热应激对奶牛生产的影响及应对策略

奶牛热应激是气候变化对奶牛生产性能和生理性反应的总称.随着近年来全球气候变暖,热应激严重影响了奶牛的健康和生产性能,给奶牛养殖业造成了巨大的经济损失.综述了热应激对奶牛生产影响的因素、机制及缓解途径.     

奶牛热应激的危害及防治措施

奶牛热应激是奶牛机体应对高温天气的非特异性应答反应,严重影响奶牛生产性能与健康.本文综述了奶牛热应激的概念机理、诊断方法以及防治措施,为进一步研究提供参考.奶牛是一种耐寒怕热的动物,适合于气候凉爽地带饲养.每年夏季高温天气,我国南方大部分地区奶牛均会发生不同程度的热应激反应,严重影响奶牛生产性能和健康.随着奶牛养殖业的高度集约化发展,奶牛热应激综合征发生率不断上升,其危害日益突出,并已成为阻碍奶业发展的最活跃因素之一.     

奶牛对热应激的适应性机制及牧场缓解热应激策略

热应激是限制奶牛生产最重要的因素之一,它对奶牛的生产力、健康、繁殖和整体福利都会产生重大影响,并且随着热应激程度的加深对奶牛造成致命性影响。全球变暖加剧了热应激的负面影响。动物会通过改变其表型和生理特征来应对不断变化的环境,动物的生存能力通常取决于其应对或适应现有条件的能力。奶牛是恒温动物,通过减少代谢热量产生与体温调节等来应对并适应热应激,但这会以牺牲掉部分生产性能为代价。本文综述了热应激对奶牛泌乳性能的影响、热应激下泌乳性能降低的原因、奶牛对热应激的适应机制以及牧场应对热应激的策略,为奶牛热应激的研究及生产中改善奶牛热应激等提供参考。     

奶牛热应激及其营养调控研究进展

随着全球性气候变暖,奶牛生产规模化程度不断提高、高产奶牛不断选育,热应激已成为全球乳制品行业面临的重要挑战。热应激程度与外界环境因素和奶牛自身因素有关。夏季热应激会导致奶牛产奶量降低、乳成分改变和繁殖性能下降,还会给奶牛健康、免疫和福利带来负面影响。营养调控措施在缓解奶牛热应激方面起到重要作用。本文概述了奶牛热应激的产生及其对生产、繁殖、健康与福利的影响,总结了通过营养调控策略缓解奶牛热应激的研究进展,展望了奶牛热应激的未来研究方向。     

热应激对奶牛的危害及营养调控措施

随着全球气候变暖，奶牛养殖中的热应激成为畜牧养殖行业的研究热点之一。热应激对奶牛的生产性能及机体健康福利均会造成不同程度的负面影响，不仅会降低奶牛的采食量和产奶性能，还会损害其繁殖能力和机体免疫力。文章总结了热应激对奶牛的危害，并从饲粮结构、饲料添加剂等方面阐述了预防与缓解奶牛热应激的营养调控措施，从而降低热应激对奶牛的负面影响。文章对提高高温季节奶牛产奶量、改善乳品质具有重要意义。     

浅析热应激对奶牛生理机能的影响

热应激会导致奶牛采食量减少、营养负平衡、免疫力降低等,使得奶牛健康水平严重下降,甚至影响奶牛的生产性能,降低牧场的经济效益,影响奶牛养殖业的可持续健康发展。本文就夏季热应激对奶牛生理机能造成的危害进行探讨,旨在为牧场防控热应激提供理论依据。     

热应激对奶牛生产的影响及应对策略

奶牛热应激是气候变化对奶牛生产性能和生理性反应的总称。随着近年来全球气候变暖,热应激严重影响了奶牛的健康和生产性能,给奶牛养殖业造成了巨大的经济损失。综述了热应激对奶牛生产影响的因素、机制及缓解途径。     

热应激对奶牛生产的影响及应对策略

奶牛热应激是气候变化对奶牛生产性能和生理性反应的总称。随着近年来全球气候变暖,热应激严重影响了奶牛的健康和生产性能,给奶牛养殖业造成了巨大的经济损失。综述了热应激对奶牛生产影响的因素、机制及缓解途径。     

巧用饲料添加剂预防奶牛热应激

在高温季节,大部分奶牛会发生不同程度的热应激反应,严重影响奶牛生产性能和健康.许多研究发现,日粮中加入某些饲料添加剂,可以缓解热应激对奶牛的不良影响.     

热应激对奶牛生产和健康的影响及其减缓措施研究进展

夏季热应激给奶牛的产奶性能、瘤胃健康、免疫机能和繁殖性能等方面带来了一定的负面影响,严重危害着奶牛健康,成为制约我国奶业健康发展的重要因素之一。本文探讨了热应激发生的原因及对奶牛生产的负面影响,并从品种选育、饲养管理和营养调控等方面总结了减缓热应激相关措施的研究进展,以期为奶牛热应激的综合防控提供参考。     

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.     

Furosemide continuous rate infusion in the horse: evaluation of enhanced efficacy and reduced side effects

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.     

Prevalence of gastric lesions in racing Alaskan sled dogs

Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.     

The Epidemiology of Gastrointestinal Nematodes of Dairy Cattle in Central Kenya

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bi-monthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March–June and October–December) and lowest during the dry seasons (July–September and January–February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.     

Diversity of Ectoparasites in Sheep Flocks in Sa~o Paulo,Brazil

The occurrence of ectoparasites in sheep flocks is frequently reported but seldom quantified. Sheep production used to be a predominantly family activity in the state of Sa~o Paulo (Brazil), but it began to become a commercial activity in the past decade. Thus, information about the ectoparasites existing in sheep flocks has become necessary. The present data were obtained by means of questionnaires sent to all sheep breeders belonging to the `Associaça~o Paulista de Criadores de Ovinos' (ASPACO; Sa~o Paulo State Association of Sheep Breeders). Response reliability was tested by means of random visits paid to 10.6% of the respondents. Most of the properties (89.5%) reported the presence of one or more ectoparasites. Screw-worm (Cochliomyia hominivorax) was the most frequent ectoparasite (72.5%), followed by bot fly larvae (Dermatobia hominis, 45.0%), ticks (Amblyomma cajennense) and Boophilus microplus, 31.3%) and finally lice (Damalinia ovis, 13.8%). Combined infestations also occurred, the most common one being screw-worm with bot fly larvae (36.0%) followed by bot fly larvae with ticks (13.9%), screw-worm with ticks (9.3%), bot fly larvae with lice (6.9%), and ticks with lice (5.0%). The most common triple combination was screw-worm, bot fly larvae and ticks (12.8%). Breeds raised for meat or wool were attacked by bot fly larvae and ticks more often than other breeds. Lice were only absent from animals of indigenous breeds. The relationships among these ectoparasites are discussed in terms of sheep breeds, flock size, seasonality and the ectoparasitic combinations on the host.     

Evaluation of biohydrogenation rate of canola vs. soya bean seeds as unsaturated fatty acids sources for ruminants in situ

An experiment was conducted to study disappearance of C14 to C18 fatty acids, lag times and biohydrogenation (BH) rates of C18 fatty acids of ground soya bean and canola seeds in situ. Three ruminally fistulated Dallagh sheep were used to determine ruminal BH of unsaturated fatty acids (UFAs). Differences in the disappearance of fatty acids through the bags and lag times were observed between the oilseeds. We saw that the longer the incubation time of the oilseeds in the rumen, the lower the content of C18:2 and C18:3. Significantly higher lag times for both C18:2 and C18:3 were observed in ground canola compared to ground soya bean. BH rates of C18:2 and C18:3 fatty acids in soya bean were three times higher than those of canola. These results suggest that the fatty acid profile of fat source can affect the BH of UFAs by rumen micro‐organisms. So that UFAs of canola had higher ability to escape from ruminal BH. It seems that fatty acid profile of ruminant products is more affected by canola seed compared to soya bean seed.     

Serum biochemical values and mineral element contents of tissues in yaks

Serum biochemical values and the wet weight to dry weight ratios of tissues were determined in yaks in Shandan county of Gansu province. The liver, kidney, heart and muscle contents of seven elements in yaks were also analysed. Most serum biochemical values were similar to those of cattle, camels and sheep, but the calcium concentration was considerably above the normal range for other ruminants. The liver contained the highest concentrations of copper, manganese and cobalt and the kidney of selenium, iron and calcium.Abbreviations Alb albumin - ALT alanine aminotransferase - AST aspartate aminotransferase - BUN blood urea nitrogen - Chol cholesterol - Glob globulin - -GT -glutamyl transpeptidase - IP inorganic phosphorus - TP total protein     

Avian brood parasitism — a growing research area in behavioral ecology (part Ⅱ)

正We are pleased to publish the second special issue on avian brood parasitism and to be responsible guest editors for the two special issues of Chinese Birds (Vol. 3, No. 4, 2012 and Vol. 4, No. 1, 2013), entitled "Avian Brood Parasitism - A Growing Research Area in Behavioral Ecology". The first issue was published in December 2012. The goal of the two special issues is to publish accumulated knowledge and some of the recent developments in     

Internal Parasites and Haematological Values in Cattle Slaughtered in Buea Subdivision of Cameroon

Tropical Animal Health and Production -