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Short duration, intensive grazing management with high stocking rates may result in sufficient turn-over of nitrogen (N) to compensate for production-limiting soil-N deficiencies for grass pasture. In central Alberta a 0.5 ha block was seeded to ‘Fleet’ meadow bromegrass (Bromus riparius Rehmann) in August, 2002. Within this block, six fenced (9 x 30 m) treatments were established in three replicates. They were: 1. ungrazed–clip removal; 2. grazed – alone; 3 grazed– fertilizer; 4. grazed – fertilizer-compost; 5. grazed - hog manure; 6. grazed – alfalfa (Medicago sativa L.) -grass. Measurements were conducted over a 4-year period between 2003 and 2006 and grazing occurred at identical times as vegetative mass permitted. Biomass was harvested before and after grazing for calculation of dry matter (DM) yield and biomass consumed. Subsamples were used for determination of N concentration and in vitro digestibility. Mean herbage N-yield for grazed treatments was 131% of ungrazed and greatest for grazed-fertilizer and grazed-fertilizer plus compost. Grazed paddocks with no added N produced similar DM yield to those with added N. Estimated nitrogen fixation contributed an annual average of 82 kg ha-1 to herbage-N yield from the alfalfa-grass paddocks. Barley (Hordeum vulgare L.) silage grown after termination of the grazed pastures produced 72% more herbage DM from grazed paddocks than ungrazed, but no significant (P. < 0.05) differences occurred among amendments.

The objectives of this study were to quantify the effect of post-weaning residual feed intake (RFI) on subsequent grazed forage intake, methane (CH4), and carbon dioxide (CO2) emissions. Beef heifers classified for RFI adjusted for off-test backfat (RFIfat; 55 high and 56 low) at 9 mo of age were monitored 7 mo later for CH4 and CO2 emissions using the GreenFeed Emissions Monitoring system. About 56 of these heifers were also monitored as high and low RFIfat groups using open-path Fourier-transform infrared spectroscopy (OP-FTIR). Heifers were dosed with 1 kg of C32-labelled pellets once daily for 15 d, with twice daily fecal sampling the last 8 d to determine individual grazed forage intake using the n-alkane method. Low RFIfat pregnant heifers consumed less forage (10.25 vs. 10.81 kg dry matter d−1; P 4 (238.7 vs. 250.7 g d−1; P = 0.009) and CO2 (7578 vs. 8041 g d−1; P fat animals. Results from the OP-FTIR further confirmed that low RFIfat heifers emitted 6.3% less (g d−1; P = 0.006) CH4 compared with their high RFIfat cohorts. Thus, selection for low RFIfat will decrease daily CH4 and CO2 emissions from beef cattle.

This study quantified methane (CH4) and carbon dioxide (CO2) production from beef heifers and cows classified for residual feed intake adjusted for off-test backfat thickness (RFIfat) and reared in drylot during cold winter temperatures. Individual performance, daily feed intake, and RFIfat were obtained for 1068 crossbred and purebred yearling heifers (eight trials) as well as 176 crossbred mature cows (six trials) during the winters of 2015–2017 at two locations. A portion of these heifers (147 high RFIfat; 167 low RFIfat) and cows (69 high RFIfat; 70 low RFIfat) was monitored for enteric CH4 and CO2 emissions using the GreenFeed Emissions Monitoring (GEM) system (C-Lock Inc., Rapid City, SD, USA). Low RFIfat cattle consumed less feed [heifers, 7.80 vs. 8.48 kg dry matter (DM) d−1; cows, 11.64 vs. 13.16 kg DM d−1] and emitted less daily CH4 (2.5% for heifers; 3.7% for cows) and CO2 (1.4% for heifers; 3.4% for cows) compared with high RFIfat cattle. However, low RFIfat heifers and cows had higher CH4 (6.2% for heifers; 9.9% for cows) and CO2 yield (7.3% for heifers; 9.8% for cows) per kilogram DM intake compared with their high RFIfat pen mates. The GEM system performed at air temperatures between +20 and −30 °C. Feed intake of heifers and mature cows was differently affected by ambient temperature reduction between +20 and −15 °C and similarly increased their feed intake at temperatures below −15 °C. In conclusion, low RFIfat animals emit less daily enteric CH4 and CO2, due mainly to lower feed consumption at equal body weight, gain, and fatness.

Background Feed costs are the largest expense in commercial beef production. Increasing cattle (Bos taurus) feed efficiency should reduce feed costs and increase beef profitability. This study used data from two years of a backgrounding trial conducted in Lacombe, Alberta, Canada. The evaluation looked at economic and predicted CH4 emission impacts of diet quality and cattle efficiency type in backgrounding systems. The hypothesis was that diet quality from use of barley (Hordeum vulgare c.v. Canmore) or triticale (x Triticosecale c.v. Bunker) silage-based diets and cattle efficiency type would interact to affect profitability and CH4 emissions. Results The experimental design was a four (cattle efficiency type; defined by residual feed intake (RFI)) by two (barley or triticale silage-based rations) factorial treatment with two replicates (pen of eight steers)/treatment/year over two years. Year was a random blocking factor. Cattle weight, intake, and diet composition data were combined with market prices to assess profitability. Methane emissions data were predicted from observed performance using a nutrient requirement model. Effects of diet and cattle efficiency type on profitability and CO2e emissions were assessed using statistical and stochastic risk simulation. By supporting greater gain and feed efficiency, the barley silage diet provided higher net revenue (NR) and lower CO2e emission (P 2e emission and little evidence of interaction between cattle efficiency type and diet quality. The difference in certainty equivalent (~$30/steer) of efficient steers on barley silage and inefficient steers on barley silage or efficient or inefficient steers on triticale silage supports a beef backgrounding producer focus on diet quality and cattle efficiency type. However, inefficient steers on barley silage still generated higher certainty equivalent per steer than efficient or inefficient steers on triticale silage. This study did not address potential agronomic differences, including yield, which could provide nuance to forage choice.

In western Canada, short-season corn silage production is increasing due to its potentially high nutritive value. The objective of this study was to determine variability and relationships among nutrient concentration, degradability, and methane (CH4) production of short-season whole-plant corn hybrids harvested before or after light frost (−1.5 °C). Four hybrids, based on their corn heat unit rating (≤2600, CHU rating), were grown in 2 yr in central and southern Alberta (AB) with two field replications. The batch culture and Daisy fermenter techniques were used to characterize degradability and gas production measurements. At both locations, dry matter (DM) concentration was affected by harvest and hybrid (P ≤ 0.02). However, starch and neutral detergent fiber (NDF) concentrations differed (P ≤ 0.01) or tended (P = 0.07) to differ among harvest and hybrid only in central AB. Over both locations and harvest times, CH4production was related negatively to propionate and positively to acetate proportions. In conclusion, harvesting southern AB hybrids after frost increased DM concentration and NDF degradability with no effect on CH4emissions, but the high DM concentration may negatively affect silage quality and animal performance. Harvesting central AB hybrids after frost increased DM and starch concentrations, while reducing CH4emissions but had limited effects on nutrient degradability.

This study compares yield, nutritive value, and kernel properties of whole plant corn (WPC) harvested before and after a light frost in short growing season areas. Six corn hybrids grown in two years at three locations within Alberta (Canada) were harvested before or after the first frost. Samples of WPC were analyzed for dry matter (DM) content, neutral detergent fiber (NDF) concentration, starch concentration, and 48-h in vitro DM and NDF digestibility (DMD and NDFD, respectively). Cob samples were analyzed for DM, and kernels were analyzed for DM, hardness, particle size distribution, density, and stage of maturity. Delaying harvest to after frost increased DM content of WPC at all locations but exceeded the recommended range (32–38%) in the two warmest locations. Whatever the year and hybrid, DM yield was either not affected or decreased after frost. Postfrost harvest increased starch concentration and modified kernel characteristics only if these were less than expected before frost. Fiber concentration was not affected by harvesting time. Frost had either no impact or increased DMD or NDFD of WPC. We conclude that delaying harvest until after frost in short growing season areas can be beneficial when whole-plant DM content is low before frost.

Reduction in greenhouse gas emission from beef production is essential to the survival of the beef industry from environmental and social-economic perspectives. There are different systems available to measure methane from animals, but they are expensive, not easily accessible, and not suitable for large-scale methane measurements on the farm. Therefore exploring indicator traits, which are easy to measure, cost-effective, and suitable for large-scale measurement, are recommended. The objectives of this study were to examine the diversity of fecal methanogen profile among efficient and inefficient beef heifers on pasture and investigate methanogen profile as a possible proxy to predict methane emission in beef cattle consuming a forage diet. Forty pregnant (1st trimester) heifers previously classified for postweaning residual feed intake adjusted for off-test back fat (RFIfat; 20 high and 20 low) were included in this study. To determine individual pasture grazing intake, heifers were dosed with 1 kg of C32 labeled pellets once per day from Day 0 to Day 12, and fecal samples were collected twice daily from Day 8 to Day 15. Fecal samples from Days 8, 10, and 12 were analyzed for their methanogen profile. Animals were monitored individually for methane and carbon dioxide production using a GreenFeed Emissions Monitoring system. Total methanogen population and methanogenic community diversity of fecal samples were not different (P > 0.1) between low and high RFIfat groups, as measured by quantitative PCR and α- and β-diversity indices. However, both groups had a different methanogen profile; the relative abundance of Methanobrevibacter wolinii and relatives were higher (P

Winter survival is a determinant factor for the persistence of perennials grown in northern climates. High winter survival cultivars, however, have lower yield due to their early transition into a dormant state in the fall. Here we describe a whole plant assay entirely performed indoor in growth chambers and walk-in freezers to identify low-dormant genotypes with superior freezing tolerance within populations of open pollinated species. Three successive freezing stresses are applied to a broad base of 3000 genotypes to progressively eliminate 97% of the population and to retain only the 3% best performing genotypes. This approach can be used to generate recurrently selected populations in different species.

Winter survival is a determinant factor for the persistence of perennials grown in northern climates. High winter survival cultivars, however, have lower yield due to their early transition into a dormant state in the fall. Here we describe a whole plant assay entirely performed indoor in growth chambers and walk-in freezers to identify low-dormant genotypes with superior freezing tolerance within populations of open pollinated species. Three successive freezing stresses are applied to a broad base of 3000 genotypes to progressively eliminate 97% of the population and to retain only the 3% best performing genotypes. This approach can be used to generate recurrently selected populations in different species.

This study evaluated the effects of three genomic indicators of heterosis on female fertility and lifetime productivity, and quantified changes over 11 production cycles in a crossbred cow herd. Pedigree-based breed composition (pBC) was determined and used to calculate retained heterozygosity for 412 replacement heifers born from 2004 to 2014 at the Lacombe Research and Development Centre (AB, Canada). Heifers were followed as cows over 1050 mating opportunities, 11 production cycles, and five parities. Heifers and their sires (51) were genotyped and these genotypes were used to predict each animal’s genomic breed composition (gBC) and three genomic indicators of heterosis: (1) retained heterozygosity (RHETg), (2) heterozygous proportion (H), and (3) retained heterosis (RHg). Correlations between pedigree and genomic breed fractions for Angus, Hereford, and Charolais were high (rp = 0.74–0.94; P p = 0.61 for RHETg vs. H; 0.71 for RHg vs. H; 0.96 for RHETg vs. RHg; P

Crop rotations on the Canadian prairies commonly include sequences of pulses, oilseeds, and cereals; however, limited information is available regarding the influence that different crop types and sequences may have on direct nitrous oxide (N2O) emissions. A 3 yr field study was conducted on a site near Scott, SK, to compare N2O emissions from selected crop phases of rotations containing pea (Pisum sativum L.), wheat (Triticum aestivum L.), and canola (Brassica napus L.) and to examine the potential influence of these residues on N2O emissions during the subsequent crop phase. Nitrous oxide losses from N-fertilized canola or wheat crops were generally higher than losses from pea or the control treatments. Nitrous oxide losses from N-fertilized wheat or canola crops grown on pea residue were comparable or lower than losses from N-fertilized wheat or canola crops grown on wheat residues. Cumulative N2O loss over the 3 yr was significantly higher from N-fertilized wheat grown on canola compared with pea or wheat residues. Losses from wheat grown on canola residue were 67% and 56% higher than from wheat grown on pea or wheat residue, respectively. This indicates that the emission factors used to estimate direct N2O loss may need to be adjusted upwards for N-fertilized crops grown on canola compared with wheat or pea residues.

Micrometeorological techniques offer the possibility of a non-interfering measurement of enteric emissions from cattle in their natural environment, where animals do not need to be encumbered or handled. However, the grazing environment is a difficult application for these techniques. This study reports on an experimental design using an inverse dispersion method (IDM) to measure enteric methane (CH4) emissions, and its application to 15 rather distinct cattle trials in three types of feeding situations: summer grazing, winter swath grazing, and winter feeding. The IDM design was based on long and narrow animal paddocks with line-averaging sensors measuring CH4 concentration alongside the long axes of the paddock. Emissions were calculated based on the difference in concentration between the two measurement paths. The narrow paddock has many advantages for an IDM calculation: it avoids the need to monitor animal positions; it helps ensure measurable downwind concentration; and it increases the range of useable wind directions. Four different sensor configurations were used in the trials, differing in the number of concentration sensors (one or two) and sensor paths (two or four). Some configurations used sensor aiming motors to give multiple measurement paths and others used mirrors to create segmented paths (i.e., to go around a paddock corner). Cattle emissions measured with the IDM design showed good agreement across the 15 trials, consistent with high forage diets. When expressed in terms of CH4 yield (g/kg dry matter intake), the three feeding situations averaged 21.3 (summer grazing), 23.4 (winter grazing), and 23.9 (winter feeding). Based on the trial-to-trial consistency of the results, the similarity with other literature studies, and the success of a previous tracer-release study, we conclude that the narrow paddock IDM design provides a flexible and accurate method for calculating CH4 emissions from grazing cattle.

The objective of this in situ study was to evaluate the rumen degradability of kernels from short-season corn hybrids grown for silage in Western Canada (Lacombe, AB) and determine whether decreasing kernel particle size would enhance ruminal degradability in a similar manner for all hybrids. The study was a completely randomized design with 3 beef cows (replicates) and a 6 (hybrid) × 3 (particle size) factorial arrangement of treatments. Kernels were processed to generate three different particle sizes: large (2.3 mm), medium (1.4 mm), and small (0.7 mm). Processed samples were incubated in the rumen for 0, 3, 6, 12, 24, and 48 h using the in situ method and degradation kinetics of DM and starch were determined. Effective rumen degradability (ED) was estimated using a passage rate of 0.04 (ED4), 0.06 (ED6), and 0.08/h (ED8). Hybrids exhibited a range in whole plant DM content (23.7 to 25.0%), starch content (15.9 to 28.1% DM), kernel hardness (21.9 to 34.4 s/20 g) and density (3.57 to 4.18 g/mL), and prolamin content (8.24 to 11.34 g/100 g starch). Differences in digestion kinetics among hybrids were generally more pronounced for starch than DM. The hybrids differed in starch degradability (P < 0.05), with earlier maturing hybrids having lower A fraction, lower kd, and lower ED, with hybrid effects on ED being accentuated with faster passage rate. Kernel DM content (r = −0.85, −0.87), hardness (r = −0.89, −0.86), and density (r = −0.84, −0.85) were negatively correlated with ED4 and ED8 of starch, respectively, due mainly to decreased kd of fraction B. Reducing the particle size of kernels increased ED of starch due to increased A fraction and kd of the B fraction. A tendency (P = 0.09) for hybrid × processing effects for ED6 and ED8 indicated that processing had greater effects on increasing ED of starch for earlier maturing hybrids. We conclude that short-season hybrids that mature early may have lower ED of DM and starch and would benefit from prolonged ensilage time. Kernel processing during silage making is recommended for short-season corn hybrids as a means of enhancing rumen availability of starch.

Grazing is a common practice in the beef cattle industry and is an integral component of pasture and rangeland management. The objective of this study was to evaluate impacts of grazing management scenarios on greenhouse gas (GHG) intensity [kg carbon dioxide equivalents (CO 2 e) kg − 1 beef] at the farm-gate for beef production systems in western Canada using life cycle assessment. A life cycle assessment over an 8-year period was conducted on a hypothetical but typical beef farm that managed 120 cows, 4 bulls, and their progeny. Calves were backgrounded (raised) on rangeland and market cattle were finished on grain for an average of 134 ± 11 d. Four grazing management scenarios were examined: i) light continuous grazing (LC) for all cattle, ii) heavy continuous grazing (HC) for all cattle, iii) light continuous grazing for cow-calf pairs and moderate rotational grazing for backgrounded cattle (LCMR), and iv) heavy continuous grazing for cow-calf pairs and moderate rotational grazing for backgrounded cattle (HCMR). Greenhouse gas emissions from various sources within the farm were estimated using the whole-farm model, Holos. Soil organic carbon (C) change due to each grazing management scenario was estimated using the Introductory Carbon Balance Model. Primary model inputs came from short- and long-term grazing management studies. Greenhouse gas intensity of beef varied among grazing management scenarios, ranging from 14.5–16.0 kg CO 2 e kg − 1 live weight and 24.1–26.6 kg CO 2 e kg − 1 carcass weight. Greenhouse gas intensity decreased with increasing stocking rate: that of HC grazing management was 9.2% lower than that of LC treatment (14.5 vs 16.0 kg CO 2 e kg − 1 live weight, respectively). Greenhouse gas intensity was similar ( vs 14.6 kg CO 2 e kg − 1 live weight, respectively). Average farm production efficiency (kg beef per unit land area) was 17–25% higher for the HC and HCMR grazing management scenarios than the LC and LCMR scenarios. Regardless of grazing management, methane emission from enteric fermentation was the major source of emissions (67–68% of total), followed by nitrous oxide (14–16% of total) from manure management. The rate of soil C sequestration ranged from 0.01 Mg C ha − 1 yr − 1 for rangeland under HC to 0.46 Mg C ha − 1 yr − 1 for a triticale field used for swath grazing. When soil C sequestration was included in the total emission analysis, GHG intensity estimates decreased by 12–25%, and there was no difference in intensity estimates among the scenarios. The largest reduction in GHG intensity arising from soil C sequestration was observed for LC (22%) and LCMR (25%) because they sequestered more C than HC and HCMR. Overall, results of our study indicated that grazing management impacted GHG intensity of beef production by influencing diet quality, animal performance and soil C change. It also emphasizes the importance of accounting for all emission sources and sinks within a beef production system when estimating its environmental impacts.

Climate change is expected to increase agricultural productivity in Canada and in other northern countries but this increase will likely affect the environmental performance of dairy farms, one of the most important agricultural sectors in Canada. The objective of this study was to project the impact of climate change on the agronomic and environmental performance of a virtual dairy farm in each of three climatically contrasting areas of Canada through near future (2020–2049) and distant future (2050–2079) periods, using the Integrated Farm System Model (IFSM) and three climate models (CanESM2, CanRCM4, and HadGEM2). Under future climate conditions and relative to a reference period (1971–2000), projected yields of perennial forages and warm-season crops increased, whereas those of small-grain cereals decreased slightly. Projected ammonia emissions increased on virtual farms of the three areas and in all future scenarios (+ 18% to + 54%). Methane emissions from manure storage increased (+ 26% to + 120%), whereas those from enteric fermentation and field manure application decreased. Projected farm N 2 O emissions changed only slightly relative to the reference period. Fossil fuel CO 2 emissions related to field operations increased slightly, due to a larger number of forage cuts per year in future scenarios, but CO 2 emissions related to grain drying decreased substantially. Projected losses of P increased on virtual farms of the three areas. The projected reactive N footprint of dairy farms in future scenarios varied more (− 15% to + 46%) relative to the reference period than the C footprint (− 5% to + 9%). Although greenhouse gas mitigation should be a priority for dairy farms under future climate conditions, it should not overshadow the need for strategies to reduce reactive N losses.

Overwintering beef cows is a major cost in Canadian cow-calf production systems and swath grazing is a potential alternative to reduce winter feeding cost relative to the traditional drylot feeding systems. The objective was to estimate and compare greenhouse gas (GHG) emissions from winter feeding systems: i) swath grazing on triticale, ii) swath grazing on corn, and iii) conventional drylot feeding systems (control). Data were obtained from a study conducted over three production cycles (2008/2009, 2009/2010, 2010/2011) at the Lacombe Research Center in western Canada. Greenhouse gas emissions were estimated by calculating methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions from different sources using Intergovernmental Panel on Climate Change (IPCC) Tier 2 approach. Methane emissions were estimated from enteric fermentation and manure, N2O emissions from fertilization and manure, and CO2 emissions from energy use for farm activities related to feed production and processing, feed and bedding delivery and manure removal. Total emission expressed per kg of feed produced and fed were significantly (P

This paper analyses a trace gas dispersion experiment with multiple point sources and line-averaging laser gas detectors on gently rolling terrain. The objective of the experiment was to establish how well emission rate can be inferred by “inverse dispersion” (ID), using a Lagrangian stochastic wind transport model (WindTrax) that (strictly) is appropriate only in horizontally-homogeneous winds. Measured mean wind speeds at fixed height above ground revealed spatial variation of order ±10% over the site. However the results of the inversion to estimate source strength Q from the concentration field suggest that the unwanted impact of the terrain is adequately compensated by representing detector light paths as curves, approximating their true height above ground. Under that treatment the mean and standard deviation of the ratio Q IDM / Q of inferred to true source strength, over an ensemble of 96 fifteen minute intervals, were respectively 〈 Q IDM / Q 〉=1.04 and σ Q | Q = 0.15, with little distinction between outcomes under unstable and stable stratification. We also used the measurements to study the influence (on the accuracy of retrieved source strength) of discretionary elements of inverse dispersion procedure: data quality criteria; optimal placement of detectors relative to the source(s); and the impact of alternative spatial representations of the source, supposing one had but partial information in that regard. Because the sources were always rather close to the downwind detector, the quality of the inversions was less sensitive to extremes of stratification than has been reported for other trials. Inversions that treated the actual point sources as an aggregate area source proved acceptable, provided this was placed at or near the height of the (true) point sources. An idealized distribution of elevated point sources can also be satisfactory, but bad inversions may result if placement of the token sources is biased in the cross-plot direction relative to the actual source(s).

The aim of this study was to investigate the changes in environmental performance over time of canola production due to changes to management and production practices on the Canadian prairies. Selected environmental impacts of canola production in 2010 and in 1990 in the Gray, Black, and Dark Brown/Brown soil zones of Western Canada were quantified (1990 analysis was limited to Alberta due to data availability). The life cycle assessment (up to the farm gate) was carried out on a per-tonne-of-canola basis. There were limited differences in impacts across soil zones for the 2010 production system. Differences across soil zones were generally more pronounced for the 1990 production system. The production and use of fertilizers (both production and field emissions) and the use of farm equipment (for tillage, harvest, etc.) were the major contributors, accounting for up to 95% of the environmental impacts of canola production in both time periods. Overall, the environmental impacts of producing one tonne of canola were reduced between the 1990 and 2010 time periods. Over the past two decades, the on-farm fuel use and fertilizer applied per tonne of canola decreased, which led to reduced greenhouse gas emissions and improved ecosystem quality (acidification being the exception). The improvements in the environmental profile of canola production between 1990 and 2010 were due to a combination of factors, particularly the advances in crop management practices including tillage and large-scale adoption of herbicide tolerant hybrid canola, that have led to increases in average yields and in efficiency of inputs use.

A new micrometeorological technique is applied to measure gas emissions from soils. The technique relies on a single open-path FTIR sensor (OP-FTIR) with motorized aiming to give gas concentrations along vertically separated paths (not necessarily parallel with each other). Emission rates are inferred from the vertical difference in concentration using two alternative methods: flux-gradient and inverse dispersion calculations. Our objective is to assess the capability of the technique in a field study measuring nitrous oxide (N2O) and ammonia (NH3) emitted from cattle overwintering areas during the spring thaw. Two field configurations were examined: a slant path configuration in which the OP-FTIR is aimed directly at high and low reflectors at the far end of the path (average vertical path separation ∼ 1 m), and a periscope configuration where the lower FTIR path was directed closer to ground along the whole path (average path separation ∼ 1.5 m). Measured emission rates were generally above the detectability threshold of the system and consistent with the scientific literature showing an emission rise during thawing. At one of our sites the pulse of N2O emitted during thawing was among the largest reported (9.9 kg N-N2O ha−1 during April). Of the two alternatives tested for calculating emissions, the inverse dispersion approach is more flexible, but with a computation time that can be prohibitive. With large measurement fetches the flux-gradient approach can be equally good and computationally faster. We conclude that the open-path gradient system provides a practical option for studying emissions in difficult environments.

Agricultural soils in Canada have been observed to emit a large pulse of nitrous oxide (N2O) gas during the spring thaw, representing a large percentage of the annual emissions. We report on three years of spring thaw N2O flux measurements taken at three Alberta agricultural sites: a crop production site (Crop), cattle winter-feeding site (WF), and a cattle winter-grazing site (WG). Soil fluxes were calculated with a micrometeorological technique based on the vertical gradient in N2O concentration above each site measured with an open-path (line-averaging) FTIR gas detector. The Crop and WG sites showed a clear N2O emission pulse lasting 10 to 25 days after thawing began. During this pulse there was a strong diurnal cycle in emissions that paralleled the cycle in near-surface soil temperature. The emission pulse was less pronounced at the WF site. The average spring thaw losses (over 25 to 31 days) were 5.3 (Crop), 7.0 (WF), and 8.0 (WG) kg N2O-N ha−1, representing 1 to 3.5% of the annual nitrogen input to the sites. These large losses are higher than found in most previous western Canadian studies, and generally higher than the annual losses estimated from the Intergovernmental Panel on Climate Change and Canadian National Inventory Report calculations. The high N2O losses may be explained by high soil nitrate levels which promoted rapid denitrification during thawing. The application of a high resolution (temporal) micrometeorological technique was critical to revealing these losses.

Data from a total of 4842 animals were used to test whether the regular dry matter intake (DMI) data collection and residual feed intake (RFI) estimation period could be decreased. Eighty-three sho...

Baron, V. S., Doce, R. R., Basarab, J. and Dick, C. 2014. Swath-grazing triticale and corn compared to barley and a traditional winter feeding method in central Alberta. Can. J. Plant Sci. 94: 1125–1137. A 5-yr study compared swath-grazed triticale (× Triticosecale Wittmack), corn (Zea mays L.) and barley (Hordeum vulgare L.) with a traditional pen-fed, wintering diet for gestating beef cows on the basis of dry matter (DM) yield, carrying capacity, nutritive value, cow performance and total daily feeding cost. Cows (690±70 kg BW) were fed a control total mixed ration (TMR) or allocated to swath-grazed treatments in 2.5-ha paddocks. Triticale yielded 15% more than corn and corn 32% more than barley. Carrying capacity of triticale (1145 cow-d ha−1) and corn (1004 cow-d ha−1) were similar and both were greater (P−1) and barley (554 cow-d ha−1). Average utilization for triticale (83.7%) was greater (P−1), followed by triticale (620 g kg−1), then barley (570 g kg−1) and the control TMR (571 g kg−1). Average cow mean body condition score (BCS) was higher (P−1)−1)−1)−1).

Several models for simulating the growth and nutritive value of forage crops have been developed in past decades but most of them are specific to one crop species and focus only on agronomic outputs. In this study, we calibrated and evaluated the performance of the STICS crop model for the simulation of the growth and nutritive value (cell wall concentration and digestibility, in vitro true dry matter [DM] digestibility, and N concentration) of timothy (Phleum pratense L.) under Canadian growing conditions. Equations used for calculating nutritive value attributes were derived from the CATIMO model (CAnadian TImothy MOdel). The calibration included two datasets, one for eastern Canada (cultivar Champ) and one for western Canada (cultivar Climax). Very good agreement between simulations and measurements was obtained for the calibration dataset (RMSE% ≤10% for all variables). Twenty-two datasets including leaf area index (LAI), forage DM yield, N concentration, cell wall concentration and digestibility, and in vitro true DM digestibility were then used to evaluate model performance. The model simulated LAI, forage DM yield, nitrogen concentration and nutritive value of the primary growth fairly well for all sites (RMSE%

The process-based grass model, CATIMO, simulates the spring growth and nutritive value of timothy (Phleum pratense L.), a forage species widely grown in Scandinavia and Canada, but the nutritive value of the summer regrowth has never been simulated. Our objective was to improve CATIMO for simulating the N concentration, neutral detergent fiber (NDF), in vitro digestibility of NDF (dNDF), and in vitro true digestibility of dry matter (IVTD) of summer regrowth. Daily changes in summer regrowth nutritive value were simulated by modifying key crop parameters that differed from spring growth. More specifically, the partitioning fraction to leaf blades was increased to increase the leaf-to-weight ratio, and daily changes in NDF and dNDF of leaf blades and stems were reduced. The modified CATIMO model was evaluated with data from four independent experiments in eastern and western Canada and Finland. The model performed better for eastern Canada than for the other locations, but the nutritive value attributes of the summer regrowth across locations (range of normalized RMSE = 8–25%, slope 0.61). These modeling results highlight knowledge gaps in timothy summer regrowth and prospective research directions: improved knowledge of factors controlling the nutritive value of the timothy summer regrowth and experimental measurements of leaf-to-weight ratio and of the nutritive value of leaves and stems.

Genetic selection for residual feed intake (RFI) is an indirect approach for reducing enteric methane (CH4) emissions in beef and dairy cattle. RFI is moderately heritable (0.26 to 0.43), moderately repeatable across diets (0.33 to 0.67) and independent of body size and production, and when adjusted for off-test ultrasound backfat thickness (RFI fat) is also independent of body fatness in growing animals. It is highly dependent on accurate measurement of individual animal feed intake. Within-animal repeatability of feed intake is moderate (0.29 to 0.49) with distinctive diurnal patterns associated with cattle type, diet and genotype, necessitating the recording of feed intake for at least 35 days. In addition, direct measurement of enteric CH4 production will likely be more variable and expensive than measuring feed intake and if conducted should be expressed as CH4 production (g/animal per day) adjusted for body size, growth, body composition and dry matter intake (DMI) or as residual CH4 production. A further disadvantage of a direct CH4 phenotype is that the relationships of enteric CH4 production on other economically important traits are largely unknown. Selection for low RFI fat (efficient, -RFI fat) will result in cattle that consume less dry matter (DMI) and have an improved feed conversion ratio (FCR) compared with high RFI fat cattle (inefficient; +RFI fat). Few antagonistic effects have been reported for the relationships of RFI fat on carcass and meat quality, fertility, cow lifetime productivity and adaptability to stress or extensive grazing conditions. Low RFI fat cattle also produce 15% to 25% less enteric CH4 than +RFI fat cattle, since DMI is positively related to enteric methane (CH4) production. In addition, lower DMI and feeding duration and frequency, and a different rumen bacterial profile that improves rumen fermentation in -RFI fat cattle may favor a 1% to 2% improvement in dry matter and CP digestibility compared with +RFI fat cattle. Rate of genetic change using this approach is expected to improve feed efficiency and reduce enteric CH4 emissions from cattle by 0.75% to 1.0% per year at equal levels of body size, growth and body fatness compared with cattle not selected for RFI fat.

The current study examined the effects of inclusion of flaxseed in a red clover silage diet on growth, carcass quality, adipose tissue and muscle fatty acid (FA) profiles of beef steers. Twelve British×Continental crossbred steers (363±26.5 kg) were randomly assigned to two pens and fed diets containing 70% red clover silage, 15% steam rolled barley/vitamin–mineral supplement and either additional 15% steam rolled barley or 15% triple rolled flaxseed (all DM basis) for 215 d. Diet had no effect (P>0.05) on average daily gain or carcass quality atributes. Overall, FA profiles in all tissues followed similar trends when flaxseed was added to the diet but intramuscular fat had the highest proportions of n-3 and n-6 polyunsaturated FA (PUFA) while subcutaneous fat had largest proportions of conjugated linoleic acids (CLA) and perirenal fat had the highest proportions of trans-18:1 isomers, particularly vaccenic acid (VA). Feeding flaxseed increased (P

a b s t r a c t We analyzed net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust "light-soil temperature- VPD"-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO2 exchange com- ponents and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depend- ing on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, � VPD. In 78% of the 27 site-years of observations, annual gross pho- tosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO2 m−2 year−1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in

Swath-grazed oat (Avena sativa L.) and stockpiled meadow bromegrass (Bromus riparius Rhem) were compared with (Control) a pen-fed straw-based total mixed ration (TMR) for dry, pregnant beef cows (670 ± 88 kg BW) using carrying capacity, nutritive value, cow performance, daily feeding, yardage, and total daily costs. Carrying capacity ranked (P Control (454 cow-d ha−1) > stockpiled grass (189 cow-d ha−1). In vitro true digestibility (IVTD) ranked (P oat (588 g kg−1) > Control (530 g kg−1). Average cow body condition score (BCS) off pasture was (P oat (3.0), while the control was intermediate (3.3). The daily feed cost ranked: stockpiled grass ($0.38 cow-d−1)

Aging explained >45% of the variability in beef tend erness, whereas electrical stimulation explained >12%. The effect of electrical stimulation was significant for calf-fed steers up to 27 d of aging. However, this effect did not persist beyond 6 d of aging for yearling-fed steers. However, electrical stimulation prevents cold toughen- ing in lighter, leaner carcasses. Le vieillissement explique >45 % de la variabilité dans la tendreté du b œ uf (>45 %), tandis que la stimulation électrique explique >12 %. L ’ effet de la stimulation électrique était significatif chez les jeunes bovins jusqu ’ à27jours de vieillissement. Par contre, l ’ effet ne persistait pas au-delà de 6 jours de vieillissement dans le groupe de bovins d’ un an. La stimulation électrique prévient le durcissement à froid dans les carcasses plus légères et moins grasses.

López-Campos, Ó., Basarab, J. A., Baron, V. S., Aalhus, J. L. and Juárez, M. 2012. Reduced age at slaughter in youthful beef cattle: Effects on carcass merit traits. Can. J. Anim. Sci. 92: 449–463. Two-hundred and twenty-four spring-born British×Continental crossbred steers were used in a 2-yr project to evaluate the effect of production system (calf-fed vs. yearling-fed) and its interaction with breed cross and hormone implant strategies, with and without β-adrenergic agonist on carcass characteristics. Carcasses from yearling-fed steers were 32% heavier (P0.05) was observed for marbling scores between production systems. Use of hormonal implants increased (P50%) had a higher proportion of lean and bone and a lower proportion of fat than carcasses from 50–75% British steers (P

Several process-based models for simulating the growth of perennial grasses have been developed but few include the simulation of regrowth. The model CATIMO simulates the primary growth of timothy ( Phleum pratense L.), an important perennial forage grass species in northern regions of Europe and North America. Our objective was to further develop the model CATIMO to simulate timothy regrowth using the concept of reserve-dependent growth. The performance of this modified CATIMO model in simulating leaf area index (LAI), biomass dry matter (DM) yield, and N uptake of regrowth was assessed with data from four independent field experiments in Norway, Finland, and western and eastern Canada using an approach that combines graphical comparison and statistical analysis. Biomass DM yield and N uptake of regrowth were predicted at the same accuracy as primary growth with linear regression coefficients of determination between measured and simulated values greater than 0.79, model simulation efficiencies greater than 0.78, and normalized root mean square errors (14–30% for biomass and 24–34% for N uptake) comparable with the coefficients of variation of measured data (1–21% for biomass and 1–25% for N uptake). The model satisfactorily simulated the regrowth LAI but only up to a value of about 4.0. The modified CATIMO model with its capacity to simulate regrowth provides a framework to simulate perennial grasses with multiple harvests, and to explore management options for sustainable grass production under different environmental conditions.

Simple Summary A spring calving herd (~350 beef cows) over two production cycles was used to compare the whole-farm greenhouse gas (GHG) emissions among calf-fed vs. yearling-fed production systems, with and without growth implants. Farm GHG emissions initially included enteric CH4, manure CH4 and N2O, cropping N2O, and energy use CO2. The carbon footprint ranged from 19.9–22.5 kg CO2e per kg carcass weight. Including soil organic carbon loss from annual cropping and carbon sequestration from perennial pastures and haylands further reduced the carbon footprint by 11–16%. The carbon footprint of beef was reduced by growth promotants (4.9–5.1%) and by calf-fed beef production (6.3–7.5%). Abstract A spring calving herd consisting of about 350 beef cows, 14–16 breeding bulls, 60 replacement heifers and 112 steers were used to compare the whole-farm GHG emissions among calf-fed vs. yearling-fed production systems with and without growth implants. Carbon footprint ranged from 11.63 to 13.22 kg CO2e per kg live weight (19.87–22.52 kg CO2e per kg carcass weight). Enteric CH4 was the largest source of GHG emissions (53–54%), followed by manure N2O (20–22%), cropping N2O (11%), energy use CO2 (9–9.5%), and manure CH4 (4–6%). Beef cow accounted for 77% and 58% of the GHG emissions in the calf-fed and yearling-fed. Feeders accounted for the second highest GHG emissions (15% calf-fed; 35–36% yearling-fed). Implants reduced the carbon footprint by 4.9–5.1% compared with hormone-free. Calf-fed reduced the carbon footprint by 6.3–7.5% compared with yearling-fed. When expressed as kg CO2e per kg carcass weight per year the carbon footprint of calf-fed production was 73.9–76.1% lower than yearling-fed production, and calf-fed implanted was 85% lower than hormone-free yearling-fed. Reducing GHG emissions from beef production may be accomplished by improving the feed efficiency of the cow herd, decreasing the days on low quality feeds, and reducing the age at harvest of youthful cattle.

The objective of the study was to examine whether residual feed intake (RFI) reranking exists between 2 consecutive periods in replacement heifers fed the same diet. The study collected feed intake and BW data from 190 crossbred heifers over a 3-yr period (61 in 2007, 68 in 2008, and 61 in 2009) during the winter-spring season. The heifers were fed a roughage-based diet (90% barley silage and 10% rolled barley grain) throughout the feeding trial, which was broken down into 2 feeding periods with ADG of 0.94 and 0.90 kg•d(-1) in the first and second periods, respectively. The RFI was calculated for the entire period using different models, which included ADG, mid-metabolic BW, body composition, and feeding activity. Gain:feed ratio and Kleiber ratio were also calculated. Rank correlations among the RFI calculated from different models were obtained, as well as rank correlations between the 2 feeding periods for the feed efficiency measures. Including body composition and feeding activity only improved the R(2) by 1 to 5%. The rank correlations among the different models were high (90 to 95%) for RFI calculated for the entire feeding period. However, the RFI calculated within the second feeding period had greater rank correlation than the RFI calculated from the entire feeding period. Compared with G:F and Kleiber ratio, RFI gave lesser reranking between periods 1 and 2. About 49% of the heifers maintained their RFI class, whereas 51% of the heifers had a different RFI class in period 2. Furthermore, 41% of the heifers changed their RFI in period 2 by

In order to investigate the effects of increasing beef n-3 fatty acid content and the protective effects of vitamin E antioxidant activity on meat quality characteristics, 80 feedlot steers were fed 4 different diets (control, high vitamin E, 10% ground flaxseed or high vitamin E-10% ground flaxseed). While dietary treatments had no effect (P0.05) on meat composition or tenderness values, the increase in oxidation products was lower (P=0.046) in meat from vitamin E supplemented steers and higher (P=0.006) in meat from flaxseed fed animals. The increase in α-tocopherol tissue levels (P0.001) in meat from animals fed flaxseed and increased dietary vitamin E resulted in the lowest drip loss values (P=0.013). As expected, display time had a large effect on retail traits in both steaks and patties (P0.001). While retail traits of steaks were not affected by the dietary treatments (P0.05), feeding flaxseed decreased (P0.05) ground beef retail scores, which were not corrected by higher levels of dietary vitamin E. Finally, although no effect (P0.05) was observed among treatments for sensory attributes in steaks, the correlations of a combined n-3:α-tocopherol ratio against retail and sensory attributes (P0.05) suggest that increased n-3 fatty acids levels require increased dietary antioxidants, such as vitamin E to avoid negative effects on meat quality from a loss in oxidative stability.

Basarab, J. A., Colazo, M. G., Ambrose, D. J., Novak, S., McCartney, D. and Baron, V. S. 2011. Residual feed intake adjusted for backfat thickness and feeding frequency is independent of fertility in beef heifers. Can. J. Anim. Sci. 91: 573–584. This study examined the effects of residual feed intake (RFI), RFI adjusted for off-test backfat thickness (RFIfat) and RFI adjusted for off-test backfat thickness and feeding event frequency (RFIfat & activity) on heifer fertility and productivity. Beef heifers (n=190) were monitored for individual daily feed intake and feeding event activity over 108–112 d using the GrowSafe System® and assessed for age at puberty based on plasma progesterone concentration. Individual animal daily feed intake, feeding event activity and off-test backfat thickness were then used to calculate RFI, RFIfat and RFIfat & activity and group heifers as either negative ([−], RFI−1 (SD=0.21), consumed 7.62 kg DM head−1 d−1 (SD=0.84) and had a feed conversion ratio of 8.93 (SD=2.43). Age (351 d, SD=43) and weight (367.3 kg, SD=45.0) at puberty were similar between [−] and [+] RFI heifers, but age at puberty was delayed in [−] RFIfat (P=0.04) and RFIfat & activity (P=0.08) heifers compared with [+] RFIfat and RFIfat & activity heifers. Efficient or [−] RFI heifer exhibited a lower pregnancy (76.84 vs. 86.32%, P=0.09) and calving rate (72.63 vs. 84.21%, P=0.05) compared with [+] RFI heifers. These differences were partially removed in [−] RFIfat and completely removed in [−] RFIfat & activity compared with their [+] RFI counterparts (pregnancy rate, 80.85 vs. 82.29%, P=0.80; calving rate, 75.53 vs. 81.25%, P=0.34). No differences were observed between efficient and inefficient heifers in calving difficulty, average calving date, age at first calving, calf birth weight, calf pre-weaning ADG, calf weaning weight and heifer productivity. However, [+] RFI heifers exhibited a 1.9-fold higher calf death loss compared with [−] RFI heifers (11.11% vs. 5.71%, P=0.24). This difference was more pronounced in [+] RFIfat and [+] RFIfat & activity heifers, which exhibited 2.2-fold (11.84% vs. 5.33%, P=0.15) and 3.0-fold (12.66% vs. 4.17%, P=0.06) higher calf death loss compared with [−] RFI heifers. There was no relationship of RFI adjusted for backfat thickness and feeding activity on fertility traits indicating that backfat thickness and feeding activity may be associated with feed intake and should be considered when selecting heifers for improved feed efficiency.

Article history:Received 3 September 2010Received in revised form 24 November 2010Accepted 21 January 2011Keywords:BeefLinseedOmega-3Oxidationα-tocopherol ToelucidatetheeffectsofdietaryvitaminEwithorwithoutflaxseedonbeeffattyacidcomposition,80feedlotsteers were fed 4 diets: Control-E (451 IU dl-α-tocopheryl acetate/head/day), Control+E (1051 IU dl-α-tocopheryl acetate/head/day), Flax-E (10% ground) and Flax+E. Vitamin E had no effect on animal growth orcarcass weight (pN0.05), while flaxseed-fed steers had greater average daily gain (p=0.007), final liveweight (p=0.005) and heavier carcasses (p=0.012). Feeding flaxseed increased the total n−3 fatty acidcontent of beef and this response was further accentuated by the inclusion of high levels of vitamin E in thediet. Feeding flax increased levels of some 18:3n−3 partial hydrogenation products including c15- and t13/14-18:1 and several 18:2 isomers (pb0.001) but decreased t10-18:1 (pb0.001). Vitamin E enhancedintramuscular levels of 18:3n−3 and its biohydrogenation products leading to greater accumulations of totaln−3 fatty acids in lean ground beef. The consequences of increasing the concentrations of partiallyhydrogenated products on human health have yet to be investigated.Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved.

To evaluate meat quality of beef with different ?-tocopherol tissue levels, 55 feedlot steers were fed a barley-based finisher diet with four vitamin E supplementation levels (0, 350, 700 and 1400 IU DL-?-tocopheryl acetate/animal per day) for 120 days. Although the increase in oxidation levels overtime was much smaller (P < 0.001) in the high-medium and high groups, ?-tocopherol tissue levels did not affect (P > 0.05) pH, proximate analysis, drip and cooking losses, and shear force of steaks. No effect of ?-tocopherol tissue levels was found in retail evaluation of steaks after a short ageing time of 6 days, but with 21 days of ageing, a delay in formation of metmyoglobin (P = 0.008) was observed in steaks with higher tissue levels of ?-tocopherol. Similar results were found for ground beef (25% fat) prepared from 6-day aged meat. Thus, higher ?-tocopherol tissue levels protect ground beef and long-aged steaks from discolouration and lipid oxidation. Made available in DSpace on 2022-07-21T19:20:02Z (GMT). No. of bitstreams: 1 PROCI-00089.pdf: 214019 bytes, checksum: f3300d99f4d52435a5d83460380bd877 (MD5) Previous issue date: 2011

Supplementing irrigation water with effluents could reduce the need for potable water for irrigation and promote nutrient recycling, but may require additional amendments to deal with Na. In a growth chamber experiment, winter wheat was seeded into a control soil and to soil amended with either gypsum or wood ash applied at an equivalent rate of 15 dry t ha-1. Wheat was irrigated at a rate of 6 mm d-1 with distilled water (DW), kraft pulp mill effluent (KPME) and waste-activated sludge (WAS), and three KPME/WAS combinations. This included two KPME/WAS combinations diluted with DW to 25 and 50% (KPME/WAS:DW) to evaluate the effect on the nutrient uptake and biomass and the impact on soluble ions in the soil. Effluent applications increased wheat biomass up to 70%, and increases of 97 and 140% were observed in soils amended with gypsum and ash, respectively. Effluent applications increased soluble Na, Ca, and SO4, but only on the gypsum-amended soils, except those irrigated with WAS, had lower sodium adsorption ratio (SAR) than control soils by 0.7 to 3 units. Effluent combinations at the lower dilutions in combination with gypsum could be used to provide supplemental water with moderate increases in electrical conductivity (ECe) and SAR that would still be within tolerable limits of many crops.Key words: Effluent irrigation, electrical conductivity, gypsum, sodium adsorption ratio, wood ash

Two hundred and twenty-two yearling calves and their dams were used to examine the phenotypic (rp) relationships between progeny residual feed intake (RFI) and maternal productivity across 10 production cycles. Progeny RFI ranged from -3.95 to +2.72 kg as fed d-1 (SD = 0.94), while RFI adjusted for off-test backfat thickness (RFIadj), ranged from -2.48 to +1.53 kg as fed d-1 (SD = 0.88). Progeny RFI and RFIadj were unrelated to on-test age, body weight, growth rate, and ultrasound longissimus thoracis area and positively related to feed intake (rp = 0.51 to 0.53; P < 0.001), feed to gain ratio (rp = 0.44 to 0.46; P < 0.001), feeding behaviour traits (rp = 0.29 to 0.36; P < 0.001) and cow RFI (rp = 0.30, P < 0.05). Progeny RFI was positively related to measures of body fat (rp = 0.21 to 0.27; P < 0.05), but these relationships disappeared when RFI was adjusted for off-test backfat thickness. Cows that had produced LOW (≤ 0.5 SD), MEDIUM (± 0.5 SD) or HIGH (≥ 0.5 SD) RFIadj progeny were similar in pregnancy (95.6 vs. 95.3 vs. 96.0%, P = 0.90), calving (84.9 vs. 83.4 vs. 86.3%, P = 0.62) and weaning (81.5 vs. 80.2 vs. 82.3%, P = 0.79) rates. However, cows that produced HIGH RFIadj progeny had a higher twinning rate (3.77 vs. 0.35 vs. 0.00%, P < 0.001) and an increased calf death loss (8.06 vs. 4.24 vs. 4.02%, P = 0.10) compared with cows that produced MEDIUM or LOW RFIadj progeny. Cow body weight over 10 production cycles was similar at weaning, pre-calving and pre-breeding for dams that had produced LOW, MEDIUM and HIGH RFIadj progeny, and dams that produced LOW RFIadj progeny consistently averaged 2–3 mm more back fat thickness than dams that produced HIGH RFIadj progeny. Calf birth weight, pre-weaning ADG and 200-d weight, and cow production efficiency and calving interval were similar among dams that produced LOW, MEDIUM and HIGH RFIadj progeny. In addition, dams that produced LOW RFIadj progeny consumed less feed during their second trimester of pregnancy (10.9 vs. 11.6 vs. 12.2 kg DM d-1, P < 0.05), had lower RFI values (-0.05 vs. 0.44 vs. 1.88 kg as fed d-1, P = 0.018) and calved later in the year (96 vs. 90 vs. 91 d Julian, P < 0.001) than dams that produced MEDIUM and HIGH RFIadj progeny. These results showed that efficient RFI progeny and dams consumed less feed, had improved feed to gain ratio and spent less time in feed activity than inefficient cows and calves. In addition, cows that produced efficient calves were fatter, had fewer twins, less calf death loss and produced the same weight of calf weaned per cow exposed to breeding compared with cows that produced inefficient progeny. However, cows that produced efficient or low RFI progeny calved 5–6 d later in the year than cows that produced inefficient or high RFI progeny, indicating a need to monitor reproductive fitness in low RFI replacement heifers and breeding bulls. Key words: Residual feed intake, cow reproduction, lifetime production efficiency

Periodic and prolonged drought can be devastating to pasture production, which increases the financial risk for grazing enterprises. A study was conducted during 2 drought years (2002 and 2003) in the aspen parkland at Lacombe, Alberta, Canada, to compare the soil water regime of meadow bromegrass (Bromus riparius Rhem.), alfalfa (Medicago sativa L.), and annual [oat (Avena sativa L.) and winter triticale (X Triticosecale Wittmack)] pastures with a naturalized, old grass pasture consisting of quackgrass (Elytrigia repens L.), smooth bromegrass (Bromus inermis Leyss.), and Kentucky bluegrass (Poa partensis L.). The pasture soil was an Orthic Black Chernozem of fine sandy loam to loam texture. Soil water measurements were conducted between May and October over 2 yr using a neutron scattering hydroprobe to a depth of 1.6 m. Annual and meadow bromegrass had similar and highest cumulative and volumetric water contents and old grass had the lowest. All pastures tended to use all water available by the end of the season, but annual pasture had higher soil water in spring and early summer due to delayed canopy development. Soil in the upper 40 cm of annual and meadow bromegrass pastures was at wilting point 5 to 10% of all measurement times compared with 65 to 71% of measurement times for alfalfa and old grass. Annual and meadow bromegrass pastures did not extract water below 1.2 m, while the other pastures did, and on the basis of soil water regimes, appear to be lower risk options than status quo old grass and alfalfa pastures during drought. Key words: Soil water, forages, rotational grazing, drought, wilting point, field capacity

This study examined the effects of whole sunflower seed (WSS) supplementation on production parameters, carcass traits, and organoleptic characteristics of beef from steers slaughtered directly off pasture or after receiving a finishing diet. Ninety-six yearling steers (410 kg; SD = 44 kg) were randomly allocated to three pasture (P) dietary treatments: (1) supplemented with P-WSS (n = 48), (2) supplemented with cracked barley grain (P-BAR, n = 24), and (3) not supplemented (P-CON, n = 24). Steers rotationally grazed meadow bromegrass-alfalfa pasture for 66 d during the summer and consumed WSS and BAR at a rate of 0.75 and 1.79 kg head-1 d-1, respectively. At the end of summer grazing half the steers from each pasture dietary treatment group were moved to a feedlot (F) where they were fed high barley-based finishing diets. The remaining 48 steers continued with their dietary treatments on stockpiled pasture for an additional 47 d (SD = 11) until they were slaughtered directly off pasture. In the feedlot, half the steers from each pasture dietary treatment were fed either a control [83% rolled barley, 10% alfalfa hay, 5% barley silage, 1% molasses and 1% vitamin/mineral mix on a dry matter (DM) basis; F-CON] or a F-WSS diet (68% rolled barley, 15% WSS, 10% alfalfa hay, 5% barley silage, 1% molasses and 1% vitamin/mineral mix on a DM basis) for a further 94 d until slaughter. Supplementation of BAR on pasture increased average daily gain (ADG), while supplementation of WSS had no effect on ADG compared with no supplementation (0.73 vs. 0.58 vs. 0.55 kg d-1, P = 0.023). Inclusion of 15% WSS in the finishing diet decreased ADG (1.46 vs. 1.72 kg d-1, P = 0.038), dry matter intake (DMI) (11.6 vs. 12.6 kg d-1, P = 0.058) and had no effect on feed to gain ratio (8.0 vs. 7.4 kg d-1, P = 0.160). Provision of WSS on pasture or in finishing diets had no effect on carcass traits and organoleptic characteristics of beef from steers slaughtered directly off pasture or after receiving a finishing diet. Slaughtering steers directly off pasture, regardless of pasture dietary treatment, adversely affected most carcass merit, meat quality and retail appearance and acceptability parameters compared with steers finished on a high-barley grain diet. These results indicate that increasing the dietary polyunsaturated fatty acids threefold in the pasture dietary treatment or greater than eightfold in the finishing diets had a small negative effect on animal growth rate and no adverse effect on carcass merit, meat quality and retail acceptability. Key words: Polyunsaturated fatty acids, retail acceptability, beef cattle