Abstract:

This study aimed to elucidate the effects of pine needle （Pinus） essential oil on the quality and aerobic stability of Broussonetia papyrifera silage， and thereby provide technical data to facilitate its processing and utilization. B. papyrifera was fermented spontaneously with no addition of pine needle oil （CK）， or with addition of 160 mg·kg^-1 （Ⅰ）， 320 mg·kg^-1 （Ⅱ） or 480 mg·kg^-1 （Ⅲ） pine needle oil in a single-factor experiment. Various parameters， including the nutritional composition， fermentation quality and microbial count of the B. papyrifera silage were evaluated throughout the ensiling process （3， 7， 15， 30 and 60 days）. Additionally， aerobic stability was assessed at 60 days. It was found that on day 3 of ensiling， the water-soluble carbohydrate （WSC） content， lactic acid （LA） concentration， and acetic acid （AA） concentrations in groups Ⅰ， Ⅱ， and Ⅲ were significantly higher than those of CK （P<0.05）. Conversely， pH level， ammonia nitrogen∶total nitrogen （NH₃-N∶TN）， propionic acid （PA） concentration， and mold count were significantly lower in the treated silages than in CK （P<0.05）. Lactic acid bacteria counts and yeast counts in groups Ⅱ and Ⅲ differed significantly from those of CK （P<0.05）. On day 7 of ensiling， lactate concentration， acetic acid concentration， and lactic acid bacteria count in groups Ⅰ， Ⅱ， and Ⅲ were significantly higher than those in the CK group （P<0.05）. In contrast， pH level， NH₃-N∶TN， PA concentration， yeast counts and mold counts on day 7 were significantly lower in these groups than in CK （P<0.05）. Additionally， the dry matter （DM） content and WSC content in groups Ⅱ and Ⅲ were also significantly higher than those observed in CK （P<0.05）. On day 15， the crude protein （CP） content， WSC content， lactate concentration， acetic acid concentration and lactic acid bacteria count in groups Ⅰ， Ⅱ， and Ⅲ were significantly higher than in CK （P<0.05）. Conversely， pH level， NH₃-N∶TN， PA concentration， yeast count and mold count in groups Ⅰ， Ⅱ， and Ⅲ were significantly lower than in CK （P<0.05）. On day 30， the WSC contents， lactate concentrations， acetic acid concentrations， and lactic acid bacteria counts in groups I， Ⅱ， and Ⅲ were significantly elevated compared to CK （P<0.05）. Conversely， there was a significant reduction in the pH level， NH₃-N∶TN， PA concentration， and yeast counts compared to the CK （P<0.05）. On day 60， the CP content， WSC content， lactic acid concentration， acetic acid concentration， and lactic acid bacteria counts in groups I， Ⅱ， and Ⅲ were significantly higher than in CK （P<0.05）. As earlier， pH level， NH₃-N∶TN， PA concentration， and yeast counts were significantly decreased compared with the CK （P<0.05）. The aerobic stability of groups Ⅱ and Ⅲ was notably superior to that of both group I and CK （P<0.05）. In summary， pine needle essential oil effectively reduced the loss of CP and WSC during silage production. It increased lactate concentration， acetic acid concentration， and lactic acid bacteria count， while lowering pH level， and inhibiting mold proliferation. Furthermore， it significantly improved the aerobic stability of B. papyrifera silage. The addition of 480 mg·kg^-1 produced the most pronounced silage fermentation improvement effect.

Key words: pine needle essential oil, Broussonetia papyrifera silage, nutrient composition, fermentation quality, aerobic stability