The effect of cultivar, wilting and storage period on fermentation and the clostridial community of alfalfa silage

Abstract

The objective of this study was to gain deeper insights into chemical transformations and the clostridial community dynamics during the ensiling of alfalfa. A factorial experiment was conducted with four alfalfa cultivars [Sanditi (A1), AC Caribou (A2), WL319HQ (A3) and 4030 (A4)] Â three wilting durations [0 h (direct-cut), 2 h and 4 h] Â three storage periods (14, 28 and 56 days). The clostridial community was examined using denaturing gradient gel electrophoresis. High butyric acid and ammonia nitrogen (NH 3 -N) contents and clostridia numbers were observed in direct-cut silage, with higher values observed in A4 than in the other three cultivars. However, butyric acid and NH 3 -N contents and clostridia numbers decreased with wilting regardless of the cultivar. Although Clostridium ghonii and Clostridium sartagoforme were common to all direct-cut and wilted silages, bands for these species were faint. Differences in the appearing time of these species were observed, bands for C. ghonii were found after 14 and 28 days of ensiling, while those for C. sartagoforme were only found after 56 days. In addition, in direct-cut silage, distinct bands for Clostridium perfringens were detected in A1, A2 and A3, while those for Clostridium sporogenes were detected in A4. The inactive spores of clostridia could be observed in 4-h wilted silage as no butyric acid was detected. It was concluded that the enhanced clostridial fermentation of direct-cut silage was attributed mainly to C. perfringens and C. sporogenes, while C. ghonii and C. sartagoforme were involved in the restricted clostridial fermentation of 2-h wilted silage. ARTICLE HISTORY

Impact of wilting and additives on fermentation quality and carbohydrate composition of mulberry silage

“…This may be because low pH value can lead to the acid hydrolysis of fibre [20] and inhibit the growth of undesirable bacteria [3]. This result was in agreement with the study of Zheng et al [5], who concluded that a low DM content always coupled with low WSC, and this is readily subjected to clostridial fermentation.…”

“…Additionally, wilting had significant effects on the CP and BC in this study. The CP content in the wilted material was lower than that in the non-wilted material, and this result is similar with the finding of Zheng et al [5]. The reason might be that the plant cells still survived after harvesting, and the degrading enzymes in cells degraded the proteins into small molecules of ammonia during wilting [15].…”

“…After 30 days of ensiling, the 0 h-wilted silages (except for the L1-treated silages) had higher lactic acid and acetic acid concentration compared with the 4 h-wilted silages. This result can be explained by the low bacterial activity and fermentation acid concentrations due to lower moisture content [5]. Therefore, wilting can influence the growth and reproduction of LAB which is essential to silage fermentation.…”

“…The silages treated with L1 also had a lower NH 3 -N content (21.94 to 45.75 g/kg TN) than the other treatments at the three wilting rates. This result could be attributed to a sharp decrease in the pH value which inhibited aerobic bacteria and clostridia and decreased protein degradation [5]. The NH 3 -N content is a reliable indicator of proteolysis in silages, and for well-preserved silages, the NH 3 -N content is less than 100 g/kg of TN [7].…”

“…The CE addition might be beneficial for degradation of the cell walls, which could contribute to releasing fermentable substrate for LAB growth. Except additives, wilting is often recommended to restrict the clostridia growth and the proteolysis [5].…”