Observations on the effects of long-term withdrawal on carcass composition and residue concentrations in clenbuterol-medicated cattle

The detection of the illegal use of clenbuterol (CBL) as a growth promoter has relied on detecting residual concentrations of the drug in body fluids or tissues. Analysis of retinal extracts has recently been shown to considerably extend the detection period following withdrawal. The withdrawal periods required to eliminate residues from the liver and retina were investigated by medicating 20 cattle with CBL for 30 days; 6 control animals remained unmedicated. Residual concentrations were monitored throughout this period and for the subsequent 140 days. Concurrent changes in muscle areas and backfat thicknesses were recorded by ultrasound.CBL was detectable in liver up to the 56th day of withdrawal (0.35 ng/g, SD=0.5), but retinal concentrations remained well above detectable concentrations throughout the withdrawal period (22.5 ng/g, SD=6.5). There were small gains (3–4%) in the muscle areas of treated cattle during medication as compared to controls (p>0.05). These comparative gains remained during withdrawal. Backfat thicknesses in treated animals were 40% lower than in controls at the end of medication (p<0.01). However, by 70 days after withdrawal this difference had disappeared (p>0.05) owing to accelerated fat deposition in the treated group. The retina has been shown to be a highly effective target matrix for detecting CBL administration after long withdrawal periods.Abbreviations CBL clenbuterol - CIM cimaterol - EC European Community - EIA enzyme immunoassay - GC-MS gas chromatography-mass spectrometry - HRPo horseradish peroxidase - L. dorsi, Longissimus dorsi - MRL maximum residue level - SD standard deviation - SED standard error of the difference     

奶牛温氏支原体16SrRNA基因的PCR扩增、克隆及分析

目的对奶牛温氏支原体16SrRNA基因进行PCR扩增及克隆分析。方法从自然感染体的广西奶牛无菌采集血液,分离温氏支原体并提取病原基因组,用血营养菌的16SrRNA基因的通用引物进行PCR扩增,将扩增产物克隆到PGEM-Teasy载体后进行溺,I序和分析,并与Genebank上搜索的温氏支原体相应序列进行比较,建立系统发育树。结果PCR扩增得到长约1．5kb的扩增片段,测序结果显示该片段全长为1453bp,同源性分析表明该序列与Neimark公布的温氏支原体（前称温氏附红细胞体）（AF016546）的16SrRNA基因序列同源性达到97．4％,与系统发育进化树表明本株温氏支原体同本地株的关系较近,而与国外株的新缘关系较远。国内公布的广西株同源性为99．8％。结论结果表明证实该病原为温氏支原体,从分子生物学水平证实了温氏支原体在广西的存在。由于本试验分离得到的牛温氏支原体与国外发表的牛温氏支原体核苷酸序列相差2．6％,因此两者的基因型存在一定的差异,这对该病的分子流行病学分析具有一定的意义。     

四种基质对大根报春苣苔叶插繁殖的影响

为探明不同基质对大根报春苣苔(Primulina macrorhiza)叶插繁殖的影响,以大根报春苣苔的全叶片为试验材料,采用正交试验设计,研究泥炭、珍珠岩、蛭石、稻壳炭4种基质对叶片扦插成活率、子株数、新叶总数的影响,并筛选出最优组合。结果表明,在试验的9个处理中,扦插基质以泥炭∶珍珠岩∶蛭石∶稻壳炭为4∶2∶2∶1(体积比)为佳。泥炭对成活率、子株数、新叶总数均有显著影响(P0.05);珍珠岩对成活率、子株数、新叶总数均无显著影响(P0.05);蛭石仅对新叶总数有显著影响(P0.05);稻壳炭仅对子株数有显著影响(P0.05)。正交分析并推理出,以4种成分为扦插基质时,泥炭、珍珠岩、蛭石和稻壳炭的最佳配比为2∶1∶1∶1(体积比)。     

ACCURACY OF DIAGNOSTIC ULTRASOUND FOR DETECTION OF CYSTIC LESIONS: DETERMINATION USING RECEIVER OPERATING CHARACTERISTIC CURVE ANALYSIS OF FINDINGS IN PHANTOM STUDIES

Anechoic, spherical cystic lesions are important findings on ultrasound examination. In polycystic renal disease of cats, they may be the only ultrasonographic sign of disease. This study assesses the accuracy of ultrasound, as used in a veterinary setting, for the detection of cysts. Using a spherical lesion ultrasound imaging phantom and 7.5- to 8-MHz linear array transducers, images of cysts of 2- and 4-mm diameter were created at various imaging depths from 0 to 6 cm. These were digitized and given to a panel of readers for interpretation. Area under receiver operating characteristic curves were used to evaluate test accuracy. It was shown that test accuracy was different at different imaging depths and differed with machines of differing price category. It is suggested that when setting standards for quality control in ultrasound, criteria used might be better related to imaging outcome studies rather than to aspects of machine specification.     

High temperature effects on gas exchange for the invasive buffel grass (Pennisetum ciliare [L.] Link)

Buffel grass was introduced to the Sonoran Desert in the mid-twentieth century, where it has aggressively invaded new areas. Given its ecological success at a place where the air temperature can approach 50°C, the effects of high air temperatures on gas exchange were studied for this species. The carbon dioxide uptake and water use efficiency were maximal at day/night air temperatures of 30/20°C for potted plants, substantially decreasing at higher temperatures until the plants died at 45/35°C.     

BOOK REVIEW

The 5-MinuteVeterinary Consult: Canine and Feline . 2nd edn. Tilley LP, Smith FWK, Lippincott Williams & Wilkins     

Nitrogen metabolism and fertility in cattle: II. Development of oocytes recovered from heifers offered diets differing in their rate of nitrogen release in the rumen

In vitro blastocyst production was determined for oocytes recovered postmortem from 48 beef x dairy heifers offered low (Low NH3) or high (High NH3) plasma ammonia-generating diets during the period of late antral follicle development. Following the establishment of a reference estrus (d 0), the experimental diets were offered for an 18-d period starting on d 3 and during which a second estrus was induced (d 16) 4 d before the animals were slaughtered. Blood samples collected at varying intervals were analyzed for ammonia, urea, progesterone, and LH. Ovarian folliculogenesis was monitored daily by transrectal ultrasonography. Ovaries were collected at slaughter and cumulus-oocyte complexes were aspirated from small (1 to 4 mm) and medium-sized (> 4 to 8 mm) sized follicles. In vitro-matured and -fertilized putative d-1 zygotes were cultured for a further 7 d in vitro and embryo development and metabolism were assessed. Relative to the low-NH3-generating diet, the high-NH3-generating diet increased peak postprandial levels of plasma ammonia (326.1 +/- 43.3 vs 52.1 +/- 7.4 micromol/L; P < .001), mean levels of plasma urea (7.0 vs 5.7 mmol/L; SED = .2; P < .001), peak levels of plasma progesterone prior to induced luteolysis (8.9 +/- .4 vs 6.8 +/- .3 microg/L; P < .001), and follicular fluid levels of ammonia (267 +/- 18 vs 205 +/- 20 nmol/mL; P < .05) and progesterone (351 +/- 69 vs 199 +/- 26 ng/mL; P < .05). The timing and level of the preovulatory LH surge was not affected by dietary treatment. Of oocytes cultured, cleavage (47.4 vs 62.4%; P = .02) and blastocyst production (10.9 vs 20.6%; P = .06) rates were reduced when the oocytes were derived from heifers offered the high- rather than the low-NH3-generating diets. There were interactions between dietary treatment and follicle size class, which indicated that fewer blastocysts were produced from cleaved oocytes derived from medium-sized follicles of heifers offered the high-NH3 treatment but that de novo protein synthesis was increased in such embryos. In conclusion, exposure to high levels of ammonia and(or) urea in vivo can significantly compromise the subsequent capacity of oocytes to develop to blastocysts in vitro, and oocytes recovered from medium-sized follicles are particularly sensitive to this effect.