923 resultados para L-LACTIC ACID


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Probiotic bacteria have gained popularity as a defence against disorders of the bowel. However, the acid sensitivity of these cells results in a loss of viability during gastric passage and, consequently, a loss of efficacy. Probiotic treatment can be supplemented using ‘prebiotics’, which are carbohydrates fermented specifically by probiotic cells in the body. This combination of probiotic and prebiotic is termed a ‘synbiotic’. Within this article a multiparticulate dosage form has been developed, consisting of poly(d,l-lactic-co-glycolic acid) (PLGA) microcapsules containing prebiotic Bimuno™ incorporated into an alginate–chitosan matrix containing probiotic Bifidobacterium breve. The aim of this multiparticulate was that, in vivo, the probiotic would be protected against gastric acid and the release of the prebiotic would occur in the distal colon. After microscopic investigation, this synbiotic multiparticulate was shown to control the release of the prebiotic during in vitro gastrointestinal transit, with the release of galacto-oligosaccharides (GOS) initially occurred over 6 h, but with a triphasic release pattern giving further release over 288 h. Encapsulation of B. breve in multiparticulates resulted in a survival of 8.0 ± 0.3 log CFU/mL cells in acid, an improvement over alginate–chitosan microencapsulation of 1.4 log CFU/mL. This was attributed to increased hydrophobicity by the incorporation of PLGA particles.

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The prebiotic lactulose, a probiotic strain of Lactobacillus plantarum (L. plantarum) and a synbiotic combination of these two agents were evaluated as growth promoters in 25–39-day old commercial weaning pigs. Ninety-six weaning pigs were allocated into 32 pens, taking initial weight into account, and distributed into four groups as follows: a control diet (CTR), the same diet supplemented daily with L. plantarum (109 CFU/mL sprayed on top; 20 mL/pig) (LPN); 10 g/kg lactulose (LAC) or a combination of both treatments (SYN). At day 14, eight piglets from each group were euthanized and proximal colon digesta was sampled for luminal pH, short-chain fatty acids (SCFA) and lactic acid concentrations. Deoxyribonucleic acid was extracted from colonic digesta and the microbial community was profiled by terminal restriction fragment length polymorphism analysis (T-RFLP) and qPCR. Blood urea nitrogen (BUN) and acute-phase proteins (Pig-MAP) were measured. Lactulose treatment (LAC) improved feed intake (P<0.05), average daily gain (P<0.01), feed:gain ratio (P<0.05) and reduced BUN (P<0.01). Both, LAC and LPN treatment, decreased the Enterobacteriaceae:Lactobacillus spp. ratio in the colonic luminal contents (P<0.05). Moreover LPN treatment promoted a decrease in the percentage of branched fatty acids (P<0.01) suggesting a reduction in proteolytic microbial activity. Microbial profiling of colonic luminal contents by T-RFLP revealed changes in some microbial species. Terminal restriction fragments (TRFs) compatible with Bifidobacterium thermoacidophilum were more frequently detected in experimental diets compared to CTR (P<0.05). Pigs receiving SYN diet demonstrated the combined positive effects of individual LAC and LPN treatment although we were not able to show a specific increase in the probiotic strain with the inclusion of lactulose. Collectively, these data suggest the combination of lactulose and L. plantarum acts as a complementary synbiotic, but not as a synergistic combination.

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Our aim was to investigate the immediate effects of bilateral, 830 nm, low-level laser therapy (LLLT) on high-intensity exercise and biochemical markers of skeletal muscle recovery, in a randomised, double-blind, placebo-controlled, crossover trial set in a sports physiotherapy clinic. Twenty male athletes (nine professional volleyball players and eleven adolescent soccer players) participated. Active LLLT (830 nm wavelength, 100 mW, spot size 0.0028 cm(2), 3-4 J per point) or an identical placebo LLLT was delivered to five points in the rectus femoris muscle (bilaterally). The main outcome measures were the work performed in the Wingate test: 30 s of maximum cycling with a load of 7.5% of body weight, and the measurement of blood lactate (BL) and creatine kinase (CK) levels before and after exercise. There was no significant difference in the work performed during the Wingate test (P > 0.05) between subjects given active LLLT and those given placebo LLLT. For volleyball athletes, the change in CK levels from before to after the exercise test was significantly lower (P = 0.0133) for those given active LLLT (2.52 U l(-1) +/- 7.04 U l(-1)) than for those given placebo LLLT (28.49 U l(-1) +/- 22.62 U l(-1)). For the soccer athletes, the change in blood lactate levels from before exercise to 15 min after exercise was significantly lower (P < 0.01) in the group subjected to active LLLT (8.55 mmol l(-1) +/- 2.14 mmol l(-1)) than in the group subjected to placebo LLLT (10.52 mmol l(-1) +/- 1.82 mmol l(-1)). LLLT irradiation before the Wingate test seemed to inhibit an expected post-exercise increase in CK level and to accelerate post-exercise lactate removal without affecting test performance. These findings suggest that LLLT may be of benefit in accelerating post-exercise recovery.

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Strategies for the development of new vaccines against Streptococcus pneumoniae infections try to overcome problems such as serotype coverage and high costs, present in currently available vaccines. Formulations based on protein candidates that can induce protection in animal models have been pointed as good alternatives. Among them, the Pneumococcal Surface Protein A (PspA) plays an important role during systemic infection at least in part through the inhibition of complement deposition on the pneumococcal surface, a mechanism of evasion from the immune system. Antigen delivery systems based on live recombinant lactic acid bacteria (LAB) represents a promising strategy for mucosal vaccination, since they are generally regarded as safe bacteria able to elicit both systemic and mucosal immune responses. In this work, the N-terminal region of clade I PspA was constitutively expressed in Lactobacillus casei and the recombinant bacteria was tested as a mucosal vaccine in mice. Nasal immunization with L. casei-PspA 1 induced anti-PspA antibodies that were able to bind to pneumococcal strains carrying both clade 1 and clade 2 PspAs and to induce complement deposition on the surface of the bacteria. In addition, an increase in survival of immunized mice after a systemic challenge with a virulent pneumococcal strain was observed. (C) 2008 Elsevier Masson SAS. All rights reserved.

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This study examined the effect of reduced plasma free fatty acid (FFA) availability on carbohydrate metabolism during exercise. Six untrained women cycled for 60 minutes at approximately 58% of maximum oxygen uptake after ingestion of a placebo (CON) or nicotinic acid (NA), 30 minutes before exercise (7.4 ± 0.5 mg·kg−1 body weight), and at 0 minutes (3.7 ± 0.3 mg·kg−1) and 30 minutes (3.7 ± 0.3 mg·kg−1) of exercise. Glucose kinetics were measured using a primed, continuous infusion of [6,6-2H] glucose. Plasma FFA (CON, 0.86 ± 0.12; NA, 0.21 ± 0.11 mmol·L−1 at 60 minutes, P < .05) and glycerol (CON, 0.34 ± 0.05; NA, 0.10 ± 0.04 mmol·L−1 at 60 minutes, P < .05) were suppressed throughout exercise. Mean respiratory exchange ratio (RER) during exercise was higher (P < .05) in NA (0.89 ± 0.02) than CON (0.83 ± 0.02). Plasma glucose and glucose production were similar between trials. Total glucose uptake during exercise was greater (P < .05) in NA (1,876 ± 161 μmol·kg−1) than in CON (1,525 ± 107 μmol·kg−1). Total fat oxidation was reduced (P < .05) by approximately 32% during exercise in NA. Total carbohydrate oxidized was approximately 42% greater (P < .05) in NA (412 ± 40 mmol) than CON (290 ± 37 mmol), of which, approximately 16% (20 ± 10 mmol) could be attributed to glucose. Plasma insulin and glucagon were similar between trials. Catecholamines were higher (P < .05) during exercise in NA. In summary, during prolonged moderate exercise in untrained women, reduced FFA availability results in a compensatory increase in carbohydrate oxidation, which appears to be due predominantly to an increase in glycogen utilization, although there was a small, but significant, increase in whole body glucose uptake.

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This thesis covers the development of the traditionally fluorescent bis(8-quinolinol-5-sulfonic acid) magnesium (II) fluorophore as a chemiluminescent emitter. A brief description of luminescence spectroscopy and its application to analytical chemistry lays the foundation to the discussion of the results obtained herein. This includes the synthesis and identification of two so called ‘water soluble’ aryl oxamides 2,2’-oxalyl-bis(trifluoromethanesulfonyl) imino] ethylene-bis(N- methylpyridinium) trifluoromethane sulfonate (PETQ) and 2,2’-oxalyl-bis(trifluoromethanesulfonyl) imino]ethylene-bis(N-pyridinium) chloride (PETH), previously developed for the US navy as a possible emergency light source, yet the synthetic methodology were incomplete. The inconsistencies of the synthetic methods for PETQ and PETH were overcome with yields satisfactory for their preliminary analytical evaluation. The evaluation of these aryl oxamides, including 4,4’-oxalyI- bis[(trifluoromethanesulfonyl) imino]ethylene-bis(l-methyM-benzylpiperidinium) trifluoromethanesulfonate (BPTQ), 4,4’-oxalyl-bis [(trifluoromethylsulfonyl)imino] ethylene-bis(N-methylmorpholinium)trifluoromethanesulfonate (METQ) and the oxalate bis(2,4,6-trichlorophenyl) oxalate (TCPO) were performed with the peroxyoxalate chemiluminescent reaction using bis(8-quinolinol-5-sulfonic acid) magnesium (II) as the fluorophore. A univariate optimisation of this system resulted in 0,0082 mol 1-1 the detection limit of magnesium in the absence of cationic surfactants and 0.0041 mol 1-1 in their presence for the majority of these compounds. The oxamides were found to be insoluble in water with long ulrasonication periods required to dissolve the compound, with solvents such as acetonitrile preferred. The determination of other chemiluminescent metal-8HQS chelates to replace magnesium -8HQS in the peroxyoxalate were limited to Al (III), Cd (II), Ca (II), In (II) and Zn (II), unfortunately these metals all possessed poorer detection limits than those obtained using magnesium The base reaction conditions used for the flow injection system with chemiluminescent detection were transferred to an ion chromatographic configuration for the separation of magnesium from other cations on an exchange column. After a univariate and simplex optimisation of these conditions, the detection limit of magnesium was found to be 0.0411 mol 1-1 which was less than the limits that could be achieved with fluorescent detection, The further development of this reaction to incorporate the displacement of magnesium from Mg-EDTA by other metals that possessed a higher conditional stability constant than magnesium also proved to be problematic with interferences from not only EDTA but from the eluant (lactic acid) from the cation column. Using this system the detection limits of the displacing metals were found to be in the order of 10 mg 1-1 which was substantially less that what was observed when exactly the same configuration was used with fluorescent detection. The final component of the thesis entails the discussion of the background emission that results from the reaction of oxamides/oxalates with hydrogen peroxide. A detailed investigation into the reaction of TCPO and hydrogen peroxide in the presence of various additives, such as imidazole , heavy atoms and triethylamine illustrated the existence of a further intermediate in fee mechanism for this reaction. The species responsible for this emission was attributed to the degradation product 2,4,6-trichlorophenyi of TCPO, which was supported by the non-existent background present with the oxamides that do not contain this degradation product.

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The thermoregulatory responses of subjects wearing two different forms of rugby league jersey, one with plastic sponsorship recognition and numbering (trial Gl) and one without (trial G2), and a lightweight alternative (trial G3), were compared with a trial without any form of upper body garment (trial GO). Ten male volunteers, mean age 20.9 (±2.3) years, height 179.8 (±4.7) cm, weight 80.2 (±8.9) kg, and body surface area 1.99 (±0.13) m2, participated in this study. Subjects had a mean maximal oxygen uptake capacity of 56.0 (±6.3) ml.kg.min-1 and a sum of 8 skinfolds of 80.6 (±23.8) mm. Subjects were exercised at approximately 50% of maximal oxygen uptake in a warm humid environment for 50 minutes. Mean ambient temperature was 27.6°C (±0.32) with a relative humidity of 64.7% (±1.44). Measurements of core and skin (7 sites) temperature, heart rate, oxygen uptake, plasma volume, peak lactate concentration, and pre- and post-trial body weight, hematocrit and garment weight were recorded. The statistical results showed that all subjects experienced significant (p ≤.0001) decreases in body weight representing a percentage decrease ranging from 1.2-1.3%. No significant difference was found between trials with respect to body weight change. No significant effect of garment type was found on pre- and post-trial hematocrit, plasma volume changes or peak blood lactic acid concentration. However, mean peak lactate was highest for trial Gl (5.6 mmol.L-1 ±2.2) and lowest for trial G3 (4.6 mmol.L-1 ±1.27). Post-trial core temperature was significantly (p≤ .0001) higher than the resting value; no significant difference was found between trials. The mean absolute increase for all experimental trials was 0.9°C. A significant (p≤.005) difference between mean total (7 sites) skin temperature was found with a post-hoc test revealing that trials Gl and G2 were significantly higher than trial GO; no significant difference was found when comparing trial G3 with trial GO or when comparing the garments between each other. Mean skin temperature under the garment (4 sites) was found to be significantly (p≤.05) higher for all trials involving a garment when compared with mean skin temperature outside (3 sites) the garment; no significant difference was found between trials. Mean oxygen uptake was significantly different between trials (p≤.005), with trial Gl and G3 found to be significantly lower than trial GO; no difference was found when comparing the garments with each other. Post-trial garment weights were significantly (p≤.001) heavier than pre-trial and were significantly (p≤.0001) different when compared with each other. There was no significant effect on heart rate, haematocrit, plasma volume changes, peak blood lactic acid concentration, or core temperature due to garment type. However, differences in skin temperature suggest that the garment used in trial G3 may have a benefit. Further research should consider the impact of increased exercise intensity and/or environmental temperature and humidity on the measured parameters while wearing the garments described in this study.

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1. The role of adrenaline in regulating hepatic glucose production and muscle glucose uptake during exercise was examined in six adrenaline deficient, bilaterally adrenalectomised humans. Six sex and age matched healthy individuals served as controls (CON).

2. Adrenalectomised subjects cycled for 45 min at 68 ± 1% maximum pulmonary Oμ uptake (VOμ,max), followed by 15 min at 84 ± 2% VOμ,max without (−ADR) or with (+ADR) adrenaline infusion, which elevated plasma adrenaline levels (45 min, 4·49 ± 0·69 nmol l¢; 60 min, 12·41 ± 1·80 nmol l¢; means ± s.e.m.). Glucose kinetics were measured using [3_ÅH]glucose.

3. Euglycaemia was maintained during exercise in CON and −ADR, whilst in +ADR plasma glucose was elevated. The exercise induced increase in hepatic glucose production was similar in +ADR and −ADR; however, adrenaline infusion augmented the rise in hepatic glucose production early in exercise. Glucose uptake increased during exercise in +ADR and −ADR, but was lower and metabolic clearance rate was reduced in +ADR.

4. During exercise noradrenaline and glucagon concentrations increased, and insulin and cortisol concentrations decreased, but plasma levels were similar between trials. Adrenaline infusion suppressed growth hormone and elevated plasma free fatty acids, glycerol and lactate. Alanine and â_hydroxybutyrate levels were similar between trials.

5. The results demonstrate that glucose homeostasis was maintained during exercise in adrenalectomised subjects. Adrenaline does not appear to play a major role in matching hepatic glucose production to the increase in glucose clearance. In contrast, adrenaline infusion results in a mismatch by simultaneously enhancing hepatic glucose production and inhibiting glucose clearance.

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In an effort to compare the disturbances in leg muscle pH during sprint running, muscle biopsies were obtained from the gastrocnemius and vastus lateralis muscles of six healthy men (three endurance-trained and three nonendurance-trained) before and after a treadmill sprint run (TSR) to fatigue (54-105 s) at roughly 125% of their aerobic capacities. Following the TSR, repeated blood samples were taken from a hand vein and later analyzed for pH, PCO2, and lactic acid (HLa). The muscle specimens were analyzed in duplicate for pH and HLa. Resting-muscle pH was 7.03 +/- 0.02 (means +/- SE) and 7.04 +/- 0.01 for the gastrocnemius and vastus lateralis muscles, respectively. At the termination of the TSR, the pH in these muscles was 6.88 +/- 0.05 and 6.86 +/- 0.03, respectively. After a 400-m timed run on the track, the pH in the gastrocnemius of four of the subjects averaged 6.63 +/- 0.03, while blood pH and HLa were 7.10 +/- 0.03 and 12.3 mM, respectively. Although no differences in pH and HLa were observed between the vastus lateralis and gastrocnemius muscles at the end of the treadmill trial, it is speculated that the lesser disturbance in acid-base balance seen in endurance performers may have been due to a lesser production of metabolites in their running musculature when compared to nonendurance performers.

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Cell-envelope proteinases (CEPs) are a class of proteolytic enzymes produced by lactic acid bacteria and have several industrially relevant applications. However, soluble CEPs are economically unfavorable for such applications due to their poor stability and lack of reusability. In a quest to prepare stable biocatalysts with improved performance, CEP from Lactobacillus delbrueckii subsp. lactis 313 and trypsin (as a model enzyme) were immobilized onto nonwoven polyester fabrics in a three-step protocol including ethylenediamine activation and glutaraldehyde crosslinking. Immobilization gave protein loading yields of 21.9% (CEP) and 67.7% (trypsin) while residual activity yields were 85.6% (CEP) and 4.1% (trypsin). The activity of the immobilized enzymes was dependent on pH, but was retained at elevated temperatures (40-70°C). An increase in Km values was observed for both enzymes after immobilization. After 70 days of storage, the immobilized CEP retained ca. 62% and 96% of initial activity when the samples were stored in a lyophilized form at -20°C or in a buffer at 4°C, respectively. Both immobilized CEP and trypsin were able to hydrolyze proteins such as casein, skimmed milk proteins and bovine serum albumin. This immobilization protocol can be used to prepare immobilized biocatalyst for various protein degradation processes.

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In this paper, a new amino acid derivative, namely Adenine-L-Alanine ramification (ALAR) was synthesized and investigated as a green corrosion inhibitor for X80 pipeline steel in 0.1 mol/L hydrochloric acid solution using the weight loss, AC impedance, and polarization curve method. The structure of the derivative was characterized by IR and UV–vis spectrum. The weight loss and AC impedance found that the inhibition efficiency increased with the increase in concentration of the inhibitor but decreased with rise in temperature, the corrosion inhibition efficiency attains 91.26% in 8 × 10−2 g/L concentration at 30 °C. The polarization studies showed that the studied amino acid derivative can be used as a corrosion inhibitor. The surface of inhibited and uninhibited specimens was analyzed by scanning electron microscopy and the adsorption of the inhibitor on the mild steel surface obeys Langmuir adsorption isotherm. The quantum chemical descriptors such as the energy of highest occupied molecular orbital, energy of lowest unoccupied molecular orbital were calculated and the inhibition mechanism can be analyzed by the distribution of electrons. Analysis indicated that the inhibitor molecular and empty d orbital of metal forms the coordination bond, covers on the surface of metal, and prevents corrosion reaction.

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This study provides a versatile validated method to determine the total vitamin C content, as the sum of the contents of L-ascorbic acid (L-AA) and dehydroascorbic acid (DHAA), in several fruits and vegetables and its degradability with storage time. Seven horticultural crops from two different origins were analyzed using an ultrahigh-performance liquid chromatographic–photodiode array (UHPLC-PDA) system, equipped with a new trifunctional high strength silica (100% silica particle) analytical column (100 mm×2.1 mm, 1.7 μm particle size) using 0.1% (v/v) formic acid as mobile phase, in isocratic mode. This new stationary phase, specially designed for polar compounds, overcomes the problems normally encountered in HPLC and is suitable for the analysis of large batches of samples without L-AA degradation. In addition, it proves to be an excellent alternative to conventional C18 columns for the determination of L-AA in fruits and vegetables. The method was fully validated in terms of linearity, detection (LOD) and quantification (LOQ) limits, accuracy, and inter/intraday precision. Validation experiments revealed very good recovery rate of 96.6±4.4% for L-AA and 103.1±4.8 % for total vitamin C, good linearity with r2-values >0.999 within the established concentration range, excellent repeatability (0.5%), and reproducibility (1.6%) values. The LOD of the method was 22 ng/mL whereas the LOQ was 67 ng/mL. It was possible to demonstrate that L-AA and DHAA concentrations in the different horticulture products varied oppositely with time of storage not always affecting the total amount of vitamin C during shelf-life. Locally produced fruits have higher concentrations of vitamin C, compared with imported ones, but vegetables showed the opposite trend. Moreover, this UHPLC-PDA methodology proves to be an improved, simple, and fast approach for determining the total content of vitamin C in various food commodities, with high sensitivity, selectivity, and resolving power within 3 min of run analysis.

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The environmental impact caused by the disposal of non-biodegradable polymer packaging on the environment, as well as the high price and scarcity of oil, caused increase of searches in the area of biodegradable polymers from renewable resources were developed. The poly (lactic acid) (PLA) is a promising polymer in the market, with a large availability of raw material for the production of its monomer, as well as good processability. The aimed of this study was synthesis PLA by direct polycondesation of lactic acid, using the tool of experimental design (DOE) (central composite rotatable design (CCRD)) to optimize the conditions of synthesis. The polymer obtained was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), viscosimetric analysis, differential scanning calorimeter (DSC) and size exclusion chromatography (SEC). The results confirmed the formation of a poly (lactic acid) semicrystalline in the syntheses performed. Through the central composite rotatable design was possible to optimize the crystallization temperature (Tc) and crystallinity degree (Xc). The crystallization temperature maximum was found for percentage of catalyst around the central point (0,3 (%W)) and values of time ranging from the central point (6h) to the upper level (+1) (8h). The crystallization temperature maximum was found for the total synthesis time of 4h (-1) and percentage of catalyst 0,1(W%) (-1). The results of size exclusion chromatography (SEC) showed higher molecular weights to 0,3 (W%) percent of catalyst and total time synthesis of 3,2h

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Avaliou-se o efeito da inclusão de aditivos na ensilagem de cana-de-açúcar (Saccharum officinarum L.) sobre a composição químico-bromatológica das silagens, o comportamento ingestivo, o consumo voluntário e a digestibilidade em bovinos de corte. Utilizaram-se cinco novilhos da raça Nelore providos de cânula ruminal, alocados em delineamento quadrado latino 5 ´ 5 e alimentados com dietas com 65% de volumoso na MS. Foram avaliadas cinco silagens (base úmida): controle - cana-de-açúcar sem aditivos; uréia - cana-de-açúcar + 0,5% uréia; benzoato - cana-de-açúcar + 0,1% de benzoato de sódio; LP - cana-de-açúcar inoculada com Lactobacillus plantarum (1 ´ 10(6) ufc/g MV); LB - cana-de-açúcar inoculada com L. buchneri (3,6 ´ 10(5) ufc/g forragem). A forragem foi armazenada em silos do tipo poço por 90 dias antes do fornecimento aos animais. A composição químico-bromatológica da cana-de-açúcar foi alterada após a ensilagem, em relação à cana-de-açúcar original, com redução no teor de carboidratos solúveis e na digestibilidade in vitro e elevação relativa nos teores de FDN e FDA. Os teores de etanol (0,30% da MS) e ácidos orgânicos (0,99% de ácido lático e 2,31% de acético) foram baixos e semelhantes entre as silagens. Os aditivos aplicados na ensilagem não promoveram alterações no consumo e na digestibilidade aparente da MS (7,2 kg/dia e 63,6%, respectivamente). O comportamento ingestivo dos animais também não foi alterado, com tempos médios de 230,6; 519,6 e 672,8 minutos/dia despendidos com ingestão de ração, ruminação e ócio, respectivamente. Os aditivos acrescidos à cana-de-açúcar promoveram pequenas alterações na maioria das variáveis avaliadas.