G. Getachew

Relationships between chemical composition, dry matter degradation and in vitro gas production of several ruminant feeds

Abstract Thirty-eight samples of 12 feedstuffs were used to study relationships between in vitro true digestibility of dry matter (IVTD) and in vitro gas production. Influences of chemical constituents on gas and volatile fatty acid (VFA) production were investigated. There was a negative ( P P P P P P P

Laboratory variation of 24 h in vitro gas production and estimated metabolizable energy values of ruminant feeds

Intra- and inter-laboratory variation of in vitro gas production and calculated metabolizable energy (ME, MJ/kg DM) values were studied using 16 test feeds in 7 laboratories. Intra-laboratory variation was low, with six of the seven laboratories having very high relationships in gas production between runs (R 2 ≥ 0.96) and slopes that did not differ from unity. Inter-laboratory differences were higher with highly significant ( P< 0.001) differences among laboratories in both gas production and calculated ME values. Three of the six test laboratories generated predicted ME values that did not differ from the seventh (reference) laboratory. Combining intra-laboratory variation in gas production and inter-laboratory variation in predicted ME values, three of the six test laboratories were judged acceptable overall. ME values predicted by the gas production technique by laboratories in different parts of the world cannot be considered absolute.

Biomass accumulation and potential nutritive value of some forages irrigated with saline-sodic drainage water

A controlled study using a sand-tank system was conducted to evaluate 10 forage species (bermudagrass, ‘Salado’ and ‘SW 9720’ alfalfa, ‘Duncan’ and ‘Polo’ Paspalum, ‘big’ and ‘narrow leaf’ trefoil, kikuyugrass, Jose tall wheatgrass, and alkali sacaton). Forages were irrigated with sodium-sulfate dominated synthetic drainage waters with an electrical conductivity of either 15 or 25 dS/m. Forage yield was significantly reduced by the higher (25 dS/m) salinity level of irrigation water compared to the lower (15 dS/m) level. There was wide variation in the sensitivity of forage species to levels of salinity in irrigation water as reflected by biomass accumulation. With the exception of bermudagrass, which increased accumulation at the higher level of salinity, and big trefoil, which failed to establish at the higher level of salinity, ranking of forages according to the percent reduction in biomass accumulation due to the higher level of salinity of irrigation water was: Salado alfalfa (54%) = SW 9720 alfalfa (52%) > Duncan Paspalum (41%) > narrow leaf trefoil (30%) > alkali sacaton (24%) > Polo Paspalum (16%) > Jose tall wheatgrass (11%) = kikuyugrass (11%). Bermudagrass and Duncan Paspalum were judged to be the best species in terms of forage yield and nutritive quality. Kikuyugrass, which had the third highest biomass accumulation, was judged to be unacceptable due to its poor nutritional quality. Although narrow leaf trefoil had a relatively high nutritional quality, its biomass accumulation potential was judged to be unacceptably low. Alfalfa cultivar’s biomass accumulations were the most sensitive to the higher level of salinity, among forages that survived at the higher salinity level, although actual accumulations at the higher salinity were high relative to other forages. Increased salinity influenced several forage quality parameters, including organic matter (OM), crude protein (CP), neutral detergent fibre (NDF), and in vitro gas production, generally leading to higher nutritional quality at the higher salinity level, although their significance varied amongst species and cuttings.

In vitro rumen fermentation and gas production: influence of yellow grease, tallow, corn oil and their potassium soaps

The effect of addition of fat on in vitro gas production, volatile fatty acid (VFA) production, in vitro true digestibility (IVTD), and ammonia-N concentration was assessed by incubation of a simulated total mixed ration in buffered rumen fluid using an in vitro gas technique. Fat sources were corn oil (CO), tallow (TL), yellow grease (YG), and potassium soaps (K-soaps) of CO, YG, and TL. Addition of YG increased (P<0.001) in vitro gas production while TL had no effect. Neither YG nor TL affected IVTD and total VFA production. Addition of either YG or TL decreased acetate production and increased propionate production. Addition of CO increased in vitro gas production, but had no effect on IVTD and total VFA production. However, CO decreased acetate and increased propionate production with a concomitant decrease in the acetate to propionate ratio. Addition of K-soaps of CO, TL and YG depressed in vitro gas production, IVTD, VFA and ammonia-N concentrations. K-soaps also caused a marked decrease in acetate and increase in propionate production. The absence of negative effects on rumen fermentation parameters in response to the inclusion of fat in the form of triglycerides to an in vitro system at up to 25% DM suggests that triglycerides have much less effect on rumen fermentation parameters than corresponding free fatty acids. In contrast, the K-soaps of each respective fat had detrimental effects on in vitro rumen fermentations.

HOW TO CONVERT BIOLOGICAL CARBON INTO GRAPHITE FOR AMS

Isotope tracer studies, particularly radiocarbon measurements, play a key role in biological, nutritional, and environmental research. Accelerator mass spectrometry (AMS) is now the most sensitive detection method for radiocarbon, but AMS is not widely used in kinetic studies of humans. Part of the reason is the expense, but costs would decrease if AMS were used more widely. One component in the cost is sample preparation for AMS. Biological and environmental samples are commonly reduced to graphite before they are analyzed by AMS. Improvements and mechanization of this multi-step procedure is slowed by a lack of organized educational materials for AMS sample preparation that would allow new investigators to work with the technique without a substantial outlay of time and effort. We present a detailed sample preparation protocol for graphitizing biological samples for AMS and include examples of nutrition studies that have used this procedure.

In vitro gas production as a method to compare fermentation characteristics of steam-flaked corn

An in vitro gas production technique was used to determine differences in starch availability that occurred with steam flaking of corn among eight feed mills (MILL) in California. Whole corn (WC) and steam-flaked corn (SFC) grain samples were obtained from six commercial mills and two mills at the University of California (Davis and El Centro, CA). The WC sample was collected prior to the steam chest and represented unprocessed corn. The SFC sample was collected at the rolls and represented a typically processed corn. Ground samples of WC and SFC were evaluated by incubation in buffered rumen fluid using an in vitro gas technique for a 72 h incubation period to compare processing (PROCESS) method. Starch reactivity was determined as the percentage of starch degraded to glucose by amylase after 4 h of incubation. Starch reactivity of SFC was higher (P<0.01) than WC. Starch reactivity was different for MILL (P<0.01) and the interaction of MILL and PROCESS was significant (P<0.01). Total gas produced at 8 h of incubation was higher (P<0.01) for SFC than WC, but total gas production did not differ for PROCESS at 24 and 72 h. Gas production after 8 h also differed for MILL (P<0.01). Time required for 25, 50, 75, and 90% disappearance of starch was estimated and in general disappearance of starch occurred sooner for SFC than WC. Fifty percent disappearance of starch occurred at 6.8 h for WC and at 5.5 h for SFC. Total volatile fatty acids (VFA) production did not differ for MILL or PROCESS at 8 or 72 h of incubation. Propionate production was higher (P<0.01) for SFC than WC at both 8 and 72 h. This in vitro gas production technique can be used to determine the effect of grain processing on fermentation rate and to identify differences among mills in potential digestibility of the processed grain.

Kinetics of 14C distribution after tracer dose of 14C-lutein in an adult woman

Lutein is an oxygenated carotenoid (xanthophyll) found in dark green leafy vegetables. High intakes of lutein may lower the risk of age-related macular degeneration. Current understanding of human lutein metabolism as it might occur in vivo is incomplete. Therefore, we conducted a feasibility study where we dosed a normal adult woman with 14C-lutein (125 nmol, 36 nCi 14C), dissolved in olive oil (0.5 g/kg body weight) and mixed in a banana shake. Blood, urine, and feces collected before the dose was administered served to establish baseline values. There-after, blood was collected for 63 d following the dose, while feces and urine were collected for 2 wk post-dose. The 14C contents in plasma, urine, and feces were measured by accelerator MS. The 14C first appeared in plasma 1 h after dosing and reached its highest level,≈2.08% of dose/L plasma, at 14 h post-dose. The plasma pattern of 14C did not include a chylomicrons/VLDL (intestinal) peak like that when the same subject received 14C-β-carotene (a previous test), suggesting that lutein was handled differently from β-carotene by plasma lipoproteins. Lutein had an elimination half-life (t1/2) of≈10 d. Forty-five percent of the dose of 14C was eliminated in feces and 10% in urine in the first 2 d after dosing. Quantifying human lutein metabolism is a fertile area for future research.

The impact of lignin downregulation on alfalfa yield, chemical composition, and in vitro gas production: The impact of lignin downregulation on alfalfa yield, chemical composition

BACKGROUND Lignin is a complex, phenolic polymer found in plant cell walls that is essential for mechanical support, water and mineral transport, and defense in vascular plants. Over ten different enzymes play a role in the synthesis of lignin in plants. Suppression of any one enzyme or combinations of these enzymes may change the concentration and composition of lignin in the genetically transformed plants. Two lines of alfalfa that were downregulated for caffeoyl coenzyme A O-methyltransferase were used to assess the impact of lignin downregulation on chemical composition and fermentation rate and extent using an in vitro gas production technique. A total of 64 samples consisting of two reduced lignin (RL) and two controls (CL), four field replicates, two cutting intervals (CIs; 28 and 35 days), and two cuts (Cut-1 and Cut-3) were used. RESULTS No differences were detected in yield, crude protein, neutral detergent fiber (aNDF), and acid detergent fiber between the lines when harvested at the 28-day CI. The acid detergent lignin (ADL) concentration in RL alfalfa lines was significantly (P < 0.001) lower than in the CL. In alfalfa harvested at the 35-day CI, the RL alfalfa resulted in lower (P < 0.001) yield than CL. RL alfalfa lines had 24% and 22% lower (P < 0.001) ADL in Cut-1 and Cut-3 respectively than CL lines. The in vitro dry matter digestibility and aNDF digestibility (both as determined by the near-infrared reflectance method) were greater (P < 0.001) in RL than in CL lines harvested at the 35-day CI. In alfalfa harvested at the 35-day CI, extent of in vitro gas production and metabolizable energy content were greater in RL than in CL alfalfa. RL lines had 3.8% indigestible aNDF per unit ADL, whereas CL had 3.4% (P < 0.01). The positive effect of lignin downregulation was more pronounced when intervals between harvests were longer (35-day CI compared with the 28-day CI). CONCLUSION Lignin downregulation in alfalfa offers an opportunity to extend harvesting time (CI) for higher yield without compromising the nutritional quality of the alfalfa forage for dairy and livestock feeding. However, the in vitro results reported here warrant further study using in vivo methods.