Effects of steaming and storage on microbial quality and nutrient losses of hay.

BACKGROUND: Steaming reduces microbial content of hay but the effect of steaming on nutrient quality and the effects of storage after steaming on microbial content are incompletely known. AIMS/OBJECTIVES: It was hypothesized that steamed hay can be stored for up to 24 hours without an increase in microbial content and that steaming of hay favors the increase in measurable Maillard reaction products. METHODS: Spoiled hay was steamed and then stored in hay nets, buckets or the hay steamer itself under summer and winter climate conditions. Microbial content was assessed by bacterial and fungal culture before and after steaming and after 12 and 24 hours of storage. Nutrient analysis before and after steaming followed VDLUFA standard methods. Carboxymethyllysine (CML) and furosine were determined by liquid chromatography-mass spectrometry and ion exchange chromatography, respectively. RESULTS: Steaming reduced dry matter content of hay, which increased again following 24h of storage in a hay net (summer) or bucket (winter). Steaming reduced mesophilic aerobic total bacterial counts by 96.46 - 99.90 %. Microbial counts remained below VDLUFA benchmarks after 24 h of storage; however, counts for indicator groups 4 and/or 5 were above benchmarks after 12 h of storage in some experiments. Furosine doubled (P = .02) and CML tripled (P = .00) after steaming. CONCLUSIONS: Steamed hay can be stored under various practical conditions for 24 hours without significant microbial recontamination. Hay steaming leads to a loss preceacal digestible protein and an increase in Maillard Reaction product.