Short communication: measurements of methane emissions from feed samples in filter bags or dispersed in the medium in an in vitro gas production system.

The objective of this study was to compare methane (CH4) emissions from different feeds when incubated within filter bags for in vitro analysis or directly dispersed in the medium in an automated gas in vitro system. Four different concentrates and 4 forages were used in this study. Two lactating Swedish Red cows were used for the collection of rumen fluid. Feed samples were milled to pass a 1.0-mm screen. Aliquots (0.5 g) of samples were weighed directly in the bottles or within the F 0285 filter bags that were placed in the bottles. Gas samples were taken during 24 and 48 h of incubation, and CH4 concentration was determined. The data were analyzed using a general linear model. Feeds differed significantly in CH4 emission both at 24 and at 48 h of incubation. The interaction between feed and method on methane emission in vitro was significant, indicating that the ranking of feeds was not consistent between the methods. Generally, greater amounts of CH4 were emitted from samples directly dispersed in the medium compared with those incubated within the filter bags, which could be a result of lower microbial activity within the filter bags. The ratio of CH4 to total gas was greater when the feeds were incubated within bags compared with samples directly dispersed in the medium. Incubating samples in filter bags during 48 h of incubation cannot be recommended for determination of CH4 emission of feeds in vitro.

Comparison of some aspects of the in situ and in vitro methods in evaluation of neutral detergent fiber digestion.

The objective of the present study was to compare digestion rates (kd) of NDF for different feeds estimated with the in situ method or derived from an automated gas in vitro system. A meta-analysis was conducted to evaluate how in situ derived kd of NDF related to in vivo digestibility of NDF. Furthermore, in vitro true digestibility of the feed samples incubated within filter bags or dispersed in the medium was compared, and kd for insoluble and soluble components of those feeds were estimated. Four different concentrates and 4 forages were used in this study. Two lactating Swedish Red cows fed a diet of 60% grass silage and 40% concentrate on DM basis were used for in situ incubations and for collection of rumen fluid. The feed samples were ground through a 2.0-mm screen before the in situ incubations and a 1.0-mm screen before the in vitro gas incubations. In situ nylon bags were introduced into the rumen for determination of kd of NDF. Additional kinetic data were produced from isolated NDF and intact samples subjected to in vitro incubations in which gas production was recorded for 72 h. Samples were weighed in the bottles or within filter bags (for fiber and in vitro studies) that were placed in the bottles. The interaction between feed and method was significant (P < 0.01); kd of NDF for grass hay tended (P = 0.06) to be less whereas kd of NDF for alfalfa, barley grain, canola meal, and dried sugar beet pulp were greater (P < 0.01) when estimated with the in situ method than from gas production recordings. The meta-analysis suggested that in situ derived kd of NDF were biased and underestimated in vivo digestibility of NDF. Digestion rates of the intact samples were lower for all feeds, except for the hay, when incubated within the bags compared with dispersed in the medium (P < 0.01). Less OM and NDF were digested for all feeds when incubated within bags than dispersed in the medium (P < 0.01). It is concluded from the in vitro study that microbial activity within the bags is less than in the medium. Significant interactions between method (in situ vs. in vitro) and feed suggest that one or both methods result in biased estimates of digestion kinetics.

Quantifying differences in total tract nutrient digestibilities between goats and sheep.

Conclusions from narrative qualitative reviews on differences in total tract digestibilities between goats and sheep did not account for variability among studies. Therefore meta-analytic techniques were used to describe the magnitude of these differences with numerical values. A unitless effect size (Hedges' g) was applied within studies to measure differences in digestibilities of dry matter (DM; 104 comparisons), organic matter (OM; 93 comparisons), crude protein (CP; 85 comparisons), neutral detergent fibre (NDF; 74 comparisons), acid detergent fibre (ADF; 59 comparisons), cellulose (24 comparisons), hemicellulose (18 comparisons) and gross energy (GE; 29 comparisons). The absence and inability to describe independent factors which contributed to variation among studies necessitated the use of frequentist random effects and hierarchical Bayesian models in the calculation of summary statistics across studies. Digestibilities of DM, OM, CP, NDF, ADF and hemicellulose were higher (p < 0.05) in goats than sheep when all-forage diets were fed. When concentrates were included in the diets, there were no such differences. Differences between goats and sheep in DM intake were found to be non-significant. Differences in nutrient digestibilities of forages as sole feed implies that species-specific values have to be used in feed formulation and feeding strategies. However, caution is needed when extrapolating results from stall-feeding, which is how digestibility data are usually measured, to grazing conditions.

Effects of dietary chromium supplementation on performance, carcass characteristics, and meat quality of growing-finishing swine: a meta-analysis.

Dietary Cr supplementation has potential to decrease fat and increase lean in carcasses of growing-finishing swine. However, effects of Cr supplementation on performance and economically important carcass and meat quality characteristics varied considerably among studies. Therefore, a meta-analysis was designed to quantitatively describe effects obtained in several independent studies. To accommodate differences in methodology among studies, standardized effect sizes (Hedges's g) were calculated for results from 31 studies, in which Cr was supplemented as complexes of Cr Met chelate, Cr nanocomposite, Cr nicotinate, Cr propionate, Cr tripicolinate, or Cr yeast in diets for growing-finishing swine. Summary statistics were calculated by frequentist fixed and random effects, and hierarchical Bayesian models. With characteristics related to carcass quality, observed heterogeneity (P < 0.10) could not adequately be explained in a meta-regression by differences in initial BW and amount of Cr supplemented. Random effects and Bayesian models to summarize effect sizes for these characteristics showed similar results. According to random effects models, dietary Cr supplementation decreased (P < 0.05) 10th-rib fat thickness (mean effect size = -0.479; 95% confidence intervals = -0.680 to -0.279; 24 studies; 59 comparisons), whereas percentage carcass lean (mean effect size = 0.614; 95% confidence intervals = 0.366 to 0.863; 22 studies; 52 comparisons) and LM area (mean effect size = 0.571; 95% confidence intervals = 0.364 to 0.778; 29 studies; 72 comparisons) increased. Average daily gain and G:F, which did not present heterogeneity, were improved by Cr supplementation, whereas no effects were detected in characteristics (CIE color, drip loss, cook loss, shear force) related to meat quality. Some publication, or other small-study bias, was evident in results on growth and feed efficiency. However, directions of mean effect sizes were not changed by application of the trim-and-fill method to correct for bias.

[Determination of mefenoxalone in substances, tablets and biological materials]. / Stanovení mefenoxalonu v substanci, tabletách a biologickém materiálu.

For the determination of mefenoxalon in substance, tablets and biological material (blood plasma), four variants were worked out. The first of them is based on the substitution of the benzene ring with bromine with the use of an excess of bromine, which is determined ionometrically. The second variant is based on direct titration of the hydrolytic product mefenoxalon, 3-(2-methoxyphenoxy)-2-hydroxypropylamine, with the use of the ion-selective electrode of the coated-wire type with a volumetric solution of tetraphenyl-borsodium. The third variant utilizes direct measurements of UV spectra of mefenoxalon in a solution of dichlorethane. The fourth variant consists in its fluorimetric measurement in a solution of dichlorethane, or ethylacetate. A detailed discussion of advantages and disadvantages of all above-mentioned variants of determination is presented.