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The present study compared the greenhouse gas (GHG) emissions, and breeding herd and land requirements of Canadian beef production in 1981 and 2011. In the analysis, temporal and regional differences in feed types, feeding systems, cattle categories, average daily gains and carcass weights were considered. Emissions were estimated using life-cycle assessment (cradle to farm gate), based primarily on Holos, a Canadian whole-farm emissions model. In 2011, beef production in Canada required only 71% of the breeding herd (i.e. cows, bulls, calves and replacement heifers) and 76% of the land needed to produce the same amount of liveweight for slaughter as in 1981. Compared with 1981, in 2011 the same amount of slaughter weight was produced, with a 14% decline in CH4 emissions, 15% decline in N2O emissions and a 12% decline in CO2 emissions from fossil fuel use. Enteric CH4 production accounted for 73% of total GHG emissions in both years. The estimated intensity of GHG emissions per kilogram of liveweight that left the farm was 14.0 kg CO2 equivalents for 1981 and 12.0 kg CO2 equivalents for 2011, a decline of 14%. A significant reduction in GHG intensity over the past three decades occurred as a result of increased average daily gain and slaughter weight, improved reproductive efficiency, reduced time to slaughter, increased crop yields and a shift towards high-grain diets that enabled cattle to be marketed at an earlier age. Future studies are necessary to examine the impact of beef production on other sustainability metrics, including water use, air quality, biodiversity and provision of ecosystems services.

Ruminants raised for meat and milk are important sources of protein in human diets worldwide. Their unique digestive system allows them to derive energy and nourishment from forages, making use of vast areas of grazing lands not suitable for arable cropping or biofuel production and avoiding direct competition for grain that can be used as human food. However, sustaining an ever-growing population of ruminants consuming forages poses a dilemma: while exploiting their ecological niche, forage-fed ruminants produce large amount of enteric methane, a potent greenhouse gas. Resolving this quandary would allow ruminants an expanded role in meeting growing global demands for livestock products. One way around the dilemma is to devise forage-based diets and feeding systems that reduce methane emissions per unit of milk or meat produced. Ongoing research has made significant strides toward this objective. A wider opportunity is to look beyond methane emissions alone and consider all greenhouse gas emissions from the entire livestock-producing system. For example, by raising ruminants in systems using forages, some of the methane emissions can be offset by preserving or enhancing soil carbon reserves, thereby withholding carbon dioxide from the air. Similarly, well-managed systems based on forages may reduce synthetic fertilizer use by more effective use of manure and nitrogen-fixing plants, thereby curtailing nitrous oxide emissions. The potential environmental benefits of forage-based systems may be expanded even further by considering their other ecological benefits, such as conserving biodiversity, improving soil health, enhancing water quality, and providing wildlife habitat. The quandary, then, can be alleviated by managing ruminants within a holistic land-livestock synchrony that considers not only methane emissions but also suppression of other greenhouse gases as well as other ecological benefits. Given the complexity of such systems, there likely are no singular "best-management" practices that can be recommended everywhere. Using systems-based approaches such as life cycle analysis, ruminant production can be tuned for local lands to achieve greatest net benefits overall. In many instances, such systems, based on forages, may maintain high output of milk and meat while also furnishing other ecosystem benefits, such as reduced overall greenhouse gas emissions.

Forage production in northern latitudes is challenging and uncertain in the future. In this case-study, the integrated farm system model (IFSM) was used to assess the impact of climate change and cropland expansion scenarios on forage production in a dairy farm in Newfoundland, Canada. Climatic projections indicated increases in temperature in the recent past (1990–2016) and under any future climate (2020–2079), thus enhancing agronomic performance. Temperature increases ranged from 2.8 °C to 5.4 °C in winter and from 3.2 °C to 6.4 °C in spring. Small precipitation increases (<10%) create narrower time windows to perform farm operations in the already stringent condition of excess moisture in the region. Results of land use scenarios including expansions of 20, 30, and 40% in cropland area, out of which 5% was dedicated to corn silage and the remainder to grass-legume mixtures, indicated increased yield and total production. Improvements in grass-legume yield ranged from 8% to 52%. The full range of production increases ranged from 11% to 105%. Increments in corn silage yield ranged from 28% to 69%. Total farm corn silage production increases ranged from 29% to 77%. An attainable cropland expansion of 20% would enable the farm to become self-sufficient in forage production under any climate scenario.

Long-term field experiments are useful for determining cropping system productivity, stability, and resource use efficiency. With 12 yr (2004With 12 yr ( -2015 of data from five cropping systems on a long-term experiment (> 30 yr) under semiarid conditions in Saskatchewan, Canada, a systems-approach was used to compare grain and protein yield, stability, nitrogen (N) dynamics, N fertilizer (FUE G,P ), and available N use efficiency (NUE G,P ) for grain and protein. Annualized grain and protein yields for wheat (Triticum aestivum L.)-canola (Brassica napus L.)-wheat-field pea (Pisum sativum L.; W-C-W-P) were 2244 and 372 kg ha −1 , respectively, 14 to 38% and 33 to 66% higher, respectively, than continuous wheat (ContW), summer fallow-wheat-wheat

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Main conclusion The improvement of photosynthesis using biotechnological approaches has been the focus of much research. It is now vital that these strategies be assessed under future atmospheric conditions.