南美洲的草地资源

南美洲有草地面积８４４．５万ｋｍ＾２,饲养着草食家畜４．２亿头,其中牛为２．６２亿头。热带稀树草原、亚热带温带潘帕斯草原、温带半荒漠、热带荒漠、热带干燥疏林与灌丛、热带雨林区的人工草地是主要草地类型。巴西和阿根廷是南美洲两个重要的草地资源大国,分别有草地面积１．６９亿ｈｍ＾２和１．４２亿ｈｍ＾２。     

亚洲的草地资源及其评价

亚洲有草地面积２０．７８亿ｈｍ＾２。中国、俄罗斯（亚洲部分）、哈萨克斯坦和蒙古国是亚洲的４个草地资源大国,它们的草地面积都在１亿ｈｍ＾２以上。亚洲的天然草地类型繁多,从资源的角度看,主要是热带稀树草原,亚热带荒漠,温带荒漠,温带草原,温带草甸,高寒草甸和冻原等。     

群牧黄牛的生物学习性观察

连续四年试验观察,证明集群放牧饲养的黄牛具有合群、护群、亲和、模仿、习惯等习性;其反刍、歇息、应激等行为亦进行了必要的阐述。     

丙丁酚对蛋鸡生产性能及蛋中胆固醇含量的影响

近年来,美国蛋的平均消费量持续下降。部分原因是由于人们厌食早餐,生活方式的改变。可是,在很大程度上是由于人们认为食品中的胆固醇会引起冠心病,从而影响了蛋的消费。因此,任何降低蛋中胆固醇含量的方法,都有助于养禽业。美国和其他国家的许多学者,对降低蛋中胆固醇含量进行了大量研究,试用了多种化学制剂,认为丙丁酚〔4,4’—(异丙叉二硫)—双(2,6—二特丁基酚)〕对降低蛋中胆固醇含量最有效。为研究丙丁酚对蛋鸡生产性能及蛋中胆固醇的影响,作者把72只40周龄星杂蛋鸡养在个体笼内(30.5×45.7cm)。试验设6种日粮处理,每种日粮设2个重复,每重复6只鸡。     

蛋鸡饮水中添加88－C微生物制剂对产蛋性能的影响

蛋鸡饮水中添加８８－Ｃ微生物制剂对产蛋性能的影响牟玉清，李诗洪（四川农业大学６２５０１４）李克弦，方盛荣，亢正生（大邑县畜牧局）“８８－Ｃ微生物”制剂，是一种高效生物增产剂。该制剂具有改善生物营养，调节生物生理机能，防病抗病，增加生物产量，改善产品品...     

规模化猪场疫病传入的外部风险因素指标体系的初探

据实际调查,运用层次分析法,将疫病传入的各外界风险因素指标划分为目标层、准则层和分准则层三个层次。采用EXCEL软件进行数据统计,依次编辑各层次结构模型,构建各层次的判断矩阵和一致性检验。结果表明：猪场的管理措施、生物安全、场址是疫病传入的主要风险因素。据此确立了I级指标和II级指标,从而构建疫病传入的风险因素指标体系。     

Determination and kinetics of enrofloxacin and ciprofloxacin in Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a liquid chromatography/mass spectrometry method

Determination and kinetics of enrofloxacin and ciprofloxacin in Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a liquid chromatography/mass spectrometry method. J. vet. Pharmacol. Therap. 34, 142-152. The fluoroquinolones enrofloxacin (EF) and ciprofloxacin (CF) residues were investigated in the edible tissues of two important Asian aquacultured species such as Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry method. Fish and prawn were treated with medicated feed with multiple doses of EF, in field conditions. A validation study of the analytical method was realized in terms of linearity, specificity, precision (repeatability and within-laboratory reproducibility), recovery and decision limit (CCα). The time needed before the antibiotic disappears from animal tissues or reach the maximum residue limit (MRL, 100μg/kg) was assessed. The concentration values of EF detected in Tra catfish tissue were between the MRL and 2×MRL concentrations, according to the fish density, 7days following the end of the enrofloxacin treatment (20mg/kg body weight per day, for seven consecutive days). The concentration value of ER in prawn tissue was lower than the MRL and the limit of quantification (LOQ, 14μg/kg) 5 and 7days after the stop of the EF treatment (50mg/kg body weight per day, for five consecutive days), respectively. The mean detected levels of CF was much lower in comparison with that of EF, indicating that only a small part of EF is metabolized into CF (<5%) in both Tra catfish and prawn.     

Revealing genetic relationships between compounds affecting boar taint and reproduction in pigs

Boar taint is characterized by an unpleasant taste or odor in intact male pigs and is primarily attributed to increased concentrations of androstenone and skatole and to a lesser extent by increased indole. The boar taint compounds skatole and indole are produced by gut bacteria, metabolized in the liver, and stored in the fat tissue. Androstenone, on the other hand, is synthesized in the testis along with testosterone and estrogens, which are known to be important factors affecting fertility. The main goal of this study was to investigate the relationship between genetic factors involved in the primary boar taint compounds in an attempt to discover ways to reduce boar taint without decreasing fertility-related compounds. Heritabilities and genetic correlations between traits were estimated for compounds related to boar taint (androstenone, skatole, indole) and reproduction (testosterone, 17β-estradiol, and estrone sulfate). Heritabilities in the range of 0.47 to 0.67 were detected for androstenone concentrations in both fat and plasma, whereas those for skatole and indole were slightly less (0.27 to 0.41). The genetic correlations between androstenone in plasma and fat were extremely high (0.91 to 0.98) in Duroc and Landrace. In addition, genetic correlations between androstenone (both plasma and fat) and the other sex steroids (estrone sulfate, 17β-estradiol, and testosterone) were very high, in the range of 0.80 to 0.95. Furthermore, a genome-wide association study (GWA) and a combined linkage disequilibrium and linkage analysis (LDLA) were conducted on 1,533 purebred Landrace and 1,027 purebred Duroc to find genome regions involved in genetic control of the boar taint compounds androstenone, skatole, and indole, and sex hormones related to fertility traits. Up to 3,297 informative SNP markers were included for both breeds, including SNP from several boar taint candidate genes. From the GWA study, we found that altogether 27 regions were significant at a genome-wide level (P < 0.05) and an additional 7 regions were significant at a chromosomal level. From the LDLA study, 7 regions were significant on a genome-wide level and an additional 7 regions were significant at a chromosomal level. The most convincing associations were obtained in 6 regions affecting skatole and indole in fat on chromosomes 1, 2, 3, 7, 13, and 14, 1 region on chromosome 6 affecting androstenone in plasma only, and 5 regions on chromosomes 3, 4, 13, and 15 affecting androstenone, testosterone, and estrogens.