Forage use to improve environmental sustainability of ruminant production12

Abstract

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.

Invited review: Sustainable forage and grain crop production for the US dairy industry

“…Reduced productivity exhibited by grazing systems also increases both the number of cows and land base required to produce a set amount of milk (Capper et al, 2008). Although profitable (Hanson et al, 1998;Tozer et al, 2003Tozer et al, , 2004, socially desirable (Chapinal et al, 2010), and beneficial from the point of view of reduced GHG emissions (Guyader et al, 2016), we predict that pasture-based systems will remain a niche system in the United States or an enhancement to confinement operations, but not a nation-wide solution to sustainability.…”

Demonstrating the Effect of Forage Source on the Carbon Footprint of a Canadian Dairy Farm Using Whole-Systems Analysis and the Holos Model: Alfalfa Silage vs. Corn Silage

“…A major advantage of ruminant systems is that forage production can recycle carbon back to the soil, thereby lowering atmospheric CO 2 and enhancing soil health [65]. Increasing soil carbon stocks is an effective opportunity to offset enteric GHG emissions in the short term, but its benefit requires long-term evaluation.…”

BOARD-INVITED REVIEW: Quantifying water use in ruminant production

“…General recommendations across all regions are also misleading, as some producers or regions raise livestock more efficiently than others. Large numbers of livestock producers, specifically those who manage ruminants, are not only practicing husbandry but are also stewards of the vast grazing lands that provide a range of ecosystem services including enhancing biodiversity and carbon sequestration (Guyader et al, 2016). In some regions of the world such as the arid areas of sub-Saharan Africa, ruminant production is the only sustainable agricultural activity due to climatic, soil-related, and socioeconomic factors.…”

“…They also make use of nutrients in food byproducts, thereby reducing the waste disposal problem. In addition, forage-based systems are known for their multiple ecological benefits, such as enhancing biodiversity, water quality, soil health, and carbon sequestration (Guyader et al, 2016). Ruminant production has also been reported to intensively use water for drinking, growing feed crops or forages, waste disposal, general cleaning, and processing of products.…”