猪源沙门氏菌毒力基因检测及脉冲场凝胶电泳分型研究

为了解上海及周边地区猪源沙门氏菌的血清型分布、毒力基因及分子分型情况,我们对21株临床分离到的猪源沙门氏菌用沙门氏菌属诊断血清鉴定血清型;采用多重聚合酶链式反应,检测17个主要的毒力基因;应用脉冲场凝胶电泳(PFGE)技术进行分子分型,探寻21株沙门氏菌之间的亲缘关系。结果显示,21株沙门氏菌中,19株血清型为7∶c∶5,1株为4∶i∶2,1株未鉴定出;21株沙门氏菌的17个毒力基因中检出16个,菌株之间无差别;经PFGE后,每个菌株产生13~18条电泳条带,用Bionumerics软件进行聚类分析表明,21株猪源沙门菌相似度在77%~100%,可分为2种不同的基因型,其中A型有19株、B型2株,亲缘关系较近。本次实验分离的沙门氏菌血清型以7∶c∶5为主,含有16个主要的毒力基因,A型为优势基因型。     

猪源肠球菌林克酰胺、截短侧耳素及链阳菌素A类耐药基因lsa(E)的检测及传播方式

为研究lsa(E)在猪源肠球菌中的流行情况及传播方式,本研究从广西某猪场分离的56株肠球菌中检测到15株携带多重耐药外排泵基因lsa(E)的肠球菌,利用脉冲场凝胶电泳(PFGE)对lsa(E)基因阳性的肠球菌进行亲缘关系分析,并对不同克隆型的菌株进行耐药表型和相关耐药基因型检测,通过Southem杂交定位lsa(E)基因在不同菌株中的位置.PFGE结果显示15株lsa(E)基因阳性的肠球菌共有7种不同的PFGE谱型,表明携带lsa(E)基因的肠球菌在同一猪场存在垂直传播的现象.药物敏感性试验结果显示,7株分离株除对红霉素、四环素、庆大霉素和环丙沙星100％耐药外,对利奈唑胺、氟苯尼考、利福平和左氧氟沙星也具有较高的耐药率,分别为57.1％、85.7％、71.4％和85.7％.耐药基因erm(B),aac(6')-Ⅰe-aph(2")-Ⅰa和aph(3")-Ⅲa的检出率分别为:100％、85.7％和72.4％;Southern杂交结果显示,lsa(E)基因在6株菌中定位于质粒22 kb～54 kb,而在1株菌中定位于染色体.本研究为临床制定合理措施控制lsa(E)快速传播提供依据.     

宠物犬及犬粮源沙门氏菌的耐药性分析及PFGE分型

为了解宠物犬和犬粮源沙门氏菌的耐药表型特征与耐药基因分布,以及不同分离菌株之间的同源性,本研究采用K-B法测定27株分离菌的药物敏感性、PCR检测耐药基因、脉冲场凝胶电泳(PFGE)进行基因分型。结果显示,27株沙门氏菌分离株对氨苄西林、阿莫西林/克拉维酸、链霉素、复方新诺明、强力霉素耐药率在29.63%~22.22%,33.33%分离菌对3种及3种以上抗生素耐药,其中阿莫西林/克拉维酸-氨苄西林-复方新诺明-强力霉素所占比率最大,为66.67%(6/9);74.07%分离菌至少含有1种耐药基因,以str A-B、bla PSE、tet B、sul1检出率最高,分别为40.7%、37.0%、29.6%、25.9%,四环素类、氯霉素类、磺胺类、β-内酰胺类耐药基因与耐药表型符合率较高,分别为100%、100%、87.5%、72.7%;27株分离菌形成12种PFGE基因型,优势型别为pt1和pt7型。本研究结果表明宠物犬和犬粮源沙门氏菌呈现多重耐药,耐药表型与其相对应的耐药基因间存在密切的相关性;PFGE基因型呈多态性,而其与血清型之间不呈相关性,但与多重耐药菌株(耐8)间存在一定程度的关联性。     

山东地区零售鸡肉中沙门菌耐药基因东地区零售鸡肉中沙门菌耐药基因、毒力基因及PFGE分型研究

为了解山东地区零售鸡肉中沙门菌耐药和毒力基因的携带状况以及PFGE分子分型情况,采用PCR方法对分离的25株沙门菌携带的耐药基因和毒力基因进行检测,并运用XbaⅠ酶进行酶切并完成PFGE分析,利用BioNumerics软件对分离菌株的指纹图谱进行聚类分析。结果显示,分离菌株携带耐药基因的携带情况与耐药表型的符合率为95%,其中88%的分离菌株携带酰胺醇类耐药基因(catⅠ)和β-内酰胺类耐药基因(blatem-1/blapsE-1/blaCMY-1/blaoxA-1);所有分离菌株均携带fimAstn、IacP、prgK四种毒力基因,其次是spvr、spva、spvc,携带率均为64%;25株沙门菌共分为10个群,包括16个不同的带型,菌株相似度为60%~100%。     

屠宰场猪链球菌分离菌株分型及其致病性和耐药性分析

为了解吉林省猪链球菌的流行情况,从屠宰场采集的猪咽拭子和鼻拭子样品中分离鉴定猪链球菌,并进行菌株血清型、基因型和毒力表型的鉴定,以及致病性和耐药性的分析。结果表明,从100份样品中共分离鉴定猪链球菌104株,其中29株鉴定为血清2型、9型和1型等几种常见的致病性血清型,其他75株不属于常见的致病性血清型。血清2型的菌株中,2株经鉴定为ST1基因型和mrp+epf+sly+毒力型,并经动物试验鉴定为强毒菌株;其他菌株均为ST28基因型和mrp+epf-sly-毒力型,具有中等毒力。血清9型的菌株,均为mrp-epf-sly-毒力型,动物试验鉴定均为强毒菌株。根据Kirby-Bauer纸片扩散法的药敏试验结果,98%的猪链球菌分离株对四环素耐药;对大环内酯类、克林霉素和链霉素的耐药率都在50%以上;对β-内酰胺类、氯霉素和喹诺酮类抗生素的耐药率小于20%。总体分析,从屠宰场分离的猪链球菌强毒菌株所占的比例并不高,但是菌株多重耐药的情况非常严重。     

山东省肉鸡屠宰生产链中沙门菌耐药性分析及毒力基因检测

通过调查山东省不同市肉鸡屠宰生产链中沙门菌分离株血清型、耐药性及毒力相关基因,为肉鸡的健康安全生产提供数据支撑。对前期获得的233株沙门菌通过血清型快速分型试剂盒鉴定其血清型,采用最小抑菌浓度(MIC)进行13种抗菌药物的药敏试验;应用PCR技术检测位于菌株毒力岛(SPI)和毒力质粒(spv)上共15种毒力基因的携带情况。结果显示,233株沙门菌共分属25种不同的血清型,其中肠炎沙门菌、印第安纳沙门菌、汤普逊沙门菌和德尔卑沙门菌为优势血清型。233株肉鸡屠宰生产链中沙门茵对庆大霉素的耐药率最高(100%);对多西环素、氨苄西林、大观霉素、四环素、氟苯尼考和磺胺异恶唑耐药率分别为84.94%、75.73%、67.78%、56%、52%和50%。72%的菌株表现为多重耐药(≥3),产生了57种耐药谱型。沙门菌的毒力岛基因sptP、sseL、mgtC、siiE、sopB的携带率是100%,毒力基因spvA、spvB、spvC、spvD、spvR、iacP、avrA、prgK、fima和stn的检出率分别是60%、34%、49%、51%、63%、99%、38%、99%、99%和99%。结果表明,在4种优势血清型中并非均出现高耐药性,出现高耐药性的血清型主要以汤普逊沙门菌为主,汤普逊沙门菌相对于其他血清型毒力基因的携带率较高,沙门菌耐药性和毒力基因的携带间并没有明显的关联性。     

宁夏地区牛源肠球菌分离鉴定及耐药性与毒力基因检测

为了了解宁夏地区牛源肠球菌的耐药性及耐药基因和毒力基因的携带情况,本试验使用显色培养基及PCR法对肠球菌进行分类鉴定;采用药敏纸片琼脂扩散法(K-B法)测定肠球菌对16种抗菌药物的敏感性;最后采用PCR方法对9种相关耐药基因与7种肠球菌毒力基因进行检测并测序。结果显示,在分离鉴定出的255株肠球菌中,屎肠球菌有78株(30.59%),粪肠球菌有53株(21.96%)。药敏试验结果显示,分离菌对磺胺异恶唑和杆菌肽耐药率达到了100%;其次是苯唑西林(92.16%)、红霉素(65.88%)、四环素(65.49%)和青霉素(56.86%)。分离菌对万古霉素和利奈唑胺高度敏感,敏感率分别为92.54%与95.29%。耐药基因检测结果显示,氨基糖苷类耐药基因aph(3)′-Ⅲ的检出率最高,为100%;其次是红霉素类耐药基因ermB,为46.27%;未检出耐万古霉素耐药基因VanA、VanB、VanC。已检测的毒力基因明胶酶gelE的携带率最高,为37.60%;其次为心内膜炎抗原efaA,为36.10%。结果表明,宁夏地区牛源肠球菌的多重耐药现象比较严重,应当加以重视。     

某规模化种鸡场沙门菌流行病学调查和耐药性分析

试验旨在调查国内某规模化种鸡场沙门菌流行状况,为种鸡场沙门菌净化提供基础资料。1 744份样品被采集进行沙门菌分离、血清型鉴定、耐药性分析及脉冲场凝胶电泳(PFGE)方法亚分型。结果显示:168株沙门菌被分离鉴定,分离率为9.63%,其中肠炎沙门菌有157株,为优势血清型(93.45%);抗生素耐药性试验表明,多重耐药现象较为严重,耐药种类在三种以上的肠炎沙门菌株有130株(77.38%);随机选取28株肠炎沙门菌进行PFGE亚分型显示,这些菌株属于同一个聚类簇,表明它们可能来自于同一克隆株。     

河北部分地区狐狸源肺炎克雷伯菌血清型鉴定、毒力基因及致病性检测

为分析河北部分地区狐狸源肺炎克雷伯菌(Klebsiella pneumoniae)的荚膜血清型、毒力基因流行情况及致病性,从河北地区养殖场中采集患病狐狸肺脏、心血、肝脏等病料组织217份,分离得到63株致病性肺炎克雷伯菌。采用PCR法分别检测63株肺炎克雷伯菌荚膜血清型及19种毒力基因;通过人工感染小鼠致病试验验证4株优势血清型流行株的半数致死量(LD_(50))。结果显示,63株肺炎克雷伯菌中23株为K2血清型,7株为K20血清型。63株肺炎克雷伯菌携带13种毒力基因,毒力基因fimH、mrkD、wabG、uge、ybt、ybtA、alls、ompK35等检出率均在58.73%以上,其他毒力基因检测率较低;分离菌株呈现多重毒力基因型,同时携带9种毒力基因的菌株最多,占致病性菌株的33.33%。优势血清型流行株KD1(K20)和KD45(K2)的致病性最强,其LD_(50)分别为3.16×10~5,3.16×10~6 CFU/mL。本研究为该地区肺炎克雷伯菌病的防控提供参考。     

北京地区腹泻犬、健康犬粪便粪肠球菌耐药性、毒力基因及多位点序列分型研究

为分析分离自北京地区腹泻犬、健康犬粪便的粪肠球菌的耐药性,研究2种犬粪便来源优势分子型粪肠球菌重要毒力基因携带情况,在中国农业大学教学动物医院收集犬粪便,并分离得到腹泻犬粪便源粪肠球菌45株,健康犬粪便源粪肠球菌32株,采用琼脂稀释法测定分离菌株对12种抗生素的最小抑菌浓度,用多位点序列分型(MLST)技术进行分子分型,并利用PCR方法检测优势分子型粪肠球菌5种不同毒力基因携带情况。结果显示,腹泻犬源和健康犬源粪肠球菌对四环素、多西环素、米诺环素、红霉素、利福平耐药率较高。腹泻犬源分离株对氯霉素、氨苄西林、阿莫西林克拉维酸、呋喃妥因耐药率较低,集中于8.9%～17.8%,对万古霉素不耐药;健康犬源分离株对青霉素、呋喃妥因耐药率较低,分别为4.8%和14.3%,对氨苄西林、阿莫西林克拉维酸、万古霉素不耐药。45株腹泻犬源粪肠球菌共发现15种序列型(ST),优势ST为ST116、ST16、ST179,32株健康犬源粪肠球菌发现18种ST,优势ST为ST16和ST27,2种来源优势ST粪肠球菌agg、gelE、cylB、esp、efaAs毒力基因检出率差异不显著(P0.05)。表明北京地区腹泻犬、健康犬肠道粪肠球菌多重耐药现象严重,需加强抗生素使用的监控和管理;腹泻犬、健康犬肠道粪肠球菌毒力基因携带率差异不显著,都具有向人传播致病性粪肠球菌的风险,兽医临床医护人员和宠物犬饲养人应注意防护。     

Pharmacokinetics and bioavailability of carbetocin after intravenous and intramuscular administration in cows and gilts

The pharmacokinetics of carbetocin, which is used to control postpartum hemorrhage after giving birth, was studied in cows and gilts after a single intravenous (IV) or intramuscular (IM) injection. Blood samples from animals were assessed by oxytocin radioimmunoassay, and then the pharmacokinetic parameters were calculated using a noncompartmental model. For gilts, there was no significant difference between half-life (T_1/2λZ), mean residue time (MRT), and maximum concentration (C_max) between IM and IV administration. Conversely, the time to reach the C_max (T_max) and MRT were higher following administration of 350 μg/animal in cows via the IM administration compared with IV. The longest T_1/2λZ was 0.85 hr, indicating carbetocin was absorbed and eliminated rapidly in both animal species after administration. The T_max was similar between cows and gilts following IM administration. Moreover, the C_max after IM injection was about half that of IV administration in both animals. The bioavailability was more than 80% in cows, suggesting administration via the IM route is efficient. This is in agreement with the longer T_1/2λZ in cows after IM administration. However, the IV route is recommended for gilts due to a lower bioavailability (35%) and shorter T_1/2λZ after IM administration compared with IV.     

Genetic diversity and antimicrobial resistance of Campylobacter and Salmonella strains isolated from decoys and raptors

Infections caused by thermotolerant Campylobacter spp. and Salmonella spp. are the leading causes of human gastroenteritis worldwide. Wild birds can act as reservoirs of both pathogens. A survey was carried out to determine the prevalence, genetic diversity and antimicrobial resistance of thermotolerant Campylobacter and Salmonella in waterfowl used as decoys and wild raptors in Andalusia (Southern Spain). The overall prevalence detected for Campylobacter was 5.9% (18/306; CI_95%: 3.25–8.52) in decoys and 2.3% (9/387; CI_95%: 0.82–3.83) in wild raptors. Isolates were identified as C. jejuni, C. coli and C. lari in both bird groups. Salmonella was isolated in 3.3% (10/306; CI_95%: 2.3–4.3) and 4.6% (18/394; CI_95%: 3.5–5.6) of the decoys and raptors, respectively. Salmonella Enteritidis and Typhimurium were the most frequently identified serovars, although Salmonella serovars Anatum, Bredeney, London and Mikawasima were also isolated. Pulsed-field gel electrophoresis analysis of isolates showed higher genetic diversity within Campylobacter species compared to Salmonella serovars. Campylobacter isolates showed resistance to gentamicin, ciprofloxacin and tetracycline, while resistance to erythromycin and tetracycline was found in Salmonella isolates. The results indicate that both decoys and raptors can act as natural carriers of Campylobacter and Salmonella in Spain, which may have important implications for public and animal health.     

Seedling Defoliation and Drought Stress: Variation in Intensity and Frequency Affect Performance and Survival

Our ability to restore rangelands is limited, and it is unknown if seedling herbivory on its own, or in interaction with other stressors, is a major contributor to restoration failure. To address this, we conducted two experiments: a No Defoliation (ND) experiment (n = 48), in which seedlings from three perennial grasses (crested wheatgrass [Agropyron cristatum {(L.} Gaertn.], bluebunch wheatgrass [Psuedoroegnaria spicata {Pursh} Á. Love], Sandberg bluegrass [Poa secunda J Presl]) were subjected to wet and dry water regimes for 4 mo, and a concurrent Defoliation (D) experiment (n = 95), in which seedlings were factorially assigned to two defoliation treatments—frequency (LOW, HIGH) and intensity (30% vegetation removal, 70% vegetation removal). Indicators of seedling performance were aboveground and belowground biomass (AGB and BGB), root:shoot ratio, tillering, and mortality. The effect size statistic, Hedge’s g, allowed for comparisons between performance measures. Water stress induced reductions in most performance measures: BGB (g = ND: –1.3; D: –1.6), root:shoot ratio (g = ND: n.s.; D: –0.2), and tillering (g = ND: –1.7; D: –1.2), though not significantly for all species. For ABG, water stress interacted with defoliation, reducing performance less at an intensity of 70% (g = –2.0) as opposed to 30% (g = –3.0), but not always significantly in the former. Water stress also caused less reduction in AGB when no defoliation occurred (ND: –0.8; g = D: –2.5). Intensity and frequency of defoliation interacted; seedlings were generally resistant to reductions in performance except at high frequency, 70% defoliation. Agropyron cristatum and P. spicata displayed similar sensitivity to treatments, mostly in terms of changes in AGB and BGB, while P. secunda also experienced increased mortality and reduced tillering. If these differences in sensitivity result in differential survival, herbivory could impact species postrestoration population demographics.     

中国伞形科当归属及相关类群毛状体和果实结构的系统学价值

深入研究了当归属及其相关7属,古当归属,高山芹属,柳叶芹属,独活属,欧当归属,山芹属及前胡属毛状体和果实结构。结果显示毛状体及果实结构(如:毛状体细胞,翅,油管,维管束,中果皮,内果皮,结合面及结晶)可以用于区分当归属及其相关类群。滇南当归及隆萼当归应从当归属移入独活属,其余当归属物种分为结合面宽及结合面窄两组,前者与前胡属较为相似,但与独活属差别较大,后者与古当归属,高山芹属,柳叶芹属,欧当归属有相似之处。支持分子系统学揭示的当归属不是个自然类群,当归属与前胡属共同位于当归分支,而独活属位于独活分支。山芹属果实结构与其他属不同,翅的中果皮无细胞,且伴生油管位于维管束内侧,为分子系统学显示此属与高山芹属,柳叶芹属,及欧当归属亲缘关系较远提供了形态学依据。     

Genetic and phenotypic parameters and annual trends for growth and fertility traits of Charolais and Hereford beef cattle breeds in Kenya

This study estimated genetic and phenotypic parameters and annual trends for growth and fertility traits of Charolais and Hereford cattle in Kenya. Traits considered were birth weight (BW, kg), pre-weaning average daily gain (ADG, kg/day) and weaning weight (WW, kg); calving interval (CI, days) and age at first calving (AFC, days). Direct heritability estimates for growth traits were 0.36 and 0.21; 0.25 and 0.10; 0.23 and 0.13 for BW, ADG and WW in Charolais and Hereford, respectively. Maternal heritability estimates were 0.11 and 0.01; 0.18 and 0.00; 0.17 and 0.17 for BW, ADG and WW in Charolais and Hereford, respectively. Direct-maternal genetic correlations ranged between −0.46 and 1.00; −0.51 and −1.00; −0.47 and −0.39 for BW, ADG and WW in Charolais and Hereford, respectively. Genetic correlations ranged from −0.99 to unity and −1.00 to unity for growth and fertility traits respectively. Prospects for improvement of growth and fertility traits exist.     

Sanguinarine metabolism and pharmacokinetics study in vitro and in vivo

Sanguinarine (SA) is a benzo[c] phenanthridine alkaloid which has a variety of pharmacological properties. However, very little was known about the pharmacokinetics of SA and its metabolite dihydrosanguinarine (DHSA) in pigs. The purpose of this work was to study the intestinal metabolism of SA in vitro and in vivo. Reductive metabolite DHSA was detected during incubation of SA with intestinal mucosa microsomes, cytosol, and gut flora. After oral (p.o.) administration of SA, the result showed SA might be reduced to DHSA in pig intestine. After i.m. administration, SA and DHSA rapidly increased to reach their peak concentrations (C_max, 30.16 ± 5.85, 5.61 ± 0.73 ng/ml, respectively) at 0.25 hr. Both compounds were completely eliminated from the plasma after 24 hr. After single oral administration, SA and DHSA rapidly increased to reach their C_max (3.41 ± 0.36, 2.41 ± 0.24 ng/ml, respectively) at 2.75 ± 0.27 hr. The half-life (T_1/2) values were 2.33 ± 0.11 hr and 2.20 ± 0.12 hr for SA and DHSA, respectively. After multiple oral administration, the average steady-state concentrations (C_ss) of SA and DHSA were 3.03 ± 0.39 and 1.42 ± 0.20 ng/ml. The accumulation indexes for SA and DHSA were 1.21 and 1.11. The work reported here provides important information on the metabolism sites and pharmacokinetic character of SA. It explains the reasons for low toxicity of SA, which is useful for the evaluation of its performance.     

Intake, live animal scores/measurements and carcass composition and value of late-maturing beef and dairy breeds

The objectives of this study were to compare the progeny of 1) late-maturing beef with dairy breeds and 2) Charolais (CH), Limousin (LM), Simmental (SM) and Belgian Blue (BB) sires bred to beef suckler dams, for feed intake, blood hormones and metabolites, live animal measurements, carcass traits and carcass value in bull and steer production systems. The bull system included 50 late-maturing beef breeds and 22 Holsteins (HO) slaughtered at approximately 15 months of age, whereas the steer system consisted of 56 late-maturing beef breeds and 23 British Friesians (FR) slaughtered at approximately 24 months of age. Beef breeds were suckled until approximately 8 months of age, while dairy breeds were artificially reared until weaning at approximately 3 months of age. All animals were finished on an ad libitum concentrate diet. Mean live weight, live weight gain, carcass gain and feed efficiency were greater (P < 0.05) in beef than dairy breeds in both systems during the finishing period when offered concentrates. Although there was no difference in feed intake between beef and dairy breeds, intake expressed relative to live weight was lower (P < 0.001) in beef breeds in both systems. At 10 months of age and pre-slaughter, beef breeds had higher (P < 0.001) muscularity scores and greater scanned muscle depth (P < 0.001) than their dairy contemporaries. Carcass weight, kill-out proportion, carcass conformation score, meat proportion and value were greater (P < 0.001) and carcass fat and bone proportions were lower (P < 0.05) in beef than dairy breeds in both systems. Insulin concentrations were lower (P < 0.001) in beef than dairy breeds, whereas there was no difference in blood metabolites or IGF-1 concentrations. Feed intake expressed relative to live weight or feed efficiency did not differ between CH, LM, SM or BB sired progeny. Muscularity scores were greater (P < 0.05) in BB than SM, whereas skeletal scores were lower (P < 0.05) in LM than SM. Limousin had lower (P < 0.05) carcass gain per day of age than CH and SM, whereas SM had a lower (P < 0.05) carcass conformation score than BB and CH and a higher (P < 0.05) carcass fat score than CH. Simmental had a lower (P < 0.05) carcass meat proportion and a higher (P < 0.05) carcass fat proportion than CH, LM and BB, which were similar (P > 0.05). The improvement obtained for beef over dairy breeds in live weight gain was 12%, while the improvements in carcass gain and meat produced was 24% and 33%, respectively. This demonstrates that the importance of carcass data contributing to breed comparison studies cannot be over-emphasised.     

Melatonin and CIDR improved the follicular and luteal haemodynamics,uterine and ovarian arteries vascular perfusion,ovarian hormones and nitric oxide in cyclic cows

This study hypothesizes that melatonin with exogenous progesterone (CIDR) can improve follicular, luteal, ovarian and uterine haemodynamic of heat-stressed cows. Holstein cows (N = 12) studied for two spontaneous oestrous cycles during winter then divided equally during summer into the CIDR group received CIDR for 7 days and the melatonin group (Mel) received three injections of melatonin (75 mg/head) at the CIDR insertion, removal and ovulation days. Blood samples were collected to assay oestradiol (E2), progesterone (P4) and nitric oxide (NO). On day 0 (Ovulation), Mel had more small follicles (p < .05), higher ipsilateral and contralateral ovarian arteries (Ov.A.) peak systolic velocity (PSV), higher ipsilateral uterine artery (Ut.A.) PSV (p = .031) and blood flow volume (BFV), also Mel elevated contralateral Ut.A. PSV and BFV (p < .0001) but lowered contra Ut.A. pulsatility index (PI, p < .0001), E2 (p < .01) and NO (p < .0001). Mel increased the corpus luteum diameter (CL, p < .001), coloured area (p < .007) and P4 (p < .0001) on day 5 and reduced them (p < .05; p < .01) on Day 14. On day 10, Mel obtained CL diameter (p < .03) and coloured area (p < .002) of spontaneous that was higher than CIDR and decreased P4 (p < .003). Mel increased CL diameter, area and coloured area and decreased them thereafter. Mel increased the ipsilateral ovarian and uterine arteries PSV and BFV before ovulation and until day 8. Mel increased P4 and decreased NO until days 6 and 14. In conclusion, the improvement in follicular, luteal, ovarian and uterine haemodynamic and the decrease of NO production proved our hypothesis Melatonin doses higher than 75 mg/head is recommended to improve the heat-stressed cow's fertility.