不同浓度赤霉酸对饲料添加菌生长的影响

为研究不同浓度的赤霉酸对饲料添加菌生长的影响,用2种不同浓度的赤霉酸溶液单独添加饲料乳酸菌（A4+A7）和纤维素分解菌（Nf+Y6）进行培养52 h,其中每4 h作一个单位测定出OD_{600 nm}值并绘制生长曲线,分析不同浓度的赤霉酸对饲料添加菌生长的影响。结果表明,赤霉酸浓度为10 mg/L时,各组OD_{600 nm}值分别为0.64、0.70、0.84、0.78、0.72,其中试验组2的OD_{600 nm}值与对照组和其他试验组相比有明显增高,总活菌数高达11.6×10⁸ CFU/mL,比对照组（1.63×10⁸ CFU/mL）高7倍以上;当赤霉酸浓度增加到20 mg/L时,各组OD_{600 nm}值分别为0.64、0.60、0.59、0.59、0.63,其中各试验组的OD_{600 nm}值与对照组相比无明显差异（P>0.05）,试验组活菌数（1.60×10⁸ CFU/mL）与对照组相比（1.63×10⁸ CFU/mL）无明显差异（P>0.05）。通过试验数据和生长曲线得知赤霉酸浓度在10 mg/L时能促进乳酸菌和纤维素分解菌的生长繁殖;赤霉酸浓度为20 mg/L时乳酸菌和纤维素分解菌的生长速度明显下降。综上提示,适当添加赤霉酸对饲料添加菌生长有明显的促进作用,赤霉酸浓度过高则饲料添加菌的生长量降低。

Effects of Different Concentrations of Gibberellic Acid on Growth of Bacteria Added in Feed Additives

In order to assess the effects of different concentrations of gibberellic acid on the growth of bacteria added in feed additives, two different concentrations （10 mg/L and 20 mg/L） of gibberellic acid solutions were added to the culture medium of lactic acid bacteria strains of A4+A7 and cellulose-decomposing bacteria strains of Nf+Y6 separately for a 52-hour-long cultivation. The OD_{600 nm} value was determined every 4 hours and the growth curve was drawn. The results showed that when the adding concentration of gibberellic acid was 10 mg/L, the OD_{600 nm} values of the different groups were 0.64, 0.70, 0.84, 0.78 and 0.72, respectively. The OD_{600 nm} value of the experimental group 2 were obviously higher than that of the control group and the other experimental groups. The total viable count of bacteria in experimental group 2 was 11.6×10⁸ CFU/mL, which was 7 times higher than that of the control group （1.63×10⁸ CFU/mL）. When the concentration of gibberellic acid increased to 20 mg/L, the OD_{600 nm} values of the different groups were 0.64, 0.60, 0.59, 0.59 and 0.63, respectively. There was no significant （P>0.05） difference in OD_{600 nm} values between the experimental groups and control group, and there was no significant （P>0.05） difference in total viable count of bacteria between the experimental group （1.60×10⁸ CFU/mL） and control group （1.63×10⁸ CFU/mL）. The experimental data and growth curve showed that the growth of lactic acid bacteria and cellulose-decomposing bacteria could be promoted when the concentration of gibberellic acid was 10 mg/L, while the growth rate of lactic acid bacteria and cellulose-decomposing bacteria was decreased significantly when the concentration of gibberellic acid was 20 mg/L. The combined data suggested that proper addition of gibberellic acid could obviously promote the growth of the bacteria added in feed additives, but the growth of bacteria was inhibited when the concentration of gibberellic acid was exorbitant.