Quitosana e líquido de castanha de caju como aditivos para bovinos

Abstract

The objective of this study was to evaluate the effect of the combination of chitosan and cashew nut shell liquid on ruminal fermentation parameters, greenhouse gas emissions, metabolomics, and digestibility in cattle fed whole-grain-based diets. Two simultaneous experiments were conducted: 1: fixed dose of chitosan with increasing doses of technical cashew nut shell liquid (CNSLt); 2: fixed dose of CNSLt with increasing doses of chitosan. Each trial included 4 animals, randomly distributed in a 4 × 4 Latin square design. The diets offered were based on 85% whole corn grain and 15% protein mineral–vitamin pellet. The treatments for the experiment with a fixed dose of chitosan and increasing doses of CNSLt were: control with monensin (MON) (25 mg/kg DM); Q+CNSLt1: 375 mg/kg DM chitosan + 300 mg/kg DM CNSLt; Q+CNSLt2: 375 mg/kg DM chitosan + 600 mg/kg DM CNSLt; Q+CNSLt3: 375 mg/kg DM + 900 mg/kg DM CNSLt. For the experiment with a fixed dose of CNSLt and increasing doses of chitosan, the treatments were: control (CON) with monensin (25 mg/kg DM); CNSLt+Q1: 600 mg/kg DM CNSLt + 375 mg/kg DM chitosan; CNSLt+Q2: 600 mg/kg DM CNSLt + 750 mg/kg DM chitosan; CNSLt+Q3: 600 mg/kg DM CNSLt + 1125 mg/kg DM chitosan. In Experiment 1, there was no effect (P > 0.05) on intake, nutrient digestibility, pH, purine derivatives, volatile fatty acids (VFA), or ammonia nitrogen. In Experiment 2, there was an effect (P < 0.05) on allantoin levels, purine derivatives, absorbed proteins, microbial nitrogen, microbial protein, and microbial efficiency. Metabolomic analysis of plasma and ruminal fluid from Experiment 1 showed that monensin and Q+CNSLt1 are similar to each other but differ from Q+CNSLt2 and Q+CNSLt3. The Q+CNSLt2 treatment showed the greatest visible difference in heat generation, while Q+CNSLt1 showed the greatest similarity when compared to the control treatment (monensin). Metabolomic analysis of plasma in Experiment 2 showed that monensin, CNSLt+Q2, and CNSLt+Q3 are similar to each other but differ from CNSLt+Q1. Analysis of ruminal fluid metabolites showed that monensin and CNSLt+Q1 are similar, but both differ from CNSLt+Q2 and CNSLt+Q3. Thus, considering the similar desirable effects, the equivalent metabolomic profile, and their effects on the ruminal fermentation process, the dose of 600 mg/kg DM + 375 mg/kg DM (treatments Q+CNSLt2 and CNSLt+Q1) proved to be a potential substitute treatment for monensin in diets of feedlot cattle fed with high grain proportions.