Microbiology and nutritive value of moist hay

Preservatives on the basis of propionic acid help to stabilise not perfectly dry hay. These past years, the interest in these types of preservatives has been growing mostly due to the increasing use of big balers. While harvesting has become more efficient, the conservation turns out to be more delicate, particularly in the case of roughage harvested with an insufficient dry matter content (DM < 85 %).The Swiss Federal Research Station of Posieux (RAP) has investigated under field conditions the microbiological quality and nutritive value of second-cut hay, which was pressed to round bales on attaining a dry matter content of 76 % and which was treated with a preservative. The two-factorial design comprised preservative dosage and baler type. Big balers with a constant press chamber proved to be better suited than those with a variable press chamber. The former produce bales with a relatively soft core which facilitates the elimination of excess moisture. Even though the preservative has limited the raise in temperature, its fungi-static effect was unsatisfactory in certain cases. Some treated bales presented a high degree of mould infection. The only distinct difference in nutrient contents between treated and untreated bales concerned sugar. The significantly lower sugar contents of untreated bales reflect microbial growth and activity. With respect to protein value, this study has confirmed that the heating-up of forage causes a noticeably reduced rumen degradability of crude protein.