Superoxide dismutase and catalase activities in the seminal plasma of normozoospermic and asthenozoospermic Beagles

We measured the blood plasma testosterone (T) levels and superoxide dismutase (SOD) and catalase activities in the seminal plasma of the ejaculates of 5 normal (2-5 years old) and 5 asthenozoospermic (AZ-) (3-5 years old) Beagles. Sperm ejaculated by AZ-dogs was incubated for 3 hr in Eagle's MEM only (controls) or Eagle's MEM containing 100 units/ml of SOD or catalase. Sperm motility was examined during incubation. The mean (+/- SE) plasma T level of the AZ-dogs (1.2 +/- 0.2 ng/ml) was significantly lower than in the normal dogs (2.5 +/- 0.2 ng/ml) (P<0.005). The mean (+/- SE) seminal plasma SOD and catalase activities (18.8 +/- 1.9 and 0.5 +/- 0.1 unit/g protein, respectively) were significantly lower in the AZ-dogs than in the normal dog (43.3 +/- 2.5 and 2.2 +/- 0.4 unit/g protein, respectively) (P<0.001 and 0.01, respectively). The motility of sperm incubated in Eagle's MEM containing SOD or catalase was significantly higher than that of control sperm incubated in only Eagle's MEM after 2 or 3 hr of incubation (P<0.05). The results of this study indicate that poor T secretion by the testes and low antioxidant enzyme activities are related to AZ in the dog.     

Therapeutic effects of vitamin E supplementation in 4 dogs with poor semen quality and low superoxide dismutase activity in seminal plasma

Four dogs with poor semen quality, low seminal plasma superoxide dismutase (SOD) activity and low blood plasma testosterone (T) levels were orally administered one vitamin E tablet containing 50 mg α-tocopheryl acetate per dog daily for 4 weeks. The mean values of semen quality were temporarily improved after the start of vitamin E treatment and the values of 4, and 5 weeks after that were significantly different from those before the treatment (P<0.05–0.001). The mean blood plasma T and seminal plasma SOD activity values slightly increased in the 4 dogs after the treatment. The results of the present study indicate that poor semen quality in dogs with low seminal plasma SOD can be improved by vitamin E treatment.     

Effects of whelping and season of the year on the interoestrous intervals in dogs

An analysis of 319 interoestrous intervals of 36 beagles, 36 German shepherd dogs and 20 labrador retrievers was made to study the influence of whelping on the length of this interval and the within-year variation in length of interoestrous intervals and timing of the oestrous periods. The mean interoestrous interval was significantly longer for beagles (247±5 days) than for German shepherd dogs and labrador retrievers (both 198±5 days)(P<0–001). For bitches that had not whelped there were no significant differences between breeds (beagles 172+10; German shepherd dogs 166±6; and labrador retrievers 172±7 days). The mean interoestrous interval after whelping was significantly lengthened in all breeds (P<0–001). This increase was more pronounced for beagles (84 days)(P<0–001) than for German shepherd dogs (58 days) and labrador retrievers (52 days). Heat periods were evenly distributed over the year for the labrador retrievers and German shepherd dogs that were kept as family pets. For the beagles kept as a colony and housed outdoors without heating or supplementary light, there were significant differences between months (P<0001), with a peak in May. The longest interoestrous intervals were found in beagle bitches that had been in oestrous and whelped during autumn.     

奶牛产后气虚血瘀证与血浆SOD、MDA变化的关系

选用产后健康奶牛18例和产后气虚血瘀证奶牛9例，于产后1、2、4、7、10、15、30d采血分离血浆，黄嘌呤氧化酶法测定超氧化物歧化酶(SOD)活性，硫代巴比妥酸法测定丙二醛(MDA)含量。结果，血浆SOD活性组内比较产后健康组整个检测期在一定范围内波动，差显不显著(P>0.05)；气虚血瘀证组产后15、30d极显著高于产后1、2d(P<0.01)，显著高于产后4d(P<0.05)；产后7、10d显著高于产后1、2d(P<0.05)。组间比较气虚血瘀证组产后1、2、4d显著低于同时间产后健康组(P<0.01或P<0.05)。血浆MDA含量组内比较产后健康组整个检测期在一定范围内波动，差异不显著(P>0.05)；气虚血瘀证组产后1d极显著高于产后10、15、30d(P<0.01)，显著高于7d(P<0.05)；产后1、2、4、7d显著高于产后15、30d(P<0.05)。组间比较气虚血瘀证组产后1、2、4、7d极显著高于同时间产后健康组(P<0.01)。结果初步表明，SOD、MDA的变化参与了产后气虚血瘀证的发生、发展与转归过程。     

Testicular superoxide dismutase activity, heat shock protein 70 concentration and blood plasma inhibin-alpha concentration of dogs with a Sertoli cell tumor in a unilateral cryptorchid testis

The proportions of Sertoli cell tumor (SCT), seminoma and Leydig cell tumor in 50 dogs with unilateral testicular tumors were 52%, 36% and 12%, respectively. The rate of occurrence of SCT in the cryptorchid testis was very high (71%). The testicular superoxide dismutase (SOD) activity, testicular heat shock protein (HSP) 70 concentration and peripheral blood plasma inhibin (INH)-alpha concentration of 10 dogs with a unilateral cryptorchid testis and no testicular tumors, 10 dogs with SCT in a unilateral cryptorchid testis and 10 normal dogs, all aged 5-15 years, were measured in order to identify high risk factors for the occurrence of SCT in the canine cryptorchid testis. The mean SOD activity in cryptorchid testes and SCTs was significantly lower and higher, respectively, than in normal testes (both P<0.01). The mean HSP 70 concentration in both cryptorchid testes and SCTs was significantly higher than in normal testes (both P<0.01). The mean plasma INH-alpha concentration of the cryptorchid and SCT dogs was significantly lower and higher, respectively, than in normal dogs (P<0.05 and 0.01, respectively). The low SOD activity in the cryptorchid testis, low blood plasma INH-alpha concentration of the cryptorchid dogs and high HSP 70 concentration in the SCTs may be related to the occurrence of SCT and tumor cell proliferation in canine cryptorchid testes.     

桦木酸对地塞米松致氧化应激小鼠血清指标的影响

本试验旨在研究桦木酸(BA)对地塞米松(Dex)诱导氧化应激小鼠血清指标的影响。将40只健康雄性昆明小鼠随机分为5组,即对照(NC)组、Dex组、0.25 mg/kg BA组、0.50 mg/kg BA组、1.00 mg/kg BA组,每组8只。NC组和Dex组灌服1%的可溶性淀粉,其余各组灌服混悬于1%可溶性淀粉溶液中不同剂量的BA,连续灌服14 d后,除NC组注射生理盐水外,其余4组均腹腔注射25 mg/kg Dex诱导氧化应激模型。15 h后,眼眶采血,收集血清。检测血清谷丙转氨酶(ALT)、谷草转氨酶(AST)和碱性磷酸酶(ALP)活性,总蛋白(TP)、白蛋白(ALB)、总胆固醇(TC)、甘油三酯(TG)、总胆红素(T-Bil)、钙离子(Ca~(2+))、细胞色素C(CytC)含量,总抗氧化能力(T-AOC)、抑制羟自由基能力、超氧化物歧化酶(SOD)活性、谷胱甘肽(GSH)和丙二醛(MDA)含量。结果显示:BA预处理后,能够显著或极显著降低Dex诱导氧化应激小鼠血清ALP活性及TG、T-Bil、CytC含量(P0.05或P0.01),且呈量效关系;低剂量BA(0.25、0.50 mg/kg)显著或极显著降低了血清MDA含量(P0.01或P0.05),但高剂量BA(1.00 mg/kg)反而极显著升高了其含量(P0.01);能够显著或极显著升高血清Ca2+和GSH含量、SOD的活性、T-AOC和抑制羟自由基能力(P0.05或P0.01),并呈量效关系;降低了血清ALT和AST活性,但影响不显著(P0.05),对血清TP和ALB含量无显著影响(P0.05)。由此可见,BA能够改善Dex引起的小鼠血清指标的变化,对Dex诱导的氧化损伤有预防性的保护作用。     

超氧化物歧化酶模拟物对肉仔鸡肉品质和超氧化物歧化酶活性的影响

本试验旨在研究日粮中添加不同水平超氧化物歧化酶模拟物(superoxdie dismutase mimics,SODm)对肉仔鸡生长性能、肉品质及超氧化物歧化酶(SOD)活性的影响。采用单因子试验设计,选取1日龄爱拔益加(AA)肉仔鸡公雏432只,随机分成6组,每组6个重复,每个重复12只。对照组饲喂基础日粮,试验组在基础日粮中分别添加0.10%、0.15%、0.20%、0.25%、0.30%SODm,试验期42 d。结果表明:①日粮添加SODm对肉仔鸡平均日采食量(ADFI)、平均日增重(ADG)和料重比(F/G)均无显著影响(P>0.05)。②添加0.20%、0.25%和0.30%SODm组胸肌亮度(L~*)值显著低于对照组(P<0.05);除0.10%SODm组外,SODm各组胸肌剪切力均显著低于对照组,滴水损失显著高于对照组(P<0.05)。SODm各组腿肌L~*值均显著低于对照组(P<0.05);0.10%和0.15%SODm组腿肌剪切力显著低于对照组(P<0.05)。③21日龄时,与对照组相比,0.30%SODm组血清SOD活性显著降低(P<0.05),其他SODm组血清SOD活性均有提高,但差异不显著(P>0.05);42日龄时,添加SODm各组血清SOD活性均显著高于对照组(P<0.05)。④21日龄时,SODm各组肝脏SOD活性均显著高于对照组(P<0.05);添加SODm对胸肌和心脏SOD活性无显著影响(P>0.05)。42日龄时,添加0.15%和0.25%SODm组肝脏和心脏SOD活性显著高于对照组(P<0.05);0.25%和0.30%SODm组胸肌和腿肌SOD活性显著高于对照组(P<0.05)。综上,本试验条件下,在日粮中添加SODm对肉仔鸡生长性能无显著影响;添加0.15%～0.25%SODm可提高肉仔鸡体内SOD活性,降低肌肉亮度和剪切力,改善肌肉嫩度。     

腹水综合征肉鸡氧自由基变化规律

利用自然病例，采取分组（对照组，轻度腹水综合征组和重度腹水综合征组）对比的方法，分别用硫代巴比妥酸法和羟胺法测定了肉鸡血清和主要组织（心脏、肝脏、肺脏、肾脏）丙二醛（malondialdehyde,MDA)含量和超氧化物歧化酶（superoxide dismutase,SOD)活性。结果表明，与对照组肉鸡比较，轻度腹水综合征组肉鸡血清和主要组织MDA含量降低（P＜0．05）或显著降低（P＜0．01），SOD活性升高（P＜0．05）或显著升高（P＜0．01）；而重度腹水综合征组肉鸡血清和主要组织MDA含量升高（P＜0．05）或显著升高（P＜0．01），SOD活性显著降低（P＜0．01）。间接证明了氧自由基和氧化损伤参与了肉鸡腹水综合征的病理过程，氧自由基产生水平与肉鸡腹水综合征病情的轻重有关。     

静脉注射L-氨基胍对肉鸡肺动脉压及其相关指标的影响

按常规饲养条件饲养AA雄性肉鸡120羽，30日龄时随机分为试验组（T组）和对照组（C组）。T组肉鸡静脉注射L-AG（40mg／kg），C组肉鸡静脉注射生理盐水。分别在注射L-AG和生理盐水1、2、4h后测定平均肺动脉压（mPAP）、诱导型一氧化氮合酶（iNOS）活性、原生型一氧化氮舍酶（cNOS）活性、一氧化氮（NO）含量、红细胞压积（PCV）、电解质浓度、pH、超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性和丙二醛（MDA）含量。结果显示：（1）试验组mPAP、NO含量和iNOS活性均显著或极显著低于对照组（P〈0．05或P〈0．01）；（2）PCV和Ca^2＋在给药后2h和4h与对照组差异显著（P〈0．05）；（3）K^＋浓度在给药1h和2h后显著或极显著低于时照组（P〈0．05或P〈0．01）。结果表明，L-AG通过抑制iNOS活性，引起肉鸡肺动脉压的升高，从而推测iNOS具有调节肉鸡体内mPAP的作用并与肉鸡肺动脉高压综合征发生有着密切的联系。     

Elimination of Staphylococcus intermedins in healthy dogs by topical treatment with fusidic acid

Cutaneous and mucosal carriage of Staphylococcus intermedius was investigated in six healthy beagles before and after application of fusidic acid to mucosal surfaces as 1 per cent viscous eye drops twice daily for seven days. Bacterial populations were determined repeatedly over four weeks using quantitative techniques. The overall cutaneous populations of S intermedius reduced significantly (P<0·01) two days after treatment but returned to pretreatment levels after a further week. The mucosal frequency of S intermedius reduced significantly (P<0·001) two days after treatment and remained reduced (P<0·01) at the end of the study. The mucosal populations were also reduced (P<0·01) two days after treatment and remained lower (P<0·05) after a further week. No such changes occurred in the control group of six beagles. The study indicates the importance of mucosae as carriage sites for S intermedius in dogs. This form of therapy may be useful as an additional tool against canine recurrent pyoderma.     

Copper,Zinc-Superoxide Dismutase Activity in Exercising Horses Fed Two Forms of Trace Mineral Supplements

Nine mature horses were used to evaluate superoxide dismutase (SOD) response to a low-intensity standard exercise test and the effect of copper (Cu) and zinc (Zn) supplement form on enzyme activity. The modified switchback experiment was conducted over seven 28-day periods. Horses were conditioned to perform an average daily workload of 3.93 kg∗km∗10⁻³ with a digestible energy (DE) demand of approximately 29 Mcal. Following a controlled Cu and Zn repletion-depletion diet sequence, horses were fed a diet intended to be marginally deficient in Cu and Zn with the minerals supplemented in either sulfate or organic chelate forms. Horses were then subjected to a standardized exercise test to enable evaluation of SOD activity during exercise and immediate recovery. In the final analyses, mineral contents of the experimental diets were significantly different (P < .05). The mean mineral concentration of the sulfate diet was 6.28 ppm Cu and 35.99 ppm Zn, while the chelate diet contained 23.62 ppm Cu and 90.67 ppm Zn. Even so, resting SOD activity was not altered by diet (1793.47 ± 323.00 U/g Hb for the sulfate diet, 1355.70 ± 148.32 U/g Hb for the organic-chelate diet), nor did SOD activity change in response to the low-intensity workout. The SOD activity was unchanged by feeding a Cu and Zn supplemented diet to horses fed to be in a mineral-deficient state. These exercise bouts did not appear to have a significant impact on SOD activity. Other types of oxidative stress should be considered when trying to evaluate the antioxidant responsiveness of this enzyme.     

实验性脾虚证与自由基代谢的相关性及四君子汤对其的调整作用

分别用小承气汤和利血平复制大鼠脾虚证模型，通过检测血清和心、肝、脾、肾等组织中抗氧化酶SOD和GSHP－Px的活性及脂质过氧化反应终产物MDA含量，研究脾虚证与自由基代谢的相关性及四君子汤对其影响。结果表明：两种方法复制脾虚证模型与对照组比较均表现为SOD活性显著升高（P＜0．05），GSH－Px活性显著降低（P＜0．05）；四君子汤反证治疗组与脾虚证组比较表现为SOD活性显著下降（P＜0．05），GSH－Px活性显著升高（P＜0．05），MDA含量显著降低（P＜0．05），与正常对照组接近。表明大鼠虚证动物模型与体内自由基代谢紊乱，脂质过氧化作用增强存在一定关系，健脾益气方药四君子汤能够提高体内抗氧化酶活性，拮抗自由基对生物膜的过氧化损伤，具有抗脂质过氧化损伤的作用。     

酪蛋白铜对仔猪生长及血清铜蓝蛋白和SOD活性的影响

选取体重 2 0kg左右杜长大仔猪 90头 ,随机分为 3组 ,分别饲喂添加 5 ,2 4 0mg/kg铜 (CuSO4·5H2 O)和5 0mg/kg酪蛋白铜的饲粮 ,试验期 3 0d ,试验第 1 5d和结束时对猪只称重 ,探讨酪蛋白铜对仔猪生长性能的影响 ,并对血液相关指标进行分析。结果表明 ,与 5mg/kg硫酸铜组相比 ,在生长前期 ,2 4 0mg/kg硫酸铜 (高铜 )的促生长效果最佳 ,日增重提高了 1 2 .3 %(P <0 .0 5 ) ,酪蛋白铜组日增重提高了 9.5 %(P <0 .0 5 ) ,但在生长后期 ,酪蛋白铜促生长作用超过了高铜 ,日增重提高了 1 7.0 %(P <0 .0 5 )。就整个生长期而言 ,酪蛋白铜的促生长效果最佳 ,日增重提高了 1 3 .6 %(P <0 .0 5 )。高铜明显降低了饲料转化率 ,降幅为 9.5 %(P <0 .0 5 ) ;高铜和酪蛋白铜组铜蓝蛋白活性分别提高了 3 4 .2 8%和 3 5 .71 %(P <0 .0 1 ) ,SOD分别提高 76 .4 %和 80 .8%(P <0 .0 1 )。由此可见 5 0mg/kg酪蛋白铜可显著影响猪的生长及血清相关指标水平 ,达到高剂量硫酸铜的效果     

A 6‐bp Deletion Variant in a Novel Canine Glutathione‐S‐Transferase Gene (GSTT5) Leads to Loss of Enzyme Function

Objectives

Glutathione‐S‐transferases (GSTs) detoxify reactive xenobiotics, and defective GST gene polymorphisms increase cancer risk in humans. A low activity GST‐theta variant was previously found in research beagles. The purpose of our study was to determine the molecular basis for this phenotype and its allele frequency in pet dogs.

Methods

Banked livers from 45 dogs of various breeds were screened for low GST‐theta activity by the substrate 1,2‐dichloro‐4‐nitrobenzene (DCNB), and were genotyped for variants in a novel canine GST gene, GSTT5. Whole‐genome sequences from 266 dogs were genotyped at one discovered variant GSTT5 locus.

Results

Canine livers ranged 190‐fold in GST‐theta activities, and a GSTT5 exon coding variant 385_390delGACCAG (Asp129_Gln130del) was significantly associated with low activity (P < 0.0001) and a marked decrease in hepatic protein expression (P = 0.0026). Recombinant expression of variant GSTT5 led to a 92% decrease in V_max for DCNB (P = 0.0095). The minor allele frequency (MAF) for 385_390delGACCAG was 0.144 in 45 dog livers, but was significantly higher in beagles (0.444) versus nonbeagles (0.007; P = 0.0004). The homozygous genotype was significantly over‐represented in Pembroke Welsh corgis (P < 0.0001) based on available whole‐genome sequence data.

Conclusions

An Asp129_Gln130del variant in canine GSTT5 is responsible for marked loss of GST‐theta enzyme activity. This variant is significantly over‐represented in purpose‐bred laboratory beagles and in Pembroke Welsh corgis. Additional work will determine the prevalence of this variant among other purebred dogs, and will establish the substrate range of this polymorphic canine enzyme with respect to common environmental carcinogens.     

甘肃省中部地区猫尾草新品系的抗寒性研究

本试验以甘肃农业大学培育的猫尾草(Phleum pratense)新品系(T)为试验材料,'川西'猫尾草品种(CK1)和'岷山'猫尾草品种(CK2)为对照,研究3个材料在低温胁迫(0℃,—10℃,—20℃,—30℃)下生理生化指标的变化,明晰其抗寒性强弱,为培育高产优质、抗性强的猫尾草新品系打下基础.结果表明:不同低温...     

Oxidative Stress and Neutrophil Function in Cats with Chronic Renal Failure

Background: Oxidative stress is an important component in the progression of chronic renal failure (CRF) and neutrophil function may be impaired by oxidative stress. Hypothesis: Cats with CRF have increased oxidative stress and decreased neutrophil function compared with control cats. Animals: Twenty cats with previously diagnosed renal failure were compared with 10 age‐matched control cats. Methods: A biochemical profile, CBC, urinalysis, antioxidant capacity, superoxide dismutase (SOD) enzyme activity, reduced to oxidized glutathione ratio (GSH : GSSG), and neutrophil phagocytosis and oxidative burst were measured. Statistical comparisons (2‐tailed t‐test) were reported as mean ± standard deviation. Results: The CRF cats had significantly higher serum blood urea nitrogen, creatinine, and phosphorus concentrations than control cats, and significantly lower PCV and urine specific gravity than control cats. The GSH : GSSG ratio was significantly higher in the CRF group (177.6 ± 197, 61.7 ± 33; P < .02) whereas the antioxidant capacity was significantly less in the CRF group (0.56 ± 0.21, 0.81 ± 0.13 Trolox units; P < .005). SOD activity was the same in control and CRF cats. Neutrophil oxidative burst after Escherichia coli phagocytosis, measured as an increase in mean fluorescence intensity, was significantly higher in CRF cats than controls (732 ± 253, 524 ± 54; P < .05). Conclusions: The higher GSH : GSSG ratio and lower antioxidant capacity in CRF cats is consistent with activation of antioxidant defense mechanisms. It remains to be determined if supplementation with antioxidants such as SOD beyond the level of control cats would be of benefit in cats with CRF.     

The effect of ticlopidine on canine platelets, fibrinogen, and antithrombin III activity

The effect of ticlopidine on platelet function, platelet number, mean platelet volume, antithrombin III activity, and fibrinogen was evaluated in 10 laboratory beagles. Ticlopidine (62 mg/kg) significantly inhibited ADP- and collagen-induced platelet aggregation within 2 days of the beginning of oral administration. Collagen-induced platelet 14C-serotonin release was not inhibited by day 9 of medication but was inhibited by day 20 in two of three beagles given medication for 32 days. Significant increases in mean platelet number were observed on days 2 and 5. The trend toward increased platelet number continued until day 16, at which time platelet number began to decrease toward baseline in three of three dogs treated for 32 days. Mean platelet volume (MPV) was significantly decreased compared to baseline on days 5 and 9. In three dogs treated for 32 days, the lowest MPV was observed on day 9 in two dogs and on day 12 in one dog. Significant changes were not observed in antithrombin III activity or fibrinogen with ticlopidine treatment.     

Population sizes and frequency of Malassezia pachydermatis at skin and mucosal sites on healthy dogs

Skin and mucosal carriage of Malassezia pachydermatis was studied in 20 healthy pet dogs of various breeds and in 20 kennelled beagles. Using swabs, anal carriage was detected in 10 pet dogs and 11 beagles and the nose, mouth, prepuce and vulva were shown to be infrequently colonised. M pachydermatis was isolated from the external ear canal of 11 beagles and two pet dogs; both the population sizes and frequency of isolation were significantly (P<0·05) greater in the beagles. The yeast was infrequently isolated from the axilla and groin in low numbers using contact plates and detergent scrub samples but was often cultured from the lower lip and the dorsal interdigital spaces; isolation frequencies and population sizes in the two groups of dogs were not significantly different. These results demonstrate that the anus, external ear canal and lip and interdigital skin of healthy dogs are frequently colonised by M pachydermatis.     

茶多酚对蛋鸡生产性能、蛋品质和抗氧化能力的影响

本试验旨在研究茶多酚(TP)对蛋鸡生产性能、蛋品质和抗氧化能力的影响。试验选用450只24周龄的健康海兰灰产蛋鸡,分为5个组,每组6个重复,每个重复15只鸡。对照组饲喂基础饲粮,试验组分别在基础饲粮中添加40、80、200和400 mg/kg TP。试验期63 d,其中预试期7 d、正试期56 d。结果表明,与对照组相比:1)400 mg/kg TP显著降低了试验期前4周的平均蛋重(P0.05);200 mg/kg TP显著改善试验期后4周的料蛋比(P0.05);TP未显著影响产蛋率和平均日采食量(P0.05)。2)饲粮中添加TP未显著影响蛋形指数、蛋壳强度、蛋壳厚度、蛋白高度、哈夫单位和蛋黄颜色(P0.05)。3)TP显著提高了血浆总超氧化物歧化酶(T-SOD)和谷胱甘肽过氧化物酶(GPx)活性(P0.05);显著提高试验期第8周时血浆总抗氧化能力(T-AOC)(P0.05)。4)TP显著提高了肝脏和蛋黄T-AOC和T-SOD活性(P0.05);显著降低肝脏和蛋黄中丙二醛(MDA)含量(P0.05)。由此可见,饲粮中添加TP未显著影响蛋鸡蛋品质;400 mg/kg TP降低了平均蛋重,200 mg/kg TP改善了料蛋比,两者均提高了蛋鸡的抗氧化能力,其中以200 mg/kg组效果最佳。     

黄芪组方中草药添加剂抗奶牛热应激效果及其作用机理的研究

本试验旨在研究黄芪组方中草药添加剂抗奶牛热应激的效果及其作用机理。采用单因子试验设计,选择健康经产、胎次相同、体重和产奶量相近的荷斯坦奶牛12头,随机分为2组,每组6头牛。对照组饲喂基础日粮,试验组在此基础上添加200 g/(d.头)的黄芪组方中草药粉剂。结果表明:试验组奶牛肛温和呼吸频率与对照组相比差异不显著(P>0.05);采食量在第2周前显著低于对照组(P<0.05),第4周显著高于对照组(P<0.05);产奶量在第5、6周显著高于对照组(P<0.05);血清T4、总SOD活力在第40天显著高于对照组(P<0.05);GSH-Px活力在第20和第40天极显著高于对照组(P<0.01);第40天血清内毒素和热应激蛋白HSP70水平与对照组相比,分别降低了20.53%和6.27%(P>0.05),MDA含量在第40天显著低于对照组(P<0.05)。由以上结果可见,黄芪组方中草药添加剂可在一定程度上通过提高血清T4水平,降低内毒素、HSP70和MDA含量,提高抗氧化酶活力,从而有效缓解奶牛热应激,减轻热应激对奶牛的危害。