热应激对奶牛的影响及防控措施

夏季气温较高会使奶牛产生热应激,导致奶牛采食量、生产性能下降,严重的还会引起奶牛死亡.本文根据当地热应激发生的状况,探讨热应激对奶牛的影响,并给出了防控热应激的措施,以期减少热应激造成的损失,提高养殖场的经济收入.     

奶牛的热应激及其防控措施

综述了热应激的发生及热应激对奶牛生产性能、繁殖力和免疫力等方面的影响,并提出奶牛热应激防控措施。     

奶牛热应激及抗热应激措施

大量实验表明,夏季酷暑季节,奶牛的呼吸频率加快、心跳次数增加、体温升高、食欲下降、奶量减少。据金仰高门988）分析调查,认为中国黑白花奶牛的适宜温度为11～16’C。由于奶牛主要靠辐射、传导、对流和蒸发方式散热,因此,当环境温度上升时,奶牛体温和环境的温差缩小,奶牛散热困难,易出现热应激现象。有试验报道：当环境温度接近24’C时,奶牛便开始出现热应激现象。表现为泌奶性能F降,同时,当环境温度持续上升时（41C）,黑白花ha往往减少乳量50％以上。据报道,由于环境温度的上升,奶牛依赖于出汗和增加呼吸的次数等方式散…     

热应激对奶牛的影响及缓解热应激的营养措施

热应激导致奶牛夏季产奶性能、繁殖性能和免疫能力降低,造成奶牛业巨大的经济损失。因此,研究奶牛热应激机制及其对策已受到国内外的广泛重视。为缓解奶牛热应激采取的主要措施包括营养调控、环境调控和育种途径。由于经济成本和奶牛品种的生物学特征等原因,目前奶牛业主要采用营养调控为主、环境调控为辅的综合措施。文章综述了奶牛热应激的作用机理与营养措施的研究进展。     

应激对奶牛生产的影响及防控措施

在集约化养殖业中,影响奶牛生理活动的应激原日趋增多,在目前无法完全消灭应激原的情况下,养殖者可针对应激产生的原因采取有效的防控措施,将应激危害降到最低,最大限度地发挥奶牛的生产性能,这对提高牧场的经济效益具有重要的意义。现对奶牛生产中常见的应激如热应激、冷应激、断奶应激、运输应激、生殖应激以及这些应激产生的原因、机制及对奶牛生产的影响予以介绍,并提出合理的防控措施。     

奶牛热应激及应对措施

热应激可导致奶牛采食量下降,能量摄入减少,处于代谢负平衡状态,影响奶牛生产性能发挥,造成繁殖障碍,代谢紊乱,已成为危害奶牛生产的重要因素。本文就奶牛热应激表现及信号,热应激的危害及应对措施进行论述,以期为广大养殖者提供参考。     

浅谈热应激对奶牛的影响及调控措施

在炎热的夏季,热应激会导致奶牛生理机能发生紊乱,采食量下降,生产性能降低,甚至导致奶牛发病,严重者造成死亡。预防夏季奶牛热应激的发生,为奶牛创造适宜的、良好的饲养环境,可使奶牛安全、顺利地度过炎热的夏季,防止热应激造成不必要的损失。笔者等从奶牛热应激发生的原因与生理机制入手,综合论述热应激对奶牛的危害和预防热应激的调控措施。     

综合营养措施对热应激奶牛的影响

作者研究了补充矿物质、添加过瘤胃蛋白、提高日粮蛋白质水平、添加烟酸等综合营养措施对采食秸秆型日粮奶牛的抗热应激能力的影响.结果表明,综合营养措施可以缓解奶牛热应激,并极显著提高干物质采食量、产奶量和经济效益(P＜0.01).     

热应激对肉鸭的影响及防控措施

肉鸭在适宜的温度范围内才能发挥其最佳的生产性能。当环境温度过高时,肉鸭就会发生热应激综合症,导致采食量减少,生长发育和饲料转化率降低,对疫病的易感性增加。在湿热的夏季应采取综合防治措施,减少肉鸭热应激的危害,发挥肉鸭群正常的生产性能,以增加养殖效益。     

热应激对奶牛血液中内毒素含量和抗氧化指标的影响

选用16头健康的中国荷斯坦奶牛,随机分为两个处理（夏季组和冬季组）,每个处理8个重复,每个重复1头牛。当夏季组奶牛牛舍温湿度指数（THI）〉72的时间连续达到15d,冬季组牛舍THI〈72的时间连续达到15d时,颈静脉采血15mL制备血清,检测血清中内毒素、超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）的活性,以及丙二醛（MDA）的含量。结果表明：夏季热应激可导致奶牛血清内毒素、MDA含量极显著升高,SOD和GSH-Px活性极显著和显著（P〈0.05）下降。     

氧化应激对奶牛的危害及其防治

氧化应激是当机体遭受到体内外各种有害刺激时,氧化系统和抗氧化系统失衡,自由基的产生量超过机体的清除能力,抗氧化系统不能及时清除过多的自由基而造成的。氧化应激与多种疾病的发生相关。奶牛的代谢水平高,更易发生氧化应激。本文就奶牛氧化应激的产生、氧化应激对奶牛的影响以及如何抑制奶牛氧化应激做一综述。     

Metabolic adaptations to heat stress in growing cattle

To differentiate between the effects of heat stress (HS) and decreased dry matter intake (DMI) on physiological and metabolic variables in growing beef cattle, we conducted an experiment in which a thermoneutral (TN) control group (n = 6) was pair fed (PF) to match nutrient intake with heat-stressed Holstein bull calves (n = 6). Bulls (4 to 5 mo old, 135 kg body weight [BW]) housed in climate-controlled chambers were subjected to 2 experimental periods (P): (1) TN (18 °C to 20 °C) and ad libitum intake for 9 d, and (2) HS (cyclical daily temperatures ranging from 29.4 °C to 40.0 °C) and ad libitum intake or PF (in TN conditions) for 9 d. During each period, blood was collected daily and all calves were subjected to an intravenous insulin tolerance test (ITT) on day 7 and a glucose tolerance test (GTT) on day 8. Heat stress reduced (12%) DMI and by design, PF calves had similar nutrient intake reductions. During P1, BW gain was similar between environments and averaged 1.25 kg/d, and both HS and PF reduced (P < 0.01) average daily gain (-0.09 kg/d) during P2. Compared to PF, HS decreased (P < 0.05) basal circulating glucose concentrations (7%) and tended (P < 0.07) to increase (30%) plasma insulin concentrations, but neither HS nor PF altered plasma nonesterified fatty acid concentrations. Although there were no treatment differences in P2, both HS and PF increased (P < 0.05) plasma urea nitrogen concentrations (75%) compared with P1. In contrast to P1, both HS and PF had increased (16%) glucose disposal, but compared with PF, HS calves had a greater (67%; P < 0.05) insulin response to the GTT. Neither period nor environment acutely affected insulin action, but during P2, calves in both environments tended (P = 0.11) to have a blunted overall glucose response to the ITT. Independent of reduced nutrient intake, HS alters post-absorptive carbohydrate (basal and stimulated) metabolism, characterized primarily by increased basal insulin concentrations and insulin response to a GTT. However, HS-induced reduction in feed intake appears to fully explain decreased average daily gain in Holstein bull calves.     

南方规模化猪场和散养户夏季热应激防控措施

热应激可影响猪的健康状况、采食量和内分泌等活动,导致体内生理生化过程发生剧烈改变,进而影响猪采食量以及饲料转化率。因此,采取有效措施缓解或消除热应激对养猪业造成的严重影响对指导规模化养猪业生产具有十分重要的意义。     

热应激对反刍动物营养物质消化、瘤胃发酵、甲烷生成的影响及缓解热应激的措施

热应激是影响动物生产的重要因素.正常的瘤胃功能是反刍动物健康生产的重要保证.了解热应激对瘤胃功能的影响,有利于针对性地采取营养措施缓解热应激造成的对反刍动物的不利影响.文章主要综述热应激对反刍动物营养物质消化、瘤胃发酵、甲烷生成的影响及缓解热应激的措施.     

Effects of short-term cooling on pregnancy rate of dairy heifers under summer heat stress

Thermal stress in cattle results in major decreases in dairy production and reproduction. A study was designed to evaluate the influence of temporary cooling on pregnancy rate in Holstein heifers during summer heat stress. Estrus was synchronized with two injections of prostaglandin (PG), administrated 11 d apart, and all heifers were housed in a shaded enclosed structure at the time of the second PG injection. After estrus detection, heifers were randomly divided into three groups: Control (C; n = 30), Sprinkler (S; n = 30) or Sprinkler and Fan (SF; n = 30). Rectal temperatures were measured 2.5 hours before AI, at the time of AI, and 1.5 and 3.5 hours after AI. Group C heifers receive no further treatment, but heifers in S and SF groups were exposed to short-term cooling from 2 hours before until 2 hours after AI with a sprinkler (S) or sprinkler and a fan (SF), respectively. Estrus detection and AI were performed by a single skilled technician; semen was from a bull of known fertility. Rectal temperature did not differ among groups 2.5 hours before AI, but at the time of AI was lower (P < 0.05) in SF group (39.3 ± 0.0°C) than in S (39.5 ± 0.0°C) and C (39.9 ± 0.1°C) groups which also differed (P < 0.05). At 1.5 and 3.5 hours after AI, rectal temperature remained lower in SF group (38.9 ± 0.0 and 38.7 ± 0.0°C, respectively) than in the S (39.4 ± 0.0 and 39.2 ± 0.0°C, respectively) and C (39.3 ± 0.0 and 39.3 ± 0.0°C, respectively) groups, which no longer differed. Pregnancy rate following AI was higher (P < 0.05) in SF group (56.7%) than in the C group (23.3%) with the S group (40%) intermediate and not different from either. The present study results indicate that cooling of dairy heifers for a short time before and after AI, especially with sprinkler and fan, can increase pregnancy rate during heat stress.     

Effects of heat stress on the endometrial epidermal growth factor profile and fertility in dairy cows

The endometrial epidermal growth factor (EGF) profile is an indicator of uterine function and fertility in cattle. The present study aimed to investigate the effects of heat stress on the endometrial EGF profile and fertility in lactating Holstein cows. The endometrial EGF profiles of 365 cows in the Hokkaido and Kyushu regions were examined between June and September (heat stress period, n = 211) and between October and January (control period, n = 154). EGF profiles were investigated using uterine endometrial tissues obtained by biopsy 3 days after estrus (Day 3). The proportion of cows with an altered EGF profile was higher between June and September than between October and January (41.2 vs. 16.2%, P < 0.05). The effects of rectal temperature on Days 0 and 3 on the endometrial EGF profile were also assessed in cows (n = 79) between June and September in the Kyushu region. A single embryo was transferred to cow on Day 7 to evaluate fertility (n = 67). Regardless of the rectal temperature on Day 3, the proportion of cows with an altered EGF profile was higher (64.1 vs. 30.0%, P < 0.05) and the pregnancy rate after embryo transfer (ET) was lower (26.7 vs. 51.4%, P < 0.05) in cows with a rectal temperature ≥ 39.5°C on Day 0 than in cows with a rectal temperature < 39.5°C on Day 0. The present results indicate that alterations in the endometrial EGF profile induced by an elevated body temperature on Day 0 contributed to reductions in fertility in lactating dairy cows during the heat stress period.     

山区牛场寄生虫病调查及防治措施

根据调查方案和流行病学特点,采取随机采样、粪检、屠宰检验和镜检等方法,对宁化县张某牛场牛感染寄生虫的情况进行初步调查。调查结果表明：不同季节、不同日龄的牛都不同程度感染不同类群的寄生虫,通过调查进而探讨牛寄生虫病的防治措施。