副猪嗜血杆菌致病性的成因

早在100年前就已确定副猪嗜血杆菌是仔猪格拉瑟病的病原,但自那时起,对该菌致病的机制研究甚少。     

价格不是生猪市场的唯一风向标——专访全国畜牧总站站长谷继承

从去年5月份以来,生猪价格与猪肉销售价格持续下跌,导致养猪利润大幅缩水,养殖户们不得不再次直面周期性的大风大浪."现在,市场上生猪价格-公斤只有9.4元左右,而一头活猪每公斤成本在11元左右,结合猪肉价格估算,饲养一头猪亏损大约150元."4月29日,安徽一名读者打来电话,谈起目前的猪价,显得非常忧虑,不知何时见底.记者在采访全国畜牧总站站长谷继承时,他认为,之所以如此,是因为导致当前生猪价格下跌的因素比以往任何时候都更为错综复杂.     

Porphyrins are not present in feline ocular tissues or corneal sequestra

Objective To determine if feline lacrimal glands, glands of the third eyelid, corneas, and corneal sequestra contain porphyrins, which could be responsible for the brown/amber discoloration of corneal sequestra and tears in affected cats. Procedures Samples of grossly normal cornea, lacrimal gland, gland of the third eyelid, and sequestra obtained via keratectomy were collected. Porphyrin concentrations of the homogenate were determined by spectrofluorometry with protoporphyrin IX and coproporphyrin III dihydrochloride used as standards. A hamster harderian gland was used as a positive control. Results Normal tissues were harvested from one eye each of 14 nonclient owned, adult, mixed‐breed, short‐hair cats euthanized for reasons not associated with this study. Eighteen sequestra were acquired from cats undergoing unilateral lamellar keratectomies. Breeds of the affected cats included eight Himalayan, five domestic shorthair, and one each of four other breeds. Only the positive control and standards contained levels of porphyrins above background. All feline samples examined were histologically normal with no evidence of porphyrins. Conclusions Porphyrins are absent in normal feline lacrimal glands, corneas, and corneal sequestra. Porphyrins do not appear to be the cause of the brown/amber color of feline corneal sequestra.     

保证鸡苗质量:地面种蛋不应孵化

地面种蛋是指在散养系统中被产蛋母鸡产在产蛋箱外的蛋。这些种蛋通常会被产在肮脏的垫料上或者其他受污染的地面上。一枚鸡蛋刚被母鸡产下时仍然保持着与母鸡体温相同的温度。当种蛋进入种鸡舍内较冷的空气和周围环境中后,种蛋将会开始冷却。这会导致蛋的内容物收缩,从而使周围环境中的空气进入鸡蛋内部。     

Prolactin concentrations are not suppressed in mares administered constant exogenous melatonin

On the summer solstice (June 21, 1996), six of 12 intact light horse mares randomly chosen from a larger herd were subcutaneously implanted with ALZET^®a osmotic minipumps containing a melatonin solution (16 mg/ml) designed to release approximately 960 μg of melatonin/day. An additional two mares received implants containing only the saline-DMSO vehicle and four remained untreated. Blood samples were collected on days 5, 26, and 59 of treatment to monitor melatonin concentrations and to verify pump function. Prolactin concentrations were determined from blood samples collected via jugular cannulae every 12 min for 8 hours on days 25,46, and 89 after initial implantation. On day 89, samples were collected hourly for 16 hours following the initial 8-hour sampling period. Melatonin and prolactin concentrations were determined in the blood samples by radioimmunoassay. Mean circulating concentrations of melatonin in treated mares (n=6) were found to be significantly elevated when compared to controls (n=6); however, there was no significant difference in prolactin concentrations between the groups. These studies demonstrate that longterm treatment with melatonin is unaccompanied by a change in prolactin secretion.     

Genital tract smooth muscle tumors are common in zoo felids but are not associated with melengestrol acetate contraceptive treatment

In a survey of gynecologic lesions in female zoo felids conducted to determine if the widely used progestin contraceptive melengestrol acetate (MGA) had adverse effects, numerous leiomyomas and leiomyosarcomas were detected. This current study aimed to characterize the morphologic features of these tumors, determine their prevalence, and assess if MGA was a risk factor for their genesis. Genital tracts from 219 zoo felids representing 23 species were evaluated, and leiomyomas were detected in 24% of the felids. Leiomyomas were often multiple and occurred in the myometrium, ovary, or adjacent broad ligament. The risk of developing leiomyomas increased with age, but MGA treatment or parity had no effect. Five other felids had leiomyosarcomas. Leiomyosarcomas were distinguished from poorly demarcated leiomyomas by the presence of local invasion, metastasis, and cellular atypia, but necrosis and mitotic rate were not distinguishing criteria. Four of five felids with leiomyosarcomas had been treated with MGA. These results indicate that leiomyomas are common spontaneous lesions in the genital tracts of zoo felids and their genesis is not linked to MGA exposure. Whether progression to malignancy is promoted by MGA warrants further investigation.     

Cattle transfers between herds under paratuberculosis surveillance in The Netherlands are not random

The rate and structure of cattle transfers between 206 Dutch cattle herds with a ‘Mycobacterium avium subsp. paratuberculosis (Map)-free’ status by November 2002, were analyzed over a 3-year period (November 1999–November 2002). Of the 206 ‘Map-free’ herds, 184 were closed herds during the period studied. In total, 280 cattle had been introduced into 22 herds at an average rate of 0.33 animals per year per 100 cattle present in the 206 herds. Assuming a random herd-contact structure, the observed rate of cattle transfers between certified ‘Map-free’ herds was sufficiently low to relax the surveillance scheme to biennial herd examinations by pooled fecal culture of all cattle ≥2 years of age.

The cattle transfers were not randomly distributed over the herds. Forty-four of the 280 cattle originated from 12 other ‘Map-free’ herds. The other 236 cattle did not originate from a ‘Map-free’ herd and were introduced into a herd before it obtained the ‘Map-free’ status. No cattle were introduced into any of the ‘Map-free’ herds from which cattle were transferred to other ‘Map-free’ herds. Thus, continued propagation of the infection by cattle transfers was impossible in the group of herds studied during the study period. Therefore the surveillance scheme may be further relaxed, and may be differentiated regarding the risk herds pose to other herds.     

Scrapie resistance alleles are not associated with lower prolificity in Rasa Aragonesa sheep

Scrapie is a prion disease characterised by the accumulation of the pathological associated form of cellular prion protein (PrP(SC)) in the central nervous system. Susceptibility to scrapie is associated with polymorphism in the ovine prion protein (PrP) gene. The European Union has implemented scrapie control programs, relying on selective breeding for scrapie resistance; the use of ARR-carrier and the exclusion of VRQ-carrier were recommended. In this study, 4323 individuals from Rasa Aragonesa Sheep breed were genotyped for the PrP gene and the individual estimated breeding values (EBV) for prolificity were calculated. Most represented PrP alleles do not work against prolificity. Only a significant association between VRQ/VRQ genotype and a lower EBV was observed (p = 0.027, eta2 = 0.002). Therefore, avoiding reproduction of VRQ/VRQ individuals would not cause negative effect regarding prolificity.     

Aquaglyceroporins but not orthodox aquaporins are involved in the cryotolerance of pig spermatozoa

Background: Aquaporins(AQPs) are a family of transmembrane water channels that includes orthodox AQPs,aquaglyceroporins(GLPs) and super AQPs. AQP3, AQP7, AQP9 and AQP11 have been identified in boar sperm,and they are crucial for sperm maturation and osmoregulation. Water exchange is an important event in cryopreservation, which is the most efficient method for long-term storage of sperm. However, the freezethaw process leads to sperm damage and a loss of fertilizing potential. Assuming that the quality of frozenthawed sperm partially depends on the regulation of osmolality variations during this process, AQPs might play a crucial role in boar semen freezability. In this context, the aim of this study was to unravel the functional relevance of the different groups of AQPs for boar sperm cryotolerance through three different inhibitors.Results: Inhibition of different groups of AQPs was found to have different effects on boar sperm cryotolerance.Whereas the use of 1,3-propanediol(PDO), an inhibitor of orthodox AQPs and GLPs, decreased total motility(P 0.05), it increased post-thaw sperm viability, lowered membrane lipid disorder and increased mitochondrial membrane potential(MMP)(P 0.05). When acetazolamide(AC) was used as an inhibitor of orthodox AQPs, the effects on post-thaw sperm quality were restricted to a mild increase in MMP in the presence of the intermediate concentration at 30 min post-thaw and an increase in superoxide levels(P 0.05). Finally, the addition of phloretin(PHL), a GLP inhibitor, had detrimental effects on post-thaw total and progressive sperm motilities,viability and lipid membrane disorder(P 0.05).Conclusions: The effects of the different inhibitors suggest that GLPs rather than orthodox AQPs are relevant for boar sperm freezability. Moreover, the positive effect of PDO on sperm quality suggests a cryoprotective role for this molecule.     

Cyclooxygenase 2 and Prostaglandin E2 are not Involved in N-Nitrosodiethylamine-Initiated Early Rat Hepatocarcinogenesis

The present study was undertaken to investigate the effect of dietary supplementation with nimesulide or eugenol on N-nitrosodiethylamine (DEN)-initiated early hepatocarcinogenesis in F344 male rats. Both compounds did not alter the expression of cytochrome P450 (CYP) 2E1, the enzyme that plays a major role in the activation of DEN to genotoxic products; however, nimesulide induced the expression of CYP1A1. Western blot analysis revealed that COX-1 and COX-2 protein expressions were not modulated by DEN compared with normal controls. Furthermore, post-initiation feeding with nimesulide or eugenol did not modulate COX-2 protein expression in normal or DEN-treated rats, whereas eugenol significantly increased the liver prostaglandin E(2) (PGE(2)) levels of DEN-injected animals compared with the DEN controls. Ultimately, nimesulide or eugenol did not modify DEN-induced hepatocarcinogenesis as evidenced by insignificant changes in the number and size of preneoplastic placental glutathione S-transferase (GST-P) positive liver foci compared with the DEN controls. These results suggest that COX-2, as well as prostaglandin E(2), may play no role in the post-initiation development of DEN-induced rat hepatocarcinogenesis at an early stage.     

Extenders containing dimethylformamide associated or not with glycerol are ineffective for ovine sperm cryopreservation

The study aimed at testing the effectiveness of dimethylformamide, alone or combined with glycerol, as cryoprotectant for freezing ram semen. Ejaculates from nine rams were cryopreserved in Tris-based extenders, containing 5% of glycerol, association of dimethylformamide with glycerol, in four proportions achieving 5% of cryoprotectors in the media and pure dimethylformamide (2, 3, 4 and 5%) in replacement to glycerol. The samples were diluted to 100 × 10(6) sptz/ml and stored in 0.25-ml straws in liquid nitrogen. After thawing (37 °C for 30 s), motility was preserved better by the extender containing 5% of glycerol (p < 0.05). The extenders containing pure dimethylformamide, or more than 2% in combination with glycerol, provided sperm motilities close to zero. Plasma and acrosomal membrane integrity were preserved better (p < 0.05) in the extender containing 5% glycerol. It can be concluded that dimethylformamide, alone or combined with glycerol, has no beneficial effects on ovine semen cryopreservation.