Evaluation of acid digestion procedures for estimating the mineral content in materials from animal trials

• Ano de defesa: 2015
• Autor(a) principal: Palma, Malber Nathan Nobre
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Minerais na nutrição animal; Digestibilidade; Espectrofotometria; Avaliação de Alimentos para Animais
• Link de acesso: http://www.locus.ufv.br/handle/123456789/6366

This dissertation was based on two experiments which were carried out to evaluate mineral contents in different materials from animal trials. In the first one, it was evaluated the accuracy of chromium contents in cattle feces using digestion techniques with different nitric to perchloric acid ratios and one or two digestion steps. The following techniques were evaluated: ratio of nitric to perchloric acid 2:1, 3:1, and 4:1 v/ v in a one- or two-step digestion; and nitric to perchloric acid 3:1 v/v without sodium molybdate in a one-step digestion. The chromium quantifications were carried out using atomic absorption spectrophotometry. The accuracy of the estimates was evaluated through standard samples containing known chromium contents (0, 2, 4, 6, 8 and 10 g of chromium per kg of feces) which were produced from feces obtained from five animals. Accuracy evaluation was performed by adjusting a simple linear regression equation of estimated chromium concentrations on actual concentrations. The chromium recovery closest to unity was obtained using the ratio 3:1 v/v, with one-step digestion and sodium molybdate as catalyst. The utilization of sodium molybdate as catalyst was found mandatory. It could be concluded that the chromium content in cattle feces is accurately evaluated using digestion procedures based on nitric to perchloric acids ratio of 3:1 v/v in a one-step digestion with sodium molybdate as catalyst. In the second experiment, acid digestion procedures were evaluated using different nitric to perchloric acid ratios and one- or two-step digestion to estimate the concentration of calcium, phosphorus, magnesium, and zinc in samples of carcass, bone, excreta, concentrate, forage, and feces. Six procedures were evaluated: ratio of nitric to perchloric acid at 2:1, 3:1, and 4:1 v/v in a one- or two-step digestion. There were no direct or interaction effects of nitric to perchloric acid ratio or number of digestion steps on magnesium and zinc contents. Calcium and phosphorus contents presented a significant interaction between sample type and nitric to perchloric acid ratio. Digestion solution of 2:1 v/v provided greater recovery of calcium and phosphorus from bone samples than 3:1 and 4:1 v/v ratio. Different acid ratios do not affect calcium or phosphorus contents in carcass, excreta, concentrate, forage, and feces. Number of digestion steps did not affect mineral content. Estimated concentration of calcium, phosphorus, magnesium, and Zn in carcass, excreta, concentrated, forage, and feces samples can be performed using digestion solution of nitric to perchloric acid 4:1 v/v in a one-step digestion. However, for bone samples, digestion solution of nitric to perchloric acid 2:1 v/v in a one-step digestion is recommended.