Abstract: The effect of bale density (50 kg·m^-3, 100 kg·m^-3, 150 kg·m^-3, 200 kg·m^-3), moisture content (14%-16%, 19%-21%, 24%-26%, 29%-31%) and addition of CaO (0%, 1%, 2%, 3%) to alfalfa hay bales were assessed to help identify the optimum conditions for storage of alfalfa hay bales. Nutrient content, feed value and in vitro digestibility of alfalfa bales stored for 360 days were analyzed using an orthogonal experimental design with three factors to determine optimum storage conditions. Experiment 1: The nutritional composition and feeding value, through different experimental treatments of the effect on alfalfa hay nutrition was initially assessed; treatments A₁₀ (density 100 kg·m^-3, moisture content 24%-26% and fungicide 3%), A₁₂ (density 200 kg·m^-3, moisture content 24%-26% and fungicide 1%), A₁₄ (density 100 kg·m^-3, moisture content 29%-31% and fungicide 2%) and A₁₅ (density 150 kg·m^-3, moisture content 29%-31% and fungicide 1%) resulted in relatively small dry matter (DM) losses with high feed value after 360 days. Experiment 2: The four best treatments were screened with A₁ (density 50 kg·m^-3, moisture content 14%-16% and fungicide 0) and A₁₆ (density 150 kg·m^-3, moisture content 29%-31% and fungicide 0) were used as controls. In vitro digestion was also assessed. The results showed that treatment A₁₄ had the highest gas production rate of 53.13 mL, significantly higher than the control treatments (P<0.05). The pH of A₁₄ bales was lower than other treatments at all times, with a mean pH of 6.64. The highest TVFA content of 61.05 mol·L^-1 occurred in A₁₄, significantly higher than other treatments (P<0.01). Degradation losses for crude protein and DM were 81.21% and 66.84% respectively, significantly higher than other treatments (P<0.01). Consideration of nutritional composition, feeding value and in vitro digestibility revealed that alfalfa hay with relatively high moisture (29%-31%), medium density (100 kg·m^-3) with 2% CaO added was superior to other treatment combinations.

Key words: alfalfa bale, fungicide, feeding value, in vitro digestion