The effect of fibrolytic enzyme, Lactobacillus plantarum and two food antioxidants on the fermentation quality, alpha-tocopherol and beta-carotene of high moisture napier grass silage ensiled at different temperatures

Abstract

Alpha-tocopherol and beta-carotene of forage are antioxidants and play important roles in the immune system of ruminants. Fermentation quality, alpha-tocopherol and beta-carotene of high moisture napier grass (Pennisetum purpureum cv. Mott) ensiled without or with additives (fibrolytic enzyme, EN; Lactobacillus plantarum, LP; tert-butylhydroquinone, TBHQ; tea polyphenols, TP) at 15°C, 30°C and 45°C were examined in the present study. After ensiling for 70days, untreated silages had lower (P<0.05) pH, butyric acid and ammonia-N content at 15°C and 45°C than at 30°C. Compared with untreated silage, EN and LP lowered (P<0.05) pH and increased (P<0.05) lactic acid content at 15°C, 30°C and 45°C; TBHQ lowered ammonia-N content (P<0.05) at 15°C, lowered (P<0.05) pH and butyric acid content at 30°C, and lowered (P<0.05) acetic acid and ammonia-N content at 45°C; TP lowered (P<0.05) pH at 15°C and lowered (P<0.05) lactic acid content at 30°C. Especially at 30°C, TP had the highest (P<0.05) acetic acid and butyric acid content among all silages. Napier grass ensiled at 30°C had higher (P<0.05) alpha-tocopherol content than before ensiling. Napier grass ensiled at 30°C and 45°C had higher (P<0.05) alpha-tocopherol content than ensiled at 15°C. EN and TP had lower (P<0.05) alpha-tocopherol content than untreated silage at 15°C, 30°C and 45°C. Napier grass ensiled at 15°C, 30°C and 45°C had lower (P<0.05) beta-carotene content than it before ensiling. Napier grass ensiled at 30°C had higher (P<0.05) beta-carotene content than ensiled at 15°C and 45°C. Additives-treated silages had lower (P<0.05) beta-carotekne contents than untreated silage at 15°C, 30°C and 45°C, except for TBHQ at 45°C (P<0.05). In conclusion, fermentation qualities of untreated and treated silages were better at 15°C and 45°C (V-score>99) than at 30°C (V-score<96). Compared with untreated silage (V-score=78.5) at 30°C, EN, LP and TBHQ improved fermentation quality (V-score>83), and TP lowered fermentation quality (V-score=74.5). Silage ensiled at 30°C increased alpha-tocopherol content and lost beta-carotene slightly. Additives did not reduce alpha-tocopherol and beta-carotene loss at any temperature, except for TBHQ ensiled at 45°C. The interactions between additives and preservation temperatures indicated that TP ensiled at 30°C had the poorest fermentation quality, LP and TBHQ ensiled at 30°C had lower alpha-tocopherol loss, and TBHQ and TP ensiled at 30°C had lower beta-carotene loss. TBHQ might be a valuable additive to ensile napier grass at 15°C, 30°C and 45°C, and to reduce beta-carotene loss of napier grass silage at 45°C.