sperm motility and increased numbers of spermatozoa with abnormal heads, proximal cytoplasmic droplets and nuclear pouch formations.     

鸡热应激与热应激蛋白的作用机理研究

高温导致畜禽热应激问题的危害正日益突出并倍受关注。针对这些问题本刊推出“热应激专栏”,目的是为缓解夏季普遍存在的畜禽热应激提供理论和技术支持,使从业者能通过一些技术手段来规避热应激带来的损失。由于时间的仓促,本期组织的稿件内容覆盖面不是很全,但是以后会陆续推出有关内容,希望大家能继续关注。同时我们也希望专家、学者能踊跃地发表真知灼见与广大读者分享,把热应激理论、防制调控推到一个更高的阶段。     

克服热应激对母猪不利影响的措施

热应激通常是指在环境温度超过动物适温区上限时,体内产热与散热失衡导致的一系列生理与行为机能上的负面表现。生猪发生热应激程度与环境温度和湿度有关,也与动物的易感程度有关,就具体因素而言,主要受基因、营养和环境影响。     

Strategies to reduce feedlot cattle heat stress: effects on tympanic temperature

Three experiments were conducted to evaluate the effect of different management strategies on body temperature of feedlot steers finished in the summer months. In Exp. 1, 24 crossbred steers were chosen to assess the effect of altered feed intake and feeding time on tympanic temperature (TT) response. Managed feeding (MF) treatments were applied for 22 d only and provided 1) ad libitum access to feed at 0800 (ADLIB), 2) feed at 1600 with amount adjusted so that no feed was available at 0800 (BKMGT), 3) feed at 1600 at 85% of predicted ad libitum levels (LIMFD). During heat stress conditions on d 20 to 22 of MF, LIMFD and BKMGT had lower (P < 0.05) TT than ADLIB from 2100 through 2400. A carryover effect of limit-feeding was evident during a severe heat episode (d 36 to 38) with LIMFD steers having lower (P < 0.05) TT than ADLIB. In Exp. 2, TT were obtained from 24 crossbred steers assigned to three treatments, consisting of no water application (CON), water applied to feedlot mound surfaces from 1000 to 1200 (AM) or 1400 to 1600 (PM). From 2200 to 0900 and 1200 to 1400, steers assigned to morning sprinkling treatment had lower (P < 0.05) TT than steers assigned to afternoon sprinkling treatment. In Exp. 3, 24 steers were utilized in a 2 x 2 factorial arrangement of treatments with factors of feeding time [0800 (AMF) and 1400 (PMF)] and sprinkling (WET and DRY). Tympanic temperatures were monitored under hot environmental conditions on d 30 to 32 and 61 to 62. A feeding time x sprinkling interaction (P < 0.001) was evident on d 30 to 32, although AMF/DRY steers had the highest (P < 0.05) TT. On d 61 to 62, TT of PMF steers was higher (P < 0.05) than AMF between 1500 to 1800. Use of sprinklers can effectively reduce TT of feedlot cattle, whereas shifting to an afternoon vs morning feeding time was most beneficial when bunks were empty several hours prior to feeding.     

The effects of mutated skeletal ryanodine receptors on hypothalamic-pituitary-adrenal axis function in boars

The objectives of the current experiment were to determine whether boars heterozygous for the mutation in skeletal ryanodine receptors (sRyR), known to cause porcine stress syndrome, differed from wild-type boars in hypothalamic-pituitary-adrenal axis (HPA) function. We have examined basal plasma ACTH, cortisol, and corticosteroid-binding globulin (CBG) concentrations; plasma ACTH and cortisol responses to a nose-snare stressor and at slaughter; dexamethasone suppression of plasma ACTH and cortisol concentrations; and glucocorticoid receptor (GR) density in the pituitary gland, hippocampus, hypothalamus, and frontal cortex. We have also examined carcass yields, composition, and meat quality to determine whether differences in HPA activity were accompanied by an increased incidence of meat quality characteristics associated with pale, soft, exudative (PSE) meat. Thirty boars either heterozygous or wild-type (n = 15 per genotype) for mutated sRyR were tested for HPA function at 7 mo of age. Heterozygous boars had lower basal plasma ACTH (P < .05) and cortisol (P < .04) concentrations. Integrated basal plasma ACTH and cortisol levels were also lower (P < .05 and P < .005, respectively). Genotype had no significant effect on basal CBG, stressor-induced (nose snare or slaughter) or dexamethasone suppression of plasma ACTH or cortisol concentrations. No differences in immunoreactive GR levels were found in the pituitary gland or any brain region examined. We did find a significant, negative correlation (r = -.62, P < .02) between peak (0800) basal plasma ACTH concentrations and hippocampal GR levels. The alterations in basal HPA function in heterozygous boars were accompanied by lighter body weights (P < .03), decreased carcass fat depth (P < .04), and increased carcass lean yields (P < .02). There was a higher incidence of meat quality characteristics associated with PSE meat in heterozygous boars indicated by higher carcass temperatures (P < .04) and meat brightness (P < .0001) with lower carcass pH at slaughter (P < .03) and after chilling (P < .003). In conclusion, we have found differences in basal and not stressor-induced HPA function between boars heterozygous and wild-type for mutated sRyR. This altered basal HPA activity was accompanied by an increased incidence of meat quality aspects associated with PSE meat in heterozygous boars.     

Both experimental hypo- and hyper-thyroidism exacerbate the adverse effects of chronic heat stress in broilers

1. The effects of hypo- and hyper-thyroidism in mitigating or exacerbating the negative changes of chronic heat stress (HS) in broilers were investigated.

2. Three-week-old broilers were distributed into six groups (n = 13 per group). Three groups were housed at ambient room temperature: control group (CN), propylthiouracil-treated group (AN) and thyroxine-treated group (TN). The other three groups were exposed to HS at 33 ± 1°C for 2 weeks: control heat stress (CH), propylthiouracil + heat stress (AH) and thyroxine + HS (TH).

3. Induced hypothyroidy significantly decreased cloacal temperature and body weight gain in the birds in both the normal and HS groups (AN, AH). Conversely, hyperthyroidy resulted in a significant elevation in cloacal temperature in the TN and TH groups and a significant decline in weight gain in the TH group. Hyperthyroidy exacerbated the HS-induced degenerative changes in jejunal mucosa and caused noticeable vascular changes. A significant increase in the expression levels of jejunal nutrient transporter genes was observed in the AH and TH groups. The hyperthyroidic state significantly upregulated the HSP70 expression level in the TH group and the reverse occurred with propylthiouracil (PTU) treatment in the AH group.

4. PTU supplementation to chicks reared under HS significantly decreased the triiodothyronine level, antibody (Ab) titre, and increased the heterophil-lymphocyte ratio. Furthermore, it induced higher hepatic glutathione peroxidase (GSH-Px) activity in the AN and AH groups and decreased the malondialdehyde content (MDA) in the AN group. Hyperthyroidy significantly increased triiodothyronine concentration, H/L ratio and decreased Hb concentration and Ab titres in the TH group. Additionally, this status increased the MDA content and decreased the GSH-Px activities.

5. In conclusion, manipulation of thyroid status is not a remedy to overcome the undesirable effects of HS in broilers.     

Endocrine and sperminogenic testicular function. 7. Relationship between testicular and plasma androgen concentrations in boars of different ages]

Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were of different age groups. Against this background, comparative studies were conducted into the relationships between testicular and plasma testosterone. A very close correlation was found to exist between the androgen values in testicular tissue and those in the blood plasma of V. spermatica interna (r = 0.9795), wich appeared to support the conclusion that by determination of blood plasma the androgen content in the testes can be established with high probability.     

热应激条件下的家禽饲养

热应激降低家禽的生产性能，导致体内许多生物化学和生理性能的改变，持续热应激可致鸡只热衰竭而死亡。通过选择性饲喂和（或）饲喂高脂肪日粮可使这些生理变化得以改善。1　热应激应激是指动物在异常或极端情况下，机体非特异性应答反应和防御机能的总和。夏季高温使动物处于应激状态，引起行为学、生物化学和生理学方面的适应性变化，导致生产性能下降。热应激对蛋鸡产蛋的危害尤其严重，影响产蛋数和蛋重，降低蛋壳厚度，破蛋率上升，经济效益降低。高效生产的理想温度范围为18～21℃。如果环境温度长期高于24℃，则总产蛋数、蛋重和蛋…     

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。     

细胞工程技术选育的草地早熟禾新种质的耐热性分析

通过对离体培养的草地早熟禾丛生芽块进行高温处理,筛选出一批耐热性好的小芽。小芽成苗后移栽到花盆在自然条件下生长。半年后对这些株系和原品种的植株进行热胁迫处理,同时测定叶绿素荧光、丙二醛含量、离子渗漏率、叶绿素含量等生理指标的变化,得出细胞工程株系的植株耐热性明显较高,热胁迫处理后损伤程度小于原品种植株。表明利用细胞工程技术能有效获得耐热性显著提高的草地早熟禾植株,为选育草地早熟禾耐热新种质提供材料。     

甜菜碱在预防热应激方面的作用

研究表明,在肉鸡日粮中添加甜菜碱将有助于减少球虫感染、降低热应激和细胞渗透性.荷兰泰高禽兔研究中心(Nutreco Poultry and Kabbit Research Centre),通过试验对此理论进行了验证.Henk Enting和Jaco Eissen对此进行了详细解释.     

家禽热应激及其应对措施

家禽热应激是指高热环境下家禽的生理平衡被破坏与恢复的过程。这一过程的实现主要依赖于交感神经系统与下丘脑-垂体-肾上腺反应轴的激活,并涉及一系列内分泌的调整,其中肾上腺分泌的激素起到了重要作用。     

基于血清代谢组学研究Kisspeptin对热应激大鼠的保护作用

运用代谢组学方法研究神经肽Kisspeptin对热应激大鼠的保护作用。本试验通过建立热应激大鼠模型,基于气相色谱-飞行时间质谱联用技术(GC/TOFMS)代谢组学方法检测大鼠血清中内源性代谢物,并采用主成分分析及偏最小二乘判别法分析对照组、热应激组和Kisspeptin干预组之间的代谢物差异,筛选出潜在的生物标志物。代谢组学结果显示热应激组大鼠的血清代谢谱与正常对照组大鼠明显不同,而Kisspeptin干预后大鼠的血清代谢谱有趋于正常的趋势。生化代谢通路分析结果显示热应激引起大鼠三羧酸循环、糖代谢、氨基酸和核苷酸代谢异常,而热应激后给与Kisspeptin处理可缓解上述代谢通路的紊乱并趋于正常状态。此外,氧化应激指标检测结果显示给与Kisspeptin处理可降低热应激大鼠血清中丙二醛(MDA)含量,并提高超氧化酶歧化酶(T-SOD)、总抗氧化能力(T-AOC)和谷胱甘肽过氧化物酶(GSH-Px)的活力,该结果表明Kisspeptin在一定程度上缓解了热应激诱导的氧化应激。该研究从代谢及抗氧化的角度研究了Kisspeptin对热应激大鼠的保护作用,为动物健康养殖和开发抗热应激的安全生物制品提供试验依据。     

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。     

家禽热应激的防制措施

在各种可能的应激中,热应激或许是最有现实意义的一类,因为它能造成严重的经济损失。为了减轻热应激的损害,科研工作者已经研究出一系列的防治措施。本文仅就如何抵御家禽的热应激问题作一论述。1加强育种工作选育抗应激品种是减少应激的根本点和出发点。只有对气候应?..