Assessment of hygienic quality of haylage fed to healthy horses

Abstract

Wrapped forages such as haylage and silage are increasing in popularity in equine feed rations, but knowledge of their microbial composition, especially of haylage, is scarce. Haylage may be more at risk of mould growth compared to silage, and methods for the assessment of hygienic quality of haylage are needed. Varying culturing conditions, including aerobic ⁄ anaerobic incubation, four substrates and three incubation temperatures were therefore evaluated for analysis of fungi in haylage samples from eighteen horse farms, taken on two occasions (autumn and the following spring). Average mould counts in forage samples were low, but fungi with the potential for producing mycotoxins, such as Aspergillus fumigatus and Penicillium spp., were present. The microbial composition and content of fermentation products were similar in haylage samples taken in autumn and in spring. The type of substrate used for cultivation did not influence mould or yeast counts, but not all mould species were present on all substrates. Incubation temperature influenced fungal counts and the presence of mould species. By using at least two substrates (malt extract agar and dichloran 18% glycerol agar) and two incubation temperatures (25 and 37°C), all mould species ⁄ genera that were identified in this study could be detected.

Filamentous fungi in wrapped forages determined with different sampling and culturing methods

“…DG18 is, however, also well suited for detection of fungi in samples with lower water activity, such as the genera Aspergillus and Penicillium, due to high concentration of sodium chloride or carbohydrates. In a previous study of hygienic quality assessment of wrapped forage with DM content at 653 (SD 89.9) g/kg, these genera were among the most common genera in the samples (Müller, Hultén, & Gröndahl, ). Müller et al.…”

Detection, identification, and typing of Listeria species from baled silages fed to dairy cows

“…The samples were immediately stored at 4 to 6°C before analysis, which was conducted later the same day. Sampling was performed, according to literature (Müller et al, 2011), by a limited number of people (the authors ET and GB). The same sampling protocol was followed at the same sampling time in each farm to avoid differences in sampling procedure that could have influenced the analytical result.…”

Microbial Counts in Forages for Horses—Effect of Storage Time and of Water Soaking Before Feeding

“…Table 2 Average microbial composition (log CFU/g) in silage, haylage, and hay after 3 and 12 months of storage, and interaction effects of forage type (silage, haylage, and hay) and storage time (lower detection limit log 1.5 CFU/g for yeast and mold, log 1.7 for lactic acid bacteria, clostridia, and enterobacteria). In a study of haylage bales on commercial horse farms, a trend for decreasing mold counts (P ¼ .06) from OctoberNovember 2007 to May-June 2008 was reported [31]. Increased storage time resulted in decreased mold counts in hay in the present study, but hay contained greater mold counts than silage and hay at all sampling occasions.…”

“…Previous investigations of effects of increased storage time of wrapped forage bales did not include counts of LAB [23,31] but reported that pH and content of lactic acid in silage and haylage, which are products of LAB activity, decreased (pH) and increased (lactic acid content) from 2 to 14 months of storage [23], which was probably due to continued growth and/or activity of LAB in the forage during storage. The reason for decreased LAB counts with increased storage time in silage and haylage in the current study remains to be explained, but lack of energy substrates or too low pH in the forages is not a likely explanation given the comparatively high DM content in both haylage and silage, resulting in restricted lactic acid fermentation [23,29].…”

“…Increased yeast counts may not pose an immediate health threat to horses, as yeast species present in forages are generally not considered pathogenic [29]. Yeast counts greater than log 5 to log 6 CFU/g have been proposed to indicate advanced aerobic deterioration of silage [30], but wrapped forages containing up to log 7.3 CFU yeast/g have been fed to horses without reports of health disturbances [31]. The increased LAB counts were not considered to be a health risk for horses.…”