Influência da adição de monensina e óleo essencial sobre os parâmetros fermentativos de silagens de TMR com elevado teor de umidade

Abstract

The nutritional quality and economic viability of TMR silages have been proven by many studies, with the main focus on evaluating the effect of macro-ingredients in the formulation of total mixed ration silages (TMRs). However, few studies have tested the possible effects of fermentation modulating additives on the quality of the TMR fermentation process, since they can jeopardise the growth of microorganisms that are fundamental to the quality of the silage fermentation process. The aim of this study was to assess the influence of different doses of monensin and limonene essential oil on the fermentation parameters of TMR silages with a high moisture content (30 per cent DM). The treatments tested were: control (TMR with no additive), MON35 (TMR with 35 mg monensin/kg DM), MON45 (TMR with 45 mg monensin/kg DM), OEL300 (TMR with 300 mg OE/kg DM) and OEL600 (TMR with 600 mg OE/kg DM). The TMR was formulated based on the nutritional requirements of dairy cows for an average production of 25 litres of milk/day (NRC, 2001). The parameters assessed were fermentation losses, pH (ensiled TMR), organic acid concentrations (ensiled TMR) and aerobic stability. The highest effluent losses were observed in the treatments that received MON35, MON45 and OEL300 (69.07 kg/t DM, 66.25 kg/t DM and 66.52 kg/t DM, respectively), but these were the treatments that showed the highest lactic acid yields (6.78% DM, 6.94% DM, 8.1% DM). Among the treatments tested, OEL600 resulted in a lower lactic acid content (4.87% DM), however, it promoted greater aerobic stability than OEL300 (91.88 and 86.06 hours, respectively). This greater aerobic stability may be associated with acetic acid, as OEL600 provided a higher acetic acid content than the other treatments tested. In view of this, the additives were beneficial for the production of TMR silage, controlled the presence and activities of harmful microorganisms in the ensiling process, and presented an adequate fermentation profile for the quality of ensiled TMR. However, for TMR silage with a high moisture content, the 600 mg/kg DM dosage of OEL is not recommended, as it provided the lowest production of lactic acid. The two dosages of MON did not show many differences in their effects on the ensiling process, and the 35mg/kg DM dosage is recommended, as production costs would be reduced, given that monensin is a high-cost product.