Effects of pre‐partum milking of dairy cows on calcium metabolism at start of milking and at calving

This experiment studied the effect of pre‐partal milk removal on calcium metabolism at start of milking and at calving. Nine cows of the Swedish Red breed were milked for 1–7 days pre‐partum. The average milk yield at the first milking was 4.8 l, and the average yield the last day prior to calving was 13.4 l. Five cows were used as control cows and were only milked post‐partum. Samples of plasma and urine were taken to determine the effect of pre‐partum milking and calving on levels of calcium, magnesium, parathyroid hormone and plasma C‐terminal crosslinked telopeptide of type 1‐collagen (CTx), used as a marker of bone resorption. Pre‐partum milking resulted in a decrease in plasma calcium that was evident 2 days after the first milking. Parathyroid hormone increased at the same time, and CTx started to increase from 24 h after the first milking. There were no effects on plasma magnesium or urinary output of calcium or magnesium. The first week after calving, there were no differences between pre‐partum milked cows and control cows in plasma or urine variables, or in milk yield. In conclusion, pre‐partum milking activated the calcium‐restoring mechanisms but did not improve calcium status at calving.     

交联聚丙烯酰胺型保水剂对水稻盘育秧秧苗素质的影响

为了研究保水剂对育秧过程中水稻秧苗素质和生理特征的影响,进行了育秧盘中添加5~30g/盘交联聚丙烯酰胺保水剂的育秧试验。结果表明:与不添加保水剂(对照)相比,添加保水剂后秧苗的株高、叶龄、叶长、叶宽、叶鞘长有所提高,其中叶宽与对照相比差异均达显著水平;20 g/盘处理与对照相比,叶龄、最长根长、假茎宽、百株鲜质量等差异显著;15 g/盘处理秧苗百株鲜质量和干质量分别为18.56 g和2.71 g,与对照相比达显著水平。15 g/盘处理秧苗的叶绿素含量、根系活力、SOD活性分别为9.35 mg/g、4.60μg/(g·h)、129.18 U/g,为所有处理的最大值;CAT活性在5~15 g/盘处理时变化不大,超过这一范围则下降。MDA含量在保水剂添加量15 g/盘以下时变化不明显,超过20 g/盘后明显上升。育秧盘中添加15~20 g/盘保水剂可提高秧苗叶绿素含量,使秧苗SOD等功能酶处于较佳的生理状态,提高水稻根系活力,促进地下部的生长,从而提高水稻盘育秧秧苗素质。     

羟甲基交联碱木质素锰肥的锰离子缓释动力学研究

为改善中国北方土壤缺锰的问题,该文以麦草碱木质素为原料制备了羟甲基碱木质素（HMAL）;以物理混合的方式添加硫酸锰,以甲醛、尿素作为交联剂使HMAL发生缩合交联制备了羟甲基交联碱木质素锰肥（CHMAL-Mn）。CHMAL-Mn肥产率为93.7%,CHMAL-Mn肥的锰离子的饱和负载量为48 mg/g;其红外光谱表明甲醛成功交联羟甲基碱木质。以7种常见动力学和概率分布的数学模型对CHMAL-Mn肥的锰离子累积释放率的动力学试验数据的进行拟合,以R2、均方误差(e)、精确因子(Af)和偏差因子(Bf)的算数平均值比较模型拟合有效性。结果表明：对CHMAL-Mn肥的锰离子累积释放率的动力学试验数据拟合性最好的模型是Ritger-Peppa模型,其R2、e、Af和Bf的平均值分别为0.9443、0.0083、0.0223和0.0003。当CHMAL-Mn肥的锰负载量为12 mg/g时,拟合模型的缓释指数n<0.45,锰离子缓释行为以Fick扩散为主。当CHMAL-Mn肥的锰负载量大于24 mg/g时,拟合模型的缓释指数0.45≤n≤0.89,缓释机理为非Fick扩散与骨架溶蚀协同作用。当CHMAL-Mn肥的锰负载量达到饱和值48 mg/g时,拟合模型的缓释指数n为0.811,该模型预测CHMAL-Mn肥对锰离子累积缓释率的极大值为79.28%,预测缓释时间为95.92 h;模型拟合准确率为96.57%。该研究为可大幅提高碱木质对肥料锰肥的负载量,为碱木质素的综合利用和促进碱木质素在现代农业可降解缓/控释载体领域的应用提供了参考。     

玉米交联淀粉的制备与特性研究

玉米淀粉与环氧氯丙烷起交联反应,制得交联淀粉。采用正交实验设计进行优化,确定最佳工艺条件:环氧氯丙烷用量为淀粉干质量的0.58%,NaOH用量为淀粉干质量的2.5%,温度40℃,反应时间2h。试验表明,原玉米淀粉经交联后很大程度上改善了淀粉的耐酸性、抗剪切性和抗老化性,提高了淀粉的稳定性。     

交联聚丙烯酰胺和AM真菌对玉米苗生长、养分吸收和生理指标的影响

在玉米育苗基质中加入交联聚丙烯酰胺(crosslinked polyacrylate amine,CPA)和接种AM真菌,研究它们对玉米苗生长、养分吸收及有关生理指标的影响。结果表明,在-CPA的基质中,接种AM真菌的玉米苗生物量高于不接种,并且增加磷含量与吸收量,提高硝酸还原酶活性;在+CPA的基质中,CPA提高了玉米苗P含量以及吸收量,适量的CPA浓度还能够提高玉米苗的生物量,CPA显著降低AM真菌的感染率,接种AM真菌后的玉米苗生物量与不接种的相似甚至更低,玉米苗养分吸收、硝酸还原酶、叶绿素和根系活力因菌株和CPA含量不同而异。由于降低AM真菌的感染率,不能进一步改善菌根玉米苗生长,菌根效应被CPA的促生作用掩盖甚至超过,故在实际育苗工作中,建议采用接种AM真菌或在基质中适量加入CPA一种方式即可。     

乳液聚合法制备染料隐色体热敏型微胶囊

采用乳液聚合法,以甲基丙烯酸甲酯和超支化不饱和聚(酰胺-酯)为壁材,染料隐色体为芯材制备了热敏型微胶囊。研究了反应条件对微胶囊粒径、包覆率的影响。采用扫描电镜,激光粒度分析仪和紫外-可见分光光度计进行分析,结果表明,所制备的微胶囊分散性好,粒径分布窄,并具有良好的热敏性能。     

Preparation and evaluation of cefquinome‐loaded gelatin microspheres and the pharmacokinetics in pigs

Cefquinome (CEF) is widely used for veterinary clinical applications because of its broad spectrum and high efficiency. However, frequent administrations are required due to its short elimination half‐life. In this study, cefquinome sulfate gelatin microspheres (CEF‐GMS) were prepared as a sustained‐release formulation using emulsion chemical cross‐linking technique. Physical properties, stability, sustained‐release property in vitro, and pharmacokinetics in pigs were assessed. The morphology of CEF‐GMS showed a good sphericity with porous structure on the surface, and the mean diameter was 8.80 ± 0.78 μm, with 90.60 ± 3.98% of the total in the range of 5–20 μm. There were no significant changes of all estimated indexes in the stability tests. In vitro drug release study showed that the release of CEF from CEF‐GMS was much slower than that from crude CEF in a release medium. Pharmacokinetic characteristics were evaluated following intramuscular administration of CEF‐GMS or Cefquinome sulfate injection (CEF‐Inj) in pigs at a dosage of 4 mg CEF/kg body weight. The plasma drug concentration–time data of CEF‐GMS and CEF‐Inj were both best fitted by two‐compartment models with first‐order absorption, and the elimination half‐life of CEF‐GMS was almost 10 times that of CEF‐Inj. Overall, CEF‐GMS might be used as a sustained‐release formulation of CEF for veterinary clinical applications.