The diagnostic value of the D-xylose absorption test in horses with unexplained chronic weight loss.

A D-xylose absorption test was performed on 40 horses with chronic weight loss which could not be explained on history, physical findings, dietary evaluation, or initial laboratory data, i.e. unexplained weight loss. Six of the horses had D-xylose malabsorption and at post-mortem examination small intestinal lesions which accounted for the malabsorption were found in five. Five of the horses with normal absorption were examined post mortem and no lesions in any organs were found to account for the weight loss. The other 29 cases were still unexplained, and lost to follow-up.     

不同栽培模式及施氮量对半旱地冬小麦氮素累积及分配的影响

【目的】研究不同栽培模式和施氮量对半旱地栽培条件下冬小麦-夏玉米轮作体系中冬小麦地上部氮素累积、分配及利用效率的影响。【方法】在陕西关中地区进行了田间试验,以常规栽培为对照,比较了补灌、覆草和垄沟等栽培模式及0,120,240 kg/hm2施氮水平,对冬小麦连续2年(2004和2005年)不同生长期各部位氮素累积量的影响。【结果】在补灌模式下,2004和2005年成熟期冬小麦叶片和茎秆的氮素累积量较其他模式低,氮素分配率也较低,而籽粒的氮素分配率较高;施用氮肥显著增加了各生长时期冬小麦叶片、茎秆、颖壳和穗轴以及籽粒的氮素累积量,当氮肥施用量由120增加到240 kg/hm2时,除籽粒外,成熟期冬小麦叶片、茎秆、颖壳和穗轴的氮素残留量均随之明显增加。与不同栽培模式相比,施用氮肥对冬小麦不同器官中氮素分配的影响较小。随着氮肥施用量的增加,氮肥利用效率、氮肥农学效率和氮肥生理效率均呈降低趋势。在不同栽培模式中,连续2年补灌栽培模式下冬小麦的氮肥利用效率、氮肥农学效率以及氮肥生理效率均较高,而其他栽培模式下这3个指标年际间的变化较大。【结论】施用氮肥可显著增加冬小麦各生长时期不同器官的氮素累积量,但对氮素在不同器官中分配比例的影响较小;与施用氮肥相比,不同栽培模式对冬小麦氮素的累积、分布无明显影响;冬季补灌有利于提高冬小麦的氮素效率。     

Spatial variability of common carp populations in relation to lake morphology and physicochemical parameters in the upper Midwest United States

Weber MJ, Brown ML, Willis DW. Spatial variability of common carp populations in relation to lake morphology and physicochemical parameters in the upper Midwest United States.
Ecology of Freshwater Fish 2010: 19: 555–565. © 2010 John Wiley & Sons A/S Abstract – Common carp (Cyprinus carpio) is a widespread invasive species that is tolerant of a wide range of environmental conditions. Despite the circumpolar distribution of the species, limited information is available describing factors related to spatial variation in population characteristics. Eighty‐four lakes and impoundments in the upper Midwest United States were sampled to investigate the relationships of common carp relative abundance with size structure, condition and growth rates. We also investigated abiotic factors (lake morphology, physical solids and water quality) that may broadly influence common carp populations. Common carp size structure and condition were inversely related to relative abundance. Common carp relative abundance increased and size structure shifted to smaller individuals with increased lake depth, whereas lake surface area, watershed:surface area ratio and physical solids were also important in explaining common carp abundance and size structure. Common carp condition was best explained by water quality parameters and increased with metrics of lake productivity. We conclude that knowledge of factors associated with variation in common carp populations among lakes provides insights into the autecology and broad provisions for management of this generalist invasive species.     

Mode of action,crop selectivity,and soil relations of the sulfonylurea herbicides

The sulfonylurea herbicides are characterized by broad-spectrum weed control at very low use rates (c. 2–75 g ha^?1), good crop selectivity, and very low acute and chronic animal toxicity. This class of herbicides acts through inhibition of acetolactate synthase (EC 4.1.3.18; also known as acetohydroxyacid synthase), thereby blocking the biosynthesis of the branched-chain amino acids valine, leucine and isoleucine. This inhibition leads to the rapid cessation of plant cell division and growth. Crop-selective sulfonylurea herbicides have been commercialized for use in wheat, barley, rice, corn, soybeans and oilseed rape, with additional crop-selective compounds in cotton, potatoes, and sugarbeet having been noted. Crop selectivity results from rapid metabolic inactivation of the herbicide in the tolerant crop. Under growth-room conditions, metabolic half-lives in tolerant crop plants range from 1–5 h, while sensitive plant species metabolize these herbicides much more slowly, with half-lives > 20 h. Pathways by which sulfonylurea herbicides are inactivated among these plants include aryl and aliphatic hydroxylation followed by glucose conjugation, sulfonylurea bridge hydrolysis and sulfonamide bond cleavage, oxidative O-demethylation and direct conjugation with (homo)glutathione. Sulfonylurea herbicides degrade in soil through a combination of bridge hydrolysis and microbial degradation. Hydrolysis is significantly faster under acidic (pH 5) than alkaline (pH 8) conditions, allowing the use of soil pH as a predictor of soil residual activity. Chemical and microbial processes combine to give typical field dissipation half-lives of 1–6 weeks, depending on the soil type, location and compound. Very short residual sulfonylurea herbicides with enhanced susceptibility to hydrolysis (DPX-L5300) and microbial degradation (thifensulfuron-methyl) have been developed.     

Tobacco rattle virus serotypes and associated nematode vector species of Trichodoridae in the bulb-growing areas in the Netherlands

Soil samples from the coastal bulb-growing areas in the provinces of North- and South-Holland and the North-East Polder in the Netherlands were examined for trichodorid nematodes and tobacco rattle virus (TRV) serotypes. At least one of a total of eight species of Trichodoridae, of whichParatrichodorus pachydermus was most prevalent, was found in 93% of the samples from the provinces of North- and South-Holland and TRV, including four serotypes, was obtained from 49% of these samples. In the North-East Polder one of three species of trichodorids, of whichP. teres occurred most frequently, was present in 72% of the samples, and TRV of one serotype was obtained from 28% of these samples. The TRV isolates recovered from these samples reacted serologically with one of four antisera to strains of TRV. Virus transmitted byP. pachydermus reacted to the PRN-, byTrichodorus viruliferus to the RQ-, byP. teres to the N5- and byT. similis, to the TS-antiserum, respectively.     

Detection of infectious bursal disease virus in experimentally infected chickens by in situ hybridization

In situ hybridization was used in a pathogenesis study of three vaccine pathotypes (Delaware variant A, D78, and BursaVac) of infectious bursal disease virus (IBDV). Tissues were excised (bursa, thymus, spleen, proventriculus, and cecal tonsils), fixed in formalin, and paraffin embedded at 12, 24, 48, 72, and 120 hr postinoculation (HPI). With an antisense VP2 gene probe, viral nucleic acid was detected in bursas from both D78- and BursaVac-infected chickens at 24, 48, 72, and 120 HPI. However, viral RNA was detected only in the Delaware variant A-infected birds at 72 HPI. Thymus and spleen were positive in the D78-infected birds at 48 HPI and in the BursaVac-inoculated group at 72 HPI. Viral nucleic acid was not present in detectable levels among any of the tissues tested at 12 HPI. However, by 24 hr, scattered positive lymphoid cells were visualized in the bursal follicles of chickens infected with D78 and BursaVac. In addition, low levels of viral nucleic acids were detected in the thymus and spleen among the D78- and BursaVac-infected birds. The sites of viral replication were consistent between the two vaccine-infected groups (D78 and BursaVac), whereas the chickens infected with Delaware variant A had limited IBDV replication in the bursa.     

Safety and efficacy of in ovo administration of infectious bursal disease viral vaccines

In ovo vaccination against Marek's disease virus and infectious bursal disease virus (IBDV) in commercial broilers in the United States is common. Little information exists as to the safety and efficacy of intermediate IBDV vaccines given in ovo. Experiments were initiated to determine the safety and efficacy of three commercially available live intermediate IBDV vaccines by in ovo route. Commonly used vaccines were given at 18 days of embryonation to specific-pathogen-free (SPF) broiler embryos (first and second study) or to commercial broiler embryos (third study) that had maternal antibody against IBDV. When any of the antigenic standard vaccines was given at full dose to SPF embryos, embryonic and 3-wk posthatch mortality increased. Vaccines also caused significant microscopic lesions in the bursa of Fabricius at 1 and 3 wk posthatch. In contrast, there was no adverse effect on embryonic or posthatch mortality when vaccines were given at half dose to SPF or commercial broiler embryos. However, significant microscopic lesions were evident at 1 and 3 wk posthatch in the bursae of SPF embryos given the vaccines at half dose. When vaccines were given at half dose to commercial broiler embryos, lesions were evident at 1 but not 3 wk of age. In the third study, in ovo vaccinated chickens were challenged with either a virulent standard (APHIS) or antigenic variant (variant E) IBDV virus at 3 wk of age. All vaccines produced at least 87% protection against the standard and 60% protection against the variant challenge IBDV, as measured by bursal weight to body weight ratios. This study was the first to examine the safety and efficacy of the three commonly used intermediate IBDV vaccines given in ovo in protection against standard and antigenic variant IBDV challenge viruses.     

Ovulation rate and litter size in gilts immunized against androstenedione and 17alpha-hydroxyprogesterone

Two experiments were conducted to evaluate the effects of the immunization of gilts against ovarian steroids on ovulation rate and litter size. In Exp. 1, gilts (n = five gilts/treatment) at 165+/-1.6 d of age were immunized against either carrier (Control), androstenedione, or 17alpha-hydroxyprogesterone. Age at puberty and estrous cycle length averaged 208+/-5.5 (P = 0.67) and 20.3+/-2.8 d (P = 0.41), respectively, and were not affected by treatment. The androstenedione- and 17alpha-hydroxyprogesterone immunized gilts had higher (P < 0.02) ovulation rates than Controls (14.2, 14.2, and 11.4+/-0.8, respectively). Total pigs born (P = 0.66) and pigs born live (P = 0.65) for the androstenedione-treated group were not different from Controls. Gestation length was not different (P = 0.36) between any of the treatments and the Controls (115+/-0.9 d). Procedures used in Exp. 2 were similar to those in Exp. 1, except that only Control (n= 18) and 17alpha-hydroxyprogesterone (n = 16) treatments were included and only litter size at farrowing was measured. Total pigs and pigs born live were higher in the 17a-hydroxyprogesterone-treated gilts than in the Controls (12.6 vs 10.5+/-0.6, P < 0.02; and 11.4 vs 9.2+/-0.6; P < 0.01, respectively). Data from this study indicate that litter size in gilts can be increased by immunization against 17alpha-hydroxyprogesterone.