Estudo sobre variações em métodos de análise de compostos fibrosos em alimentos

• Autor(a) principal: Gomes, Daiany Iris
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1803
• topic: Suplementação; Compostos nitrogenados; Fibra; Degradação ruminal; Supplementation; Nitrogen compounds; Fiber; Rumen; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

This thesis consists of four different scientific papers. The first one was carried out to evaluate the neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents in concentrates, forages and cattle feces using filter bags under pressured or non-pressured physical environments. Twenty samples of each material were used. The contents obtained under different environment were compared using a linear regression analysis. The NDF and ADF estimates were found different between physical environments for all materials (P<0.01) being the higher estimates obtained under non pressured environment. The utilization of pressured environment is recommended to avoid gas accumulation in the bags, which may compromise the detergent action. In the second paper the objective was to evaluate the contents of fibrous compounds in tropical grasses and legumes according to utilization of sodium sulfite in the neutral detergent solution or using a procedure for contaminant protein correction. Samples of ten grasses and ten legumes were used. The contents of neutral detergent fiber were decreased when sodium sulfite was used; however, more prominent reductions were verified in legumes. Sodium sulfite decreased the acid detergent fiber contents in both forage groups. The contents of neutral and acid detergent insoluble protein and lignin were reduced by sodium sulfite in legumes but no effect was observed in grasses with regard these variables. The decrease in fiber contents in legumes could be explained by the solubilization of lignin and decrease in insoluble nitrogen. However, the decreases in fiber in grasses could not be solely explained by the decrease in contaminant protein and solubilization of lignin, and loss of other fibrous compounds probably occurred. The utilization of sodium sulfite compromises the accuracy of the estimates of fibrous compounds contents in tropical forages. The precision of the estimates were not relevantly increased by sodium sulfite. The correction of insoluble fibrous compounds for protein is suggested instead of using sodium sulfite because there are no modifications on neutral detergent solution or undesirable solubilization of fibrous compounds. The third paper was based on two experiments that were performed to evaluate the utilization of industrial enzymes in the evaluation of NDF contents in high-starch materials. In the first experiment, it was verified the accuracy of estimates of NDF obtained with the utilization of three industrial enzymes (Termamyl 2X, 2.2X and Liquozyme Supra Amylase AG 300L) at different volumes (50, 100, 250 or 500 &#956;L/sample). Samples were simulated to contain 0, 100, 300, 500 and 1000 g of starch/kg dry matter, using purified cellulose as analytical standard of NDF and purified starch. It were evaluated four replications for each combination of type and amount of enzyme and starch concentration, totalizing 240 evaluations. In the second experiment, samples of corn grain and sorghum grain were used as high-starch organic matrixes. One were evaluated the enzymes and volumes used in the first experiment on each feed matrix. In addition, aliquots were evaluated without the use of enzymes. It were evaluated four replications for each combination, totalizing 104 aliquots. There was no significant bias of NDF recovery for simulated samples containing starch up to 300 g/kg. Considering those samples, none difference among enzymes was observed. It was observed a more intense decrease in NDF content according to each enzyme unit added in corn when compared to sorghum. Considering NDF evaluation in samples with mass of 0.7 to 1.0 g, it can be recommended the utilization of 250 &#956;L the &#945;-amylases Termamyl and 2X Liquozyme 2.2X with activities of 240 and 300 KNU/g, respectively. In the fourth paper, it was evaluated the variability among animals on the critical time needed to estimate the undegradable fraction of fiber using in situ incubation procedures in cattle. Five animals fitted with ruminal canullae and averaging 350 kg of body weight were used. The animals were fed a basal diet with a 80:20 forage to concentrate ratio. The diet consisted of fresh elephant grass and commercial concentrate. Animals were adapted to the diet and experimental conditions for 12 days prior to incubation. Samples of fresh sugarcane, signal grass hay, corn silage and elephant grass. The samples were put in F57 bags (Ankom®). The bags were incubated in the rumen of the animals using the following times: 0, 6, 12.18, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, and 312 hours. It was considered one bag of each sample for each animal, totalizing 300 bags. There was no significant difference among animals with regard fractional degradation rate of NDF and ADF of corn silage, signal grass hay and sugarcane. However, significant variability among animals was observed for fresh elephant grass. The results of this study seem to suggest that the variability among animals concerning degradation rate of fibrous compounds could be significant. Nevertheless, due to the limited sample size used (n=5), further studies are suggested looking for confirmation of this hypothesis, and if so, define experimental strategies for obtaining the content of undegradable compounds with accuracy and precision.