Enriquecimento Proteico de Resíduos Agroindustriais para Alimentação de Ruminantes

Abstract

This research aimed to evaluate the potential of protein enrichment of agro-industrial residues with yeast (Saccharomyces cerevisiae) as an alternative protein source in ruminant feed. Three experiments were conducted: The first study assessed the effect of including cassava fermented with S. cerevisiae on performance, feed intake, nutrient digestibility, ruminal microflora, and ruminal fermentation in cattle. The effects of yeast fermented cassava (YFC) in cattle diets were evaluated using the mean difference as the effect size. Subgroup analyses and meta-regression were conducted to investigate heterogeneity at a 5% significance level. The meta-analysis revealed that including fermented cassava significantly increased dry matter intake and nutrient digestibility. There was an increase in volatile fatty acid concentrations (P<0.001) and propionate (P<0.001), along with an increase in bacterial and fungal populations (P=0.004), and a reduction in protozoa count (P<0.001). Lactating cows fed with fermented cassava produced 1 kg/day more milk (P=0.025), with improvements in milk composition, including increases in fat (P<0.001), protein (P<0.001), and lactose (P=0.02). The inclusion of YFC in cattle concentrates improved ruminal fermentation, ruminal efficiency, dry matter intake, nutrient digestibility, milk production, and milk composition. The second study aimed to assess the use of agricultural residues as substrates for protein enrichment with S. cerevisiae. A completely randomized 4 x 2 factorial design was used, with four industrial residues (acerola bagasse, cassava root, orange bagasse, and pineapple peel) and two evaluations (before and after protein enrichment), with three repetitions. The chemical composition, carbohydrate and protein fractions, and in vitro gas production of the residues were evaluated. The enrichment process resulted in a significant increase in protein content and a reduction in the fibrous fraction in all analyzed residues (P<0.001). Enriched residues showed lower total gas production compared to untreated residues (P<0.001). Protein enrichment with S. cerevisiae is a promising alternative for increasing the protein content of agro-industrial residues. The third study evaluated the impact of replacing soybean meal with agro industrial residues enriched with yeast on ruminal fermentation kinetics and in vitro gas production. Using a completely randomized 3×5 factorial design with three repetitions, the study tested different agro-industrial residues (acerola, orange, and pineapple) and levels of replacement (0%, 25%, 50%, 75%, and 100%) based on dry matter. Cumulative gas production was measured using the Gompertz model. Results showed that including pineapple residue increased total gas production linearly (P<0.001), while acerola residue reduced this production (P<0.001). Organic matter digestibility increased with the inclusion of orange and pineapple residues (P<0.001), while acerola residue resulted in lower responses in the evaluated variables compared to the control treatment (P<0.001). The results indicate that enriched orange and pineapple residues can replace up to 100% of soybean meal in concentrates, benefiting ruminal fermentation and digestibility.