链烷技术检测蝗虫食性方法的研究

为验证链烷技术测定蝗虫食性的精确性,确定蝗虫粪便中链烷的回收率。于2007年夏季在内蒙古太仆寺旗天然草地,用优势植物羊草(Leymus chinensis)、糙隐子草(Cleistegenes squarrosa)和克氏针茅(Stipa kylovii)各500g,饲喂360只成虫的亚洲小车蝗(Oedaleus asiaticus)。试验期内每天记录蝗虫实际牧草采食量、采食成分和排粪量,利用气相色谱分析牧草和粪样的链烷含量,应用链烷技术测定蝗虫的牧草采食比例,并与实际值进行比较。结果表明,3种牧草链烷模式存在种间差异;蝗虫粪便中链烷的回收率随链烷长度的增加而线性增加;蝗虫采食羊草、糙隐子草和克氏针茅比例的测定值与实际值存在显著正相关(P<0.05),相关系数分别为0.925 5、0.956 6和0.978 2。因此链烷技术可以精确测定典型草原蝗虫的食物组成。     

Herbage intake,milk production and sward utilization of dairy cows grazing grass/white clover swards at low,medium and high allowances

Abstract

Herbage intake (HI), milk production and sward utilization of Norwegian Red Cattle dairy cows in mid-lactation, rotationally grazing grass/white clover swards at low, medium and high allowances (HA), were examined in three experiments (I, II and III). The daily target allowances per cow were 18 and 36 kg DM in Experiment I and 12, 18, and 24 kg DM in Experiments II and III. The cows were grazing in groups of seven (Experiments II and III) to ten (I) individuals. The proportions of white clover in the swards averaged 12%, 40% and 46% in Experiments I, II and III, respectively. In addition to pasture, the cows were fed concentrate mixtures in varying amounts (0–6.8 kg) with the highest amounts offered to the highest yielding cows. HI was estimated using the n-alkane technique. No effect of HA on HI was obtained in Experiment I. In Experiment II, and for II and III combined, there was a significant positive effect of HA on HI. The average increase in HI was 0.24 kg DM per extra kg DM on offer. The utilization of the sward (measured at 3 cm above ground level) decreased from 72% at the lowest HA to 51% at the highest HA in Experiment II and III. HA did not affect milk yield or milk composition significantly (P>0.05).     

Effect of maize grain and herbage allowance on estimated metabolizable energy intake and animal performance in beef cattle finishing systems

This study investigated the effects of levels of supplementation with maize grain and herbage allowance (HA) on grass herbage and maize intake, animal performance and grazing behaviour in two replicated grazing experiments with Angus beef cattle in Argentina. In Experiment 1, the response to increasing HA (2·5, 5·0 and 7·5 kg DM herbage 100 kg^?1 live weight (LW) d^?1 with and without 0·5 kg DM maize grain 100 kg^?1 LW d^?1) was investigated. In Experiment 2, the responses to level of maize grain offered (0, 0·5 and 1·0 kg DM maize grain 100 kg^?1 LW d^?1) at an HA of 2·5 kg DM herbage 100 kg^?1 LW d^?1 and an HA of 5·0 kg 100 kg^?1 LW d^?1 without maize grain were assessed. In Experiment 2, soyabean meal was added to control the crude protein concentration in the diet. Two methods were used for intake estimations: pre‐ and post‐feeding herbage mass difference, and the use of the n‐alkane and ¹³C technique. The latter predicted most accurately the metabolizable energy requirements calculated from live weights and liveweight gain of beef cattle attained in each treatment in both experiments. Increasing HA significantly increased herbage intake and liveweight gain (P < 0·01), and general quadratic relationships between these variables could be fitted across experiments despite differences in animal and pasture characteristics. Increasing the amount of maize grain offered significantly reduced herbage intake and grazing time, but increased liveweight gain and digestibility of the diet. Substitution rate increased with increasing HA in Experiment 1 but was not affected by level of maize supplementation in Experiment 2. These relationships will aid the development of grazing management models for Argentinean conditions.     

饱和链烷技术测定绵羊食性食量精确性研究

【目的】验证饱和链烷技术测定家畜食性和食量的精确性，确定绵羊粪便中链烷的回收率。【方法】于2004年秋季在中国科学院内蒙古草原生态系统定位研究站用不同放牧演替阶段的优势植物羊草（Leymus chinensis）、糙隐子草（Cleistogenes squarrosa）和冷蒿（Artemisia frigida）按一定比例混合组成日粮，饲喂9只2岁羯羊，每只羊投喂一粒QSM胶囊，试验期内每天记录绵羊实际牧草采食量、采食成分和排粪量，利用气相色谱分析牧草和粪样的链烷含量，应用链烷技术测定绵羊的排粪量、不同牧草采食比例和总干物质采食量，并与实际值进行比较。【结果】3种牧草链烷模式存在种间差异；绵羊粪便中链烷的回收率随链烷长度的增加而线性增加；绵羊排粪量测定值与实际值存在极显著的正相关（P < 0.01，r = 0.9994）；绵羊采食羊草、糙隐子草和冷蒿比例的测定值与实际值存在极显著(P < 0.01)正相关，相关系数分别为0.9913、0.9864和0.9999；绵羊干物质采食量用C33∶C32和C31∶C32比值测定的值分别比实际值低4％(±1.3％)和7％(±1.3％)，但差异不显著(P > 0.05)。【结论】饱和链烷技术可以精确测定典型草原绵羊的排粪量、食物组成和采食量。     

沈阳周边典型污灌区地下水中直链烷烃污染特征研究

采用固相萃取-气相色谱，氢火焰检测器（SPE—GC/FID）方法，研究了沈阳周边典型污灌区10个地下水样品中直链烷烃的污染特征及分布规律。结果表明，污灌区地下水已经受到不同程度的直链烷烃污染，毗邻沈阳城区的S4-S74个采样点直链烷烃平均浓度高达138．58μg·L^-1，是其他各点平均浓度的34．4倍。从分布规律上看，不同碳链长度的直链烷烃浓度呈正态分布趋势，基本在C16-C17处出现峰值。可能的原因是长期的污水灌溉和城市工业活动导致了地下水中直链烷烃污染，而烷烃自身理化性质、微生物降解作用和直链烷烃在包气带中的迁移作用促成了不同碳链长度烷烃呈现正态分布的趋势。