Context‐dependent responses of food‐hoarding to competitors in Apodemus peninsulae: implications for coexistence among asymmetrical species

Superior species may have distinct advantages over subordinates within asymmetrical interactions among sympatric animals. However, exactly how the subordinate species coexists with superior species is unknown. In the forests west of Beijing City, intense asymmetrical interactions of food competition exist among granivorous rodents (e.g. Apodemus peninsulae, Niviventer confucianus, Sciurotamias davidianus and Tscherskia triton) that have broadly overlapping habitats and diets but have varied body size (range 15–300 g), hoarding habits (scatter vs larder) and/or daily rhythm (diurnal vs nocturnal). The smallest rodent, A. peninsulae, which typically faces high competitive pressure from larger rodents, is an ideal model to explore how subordinate species coexist with superior species. Under semi‐natural enclosure conditions, we tested responses of seed‐hoarding behavior in A. peninsulae to intraspecific and interspecific competitors in the situations of pre‐competition (without competitor), competition (with competitor) and post‐competition (competitor removed). The results showed that for A. peninsulae, the intensity of larder‐hoarding increased and the intensity of scatter‐hoarding declined in the presence of intraspecifics and S. davidianus, whereas A. peninsulae ceased foraging and hoarding in the presence of N. confucianus and T. triton. A. peninsulae reduced intensity of hoarding outside the nest and moved more seeds into the nest for larder‐hoarding under competition from intraspecific individuals and S. davidianus. In most cases, the experimental animals could recover to their original state of pre‐competition when competitors were removed. These results suggest that subordinate species contextually regulate their food‐hoarding strategies according to different competitors, promoting species coexistence among sympatric animals that have asymmetrical food competition.     

甘肃省肃南县草地治蝗灭鼠工作经验

总结了肃南县１９５５年以来草原治蝗灭鼠为单一人工药物防治发展到生物新技术与新药物相结合的综合治理经验,提出了今后科技力量,开展多渠道,多学科,多部门协作防治的发展方向。     

羊草草原植被监测方法的比较研究

在草原长期生态监测和研究过程中,观测方法的一致性和可比性是保证数据质量及其控制的关键环节,预防观测误差比纠正误差要容易得多。因此,选择什么样的取样方法,在现代标准化和网络化的监测和研究活动中至关重要。通过对两种样线法、巢式样方法和1m×1m样方法等4种方法监测羊草草原植物物种丰富度和生产力的比较研究发现,在草原植被监测,尤其是长期监测过程中,宜将物种丰富度的监测与生产力的监测分离开来。在以物种丰富度为监测目的时,样线法为宜,最小样线长度为400m;在以监测羊草草原群落地上生物量为目的时,1m×1m样方法为宜,最少样方数为10。这样既可以缩小长期固定监测样地的面积,又可以节省人力、物力和财力。     

Biofilm production by pathogens associated with canine otitis externa,and the antibiofilm activity of ionophores and antimicrobial adjuvants

Otitis externa (OE) is a frequently reported disorder in dogs associated with secondary infections by Staphylococcus, Pseudomonas and yeast pathogens. The presence of biofilms may play an important role in the resistance of otic pathogens to antimicrobial agents. Biofilm production of twenty Staphylococcus pseudintermedius and twenty Pseudomonas aeruginosa canine otic isolates was determined quantitatively using a microtiter plate assay, and each isolate was classified as a strong, moderate, weak or nonbiofilm producer. Minimum biofilm eradication concentration (MBEC) of two ionophores (narasin and monensin) and three adjuvants (N‐acetylcysteine (NAC), Tris‐EDTA and disodium EDTA) were investigated spectrophotometrically (OD_570nm) and quantitatively (CFU/ml) against selected Staphylococcus and Pseudomonas biofilm cultures. Concurrently, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of planktonic cultures were assessed. 16/20 of the S. pseudintermedius clinical isolates were weak biofilm producers. 19/20 P. aeruginosa clinical isolates produced biofilms and were distributed almost equally as weak, moderate and strong biofilm producers. While significant antibiofilm activity was observed, no MBEC was achieved with narasin or monensin. The MBEC for NAC ranged from 5,000–10,000 µg/ml and from 20,000–80,000 µg/ml against S. pseudintermedius and P. aeruginosa, respectively. Tris‐EDTA eradicated P. aeruginosa biofilms at concentrations ranging from 6,000/1,900 to 12,000/3,800 µg/ml. The MBEC was up to 16‐fold and eightfold higher than the MIC/MBC of NAC and Tris‐EDTA, respectively. Disodium EDTA reduced biofilm growth of both strains at concentrations of 470 µg/ml and higher. It can be concluded that biofilm production is common in pathogens associated with canine OE. NAC and Tris‐EDTA are effective antibiofilm agents in vitro that could be considered for the treatment of biofilm‐associated OE in dogs.     

Economic evaluation of artificial insemination of sex‐sorted semen on a Brown Swiss dairy farm—A case study

Artificial insemination using sex‐sorted semen is employed to efficiently increase the number of female dairy calves born. Previous studies have determined that using sex‐sorted semen is beneficial to improve the management, but the mechanism by which it increases cattle numbers through objective indices of breeding remains unclear. This study focused on a Brown Swiss cattle herd in which frozen female sex‐sorted semen was systematically employed to increase the number of cattle. We analyzed the correlation between the increase in the number of cattle and the screening accuracy of sex‐sorted semen, measuring indices such as pregnancy rate and birth rate of female calves. Study revealed that: (1) production cost for female calves is influenced by the pregnancy rate, rate of female calves, and using sex‐sorted semen is less expensive than using nonsorted semen; (2) improvements in screening accuracy nearly doubled the number of cows and tripled the number of heifers in 5 years; and (3) use of sex‐sorted semen improved milk quality. The pregnancy rate was lower when sex‐sorted semen was used, but the birth rate of heifers was improved. Results suggest that artificial insemination using sex‐sorted semen is beneficial because it economically produces offspring to increase the herd.     

Which source and level of dietary sodium is appropriate for broiler chickens reared in a high‐altitude area?

This study investigated effect of increasing level of dietary sodium using sodium bicarbonate or sodium chloride on growth performance, mortality, characteristics of carcass, organs and tibia, calcium and phosphorus of serum in broilers reared in a high‐altitude area (1,700 m above sea level). A total of 588 Ross 308 male broiler chicks were used in seven treatments, six replicates per treatment of 14 birds per each from 1 to 38 d of age. Seven dietary treatments consisted of a basal diet (with 0.16% sodium and 0.23% chloride), top‐dressed for six diets to give three supplementary levels of sodium (0.07%, 0.14% and 0.21%) from sodium bicarbonate (respectively by 0.26%, 0.52% and 0.78%) or sodium chloride (respectively by 0.18%, 0.36% and 0.54%), resulting in seven diets with total sodium and chloride levels of 0.16% and 0.23%, 0.23% and 0.23%, 0.30% and 0.23%, 0.37% and 0.23%, 0.23% and 0.33%, 0.30% and 0.44%, 0.37% and 0.55% respectively. Increasing sodium level improved feed conversion ratio (FCR) linearly and quadratically. However, when FCR was calculated without adjusting for feed intake of mortalities, the enhanced sodium level did not improve this parameter. Increasing sodium level via sodium chloride enhanced ascites mortality, total mortality, relative weight of heart and right ventricle linearly. Increasing sodium level reduced serum calcium and enhanced serum phosphorus linearly; however, there was a linear tendency to increase tibia ash when sodium level was enhanced by sodium bicarbonate (p = 0.08) or sodium chloride (p = 0.07). Increasing sodium level via sodium bicarbonate tended (p = 0.08) to reduce tibia strength linearly. In conclusion, a diet with 0.16% sodium and 0.23% chloride is enough for broiler chicken reared in a high‐altitude area, and increasing dietary sodium level via sodium chloride has detrimental effect on survivability of broiler in such condition.     

大针茅根系构型对草地退化的响应

本研究对锡林郭勒典型草原区轻度、中度、重度和极度4个退化梯度草地中大针茅(Stipa grandis)根系构型进行研究。结果表明,1）根分叉数、根表面积和总根长3个参数是分析大针茅根系构型在不同退化程度草地中变化的主要指标,其中根分叉数对该变化的解释力最强,3个参数的累积贡献率为90.7%;2）从轻度、重度到极度退化程度的草地系列中,大针茅的根系构型小型化趋势明显;3）中度退化程度的草地中大针茅根系构型小型化特别明显;4）根系构型小型化最终导致整个植物体小型化,因此在群落退化演替进程中大针茅的建群种作用逐渐减弱并最终为其他优势种取代。