Navegando por Autor "Oliveira, M. R. C."
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Item In vitro ruminal degradation of ricin and its effect on microbial growth(Animal Feed Science and Technology, 2010-04-21) Oliveira, M. R. C.; Oliveira, A. S. de; Campos, J. M. S.; Lana, R. P.; Machado, O. L. T.; Retamal, C. A.; Detmann, E.; Valadares Filho, S. C.Ricin is a toxic protein found in castorseed (Ricinus communis L.). We hypothesized that ruminal microbiota are capable of degrading ricin, and that the toxin inhibits ruminal microbial growth. Therefore, first we evaluated the in vitro ruminal degradation of ricin from solvent castorseed meal (SCM) by SDS-PAGE and densitometry analysis of culture medium (Experiment 1). Culture medium (three replicates) were collected after 0, 3, 6, 12, 24 and 48 h of incubation content initially 0, 61, 122 and 244 μg of ricin/mL or 122 μg of ricin/mL (without ruminal inoculum). No protein compounds were detected by SDS-PAGE in the culture medium without ricin, indicating an absence of interference from the ruminal inoculum. Ricin chains remained intact in the absence of rumen inoculum, but they were degraded at rates of 0.2725, 0.1504 and 0.0648 h^−1 with ruminal inoculum, at initial ricin concentrations of 61, 122 and 244 μg/mL. Next, the effect of ricin denaturation on rumen microbial specific growth rate (SGR) (OD-600 nm) and the average ammonia concentration at the same time of incubation were investigated (Experiment 2). This experiment had a completely randomized design in a 3 × 3 factorial (three replicates) arrangement, with three sources of protein (trypticase-control; crude extract of soluble protein at pH 3.8 buffer of solvent castorseed meal (CEP) intact, containing 1.46 mg of ricin/mL; and denatured CEP with calcium oxide, containing 0.04 mg of ricin/mL) and three protein levels (0.42, 0.84, and 1.68 mg/mL). There was interaction (P=0.021) between protein level and protein source for SGR. A linear increase (P<0.001) of SGR was observed with increase of trypticase level, but there was a quadratic effect (P=0.023) with increase of intact CEP level, with a minimum value of SGR of −0.004 h^−1 at a protein level of 1.45 mg/mL (210 μg of ricin/mL) of intact CEP. There was no effect (P=0.099) of denatured CEP level, but SGR increased (P<0.001) 3.2 times with denaturation of intact CEP. Ruminal microbial growth was inhibited by 50% with 89 μg of ricin/mL. Ammonia concentration was 91% lower (P<0.001) for the CEP source when compared to trypticase, but the denaturation of intact CEP had no effect (P=0.9560) on the ammonia concentration. Although ruminal microbiota was able to degrade ricin in in vitro conditions, the toxin inhibits ruminal microbial growth. Therefore, complete detoxification of CSM before using it to feed ruminants is recommended. The denatured CEP presents potential of use as modifier of rumen microbial fermentation.Item Nutrient digestibility, nitrogen metabolism and hepatic function of sheep fed diets containing solvent or expeller castorseed meal treated with calcium hydroxide(Animal Feed Science and Technology, 2010-06-02) Campos, J. M. S.; Oliveira, M. R. C.; Valadares Filho, S. C.; Detmann, E.; Valadares, R. F. D.; Souza, S. M. de; Machado, O. L. T.; Oliveira, A. S. de; Brito, A. F.Nineteen sheep averaging 56 kg of initial body weight were used in a completely randomized design to investigate the effects of feeding Ca(OH)2-treated (40 g/kg, on fresh matter basis) or untreated castorseed meal (CSM) sources on intake, total tract digestibility, hepatic function, and microbial protein synthesis and efficiency. Animals were maintained in metabolic crates for 21 days with 16 days for diet adaptation and 5 days for data and samples collection. Sheep were fed once daily experimental diets containing one of the following 5 protein supplements (150 g/kg of the diet DM): (1) soybean meal (SBM); (2) solvent CSM (SCM); (3) SCM treated with Ca(OH)2 (TSCM), expeller CSM (ECM); or ECM treated with Ca(OH)2 (TECM). Treating SCM and ECM with Ca(OH)2 reduced the ricin concentration in 63% leading to an average decrease from 2.46 to 1.06 g/kg of BW in the ricin daily intake (P < 0.001). No clinical symptoms of ricin intoxication were observed and the serum concentrations of the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which are indicators of hepatic function, were not changed across diets (P > 0.05). There was no effect of diets on intake of nutrients (P > 0.05) with the exception of non-fibrous carbohydrates (NFC) intake, which was greater (P = 0.029) in sheep fed SBM vs. CSM diets and that of ether extract, which was lower (P = 0.049) in sheep fed solvent CSM diets vs. expeller CSM diets. However, treating SCM and ECM with Ca(OH)2 tended to increase intakes of DM, CP and NFC. Apparent total tract digestibility of nutrients was not affected by diet (P > 0.05) with the exception of ether extract digestibility, which was lower in sheep fed SBM vs. CSM diets (P = 0.001) but greater (P = 0.023) in sheep fed solvent CSM diets vs. expeller CSM diets. Treating SCM and ECM with Ca(OH)2 increased or tended (0.05 > P > 0.10) to increase the apparent total tract digestibility of nutrients with the exception NFC. Microbial protein synthesis (P = 0.013) and microbial efficiency expressed either as g of microbial CP per g of CP intake (P = 0.043) or as g of microbial CP per g of rumen-degradable CP intake (P = 0.030) were all increased by treating SCM and ECM with Ca(OH)2. Despite the increase (P = 0.022) in the urinary excretion of urea-N (g/day) by treating SCM and ECM with Ca(OH)2, the greater microbial efficiency reduced (P = 0.021) fecal-N losses expressed as proportion of N intake numerically increasing retained-N by 21.3%. Treating SCM and ECM with 40 g of Ca(OH)2/kg did not completely denaturate ricin but increased microbial protein synthesis and the efficiency of N and energy by ruminal microbes with no detrimental effect on the hepatic function of sheep.