本试验旨在研究体外连续培养条件下稀释率对培养液中氮素分配的影响。试验设3个稀释率,分别为4%/h、6%/h和8%/h,每个稀释率设3个重复。由5只瘘管山羊提供瘤胃液。结果表明:随培养时间的延续,培养液中原虫蛋白质、细菌蛋白质、可溶性蛋白质、肽、游离氨基酸氮、氨氮的含量皆呈波动变化,再次投料后变化趋势基本一致。随着稀释率的升高,培养液中原虫蛋白质、细菌蛋白质、可溶性蛋白质、肽、游离氨基酸氮、氨氮的含量均有所下降,除可溶性蛋白质外,其他指标均出现显著或极显著变化(P<0.05或P<0.01)。24 h流量结果表明,上述6个指标中氮素流量随稀释率的升高皆升高,但其在总氮素流量中所占比例的变化有所不同。其中,原虫蛋白质中氮素流量及其在总氮素流量中所占比例在4%/h、6%/h、8%/h稀释率下分别为256.32 mg/d和30%、367.20 mg/d和31%、385.92 mg/d和29%,以6%/h组的比例最高;细菌蛋白质中氮素流量及其在总氮素流量中所占比例在4%/h、6%/h、8%/h稀释率下分别为218.88 mg/d和26%、289.44 mg/d和25%、328.32 mg/d和24%,其比例随稀释率提高持续下降;微生物蛋白质(原虫蛋白质和细菌蛋白质之和)中氮素流量及其在总氮素流量中所占比例在4%/h、6%/h、8%/h稀释率下分别为475.20 mg/d和56%、656.64 mg/d和56%、714.24 mg/d和53%,以6%/h组流量相对较高,且比例没有下降;可溶性蛋白质中氮素流量及其在总氮素流量中所占比例随稀释率的升高而提高,在4%/h、6%/h、8%/h稀释率下分别为178.56 mg/d和21%、263.52 mg/d和22%;345.60 mg/d和26%。不同稀释率下,游离氨基酸氮、肽、氨氮中氮素流量在总氮素流量中所占比例范围分别为6%、5%～6%、10%～11%,总体上变化不大。综上所述,稀释率影响体外连续培养条件下培养液中氮素流量及其比例分配,并以稀释率为6%/h时的微生物蛋白质氮素流量及其在总氮素流量中所占比例较高。
The objective of this experiment was to investigate the effects of dilution rate on nitrogen distribution in culture solution under the condition of continuous culture in vitro. A single factorial experiment was designed as 3 dilution rate levels (4%/h, 6%/h, and 8%/h, respectively) with 3 replicates for each dilution rate, and 5 goats fisted with cannulas were introduced as rumen liquor donors. The results showed as follows: the contents of protozoal protein, bacterial protein, soluble protein, peptide, free amino acid nitrogen and ammonia nitrogen in culture solution showed fluctuated changes with time going on, and the change trends were similar after re-feeding. With the dilution rate increasing, the contents of protozoal protein, bacterial protein, peptide, free amino acid nitrogen and ammonia nitrogen were all decreased. The significant or extremely significant differences were detected in all above indexes (P<0.05 or P<0.01) except for the soluble protein. However, the nitrogen quantities of above 6 indexes calculated with 24 hours were all increased with the dilution rate increasing, but the percentages of individual nitrogen quantity in the total nitrogen quantity were different from each other. The nitrogen quantity of protozoal protein and the percentage of that in the total nitrogen quantity under the dilution rate of 4%/h, 6%/h and 8%/h were 256.32 mg/d and 30%, 367.20 mg/d and 31%, 385.92 mg/d and 29%, respectively, and the 6%/h group had the highest percentage. The nitrogen quantity of bacterial protein and the percentage of that in the total nitrogen quantity under the dilution rate of 4%/h, 6%/h and 8%/h were 218.88 mg/d and 26%, 289.44 mg/d and 25%, 328.32 mg/d and 24%, respectively, and were decreased with the increase of dilution rate in their percentages. The nitrogen quantity of microbial protein (defined as the sum of protozoal protein and bacterial protein) and the percentage of that in the total nitrogen quantity under the dilution rate of 4%/h, 6%/h and 8%/h were 475.20 mg/d and 56%, 656.64 mg/d and 56%, 714.24 mg/d and 53%, respectively, and the quantity in the 6%/h group was higher and the percentage did not decrease in this group. The nitrogen quantity of soluble protein and the percentage of that in the total nitrogen quantity were increased with the dilution rate increasing, and those under the dilution rate of 4%/h, 6%/h and 8%/h were 178.56 mg/d and 21%, 263.52 mg/d and 22%, 345.60 mg/d and 26%, respectively. Under the different dilution rates, the percentage ranges of nitrogen quantities in free amino acid nitrogen, peptide and ammonia nitrogen in the total nitrogen quantity were 6%, 5% to 6% and 10% to 11%, respectively, but the percentages totally had a little change. It is concluded that dilution rate affects the quantity and the percentage distribution of nitrogen under the condition of continuous culture, with 6%/h dilution rate showing comparatively high quantity and percentage in microbial nitrogen.
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