AM真菌对石漠化地区桑树的促生及养分调控作用

为确定丛枝菌根（arbuscular mycorrhizal,AM）真菌对石漠化地区植物及土壤养分化学计量特征的影响,本研究以石漠化地区经济树种桑树为研究对象,通过模拟石漠化地区季节性干旱,研究水分供应发生变化时,AM真菌对桑树幼苗和土壤中养分调控作用。为模拟石漠化地区季节性干旱,试验设置正常供水和自然干旱2个时期,每个时期均设未接种对照（-M）、接种摩西斗管囊霉（Fm）和接种根内根孢囊霉（Ri）3个处理。桑树收获后,测定植物、土壤中的C、N、P、K含量。结果表明：在正常供水、自然干旱2个时期,接菌处理对桑树幼苗的促生效果显著,干旱胁迫发生之后,Ri菌种与桑树的亲和性、促生效果均强于Fm菌种。接菌处理对桑树幼苗N、P营养改善作用尤为明显,无论水分供应条件如何,接菌处理都显著增加桑苗各部分N、P含量。对比土壤养分含量发现,接菌处理增加了土壤有效P含量,降低了土壤中C含量,正常供水条件下,接种Fm、Ri分别使得土壤C含量下降了7.00%和8.55%。对比土壤养分计量比发现,正常供水条件下,接菌处理显著提高了土壤中的碳磷比（C/P）和氮磷比（N/P）;干旱胁迫条件下,接菌处理显著增加氮磷比（N/P）。综上所述,石漠地区发生季节性干旱时,AM真菌可以影响桑树对C、N、P养分吸收和分配,依据水分供应的变化和对养分资源需求的不同,调控土壤、植物体中C、N、P配比。     

Successful treatment of mycoplasmosis in layer chickens with single dose therapy

The efficacy of treatment with single dose administration of 5 drugs at different dosages to layer hens naturally infected with Mycoplasma gallisepticum was studied. The drugs were tiamulin, which was administered orally, tylosin (parenterally and orally), spiramycin (orally), long-acting oxytetracycline (parenterally) and tylosindihydrostreptomycin (parenterally). Cure was assessed by the absence of nasal discharge. The cure rate was significantly higher (P less than 0.05) in treated hens than in untreated hens, as early as 1 day after treatment. Remission for 33 days was achieved in 60% of hens treated with 100 mg oxytetracycline, in 100% of hens treated with 100 mg or 200 mg spiramycin, in 92% and 85% of hens treated with 100 mg tylosin, parenterally and orally, and in 89% and 88% of birds given 100 mg tiamulin and tylosin-dihydrostreptomycin, respectively.     

Plasma Antimullerian Hormone as a Predictor of Ovarian Antral Follicular Population in Bos indicus (Nelore) and Bos taurus (Holstein) Heifers

In Bos taurus cattle, antimullerian hormone (AMH) has been demonstrated to have a high degree of correlation with ovarian antral follicle count and the number of healthy follicles and oocytes. To document the correlation between the plasma concentration of AMH and follicular number in Bos indicus and Bos taurus heifers, Nelore (Bos indicus, n = 16) and Holstein heifers (Bos taurus, n = 16) had their ovarian follicular waves synchronized. After synchronization, ovarian antral follicular population (AFP) was evaluated three times at 60‐day (d) intervals (T‐120 d, 120 days before plasma AMH determination; T‐60 d, 60 days before; and T0, at the time of plasma AMH determination). The plasma AMH concentration was positively correlated with the number of ovarian follicles on the day of the follicular wave emergence in Bos indicus (Nelore) and Bos taurus (Holstein) heifers at each evaluation time (p < 0.05). The AFP was higher in Bos indicus (Nelore) than in Bos taurus (Holstein) heifers (p < 0.05). Similarly, the AMH concentration was higher in Bos indicus (Nelore) than in Bos taurus (Holstein) heifers (p < 0.0001). When heifers were classified as to present high or low AFP according to the mean of the AFP within each genetic group, high‐AFP heifers presented a greater (p < 0.0001) AMH concentration than low‐AFP heifers, regardless of the genetic group. In conclusion, the AFP is positively correlated with plasma AMH concentration in both Bos indicus (Nelore) and Bos taurus (Holstein) heifers. Furthermore, Bos indicus (Nelore) heifers presented both greater plasma AMH concentrations and AFP than Bos taurus (Holstein) heifers.