Efeito da exposição ao ar sobre a qualidade da silagem: revisão sistemática e meta-análise

Abstract

This study aimed to carry out a systematic review and meta-analysis to evaluate the effect of aerobic exposure in chemical composition and nutritional value in reensiling silages. After article selection using the Cochrane Library, Embase, Scopus, Web of Science, LILACS and MEDLINE-PubMed databases and a manual search of scientific journals and the references of articles selected in the systematic review, 287 articles published through May 2022 were identified. Eleven randomized control trials eligible for review were selected. Data were grouped into subgroups by the additive type (chemical; microbial; no additive), forage type (maize; sorghum; sugarcane; Napier grass; wheat) and air exposure time (≤ 12h; between 13 and 24h; ≥ 36h). The meta-analysis was performed using the “meta” package of R software. The data were analyzed using the random effects model and the raw mean difference with a 95% confidence interval (p<0.05). The aerobic exposure of reensiling silages increased (p<0.05) the content of DM (13.94 g/kg DM), of CP (1,41 g/kg DM) and of NDF (9.04 g/kg DM). The content of ADF just incresead (p=0.002) (2.27 g/kg DM) in use of microbial additive. The content of ADIN increased in sorghum silages (0.66 g/kg DM). The DIVMD reduced (p=0.047) (12.8 g/kg DM), as NFC (p=0.008) (15.6 g/kg DM). The content of MM increased (p=0.006) just in sorghum silages. The content of WSC reduced (p<0.05) in sorghum silages (8.60 g/kg DM) and sugarcane (17.06 g/kg DM), but the losses compared to control group were twice as much as in sugarcane silage. The pH increased (p<0.05) in sorghum with aerobic exposure. The NH3-N reduced (p<0.05) (1,42 g/kg N total), as lactic acid (6.32 g/kg DM). Reensiling increased (p<0.05) acetic acid (6.32 g/kg DM) and butyric acid (0.81 g/kg DM), but no effect in propionic acid content (p>0.05). The mould count at silage opening without additives reduced (p<0.05) (0,61 log10 ufc/g) when compared a control group. The reensiling reduced (p=0.002) gas loss (5.25% DM), although efluente loss increased (p<0.05) (16.33 g/kg FM). The total dry matter loss increased (p<0.05) in maize silages (21.2% DM) and reduced (p<0.05) in sugarcane silages (29.3% DM). The aerobic exposure of reensiling silages reduced the nutritional value. Further research is nedeed about the effect of reensiling in animal performance for evaluate the conduct of this practice.