評估添加丙酸銨或接種乳酸菌對國產芻料半乾青貯草製備之成效

本研究目的在探討以丙酸銨或乳酸菌作為添加劑對國產芻料半乾青貯草發酵與保存的效果。試驗採用真空包裝袋製作實驗室規模的半乾青貯草，試驗牧草為國產苜蓿、尼羅草以及盤固草，試驗分成兩個部分，第一部分在探討不同添加量的丙酸銨（鮮重的0%、1.5%、3.0%）以及兩種發酵狀態（真空完好沒有空氣滲入的V組和以26G針頭製造空氣滲入的A組），採3×2複因子設計，共六組處理組。第二部分在探討不同乳酸菌組合對於國產半乾青貯草的影響，使用的乳酸菌包含Lactobacillus buchneri（L. buchneri, LB）、Lactobacillus plantarum（L. plantarum, LP）以及Pediococcus acidilactaci（P. acidilactaci, PA），試驗組別共四組包含對照組、3.0%丙酸銨處理組、兩種乳酸菌組合處理組（LB+ LP）和三種乳酸菌組合處理組（LB+ LP +PA），每株乳酸菌添加劑量皆為每克鮮草1×106菌落數，所有半乾青貯草製作均為有空氣滲入的發酵狀態。第一部分丙酸銨添加試驗中，在真空完好沒有空氣滲入的組別，在採樣過程中苜蓿半乾青貯草未出現目測發霉外觀、尼羅草和盤固草半乾青貯皆出現1包目測發霉，然而，在有空氣滲入下對照組出現較高比例的目測發霉，在苜蓿對照組有將近4成的目測發霉、尼羅草對照組有高達6成的目測發霉、盤固草對照組有高達8成的目測發霉，在兩次的試驗結果中，不論丙酸銨或乳酸菌添加都使目測發霉數量降至1到2成；丙酸銨的添加會降低半乾青貯草發酵過程中的乳酸產量，其中又以3.0%丙酸銨添有較低的乳酸產量（p < 0.05）；在苜蓿半乾青貯草試驗中，乳酸菌的添加在發酵初期有較高的乳酸產量（p < 0.05），在發酵後期則出現較高的乙酸產量（p < 0.05），不過pH值未能降至青貯穩定的臨界pH值4.75 (適用於乾物率40%的作物中)，黴菌毒素ZEA和DON有超標的現象；在尼羅草試驗中，乳酸菌的添加組在發酵初期有較高的乳酸產量（p < 0.05）以及較低的pH值（p < 0.01），發酵後期乳酸產量下降顯著低於對照組（p < 0.01）、乙酸產量上升但沒有顯著高於對照組，pH值在發酵後期對照組為4.5、乳酸菌組為4.3，皆低於pH臨界值4.75，且發酵過程未檢測出超標的黴菌毒素濃度；在盤固草試驗中，第二年作物水分較高（大於70%），試驗結果在發酵產物上不理想，發酵初期乳酸菌添加組並沒有出現較高的乳酸產量，發酵後期不論對照組或乳酸菌處理組都出現高濃度的丁酸濃度（2-3 % DM basis），顯示在較高水分盤固草作物乳酸菌的添加仍發酵不易，不過發酵過程未檢測出超標的黴菌毒素濃度。綜合上述，在丙酸銨和乳酸菌的添加組對於在有空氣滲入情形下，能有效抑制發霉現象，在黴菌毒素檢測中只有苜蓿出現較高的DON和ZEA濃度，其餘尼羅草和盤固草雖然發霉現象嚴重但未出現毒素超標的現象，在有機酸的產物以乳酸菌添加組有較好的產酸效果。

關鍵字

苜蓿半乾青貯草；尼羅草半乾青貯；盤固草半乾青貯；丙酸銨；乳酸菌；黴菌；黴菌毒素

並列摘要

The purpose of this study was to investigate the effect of ammonium propionate or lactic acid bacteria as an additive on the fermentation and preservation of haylage of domestic forages. The test haylage was made in a laboratory scale using vacuum bags. The experimental forage consisted of domestic Alfalfa, Nilegrass and Pangolagrass. The study was divided into two parts. The first part was to investigate the different levels of ammonium propionate (0, 1.5, 3.0 % of fresh weight) addition under two fermentation conditions (V group for vacuum condition without air infiltration and A group for air infiltration condition). The experimental design is 3×2 factorial design with a total of six treatment groups. The second part was to evaluate the effects of different lactic acid bacteria combination on haylage making. The lactic acid bacteria used include Lactobacillus buchneri (L. buchneri, LB), Lactobacillus plantarum (L. plantarum, LP) and Pediococcus acidilactaci (P. acidilactaci, PA). There were four groups including the control group, 3.0 % ammonium propionate, the mixture of two kinds of lactic acid bacteria (LB + LP) group and the mixture of three kinds of lactic acid bacteria (LB + LP + PA) group. The dosage of innoculant was 1 × 106 of fresh grass per gram for each lactic acid bacterium. All haylages were made under air infiltration condition. In the first part of the ammonium propionate addition test, the Alfalfa haylage did not show visually mouldy appearance during the sampling process under vacuum condition without air infiltration; in addition, the Nilegrass and Pangolagrass haylage only got 1 mouldy appearance. However, there is higher proportion of visually mouldy appearance occurred in the control group under air infiltration condition, and there is nearly 40% of mouldy appearance in Alfalfa haylage, up to 60% mouldy appearance in Nilegrass, up to 80% mouldy appearance in Pangolagrass. No matter ammonium propionate or lactic acid bacteria was added, the moldy appearance was reduced to 10 to 20%. In the fermentation product, the addition of ammonium propionate reduced the production of lactic acid. Especially in 3.0% ammonium propionate treatment, lactic acid production was low in all forages (p < 0.05). In the Alfalfa haylage, treatment of lactic acid bacteria produced more lactic acid in the initial fermentation stage (p < 0.05), and higher acetic acid production in the later fermentation stage (p < 0.05), but the pH value did not drop to the critical pH 4.75 (suitable for crops with a dry matter rate of 40%), the mycotoxins ZEA and DON were excessive. In the Nilegrass haylage, treatment of lactic acid bacteria had better acid production and higher lactic acid yield in the early fermentation (p < 0.05), as well as lower pH (p < 0.01). In late fermentation, lactic acid was significantly lower than control group (p < 0.01). Acetate production increased but not significant different than control group. The pH value was 4.5 in the control group, 4.3 in lactic acid bacteria group, both of them were lower than the critical pH value of 4.75, and the fermentation did not show excessive mycotoxin concentration. In the Pangolagrass haylage, the moisture was higher (greater than 70%) in second part test, showing no satisfactory results in fermentation products. The lactic acid bacteria-added group did not show higher lactic acid production in the early stage of fermentation. Both the control group and lactic acid bacteria treatment groups showed high concentration of butyric acid (2-3% DM basis), indicating that the addition of lactic acid bacteria in Pangolagrass with higher water content was still difficult to ensure better fermentation, but no excessive mycotoxin concentrations were detected. In conclusion, the addition of ammonium propionate and lactic acid bacteria can effectively inhibit mouldy appearance under air infiltration condition. Only high levels of DON and ZEA were observed in Alfalfa haylage. In Nilegrass and Panolagrass haylage, there was no high mycotoxin concentration even with mouldy appearance. In fermentation products, lactic acid bacteria-added group had better acid production.