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

Overview

• This study investigates how steaming hay affects its microbial quality and nutrient composition, particularly focusing on the changes during storage up to 24 hours post-steaming and the formation of Maillard reaction products.

Introduction and Objective

• Hay often contains microbial contaminants that can be harmful to animals consuming it.
• Steaming hay is known to reduce microbial contamination, but its effects on nutrient quality and how storage after steaming influences microbial content were not well understood prior to this study.
• The researchers hypothesized that steamed hay could be stored for up to 24 hours without a microbial increase, and that steaming would increase measurable Maillard reaction products, which are markers of nutrient changes.

Methods

• Spoiled hay samples were steamed and then stored under different practical conditions: in hay nets, buckets, or inside the hay steamer itself.
• Storage was conducted under both summer and winter climate conditions to simulate real-world variability.
• Microbial assessments included bacterial and fungal cultures taken before steaming, immediately after steaming, and after 12 and 24 hours of storage.
• Nutrient analysis followed standardized VDLUFA methods to quantify changes in dry matter and protein content.
• Two specific Maillard reaction products, carboxymethyllysine (CML) and furosine, were measured using advanced chromatography and mass spectrometry techniques.

Results

• Steaming caused a reduction in dry matter content of hay initially, but dry matter levels increased again after 24 hours of storage when stored in hay nets (summer) or buckets (winter), indicating some moisture changes during storage.
• There was a substantial reduction in mesophilic aerobic total bacterial counts by 96.46% to 99.90% immediately after steaming.
• Microbial counts remained below the VDLUFA benchmark levels even after 24 hours of storage, suggesting effective control of microbial contamination during short-term storage.
• However, certain indicator microbial groups (groups 4 and/or 5) exceeded benchmarks in some tests after just 12 hours of storage, indicating some early microbial recontamination or growth under specific conditions.
• Steaming caused a significant increase in Maillard reaction products: furosine levels doubled and CML levels tripled, highlighting the chemical changes and potential protein modifications induced by heat treatment.

Conclusions

• Steaming effectively reduces microbial contamination in hay and allows for safe storage of up to 24 hours under various practical conditions without significant microbial recontamination.
• However, steaming leads to a reduction in prececal digestible protein, indicating a loss in nutritional quality relevant for animal digestion.
• There is a marked increase in Maillard reaction products after steaming, which reflect heat-induced chemical modifications of proteins that may affect their digestibility and nutritional value.
• These findings suggest that while steaming can improve hay hygiene, its impact on nutrient quality must be considered in feed management decisions.