早期热习服对肉鸡机体的影响

由于肉鸡在胚胎和雏鸡阶段体温调节和神经反馈机制还未发育完善,通过早期热习服能够影响肉鸡的基础代谢、体温调节以及其他生理生化机能,使机体提高对高温环境适应能力,提高肉鸡后期的耐热力。1早期热习服对体温调节机能的影响热习服是一种热锻炼过程,是增加机体耐受高温能力的     

肉鸡早期热习服的研究

孵化后期热习服和育雏早期热习服对肉鸡的内分泌激素,体温调节,生产性能,热休克蛋白以及免疫机能等有着广泛的作用,且有一定的规律。本文试通过总结前人的研究成果推测肉鸡早期热习服内在的一些规律,以图为进一步的研究提供理论指导。     

肉鸡热习服时间点温湿度以及持续时间控制初探

多年来,国内外热生理学家试图通过耐热性的训练,即热习服提高肉鸡生长过程中的耐热能力。而热习服时间点、强度以及持续时间的控制对热习服的效果起着决定性的作用。本文在前人研究基础上,初探肉鸡最佳的热习服时间点、温湿度以及持续时间,以求获得肉鸡耐热能力、生产性能等的同步提高。     

早期热习服对肉鸡后期热暴露肛温、血液生化指标的影响

本试验研究了5d雏鸡经过热习服处理(温度39.0℃,RH60%,24h)在生长后期第4、5、6周龄遭受3周的35.2℃(高温)和37.6℃(极端高温)的热暴露,对肉鸡肛温和血液生化指标的影响.结果表明:早期热习服提高了机体的肛温,可能提高了对后期高温热应激的热耐受阈值;早期热习服能通过有效调节机体的白蛋白和球蛋白等生化反应能力而提高对高温环境的耐热力.     

肉鸡早期热服习的研究进展

总结分析了国内外有关肉鸡早期热服习的研究文献,归纳了肉鸡机体的体温调节机能、甲状腺和肾上腺机能、抗氧化机能、机体内脏器官的发育、血液生理生化指标以及HSP70与机体抗逆机能的相关性,探讨早期热服习提高肉鸡后期耐热力的机理。     

肉鸡早期热服习的研究进展

总结分析了国内外有关肉鸡早期热服习的研究文献,归纳了肉鸡机体的体温调节机能、甲状腺和肾上腺机能、抗氧化机能、机体内脏器官的发育、血液生理生化指标以及HSP70与机体抗逆机能的相关性,探讨早期热服习提高肉鸡后期耐热力的机理.     

孵化后期热习服对肉鸡孵化率和体温影响的研究

肉鸡在生命早期阶段是一种变温动物,低的环境温度能够降低体温,而高的环境温度对肉鸡的生长发育会产生影响。因此,对肉鸡的胚胎阶段进行高温应激可能产生行为的、生理的、内分泌的和分子水平的变化。研究通过在胚胎孵化的16~18 d进行热习服处理,旨在弄清热习服是否能够有效地改     

肉鸡早期热习服的研究

随着现代养殖业的发展,通过基因选育出的肉鸡极大地提高了肉鸡的生长速度,但同时由于内脏系统发育的迟缓促使了肉鸡在生长后期应对极端环境的能力显著降低。热应激等应激原和致病原成为了制约肉鸡养殖业健康发展的重大障碍。特别是热应激不仅可影响鸡的正常生理功能,而且对鸡的免疫功能及所用疫苗发挥正常的免疫作用产生影响,这将会成为多种疾病的诱因。人们试图通过营养调控、改善肉鸡生产设施等手段来降低热应激造成的肉鸡疾病的发生率和致死率,但效果都不太显著。肉鸡孵化后期和育雏早期的体温调节等生理机制还没有发育完善,采取适当的调…     

早期热习服对肉鸡体热调节影响的探讨

1早期热习服据发表在2001年《The Japanese Journal of Physiology》第51卷第2期上的热生理学术语表中的定义,习服(Acclimation)指动物个体在生命过程中所产生的能够缓解实验条件下某种气候因素所引起的生理紧张状态的反应。而热习服主要针对温度而言,Horowitz等(2002)[1]研究认为热     

热习服有助肉仔鸡抵御热应激

<正>高温环境中,快速生长的肉仔鸡较难散热(维持体温),会出现生产性能较差、死亡率高等问题,从而造成经济损失。早期热习服(5日龄,36℃,48 h)可提高随后生长过程中肉仔鸡对热应激的抵御能力。前期研究表明,与对照组相比,早期热习服肉仔鸡可     

A model of thermal acclimation in cattle

A model of temperature effects on cattle daily feed intake has been developed that takes into account (1) time course of thermal acclimation and (2) behavioral responses to short-term thermal stress (STTS). The key difference between this model and the classical intake-temperature model is its consideration of the acclimation state of the animal. Time course of physiological acclimation is represented by a running average temperature. The STTS is defined as the difference between the current acclimated temperature [Tacci(L)] and current daily mean temperature (Ti). Ruminants were postulated as decreasing activity in response to STTS. An empirical relationship between daily feed intake (I) and environmental temperature was derived as: I = 100% - b'[Ti - Tacci(L)]2. Length of the acclimation period, L, and value of the behavioral response coefficient, b', were determined for grazing time of free-roaming cattle and feed intake of five breeds of feedlot cattle. Cattle breeds displayed apparent differences in L but no significant differences in b'. Feeding situation (feedlot vs free-roaming) had a significant effect on b' in cattle, but not on L. Because of explicit treatment of acclimation and stress, two-dimensional representation of thermal environment may be a more meaningful expression of effective environmental temperature in fluctuating environments than mean daily temperature alone. This model may have value in the interpretation of laboratory studies, as well as field studies, because the time frame of experiments will influence the results obtained, depending upon the acclimation state of the animal.     

Effects of cool and hot humid environmental conditions on neuroendocrine responses of horses to treadmill exercise

To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline, noradrenaline, beta-endorphin and cortisol concentrations, five horses performed a competition exercise test (CET; designed to simulate the speed and endurance test of a three-day event) in cool dry (CD) (20 degrees C/40% RH) and hot humid (30 degrees C/80% RH) conditions before (pre-acclimation) and after (post-acclimation) a 15 day period of humid heat acclimation. Plasma adrenaline and noradrenaline concentrations pre-acclimation were significantly increased compared with exercise in the CD trial at the end of Phases C (P<0.05) and D (P<0.05 and P<0.01, respectively) and at 2 min recovery (P<0.01), with adrenaline concentrations still elevated after 5 min of recovery (P<0.001). Plasma beta-endorphin concentrations were increased at the end of Phases C (P<0.05) and X (P<0.01) and at 5 and 30 min recovery (P<0.05) in the pre-acclimation session. Plasma cortisol concentrations were elevated after the initial warm up period pre-acclimation (P<0.01) and at the end of Phase C (P<0.05), compared with the CD trial. A 15 day period of acclimation significantly increased plasma adrenaline concentrations at 2 min recovery (P<0.001) and plasma cortisol concentration at the end of Phase B (P<0.01) compared with pre-acclimation. Acclimation did not significantly influence noradrenaline or beta-endorphin responses to exercise, although there was a trend for plasma beta-endorphin to be lower at the end of Phases C and X and after 30 min recovery compared with pre-acclimation. Plasma adrenaline, noradrenaline, beta-endorphin and cortisol concentrations were increased by exercise in cool dry conditions and were further increased by the same exercise in hot humid conditions. Exercise responses post-acclimation suggest that adrenaline and noradrenaline may play a role in the adaptation of horses to thermal stress and that changes in plasma beta-endorphin concentrations could be used as a sensitive indicator of thermal tolerance before and after acclimation. The use of plasma cortisol as a specific indicator of heat stress and thermal tolerance before or after acclimation in exercising horses appears limited.     

The development of thermal resistance of the feather coat in broilers with different feathering genotypes and feeding regimes

1. This study compared the development of thermal resistance of the feather coat in broilers, with early or late feathering genes, and with or without the naked neck gene, allowed ad libitum or restricted feeding. 2. Male and female broilers of one of the 4 genotypes were reared to 6 weeks of age and allocated to one of the two feeding regimes. The thermal resistance of the back and crop region was measured at weekly intervals. A sample of birds were killed at the same ages and total feather weight, primary and secondary flight feather weight, liver weight and abdominal fat weight were measured. 3. All three main factors, sex, feeding and genotype, had significant effects on feather weight over time. The primary and secondary flight feathers were less affected by feed restriction than the feather coat as a whole. Birds with the naked neck gene showed a greater depression in growth rate than birds with a normal neck under conditions of restricted feeding. 4. The thermal resistance of the feathers on the back was greater in females, increased by early feather growth and decreased by restricted feeding. 5. Relative to metabolic body size, birds on restricted feeding had a greater feather weight and a smaller liver. There was a marked reduction in fat deposition, to almost negligible levels by 6 weeks of age. 6. Broilers given restricted feeding, in preparation for breeding, would benefit by a warmer environment, particularly those with feathering genotypes which confer a lower thermal resistance.     

Temperature and mass scaling affect cutaneous and pulmonary respiratory performance in a diving frog

Global climate change is altering patterns of temperature variation, with unpredictable consequences for species and ecosystems. The Metabolic Theory of Ecology (MTE) provides a powerful framework for predicting climate change impacts on ectotherm metabolic performance. MTE postulates that physiological and ecological processes are limited by organism metabolic rates, which scale predictably with body mass and temperature. The purpose of this study was to determine if different metabolic proxies generate different empirical estimates of key MTE model parameters for the aquatic frog Xenopus laevis when allowed to exhibit normal diving behavior. We used a novel methodological approach in combining a flow-through respirometry setup with the open-source Arduino platform to measure mass and temperature effects on 4 different proxies for whole-body metabolism (total O₂ consumption, cutaneous O₂ consumption, pulmonary O₂ consumption, and ventilation frequency), following thermal acclimation to one of 3 temperatures (8°C, 17°C, or 26°C). Different metabolic proxies generated different mass-scaling exponents (b) and activation energy (E_A) estimates, highlighting the importance of metabolic proxy selection when parameterizing MTE-derived models. Animals acclimated to 17°C had higher O₂ consumption across all temperatures, but thermal acclimation did not influence estimates of key MTE parameters E_A and b. Cutaneous respiration generated lower MTE parameters than pulmonary respiration, consistent with temperature and mass constraints on dissolved oxygen availability, SA:V ratios, and diffusion distances across skin. Our results show that the choice of metabolic proxy can have a big impact on empirical estimates for key MTE model parameters.     

Acclimation to high ambient temperature in Large White and Caribbean Creole growing pigs

The effect of breed [Creole (CR) vs. Large White (LW)] on performance and physiological responses during acclimation to high ambient temperature was studied in 2 experiments involving 24 (12/breed) growing pigs each. Pigs were exposed to 24 degrees C for 10 d (d -10 to -1) and thereafter to a constant temperature of 31 degrees C for 16 d (d 1 to d 16) in Exp. 1 and for 20 d (d 1 to d 20) in Exp. 2. For both experiments, the temperature change was achieved over 4 h on d 0. The first experiment began at 105 d of age, and the average BW of CR and LW pigs was 36.6 +/- 2.5 kg and 51.7 +/- 3.0 kg, respectively. The second experiment was designed to compare both breeds at a similar BW (about 52 kg on d 0). Pigs were individually housed and given ad libitum access to feed. At 24 degrees C, ADG was lower (P < 0.01) in CR than in LW (602 vs. 913 g/d and 605 vs. 862 g/d in Exp. 1 and 2, respectively), but the ADFI was not affected by breed (190 and 221 g x d(-1) x kg(-0.60) in Exp. 1 and 2, respectively). Short-term thermoregulatory responses during the 4-h transition from 24 to 31 degrees C (d 0) were analyzed according to a linear plateau model to determine the break point temperature, above which rectal temperature (RT), cutaneous temperature (CT), and respiratory rate (RR) began to change. The CT increased linearly with temperature increase (0.22 degrees C/ degrees C) and was less (P < 0.05) in CR than in LW (by -0.3 degrees C on average). In both experiments, the break point temperature for RT was not affected by breed (27.6 degrees C on average), whereas for RR it was greater (P < 0.05) in CR than in LW (27.5 vs. 25.5 degrees C, P < 0.01). On average, ADFI declined by about 50 g x d(-1) x kg(-0.60) from d -1 to d 1 (P < 0.01), and thereafter at 31 degrees C, it gradually increased (23 g x d(-1) x kg(-0.60); P < 0.05), suggesting an acclimation to high exposure. This response was not influenced by breed. After the day that marked the beginning of the acclimation response (i.e., the threshold day), RR, CT, and RT declined over the duration of exposure to 31 degrees C (P < 0.05) in both experiments. During this period, RT and CT were less in CR than in LW pigs (39.6 vs. 39.9 degrees C and 37.9 vs. 38.2 degrees C, respectively; P < 0.05), whereas RR was not affected by breed. The threshold day at which RT began to decline was less in CR than in LW pigs (0.18 vs. 1.17 d and 0.39 vs. 0.93 d in Exp. 1 and 2, respectively; P < 0.05). In conclusion, this study suggests that short- and long-term physiological reactions during heat acclimation differed when CR and LW pigs were compared at the same age or BW.     

基于KEGG通路分析紫花苜蓿的冷适应过程

低温是影响我国苜蓿(Medicago stavia L.)种植推广的限制性因素,且苜蓿对低温的冷适应机制亦不完全清楚。本研究利用高通量测序技术,测定‘肇东’和‘WL440HQ’苜蓿在冷适应前后的基因表达。筛选差异表达基因后,分析与冷适应低温环境和苜蓿抗寒性提高有关的生物通路以及造成冷适应后苜蓿抗寒性出现差异的可能原因。结果表明：细胞信号转导和物质代谢(包括糖、蛋白质和脂等)等通路,不仅是苜蓿对冷适应低温环境的响应,还可能与其抗寒性的提高有关,如植物激素信号转导、淀粉和蔗糖代谢和植物MAPK信号通路等。冷适应后苜蓿抗寒性出现差异是多种生物通路共同作用下的结果,其中主要涉及物质代谢(包括脂肪酸和氨基酸等)和能量代谢等通路,特别是氨基酸和脂肪酸代谢。本研究将为苜蓿抗寒机制的深入研究提供数据支持。     

Early life thermal stress: impacts on future temperature preference in weaned pigs (3 to 15 kg)

Thermal stress can result in productivity losses, morbidity, and mortality if proper management practices are not employed. A basic understanding of the relationship between animals and the thermal environment is crucial to assess the environment’s impact on livestock performance. Therefore, the study objective was to evaluate whether different early life thermal stressors (ELTS) altered the temperature preference of pigs later in life. Twelve sows and their litters were randomly exposed to 1 of 3 ELTS treatments from 7 to 9 d of age: early life heat stress (ELHS; cycling 32 to 38 °C; n = 4), early life cold stress (ELCS; 25.4±1.1 °C without heating lamp; n = 4), or early life thermoneutral (ELTN; 25.4±1.1 °C with a heating lamp; n = 4) conditions. From 10 to 20 d, (weaning) all piglets were exposed to ELTN conditions. At weaning, pigs were randomly assigned to groups of 4 of the same sex and ELTS treatment. Temperature preference, where pigs freely choose a temperature, was assessed in 21 groups (n = 7 groups per ELTS treatment) using 1 of 3 thermal gradient apparatuses (22 to 40 °C). Testing began at 26 ± 1.3 d of age to give pigs time to acclimate to solid food after weaning and 1 group per ELTS treatment were tested simultaneously in each apparatus. Pigs were given 24 h to acclimate followed by a 24-h testing period. Behavior (active and inactive), posture (upright, sternal, and lateral lying), and location were documented every 20 min using instantaneous scan samples. Preferred feeding temperature was determined by the latency to empty a feeder in each location. Data were analyzed using PROC MIXED in SAS 9.4. A cubic regression model was used to calculate the peak temperature preference of pigs based on the temperature pigs spent most of their time. The preference range was calculated using peak temperature preference ±SE for each ELTS treatment group. Early life thermal stress altered where pigs spent most of their time within the thermal gradient (P = 0.03) with ELTN pigs preferring cooler temperatures (peak preference of 23.8 °C) compared with their ELCS exposed counterparts (peak preference of 26.0 °C; P < 0.01). However, ELHS exposed pigs (peak preference of 25.6 °C) did not differ in their temperature preference compared with ELTN or ELCS exposed counterparts (P > 0.05). In summary, ELCS exposure altered pig temperature preference later in life indicating that ELTS can alter temperature preference in pigs.     

Housing and climatic conditions for early weaned piglets

The recent results of research carried out on housing and climatic conditions for early weaned piglets are reviewed in the present paper.Piglets weaned at 3–4 weeks of age are, in most cases, raised on a totally wired floor in weaning houses. The optimum area per animal and the number of piglets per pen depend on their age and weight at entry and leaving of the weaning house, respectively. The “all-in-all-out” management system is shown to improve the growth performance of piglets.The effects of some physical components of the thermal environment (air temperature, wind speed and relative humidity) on the growth, energy and nitrogen metabolism of the piglet were analysed. An interaction between the air temperature and the feeding level, on the one hand, and the air temperature and the management system (type of floor, piglets raised individually or in groups) on the other, was found. However, no definite conclusions can be drawn about the optimum environmental conditions for early weaned piglets.     

Thermoregulation and evaporative water loss in growing African giant rats Cricetomys gambianus

Kalahari Gemsbok National Park, Private Bag X5890, Upington, 8800 Republic of South AfricaWith an increase in mass, weaned giant rat pups Cricetomys gambianus, showed a corresponding decline in mass specific metabolism, conductance and evaporative water loss. The decline in metabolism correlates better with mass than age, while conductance correlates better with age than mass. After 77 days of age the relative importance of dry thermal conductance increased and this is attributed to the testes becoming scrotal, and acting as a thermal window. The final desertion of the nest by young is suggested to coincide with the advent of an efficient thermoregulatory capacity.