Cinética de fermentação ruminal in vitro, cinética de degradação ruminal, comportamento ingestivo, consumo, digestibilidade e partição da energia em ovinos alimentados com silagens de milho reensiladas

Abstract

In Brazil and in some regions of the world as in Israel and in the United States, corn silages are constantly exposed to the air because of the re-ensilage process. The silage transfer between properties is a valuable measure adopted to solve the bulky scarcity. In fact, this procedure has supplied the lack of bulky in many properties of several Brazilian regions. However, this practice can change the nutritional value of the silage that have been exposured to the atmospheric air. Therefore, this study aimed to determine the nutritional value of the corn silage subjected to re-ensilage in zero, 12, 24 and 48 hours after exposure to the atmospheric air. The nutritional value of the re-ensiled corn silage was determined from the evaluation of the in vitro fermentation kinectics, the ruminal degradation of the ingestive behavior kinectics, intake, digestibility and energy partition in sheep. The corn silage were planted at Embrapa Maize and Sorghum in Sete Lagoas, MG. 80 containers were provided to support the silage and, after 56 days of the process, 60 of them were taken out of the containers and re-ensiled after 12, 24 and 48 of exposure to atmospheric air. 56 days after the re-ensilage process, the containers were opened for the execution of the test to evaluate the kinetics of fermentation in vitro, the kinetics of ruminal fermentation, the kinectics of the ingestive behavior, intake, digestibility and energy partition in sheep. For the ingestive behavior, intake, digestibility and energy partition studies, 20 adult sheep were used in a completely randomized experimental design. The sheep went through a 21 day adaptation period and a 5 day sample collection of the offered material - leftovers, feces and urine. In the last two days of collection, a study of the ingestive behavior in sheep was conducted. Then, the CH4 emission was measured in open-flow respirometric chamber. During the consumption and digestibility test, samplings were carried out in the offered silage. They were pre-dried and milled to 5mm and 1mm, respectively, for the achievement of the kinetic assay in vitro fermentation and kinetics of ruminal fermentation of the reensiled corn silages. The corn silage ruminal fermentation kinectics of the re-ensiled material was determined by ruminal incubation nylon bags technique using 4 adult cows. The samples milled to 5mm were weighed in nylon bags (50 µm) and incubated in the rumen of cattle for 0, 6, 12, 24, 48, 96 and 120 hours. For the in vitro gas production kinectics experiment, the samples milled to 1mm were weighed 3536 Ankom® F-57 and incubated inside containers of fermentation for 12 and 96 hours. For all variables analyzed in this study, we adopted p<0.05 as significance level in the variance analyzes and performed regressions. The different times of the re-ensilage did not influence the in vitro fermentation kinectics, the ingestive behavior, the intake, the digestibility, the partition of energy and the production of CH4 in sheep fed with re-ensiled corn silage (P>0.05). For the ruminal fermentation kinectics of the re-ensiled corn silages it was observed that the rate of disappearance (C) of the organic matter (OM) for the control treatment (zero hour) was higher in 5.05%, 27.21% and 7.47% compared to the 12, 24 and 48 hours re-ensilage corn silage, respectively. The soluble fraction (S) of organic matter was higher for the time of zero hour of re-ensilage, being higher in 10.56%, 5.95% and 13.75% compared to the 12, 24 and 48 hours of reensilage, respectively. In this study, only some variables related to the kinetics of ruminal fermentation were influenced by different times of re-ensilage. However, such variations are not of practical importance for the recommendation of re-ensilage. Therefore, based on this study, the re-ensilage did not compromise the nutritional value of the corn silage.