Increasing harvest maturity of whole-plant corn silage reduces methane emission of lactating dairy cows.

The objective of this study was to investigate the effects of increasing maturity of whole-plant corn at harvest on CH4 emissions by dairy cows consuming corn silage (CS) based diets. Whole-plant corn was harvested at a very early [25% dry matter (DM); CS25], early (28% DM; CS28), medium (32% DM; CS32), and late (40% DM; CS40) stage of maturity. In a randomized block design, 28 lactating Holstein-Friesian dairy cows, of which 8 were fitted with rumen cannula, received 1 of 4 dietary treatments designated as T25, T28, T32, and T40 to reflect the DM contents at harvest. Treatments consisted of (DM basis) 75% CS, 20% concentrate, and 5% wheat straw. Feed intake, digestibility, milk production and composition, energy and N balance, and CH4 production were measured during a 5-d period in climate respiration chambers after an adaptation to the diet for 12 d. Corn silage starch content varied between 275 (CS25) and 385 (CS40) g/kg of DM. Treatments did not affect DM intake (DMI), milk yield, or milk contents. In situ ruminal fractional degradation rate of starch decreased linearly from 0.098 to 0.059/h as maturity increased from CS25 to CS40. Apparent total-tract digestibility of DM, organic matter, crude protein, neutral detergent fiber, crude fat, starch, and gross energy (GE) decreased linearly with maturity. Treatments did not affect ruminal pH, volatile fatty acids, and ammonia concentrations, and volatile fatty acids molar proportions. The concentration of C18:3n-3 in milk fat decreased linearly, and the concentration of C18:2n-6 and the n-6:n-3 ratio increased linearly with maturity. A quadratic response occurred for the total saturated fatty acid concentration and total monounsaturated fatty acid concentration in milk fat. Methane production relative to DMI (21.7, 23.0, 21.0, and 20.1g/kg) and relative to GE intake (0.063, 0.067, 0.063, and 0.060 MJ/MJ; values for T25, T28, T32, and T40, respectively) decreased linearly with maturity. Also, CH4 emission relative to fat- and protein-corrected milk tended to decrease linearly with maturity (13.0, 13.4, 13.2, and 12.1g/kg of fat- and protein-corrected milk, for T25, T28, T32, and T40, respectively). Intake of GE and metabolizable energy, and energy retained, all expressed per unit of metabolic body weight, did not differ among treatments. Nitrogen intake, N use efficiency (milk N/N intake), and N balance were not influenced by treatments. Increasing maturity of whole-plant corn at harvest may offer an effective strategy to decrease CH4 losses with feeding CS without negatively affecting cow performance.

Comparison of fractionation methods for nitrogen and starch in maize and grass silages.

In in situ nylon bag technique, many feed evaluation systems use a washing machine method (WMM) to determine the washout (W) fraction and to wash the rumen incubated nylon bags. As this method has some disadvantages, an alternate modified method (MM) was recently introduced. The aim of this study was to determine and compare the W and non-washout (D+U) fractions of nitrogen (N) and/or starch of maize and grass silages, using the WMM and the MM. Ninety-nine maize silage and 99 grass silage samples were selected with a broad range in chemical composition. The results showed a large range in the W, soluble (S) and D+U fractions of N of maize and grass silages and the W, insoluble washout (W-S) and D+U fractions of starch of maize silages, determined by both methods, due to variation in their chemical composition. The values for N fractions of maize and grass silages obtained with both methods were found different (p < 0.001). Large differences (p < 0.001) were found in the D+U fraction of starch of maize silages which might be due to different methodological approaches, such as different rinsing procedures (washing vs. shaking), duration of rinsing (40 min vs. 60 min) and different solvents (water vs. buffer solution). The large differences (p < 0.001) in the W-S and D+U fractions of starch determined with both methods can led to different predicted values for the effective rumen starch degradability. In conclusion, the MM with one recommended shaking procedure, performed under identical and controlled experimental conditions, can give more reliable results compared to the WMM, using different washing programs and procedures.

Estimation of the in situ degradation of the washout fraction of starch by using a modified in situ protocol and in vitro measurements.

The in situ degradation of the washout fraction of starch in six feed ingredients (i.e. barley, faba beans, maize, oats, peas and wheat) was studied by using a modified in situ protocol and in vitro measurements. In comparison with the washing machine method, the modified protocol comprises a milder rinsing method to reduce particulate loss during rinsing. The modified method markedly reduced the average washout fraction of starch in these products from 0.333 to 0.042 g/g. Applying the modified rinsing method, the fractional degradation rate (k d ) of starch in barley, oats and wheat decreased from on average 0.327 to 0.144 h-1 whereas for faba beans, peas and maize no differences in k d were observed compared with the traditional washing machine rinsing. For barley, maize and wheat, the difference in non-fermented starch in the residue between both rinsing methods during the first 4 h of incubation increased, which indicates secondary particle loss. The average effective degradation of starch decreased from 0.761 to 0.572 g/g when using the new rinsing method and to 0.494 g/g when applying a correction for particulate matter loss during incubation. The in vitro k d of starch in the non-washout fraction did not differ from that in the total product. The calculated ratio between the k d of starch in the washout and non-washout fraction was on average 1.59 and varied between 0.96 for oats and 2.39 for maize. The fractional rate of gas production was significantly different between the total product and the non-washout fraction. For all products, except oats, this rate of gas production was larger for the total product compared with the non-washout fraction whereas for oats the opposite was observed. The rate of increase in gas production was, especially for grains, strongly correlated with the in vitro k d of starch. The results of the present study do not support the assumption used in several feed evaluation systems that the degradation of the washout fraction of starch in the rumen is much faster than that of the non-washout fraction.

A new approach to estimate the in situ fractional degradation rate of organic matter and nitrogen in wheat yeast concentrates.

In the classic in situ method, small particles are removed during rinsing and hence their fractional degradation rate cannot be determined. A new approach was developed to estimate the fractional degradation rate of nutrients in small particles. This approach was based on an alternative rinsing method to reduce the particulate matter loss during rinsing and on quantifying the particulate matter loss that occurs during incubation in the rumen itself. To quantify particulate matter loss during incubation, loss of small particles during the in situ incubation was studied using undegradable silica with different particle sizes. Particulate matter loss during incubation was limited to particles smaller than ~40 µm with a mean fractional particulate matter loss rate of 0.035 h-1 (first experiment) and 0.073 h-1 (second experiment) and an undegradable fraction of 0.001 and 0.050, respectively. In the second experiment, the fractional particulate matter loss rate after rinsing in a water bath at 50 strokes per minute (s.p.m.) (0.215 h-1) and the undegradable fraction at 20 s.p.m. (0.461) were significantly larger than that upon incubation in the rumen, whereas the fractional particulate matter loss rate (0.140 and 0.087 h-1, respectively) and the undegradable fraction (0.330 and 0.075, respectively) after rinsing at 30 and 40 s.p.m. did not differ with that upon rumen incubation. This new approach was applied to estimate the in situ fractional degradation rate of insoluble organic matter (OM) and insoluble nitrogen (N) in three different wheat yeast concentrates (WYC). These WYC were characterised by a high fraction of small particles and estimating their fractional degradation rate was not possible using the traditional washing machine rinsing method. The new rinsing method increased the mean non-washout fraction of OM and N in these products from 0.113 and 0.084 (washing machine method) to 0.670 and 0.782, respectively. The mean effective degradation (ED) without correction for particulate matter loss of OM and of N was 0.714 and 0.601, respectively, and significant differences were observed between the WYC products. Applying the correction for particulate matter loss reduced the mean ED of OM to 0.676 (30 s.p.m.) and 0.477 (40 s.p.m.), and reduced the mean ED of N to 0.475 (30 s.p.m.) and 0.328 (40 s.p.m.). These marked reductions in fractional degradation rate upon correction for small particulate matter loss emphasised the pronounced effect of correction for undegraded particulate matter loss on the fractional disappearance rates of OM and N in WYC products.

A modified rinsing method for the determination of the S, W-S and D + U fraction of protein and starch in feedstuff within the in situ technique.

A modified rinsing method for the in situ technique was developed to separate, isolate and characterise the soluble (S), the insoluble washout (W-S) and the non-washout fractions (D + U) within one procedure. For non-incubated bags (t = 0 h), this method was compared with the conventional, Combined Fractionation (CF) method that measures the D + U and S fractions in separate steps and subsequently calculates the W-S fraction. The modified method was based on rinsing of nylon bags in a closed vessel containing a buffer solution (pH 6.2) during 1 h, where shaking speeds of 40, 100, and 160 strokes per minutes (spm) were evaluated, and tested for six feed ingredients (faba beans, maize, oats, peas, soya beans and wheat) and four forages (two ryegrass silages and two maize silages). The average recoveries as the sum of all fractions were 0.972 ± 0.041 for N and 0.990 ± 0.050 for starch (mean ± s.d.). The mean W-S fraction increased with increasing shaking speed and varied between 0.017 (N) and 0.083 (starch) at 40 spm and 0.078 (N) and 0.303 (starch) at 160 spm, respectively. For ryegrass silages, the W-S fraction was absent at all shaking speeds, but was present in the CF method. The modified method, in particular at 40 and 100 spm, reduced the loss of small particles during rinsing, resulting in lower W-S and higher D + U fractions for N and starch compared with the CF method. For soya beans and ryegrass silage, the modified method reduced the S fraction of N compared with the CF method. The results obtained at 160 spm showed the best comparison with those from the CF method. The W-S fraction of the feedstuff obtained at 160 spm contained mainly particles smaller than 40 µm (0.908 ± 0.086). In most feedstuff, starch was the most abundant chemical component in the W-S fraction and its content (726 ± 75 g/kg DM) was higher than in the D + U fraction (405 ± 177 g/kg DM). Alkaline-soluble proteins were the dominant N-containing components in the W-S fraction of dry feed ingredients and its relative content (0.79 ± 0.18 of total N in W-S) was higher than in the D + U fraction (0.59 ± 0.07 of total N in D + U) for all feedstuff except maize. The molecular weight distribution of the alkaline-soluble proteins differed between the W-S and the D + U fractions of all dry feed ingredients, except soya beans and wheat.

A rare mutation in AgRP, +79G>A, affects promoter activity.

The agouti-related protein is a powerful orexigenic peptide. A rare mutation, +79G>A, was identified in its minimal promoter in two white carriers. Comparison of the 45-year-old male proband, who was also a carrier of the common Ala67Thr polymorphism, with an age- and weight-matching wild-type population showed marginal differences for resting metabolic rate (RMR) and body mass index. The second carrier however was an obese 57-year-old female with reduced RMR. Functional analysis in hypothalamus- and periphery-derived cell lines showed reduced promoter activity for the +79A allele in the adrenocortical cells only, suggesting that it could affect the peripheral expression levels of AgRP. The +79G>A mutation could predispose to body weight gain (as suggested by the phenotype of the second carrier), but it could only affect the proband at an older age as he may be protected by the Ala67Thr polymorphism that is associated with resistance to late-onset fatness.

Quantification of inositol phosphates using (31)P nuclear magnetic resonance spectroscopy in animal nutrition.

A (31)P NMR method for quantitative determination of inositol phosphates in simple incubation samples of sodium phytate and Aspergillus niger phytase and in different types of complex samples, such as diets, digesta, and feces, is described. The inositol phosphates in complex samples were extracted with HCl, concentrated, and purified using freeze-drying and filtration and subsequently determined at pH 12.6 in aqueous solution using a (31)P NMR method. The (31)P NMR technique has as its main advantages over the HPLC techniques that it does not necessitate standards that may cause background matrix effects and that the spectra of inositol phosphates and orthophosphate appear in the same run without further sampling errors. The results of inositol hexaphosphate analysis with HPLC can be confirmed by this (31)P NMR method. Contents of inositol tetra-, tri-, di-, and monophosphate in the biological samples appear to be quantitatively not important. The (31)P NMR method can be applied for use in animal nutrition in general and studies of using phytase in diets for farm animals in particular, by measuring the content of inositol phosphates in feed ingredients, complete feeds, ileal contents, and feces of pigs and poultry.

Should we still use the Harris and Benedict equations?

Resting metabolic rate (RMR) is commonly predicted using the Harris-Benedict (HB) equations, but an overestimation of 10% to 15% is normally found. More recent studies have proposed equations with a better predictive value. In this study, we explore the relationship between measured RMR and HB in 67 healthy volunteers and in a data set from the literature and compared measured RMR with six more recent equations. Mean differences between RMR and HB were 21%, 12%, 10%, and 4% for the lowest to the highest RMR quartile, respectively, and 20%, 8%, 6%, and -4% for Owen's subjects. Among the six recent equations, only the World Health Organization (WHO) equations predicted RMR within 10% in 100% of the cases. Our results suggest that overestimation of RMR by HB is not a homogenous finding but is inversely related to RMR. This may have important implications for predicting RMR in women and in patients with diminished lean body mass. In addition, the WHO equations appear more precise than the HB equations.

Evaluation of systematic errors due to deproteinization, calibration and storage of plasma for amino acid assay by ion-exchange chromatography.

Three factors contributing to inter-laboratory variation in the determination of amino acids in plasma, i.e. deproteinization, calibration and storage conditions, were evaluated in this study. Deproteinization clearly enlarged the coefficient of variation in the determination of cystine, aspartic acid and tryptophan. During this process losses of hydrophobic amino acids occurred, in particular, when the volume of the supernatant was small. Correction for this effect, using an internal standard, was not possible. Delaying the removal of the supernatant for 1 h decreased the concentration of tryptophan. Correction for this effect, using an internal standard, was not possible. The use of different commercial standards also led to systematic errors during the calibration of samples. The amino acid concentrations in deproteinized plasma remained for a least 1 year when stored at a temperature of -40 degrees C or lower. Above this temperature, glutamine and asparagine were found to be degraded. This degradation could be minimized by neutralizing the samples before storage. The concentration of cystine decreased considerably during storage of non-deproteinized plasma. Correction for these changes due to storage is not advised and, in most cases, is impossible.

Modification of the analysis of amino acids in pig plasma.

Determination of amino acids in pig plasma with the classical ninhydrin system is influenced by the excessive amount of protein and lipophilic compounds in the sample, leading to a decline in resolution. This problem was eliminated by using 80 mg of sulphosalicylic acid per ml of plasma, and solid-phase extraction with a C18 cartridge as an additional clean up step. The latter resulted in significantly higher quantities of threonine, asparagine, glutamic acid, glutamine, glycine, alanine, valine and lysine, and lower levels of phenylalanine and tryptophan (P < 0.05). The use of a C18 cartridge had a minor effect on the analytical error.