Uso do pH como indicador da deterioração aeróbia em silagens de milho em condições práticas

Abstract

Corn is the most used crop for silage making on Brazilian dairy farms. However, corn silage is particularly susceptible to aerobic deterioration when exposed to oxygen. The temperature of the silage is a parameter that can be measured and related to the aerobic deterioration, but the heat generated during the fermentation process can be confused with heat of deterioration. Thus, the pH is a variable that may be used as a parameter to detect spoilage. The objective of this study was to verify the relationship between pH and aerobic deterioration on commercial dairy farms. Silage samples were collected at twenty-five properties in the South of Minas Gerais from November 2015 to December 2016. Physical, chemical, microbiological characteristics were measured at four locations at the silo face: 3 at the top (lateral, center, and an intermediate between them) and 1 at the silo core. A completely randomized design with four treatments and twenty-five replications was used. Data were submitted to analysis of variance using the PROC ANOVA of the SAS 9.1. The Pearson correlation coefficient was used using the PROC CORR of the same program. The core treatment had lower pH value and yeast counts, and higher concentration of lactic acid and sugars compared to other treatments. Yeast growth above 5 log cfu/g and was associated with higher temperature and pH values. The data from this study show that pH may be useful in detecting the aerobic deterioration process at its early stage, and can be used in combination with temperature, alerting farmers to the onset of deterioration.