Abstract
The present experiment evaluated the influence of moisture level and anaerobic fermentation on aerobic stability of total mixed ration (TMR). The dynamic changes in chemical composition and microbial population that occur after air exposure were examined, and the species of yeast associated with the deterioration process were also identified in both non-fermented and fermented TMR to deepen the understanding of aerobic deterioration. The moisture levels of TMR in this experiment were adjusted to 400 g/kg (low moisture level, LML), 450 g/kg (medium moisture level, MML), and 500 g/kg (high moisture level, HML), and both non-fermented and 56-d-fermented TMR were subjected to air exposure to determine aerobic stability. Aerobic deterioration resulted in high losses of nutritional components and largely reduced dry matter digestibility. Non-fermented TMR deteriorated during 48 h of air exposure and the HML treatment was more aerobically unstable. On dry matter (DM) basis, yeast populations significantly increased from 107 to 1010 cfu/g during air exposure, and Candida ethanolica was the predominant species during deterioration in non-fermented TMR. Fermented TMR exhibited considerable resistance to aerobic deterioration. Spoilage was only observed in the HML treatment and its yeast population increased dramatically to 109 cfu/g DM when air exposure progressed to 30 d. Zygosaccharomyces bailii was the sole yeast species isolated when spoilage occurred. These results confirmed that non-fermented and fermented TMR with a HML are more prone to spoilage, and fermented TMR has considerable resistance to aerobic deterioration. Yeasts can trigger aerobic deterioration in both non-fermented and fermented TMR. C. ethanolica may be involved in the spoilage of non-fermented TMR and the vigorous growth of Z. bailii can initiate aerobic deterioration in fermented TMR.
Highlights
There is a common practice to preserve high-moisture by-products with dry feeds as fermented total mixed ration (TMR) in recent years, and this practice avoids the energy costs associated with drying and improves the odors and flavors of the unpalatable by-products through anaerobic fermentation (Xu et al, 2007a,b; Xu et al, 2008; Cao et al, 2009)
The objectives of this study were to determine the effects of moisture level of non-fermented and fermented TMR on the dynamic changes in chemical composition and microbial population during aerobic deterioration, and to identify yeast species that are associated with aerobic deterioration in both non-fermented and fermented TMR
The other portion was first subjected to anaerobic fermentation by ensiling with approximately 40 kg TMR in a 60-L polyethylene barrel in a room with the temperature maintained at 27°C to 31°C and the fermented TMR was tested for Chemical composition (g/kg dry matter (DM))
Summary
There is a common practice to preserve high-moisture by-products with dry feeds as fermented total mixed ration (TMR) in recent years, and this practice avoids the energy costs associated with drying and improves the odors and flavors of the unpalatable by-products through anaerobic fermentation (Xu et al, 2007a,b; Xu et al, 2008; Cao et al, 2009). Fermented TMR results in highly enhanced aerobic stability (Nishino and Hattori, 2007; Wang and Nishino, 2008; Weinberg et al, 2011). When anaerobic fermentation is prolonged to a month or longer, yeast counts can recede to levels below the limit of detection (
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