A. D. Iwaasa

Effects of an exogenous enzyme preparation on microbial protein synthesis, enzyme activity and attachment to feed in the Rumen Simulation Technique (Rusitec).

The effects of an exogenous enzyme preparation, the application method and feed type on ruminal fermentation and microbial protein synthesis were investigated using the rumen simulation technique (Rusitec). Steam-rolled barley grain and chopped alfalfa hay were sprayed with water (control, C), an enzyme preparation with a predominant xylanase activity (EF), or autoclaved enzyme (AEF) 24 h prior to feeding, or the enzyme was supplied in the buffer infused into the Rusitec (EI). Microbial N incorporation was measured using (15NH4)2SO4 in the buffer. Spent feed bags were pummelled mechanically in buffer to segregate the feed particle-associated (FPA) and feed particle-bound (FPB) bacterial fractions. Enzymes applied to feed reduced neutral-detergent fibre content, and increased the concentration of reducing sugars in barley grain, but not alfalfa hay. Ruminal cellulolytic bacteria were more numerous with EF than with C. Disappearance of DM from barley grain was higher with EF than with C, but alfalfa was unaffected by EF. Treatment EF increased incorporation of 15N into FPA and FPB fractions at 24 and 48 h. In contrast, AEF reduced the 24 h values, relative to C; AEF and C were similar at 48 h. Infused enzyme (EI) did not affect 15N incorporation. Xylanase activity in effluent was increased by EF and EI, compared to C, but not by AEF. Xylanase activity in FPA was higher at 48 h than at 24 h with all treatments; it was higher with EF than C at 24 and 48 h, but was not altered by AEF or EI. Applying enzymes onto feeds before feeding was more effective than dosing directly into the artificial rumen for increasing ruminal fibrolytic activity.

Use of corn distillers' dried grains to reduce enteric methane loss from beef cattle.

There are significant emissions of greenhouse gases (GHG) from agriculture, and a major source is enteric methane (CH4) from ruminants. Our study reports the impact on enteric CH4 emissions when barley grain (35% of the dietary dry matter (DM) was replaced by corn distillers’ dried grains with solubles (DDGS, adding 30 g fat kg-1 dietary DM) in the backgrounding diet of growing beef cattle. The addition of DDGS reduced CH4 emissions (g d-1) by 19.9%, and by 16.4% when adjusted for DM intake [g (DM intake)-1] or by 23.9% when adjusted for gross energy (GE) intake (% of GE intake). Adding DDGS to cattle diets reduced CH4 emissions, but the effects of higher N content of the manure on emissions of nitrous oxide and ammonia need to be accounted for to complete the evaluation of the environmental impact of feeding DDGS to feedlot cattle. Key words: Methane, beef cattle, corn distillers’ dried grains with solubles, lipid, greenhouse gas emissions, sulphur hexafluoride

Plant assemblage composition and soil P concentration differentially affect communities of AM and total fungi in a semi-arid grassland

Adding inorganic P- and N-fixing legumes to semi-arid grasslands can increase forage yield, but soil nutrient concentrations and plant cover may also interact to modify soil fungal populations, impacting short- and long-term forage production. We tested the effect of plant assemblage (seven native grasses, seven native grasses + the domesticated N-fixing legume Medicago sativa, seven native grasses + the native N-fixing legume Dalea purpurea or the introduced grass Bromus biebersteinii + M. sativa) and soil P concentration (addition of 0 or 200 P2O5 kg ha(-1) at sowing) on the diversity and community structure of arbuscular mycorrhizal (AM) fungi and total fungi over two consecutive years, using 454-pyrosequencing of 18S rDNA and ITS amplicons. Treatment effects were stronger in the wet year (2008) than the dry year (2009). The presence of an N-fixing legume with native grasses generally increased AM fungal diversity, while the interaction between soil P concentration and plant assemblage modified total fungal community structure in 2008. Excluding interannual variations, which are likely driven by moisture and plant productivity, AM fungal communities in semi-arid grasslands appear to be primarily affected by plant assemblage composition, while the composition of other fungi is more closely linked to soil P.

Grazing improves C and N cycling in the Northern Great Plains: a meta-analysis

Grazing potentially alters grassland ecosystem carbon (C) and nitrogen (N) storage and cycles, however, the overall direction and magnitude of such alterations are poorly understood on the Northern Great Plains (NGP). By synthesizing data from multiple studies on grazed NGP ecosystems, we quantified the response of 30 variables to C and N pools and fluxes to grazing using a comprehensive meta-analysis method. Results showed that grazing enhanced soil C (5.2 ± 4.6% relative) and N (11.3 ± 9.1%) pools in the top layer, stimulated litter decomposition (26.8 ± 18.4%) and soil N mineralization (22.3 ± 18.4%) and enhanced soil NH4+ (51.5 ± 42.9%) and NO3− (47.5 ± 20.7%) concentrations. Our results indicate that the NGP grasslands have sequestered C and N in the past 70 to 80 years, recovering C and N lost during a period of widespread grassland deterioration that occurred in the first half of the 20th century. Sustainable grazing management employed after this deterioration has acted as a critical factor for C and N amelioration of degraded NGP grasslands and about 5.84 Mg C ha−1 CO2-equivalent of anthropogenic CO2 emissions has been offset by these grassland soils.

Enzymes as Direct-Feed Additives for Ruminants

Fibrolytic enzymes hold great potential to improve feed utilization and productivity in ruminants. In the past, it was believed that the endogenous activity against plant cell walls could not be augmented by supplementary exogenous enzymes. However, when diets of dairy and beef cattle are supplemented with commercial xylanases and cellulases, animal performance is significantly improved. The most likely site of action is the rumen rather than in the small intestine as is the case for poultry. Because of the complexity of the rumen environment, it has been difficult to identify the exact mode of action for this beneficial response. Since xylanases and cellulases are the main activities that occur in efficacious enzyme mixtures, it may be assumed that the enzymes are having a direct, additive effect on the hydrolysis of plant fiber in the rumen. However, evidence to date suggests that the benefits of exogenous enzymes is synergistic to ruminal endogenous enzymes. This synergy may explain why relatively small amounts of enzyme can have such large effects on animal productivity. Limitations to the exploitation of this technology are the development of an adequate screening system for new enzymes, and the identification of the specific enzyme activities that are critical for efficacy.

Shearing force of alfalfa stems as affected by seeding rate

Physical properties of forages may provide a simple method of predicting animal voluntary feed intake. Physical measurements, such as shearing force, may indicate the resistance of the forage to particle breakdown during mastication. The objective of this study is to determine the effects of seeding rate on the physical characteristics and cell wall chemical constituents of alfalfa (Medicago sativa L.) stems, and to relate these characteristics to shearing strength. Stems of eight alfalfa cultivars (120, Legend, Multiking 1, OAC Minto, Saranac, Vernal, Vertus, WL320) seeded at 6, 12 and 24 kg ha−1 were harvested in the first and second production years and divided into three 16 cm segments: top, middle and bottom, and the force required to shear each segment was measured using a modified Ottawa Texture Measuring System. For both years, shearing force, segment weight and stem diameter measurements generally decreased as seeding rate increased when measured at the middle and bottom shearing segments on the ...

AC Saltlander green wheatgrass

AC Saltlander originated from seeds collected in Turkey by United States Department of Agricultural (USDA) scientists. Plants from these seeds were grown in a nursery near Logan, UT, where researchers at the USDA Forage and Range Research Laboratory selected desirable parents to obtain caespitose growth. In a collaborative project, selected germplasm of this natural hybrid was made available to the Semiarid Prairie Agricultural Research Centre (SPARC), Agriculture and Agri-Food Canada (AAFC) for salt-tolerance testing and improvement. A series of mass selection breeding cycles was conducted at Swift Current, where the resulting plants were evaluated for resistence to root-zone salinity, winter hardiness, and desirable plant morphology, including uniform plant colour, vegetative vigour, leafiness, seed-set, and freedom from plant pests. The progenies from each cycle were cloned, half of which were transported to the Agricultural Research Service Laboratory in Utah, and half intercrossed to develop AC Saltl...

Beef cattle grazing behaviour differs among diploid and tetraploid crested wheatgrasses (Agropyron cristatum and A. desertorum)

Iwaasa, A. D., Jefferson, P. G. and Birkedal, E. J. 2014. Beef cattle grazing behaviour differs among diploid and tetraploid crested wheatgrasses (Agropyron cristatum and A. desertorum). Can. J. Plant Sci. 94: 851-855. A study was conducted over 4 yr (1999, 2000, 2002 and 2003) at Swift Current to evaluate the forage preferences of steers grazing five different crested wheatgrass (CWG) cultivars: Kirk (2n=28), Fairway (2n=14) and Parkway (2n=14) [Agropyron cristatum (L.) Gaertn.], Hycrest (2n=28) (A. cristatum×A. desertorum) and Nordan (2n=28) [(A. desertorum (Fisch. Ex Link) Schult.)]. Animal grazing frequencies for each CWG cultivar patch were converted to percentages (Grazing%) for each grazing time period. Grazing% for Kirk and Hycrest CWGs were similar with Nordan having higher (P<0.05) Grazing% compared with the hybrid and diploid CWGs. Contrasts revealed no differences (P=0.48) in Grazing% between diploid versus hybrid cultivars, while higher (P<0.01) Grazing% were observed for tetraploid compared with diploid and hybrid CWG cultivars. For forage nutritive values, significant Cultivar (P<0.01) and Year (P<0.0001) main effects were observed. Overall mean values for percent crude protein (%CP) and percent acid detergent fibre (%ADF) for Nordan, Kirk, Hycrest, Fairway and Parkway were 10.6±0.3 and 29.2±0.4, 11.0±0.3 and 28.7±0.4, 10.4±0.3 and 29.7±0.4, 9.9±0.3 and 28.5±0.4, and 10.0±0.3 and 28.7±0.4, respectively (± SE). Correlation coefficients between Grazing% and all nutritive value constituents were low and not significant. This study observed grazing preference differences among different CWG cultivars that may lead to grazing management strategies to improve pasture utilization potential and animal production.

Effects of hydrolyzable tannin with or without condensed tannin on methane emissions, nitrogen use, and performance of beef cattle fed a high-forage diet1,2

Sustainability of animal agriculture requires efficient use of energy and nitrogen (N) by ruminants fed high-forage diets. Thus, there is a need to decrease methane (CH4) emissions and prevent excessive N release into the environment. Therefore, this experiment examined the long-term effects of feeding hydrolyzable tannin (HT) with or without condensed tannin (CT) on animal performance, rumen fermentation, N use, and CH4 production in beef cattle fed a high-forage diet. A total of 75 weaned crossbred steers (292 ± 4.1 kg) were grouped by body weight (BW), housed in individual pens, and randomly assigned to 1 of 5 dietary treatments (15 animals/treatment) in a completely random design. The animals were fed a basal diet of alfalfa:barley silages (50:50; dry matter [DM] basis) with a crude protein content of 17.1% and supplemented with HT extract (chestnut, CN) or a combination (50:50) of HT and CT extracts (quebracho, Q) in a powdered form at different levels of dietary DM. The treatments for determining animal performance and N use were control (no tannin), 0.25% CN, 1.5% CN, combination of CN and Q at 0.125% each (0.25% CNQ), and CN and Q at 0.75% each (1.5% CNQ) of dietary DM. The treatments for the CH4 measurement were control, 1.5% CN, and 1.5% CNQ of dietary DM. The first 84 d of the study were used to measure animal performance, rumen fermentation, and N use, and the next 30 d were used to measure CH4 emissions with the tracer gas technique. There were no effects of treatment on DM intake (DMI), BW, average daily gain, and gain: feed (P ≥ 0.10). The plasma urea N concentration was greater (P < 0.05) for 1.5% CN and 1.5% CNQ than those fed 0.25% CNQ (120.9 and 120.4 vs. 111.7 mg/L, respectively), but not different (P > 0.05) from animals fed control or 0.25% CN (117.2 and 117.5 mg/L, respectively). Tannin inclusion did not affect rumen pH, total volatile fatty acid concentration, proportions of acetate and propionate, and total protozoa populations (P ≥ 0.16). Tannin, irrespective of type or dose, decreased (P < 0.01) ruminal ammonia concentration. Tannin type and dose did not affect (P = 0.54) daily CH4 production (154 ± 5.9 g/d) but 1.5% CNQ tended to decrease CH4 yield compared with control (20.6 vs. 22.0 g/kg DMI; P = 0.094). HT from CN alone or in combination with CT from Q can be added at a low (0.25% DM) or high (1.5% DM) level to a forage-based diet to decrease ruminal ammonia concentration in growing beef cattle fed a high-protein diet without adverse effects on animal performance. A combination of HT and CT at a concentration of 1.5% dietary DM also tended to decrease CH4 emissions without negatively affecting performance.

Selected forage crops control foxtail barley and downy brome in saline soils

Abstract: The ability of forage crops to out-compete foxtail barley (Hordeum jubatum L.) and downy brome (Bromus tectorum L.) weeds often fails in saline soils. Ten forage treatments [alfalfa (Medicago sativa L.)], Nuttall’s salt-meadow grass [Puccinellia nuttalliana (Schult.) Hitchc.], smooth bromegrass (Bromus inermis Leyss.), the “Saltmaster” forage blend, and six wheatgrass treatments: western [Pascopyrum smithii (Rydb.) Löve], northern [Elymus kronokensis (Kom.) Tzvelev], tall [Thinopyrum ponticum (Podp.) Barkw. & Dewey], and green (Elymus hoffmannii Jensen & Asay) in 30 and 15 cm rows and alternating rows with slender [Elymus trachycaulus (Link) Gould] were compared with plots left unseeded. After three growing seasons, the smooth bromegrass, tall, and the average for the three green wheatgrass treatments, respectively, limited foxtail barley shoot growth to 4%, 2%, and 1% of the total shoot biomass at a negligibly to moderately saline site near Warner, AB; downy brome was also limited to 4%, 4%, and 2%, respectively. The three green wheatgrass treatments at the moderately to severely saline site near Alsask, SK, required twice the time to limit foxtail barley growth to 5%, 8%, and 18%, respectively, of the total. At least 95% of the foxtail barley and 98% of the downy brome were suppressed by green wheatgrass in soils averaging ≤14 dS m-1.