Feed fats and oils provide significant amounts of energy to swine diets, but there is large variation in composition,quality, feeding value, and price among sources. Common measures of lipid quality include moisture, ...Feed fats and oils provide significant amounts of energy to swine diets, but there is large variation in composition,quality, feeding value, and price among sources. Common measures of lipid quality include moisture, insolubles,and unsaponifiables（MIU）, titer, and free fatty acid content, but provide limited information regarding their feeding value. Lipid peroxidation is an important quality factor related to animal growth performance and health, but maximum tolerable limits in various lipids have not been established. Several indicative assays can be used to detect the presence of various peroxidation compounds, but due to the complexity and numerous compounds produced and degraded during peroxidation process, no single method can adequately determine the extent of peroxidation. Until further information is available, using a combination of peroxide value, thiobarbituric acid reactive substances（TBARS）, and anisidine value appear to provide a reasonable assessment of the extent of peroxidation in a lipid at a reasonable cost. However, fatty acid composition of the lipid being evaluated should be considered when selecting specific assays. Predictive tests can also be used to estimate the stability or susceptibility of lipids to peroxidation and include active oxygen method, oil stability index, and oxygen bomb method. A review of 16 published studies with pigs has shown an average decrease of 11.4% in growth rate, 8.8% feed intake fed isocaloric diets containing peroxidized lipids compared to diets containing unperoxidized lipids of the same source.Furthermore, serum vitamin E content was generally reduced and serum TBARS content was increased when peroxidized lipids were fed in these studies, suggesting that feeding peroxidized lipids negatively affects metabolic oxidative status of pigs. However, it is unclear if antioxidants are useful additions to lipids to maintain optimal nutritional value, or if their addition to swine diets is beneficial in overcoming a metabolic oxidative challenge.展开更多
A microcalorimetric technique was used to investigate the influence of Zn 2+ on the growth metabolism of Bacillus thuringiensis . LKB 2277 Bioactivity Monitor was employed to obtain the power time curves, fr...A microcalorimetric technique was used to investigate the influence of Zn 2+ on the growth metabolism of Bacillus thuringiensis . LKB 2277 Bioactivity Monitor was employed to obtain the power time curves, from which the maximum peak heat output power ( P max ) in the log phase, the growth rate constants ( k ), the inhibitory ratios ( I ), the generational time ( t G) and the total heat effect ( Q total ) in 23 h for the growth metabolism of Bacillus thuringiensis at 28 ℃ can be evaluated. The results indicate that the concentration of Zn 2+ affects its growth obviously. Low concentration (0-50 μg/mL) of Zn 2+ promotes the growth of Bacillus thuringiensis while high concentration (50-500 μg/mL) of Zn 2+ inhibits its growth. When the concentration reached up to 600 μg/mL, it can not grow at all.展开更多
文摘Feed fats and oils provide significant amounts of energy to swine diets, but there is large variation in composition,quality, feeding value, and price among sources. Common measures of lipid quality include moisture, insolubles,and unsaponifiables（MIU）, titer, and free fatty acid content, but provide limited information regarding their feeding value. Lipid peroxidation is an important quality factor related to animal growth performance and health, but maximum tolerable limits in various lipids have not been established. Several indicative assays can be used to detect the presence of various peroxidation compounds, but due to the complexity and numerous compounds produced and degraded during peroxidation process, no single method can adequately determine the extent of peroxidation. Until further information is available, using a combination of peroxide value, thiobarbituric acid reactive substances（TBARS）, and anisidine value appear to provide a reasonable assessment of the extent of peroxidation in a lipid at a reasonable cost. However, fatty acid composition of the lipid being evaluated should be considered when selecting specific assays. Predictive tests can also be used to estimate the stability or susceptibility of lipids to peroxidation and include active oxygen method, oil stability index, and oxygen bomb method. A review of 16 published studies with pigs has shown an average decrease of 11.4% in growth rate, 8.8% feed intake fed isocaloric diets containing peroxidized lipids compared to diets containing unperoxidized lipids of the same source.Furthermore, serum vitamin E content was generally reduced and serum TBARS content was increased when peroxidized lipids were fed in these studies, suggesting that feeding peroxidized lipids negatively affects metabolic oxidative status of pigs. However, it is unclear if antioxidants are useful additions to lipids to maintain optimal nutritional value, or if their addition to swine diets is beneficial in overcoming a metabolic oxidative challenge.
文摘A microcalorimetric technique was used to investigate the influence of Zn 2+ on the growth metabolism of Bacillus thuringiensis . LKB 2277 Bioactivity Monitor was employed to obtain the power time curves, from which the maximum peak heat output power ( P max ) in the log phase, the growth rate constants ( k ), the inhibitory ratios ( I ), the generational time ( t G) and the total heat effect ( Q total ) in 23 h for the growth metabolism of Bacillus thuringiensis at 28 ℃ can be evaluated. The results indicate that the concentration of Zn 2+ affects its growth obviously. Low concentration (0-50 μg/mL) of Zn 2+ promotes the growth of Bacillus thuringiensis while high concentration (50-500 μg/mL) of Zn 2+ inhibits its growth. When the concentration reached up to 600 μg/mL, it can not grow at all.
