Aditivos químicos e microbianos na silagem de sorgo: efeitos sobre a qualidade, o valor nutritivo e o desempenho de ovinos confinados

Abstract

Silage is an essential practice to ensure the feeding of ruminants, especially during periods of forage scarcity, with sorghum being a viable alternative due to its resistance to adverse conditions. The quality of silage is related to the fermentative process and nutrient preservation, and the use of chemical and microbial additives has demonstrated potential to improve these aspects. The objective of this study was to evaluate the effects of chemical additives based on organic acids and microbial inoculants containing Lentilactobacillus buchneri, both individually and in combination, on fermentative quality, microbial profile, aerobic stability, and performance of sheep confined with sorghum silage. The study was conducted in two chapters. In Chapter 1, the aim was to assess the effect of two additives, one based on organic acids (OA) and L. buchneri (Lb), either individually or combined. The experiment followed a completely randomized design (CRD) in a 4 × 3 factorial arrangement, with five replications per treatment, four additives (Control, Lb, OA, and Blend), and three fermentation periods (15, 30, and 90 days). Analyses included fermentative profile, quantification of microbial populations, organic acid production, aerobic stability, and 16S rRNA gene diversity. In Chapter 2, a trial was conducted with 40 sheep fed the same silages after 90 days of fermentation. This trial also followed a CRD, with four treatments and 10 replications. Feed intake, digestibility, and losses due to discards were monitored during confinement. Microbial diversity analysis indicated that silages treated with additives exhibited a balanced microbiota, with greater predominance of L. buchneri and other beneficial lactic acid bacteria, as well as a lower presence of fungi and yeasts compared to the Control. Filamentous fungi counts were consistently higher in the Control silage, while the Lb-treated silage showed greater aerobic stability across all fermentation periods. The results from Chapter 2 demonstrated that treatments with additives, particularly the combination (Blend), significantly improved silage quality, with lower dry matter loss, higher aerobic stability, and better nutrient preservation. Dry matter intake did not differ significantly among treatments; however, animals fed treated silages, especially Blend, showed higher intake of non-fiber carbohydrates and metabolizable energy. Digestibility of dry matter, organic matter, crude protein, and ether extract was higher with the use of additives, particularly in the Blend, which also exhibited the highest total digestible nutrient content. Daily weight gain was greater in sheep receiving this treatment. Furthermore, additives improved aerobic stability and reduced losses due to feed discard during the feeding period. In conclusion, the application of chemical and microbial additives, either individually or combined, improves the conservation of sorghum silage, its nutritional value, and the performance of confined sheep. The combination of the two additives proved to be the most advantageous, primarily due to its positive impact on aerobic stability, microbial diversity, and animal productivity under the conditions imposed in the experiments.