江苏省耕地质量等别更新评价--以镇江市新区为例

运用因素法计算出耕地质量等别,利用对比分析法比较耕地自然、经济属性和耕地质量之间的相关性,掌握耕地质量与数量现状及变化状况,找出影响耕地质量的主要因素因子,发现耕地质量与耕地的自然、社会经济属性有很强的相关性:地形地貌决定耕地自然质量的高低;作物种植结构的科学性、农田水利设施的完善程度影响耕地利用质量;耕地区位决定耕地经济质量。     

A pig–human comparative RH map comprising 20 genes on pig chromosome 13q41 that harbours the ETEC F4ac receptor locus

The enterotoxigenic Escherichia coli (ETEC) F4ac is a major cause of diarrhoea in newborn and young pigs. The locus for the intestinal ETEC F4ac receptor (F4acR) has been mapped to pig chromosome (SSC) 13q41 with known homology to human chromosome (HSA) 3q21 and q29. However, the causative gene and mutation(s) remain unknown. The aim of this study was to characterize gene-derived markers on SSC13q41 for fine mapping of the F4acR locus, and construct a high-resolution pig–human comparative map to select positional candidate genes for F4acR. Pig-specific sequence-tagged site markers were developed for 20 genes that are located in a 6.8-Mb region on HSA3q21 and q29, and a total of 34 single-nucleotide polymorphisms (SNPs) were identified in 14 of 20 markers developed. Eighteen markers were mapped to SSC13q41, while the other two markers ( PLXNA1 and KLF15 ) were assigned to SSC13q32 and SSC7q13, respectively, by radiation hybrid mapping. This result showed that there was a small conserved segment on SSC7 corresponding to HSA3q21. A framework map comprising 18 markers on SSC13q41 was established, refining the synteny breakpoint on SSC13q41 to a region of 12.3 centiRay. The comparative radiation hybrid (RH) map revealed three interesting candidate genes for F4acR from the human genome, viz. MUC4 , MUC13 and MUC20 . Linkage analysis with six marker polymorphisms revealed that MUC4 had the most significant linkage with the F4acR locus.     

Origin of Clostridium perfringens isolates determines the ability to induce necrotic enteritis in broilers

Since the ban on growth-promoting antibiotics in animal feed in the European Union, necrotic enteritis has become a major cause of mortality in broiler chickens. Despite the importance of the disease, the pathogenesis is still not completely understood. In the current study, Clostridium perfringens strains isolated from healthy flocks and isolates from outbreaks of necrotic enteritis were evaluated for the ability to cause gut necrosis in an intestinal loop model in laying hens and in an experimental infection model in broilers. High, intermediate and low alpha toxin producing strains were chosen from each isolation source. Only the isolates from field outbreaks induced necrotic gut lesions, independent of the amount of alpha toxin produced in vitro. It was also shown that alpha toxin producing isolates from calf hemorrhagic enteritis cases were not able to induce necrotic enteritis in poultry. These results suggest the presence of host specific virulence factors in C. perfringens strains, isolated from chickens with intestinal necrotic enteritis lesions.     

奶牛全混合日粮添加过瘤胃脂肪饲养效果对比试验研究

[目的]为了研究日粮中添加过瘤胃脂肪能够有效降低奶牛产后负平衡效果.[方法]本试验选用围产期(产前3～4周)健康的奶牛48头,按照年龄、体重、胎次、体况评分、预产期相同或相近的原则,参考上胎产奶量或母亲产奶量等指标随机分为试验组和对照组,在试验组日粮中添加过瘤胃脂肪300 g/头·日,试验期145 d.[结果]表明:试验组日产奶量提高1.96 kg,产后初次配种间隔缩短8.86 d,差异极显著(P＜0.01);对奶牛体况的改善也有一定的作用,特别是对头胎牛的体况改善明显.[结论]在奶牛全混合日粮中添加过瘤胃脂肪可提高奶牛产奶量、繁殖性能,改善体况.     

Net requirements of calcium, magnesium, sodium, phosphorus, and potassium for growth of Nellore × Red Angus bulls, steers, and heifers

A comparative slaughter trial was conducted to assess the net requirements for gain of Ca, P, Na, K and Mg of bulls, steers and heifers of Nellore and Red Angus crossbreds. Twenty seven F1 Nellore and Red Angus crossbred calves (9 steers, 9 bulls, and 9 heifers), averaging 274 kg BW, were used. At the beginning of the trial, three animals from each gender were slaughtered to determine the initial body composition. The remaining 18 animals (3 animals of each gender) were randomly assigned to two treatments: fed 0.75 or 1.5% of BW of concentrate. The diets were based on corn silage and were isonitrogenous (2% N, DM). After three growing periods of 28 d, all animals were slaughtered. The cleaned gastrointestinal tract, organs, carcass, head, hide, tail, feet, and tissues were weighed to determine the empty BW (EBW). These parts were ground separately and subsampled for chemical analyses. The log of the contents of each mineral in the empty body was regressed on the log of the EBW to estimate the net requirement for each mineral per kg of empty body gain (EBG). There were no differences (P > 0.05) in the net requirements for growth of all macrominerals among genders. The equations of the pooled data of the net requirements for growth (g/kg EBG) were: 332.6 × EBW ^− 0.6367 for Ca, 112.1 × EBW ^− 0.5615 for P, 10.85 × EBW ^− 0.3992 for Na, 4.01 × EBW ^− 0.153 for K, and 3.589 × EBW ^− 0.462 for Mg. Our findings indicated that retained Ca and retained P were poorly related to the retained protein.     

黄土高原生态经济区功能定位研究

在以往黄土高原生态经济分区的基础上,定义了生态经济功能定位的概念,确定了黄土高原经济发展的主导性资源,并对其主导性和空间分布进行了系统论述;运用区位商分析法评价了黄土高原18个生态经济区的资源比较优势和产业比较优势,系统归纳总结了黄土高原生态功能极重要的区域及其分布格局;根据生态经济功能定位依据,运用系统分析和综合归纳法,对各生态经济区进行特征描述和功能定位,为区域可持续协调发展提供参考。     

北海市玉米品种比较试验

针对北海市玉米生产中存在的问题,为筛选出丰产性好、抗性强、生育期适宜的玉米品种,对迪卡007等10个品种进行了区域比较试验。综合评价结果表明,迪卡007综合表现最好,南校968、正大619、正大999、太平洋98抗病虫性好,抗逆性强,综合表现较好,以上5个品种适合本地种植。     

工厂化栽培杏鲍菇优良菌株筛选及菌包后熟培养研究

采用人工控制条件进行杏鲍菇的工厂化生产,经菌株对比试验,筛选到杏鲍菇1号和3号适宜工厂化生产需要。菌包满袋后经过5~6 d的后熟期再搬入冷库,杏鲍菇菌蕾分化快,形成早,子实体在冷库中生长时间最短。     

以比较优势理论分析贵州省茶叶运营新模式

通过透视贵州茶叶产业现状,分析了贵州茶叶的比较优势,提出了贵州茶叶运营新模式,并对加快贵州茶叶产业发展模式提出了建议。