Preference by sheep for endophyte-infected tall fescue grown adjacent to or at a distance from alfalfa

Two experiments were conducted to assess preference by sheep for endophyte-infected tall fescue growing in monoculture at least 5 m away from alfalfa (fescue-middle (FM)) over endophyte-infected tall fescue growing adjacent (0.2 to 1 m; fescue–alfalfa (FA)) to alfalfa (FA), and the effect of legume scent on preference for endophyte-infected tall fescue. In Experiment 1, 10 six-month-old lambs were offered for 12 days a choice of freshly harvested FA and FM. On days 13 and 14, lambs were offered the same choice, except cages (to allow access only to scent) containing freshly harvested alfalfa were put in the feeders containing FA, whereas cages containing freshly harvested FM were included with the feeders containing FM. Forage intake was measured 1 h after feeding and at three consecutive 2-h intervals thereafter. FA contained greater (P<0.002) concentrations of the alkaloid ergovaline (360±27 ppm) and CP (8±0.4%) than FM (219±27 ppm and 6±0.4%, respectively). Lambs preferred (P<0.05) FA to FM during the 1^st hour of feeding, but the differences became smaller and disappeared in later feeding periods (P<0.005). Lambs offered FA with alfalfa scent or FM with FM scent preferred (P<0.05) FA but only on the 2^nd day. In Experiment 2, 10 six-month-old lambs were offered a choice of FM with cages (to allow access only to scent) containing freshly harvested alfalfa or FM for 8 days. During the following 4 days, FM in the cages was replaced with freshly harvested sainfoin. Preference was greater (P<0.05) for FM offered with alfalfa scent than for FM offered with FM scent only on days 4 and 8. When lambs were offered FM with alfalfa or sainfoin in cages, they preferred (P<0.05) tall fescue with sainfoin scent over fescue with alfalfa scent, but intake was variable across hours and days (P<0.001). It is concluded that (1) lambs adjusted their intake of and preference for FA and FM over successive feeding bouts within each day, likely owing to an attempt to balance intakes of nutrients and alkaloids and (2) olfactory cues influenced preference, but to a lesser extent than nutrients and alkaloids in endophyte-infected tall fescue.     

Comparison of visible and near infrared reflectance spectroscopy on fat to authenticate dietary history of lambs

Since consumers are showing increased interest in the origin and method of production of their food, it is important to be able to authenticate dietary history of animals by rapid and robust methods used in the ruminant products. Promising breakthroughs have been made in the use of spectroscopic methods on fat to discriminate pasture-fed and concentrate-fed lambs. However, questions remained on their discriminatory ability in more complex feeding conditions, such as concentrate-finishing after pasture-feeding. We compared the ability of visible reflectance spectroscopy (Vis RS, wavelength range: 400 to 700 nm) with that of visible-near-infrared reflectance spectroscopy (Vis-NIR RS, wavelength range: 400 to 2500 nm) to differentiate between carcasses of lambs reared with three feeding regimes, using partial least square discriminant analysis (PLS-DA) as a classification method. The sample set comprised perirenal fat of Romane male lambs fattened at pasture (P, n=69), stall-fattened indoors on commercial concentrate and straw (S, n=55) and finished indoors with concentrate and straw for 28 days after pasture-feeding (PS, n=65). The overall correct classification rate was better for Vis-NIR RS than for Vis RS (99.0% v. 95.1%, P<0.05). Vis-NIR RS allowed a correct classification rate of 98.6%, 100.0% and 98.5% for P, S and PS lambs, respectively, whereas Vis RS allowed a correct classification rate of 98.6%, 94.5% and 92.3% for P, S and PS lambs, respectively. This study suggests the likely implication of molecules absorbing light in the non-visible part of the Vis-NIR spectra (possibly fatty acids), together with carotenoid and haem pigments, in the discrimination of the three feeding regimes.     

拉萨河流域耕地不同尺度土壤水分影响因子

土壤水分影响因子的尺度差异及作用是其尺度依赖性研究的基础.本文以青藏高原拉萨河流域耕地土壤为对象,通过遥感影像分析和野外调查,在全流域和小流域尺度上分别布设样点115和49个,采用土钻法分3层（0～20、20～40、40～60 cm）抽取土壤样本,获取土壤水分含量,然后运用生态学冗余分析和统计分析,筛选出影响耕地土壤水分的主要因子.结果表明： 在全流域尺度,受气候、海拔影响,土壤水分呈西南 东北递增趋势,其中,河谷区耕地受河流侧渗补给影响,下层土壤水分高于上层;在小流域尺度,耕地土壤水分随海拔升高及坡度增大而减少,土壤贮水能力随石砾含量增多而减弱.研究结果为拉萨河流域耕地向高海拔扩张、作物结构调整、土地整理及灌溉设施布设提供了重要依据.     

青稞HbSnRK2.4的克隆及其序列特征与表达特性分析

干旱胁迫是制约农作物生产的重要限制因素之一,研究并增强作物的抗旱性具有重要意义。Sn RK2(Sucrose nonfermenting 1-related protein kinase 2)基因编码一类蔗糖非酵解型蛋白激酶,该酶在ABA信号转录途径和抗渗透胁迫中起着重要作用。以青稞(Hordeum vulgare subsp.vulgare)抗旱品种喜马拉雅10号为材料,利用RT-PCR技术克隆获得了Sn RK2基因全长c DNA序列,命名为Hb Sn RK2.4(登录号:KJ699389)。生物信息学分析表明,该基因全长1 310 bp,编码362个氨基酸序列,蛋白分子量为41.94 k D,等电点(p I)为5.96。Prosite Scan分析结果表明,Hb Sn RK2.4含有多个干旱胁迫响应蛋白的作用位点,如酪蛋白激酶Ⅱ磷酸化位点、酪氨酸激酶磷酸化位点、蛋白激酶C磷酸化位点及N-豆蔻酰化位点等。利用实时定量PCR方法研究了Hb Sn RK2.4在干旱胁迫条件下及复水后不同时间点的表达情况,发现Hb Sn RK2.4在土壤绝对含水量为33.4%时表达量最高,随着土壤绝对含水量的下降而下调表达;当达到作物正常生长所需的土壤绝对含水量时又开始上调表达;进行干旱胁迫后(15.5%)基因表达量下降;复水后8 h时恢复正常表达水平。     

Neutralising antibodies for Mayaro virus in Pantanal, Brazil

The Pantanal hosts diverse wildlife species and therefore is a hotspot for arbovirus studies in South America. A serosurvey for Mayaro virus (MAYV), eastern (EEEV), western (WEEV) and Venezuelan (VEEV) equine encephalitis viruses was conducted with 237 sheep, 87 free-ranging caimans and 748 equids, including 37 collected from a ranch where a neurologic disorder outbreak had been recently reported. Sera were tested for specific viral antibodies using plaque-reduction neutralisation test. From a total of 748 equids, of which 264 were immunised with vaccine composed of EEEV and WEEV and 484 had no history of immunisation, 10 (1.3%) were seropositive for MAYV and two (0.3%) for VEEV using criteria of a ≥ 4-fold antibody titre difference. Among the 484 equids without history of immunisation, 48 (9.9%) were seropositive for EEEV and four (0.8%) for WEEV using the same criteria. Among the sheep, five were sero- positive for equine encephalitis alphaviruses, with one (0.4%) for EEEV, one (0.4%) for WEEV and three (1.3%) for VEEV. Regarding free-ranging caimans, one (1.1%) and three (3.4%), respectively, had low titres for neutralising antibodies to VEEV and undetermined alphaviruses. The neurological disorder outbreak could not be linked to the alphaviruses tested. Our findings represent strong evidence that MAYV and all equine encephalitis alphaviruses circulated in the Pantanal.     

Evidence for a third allele at the β-lactoglobulin (β-Lg) locus of sheep milk and its occurrence in different breeds

Summary. Milk samples from 189 Merinoland Sheep, 145 Black Faced Mutton Sheep, 89 East Friesian Milk Sheep, 36 Rhön, 36 Pleven, 23 Tsigaja, 25 Black Razka and 86 Hungarian Merino x Pleven (F1) sheep were analysed by polyacrylamide gel electrophoresis under acid conditions and isoelectric focusing in ultrathin layer polyacrylamide gels with carrier ampholytes. Six different β-lactoglobulin (β-Lg) phenotypes (A, AB, B, AC, BC and C) were observed by both methods. The occurrence of three codominant alleles (β-Lg^A, β-Lg^B, β-Lg^c) at an autosomal locus (β-Lg) was supported by family and population data on genetic equilibrium. Differences in gene frequencies between the breeds were observed.     

The possible involvement of a peroxidase in prostaglandin biosynthesis

Sheep vesicular gland microsomes have been found to have an unusual peroxidase activity with a wide peroxide specificity and capable of oxidizing cofactors of prostaglandin synthetase. The peroxidase was also similar to the synthetase in its cellular location, its activation by hemin, inhibition by heme ligands and its inactivation by different peroxides. The inhibition by 2,7-naphthalenediol (K_i = 2 μM) also suggests that the peroxidase is an integral part of the synthetase complex.