Grazing of Herbivores including Cattle is Essential for Wildlife Success

Phillip Lancaster, PhD
BCI Nutritionist

Wildlife are important to overall ecosystem function, are asthethically pleasing on range and pasture landscape, and provide recreation. When parts of the ecosystem change so can wildlife populations, and human activities have greatly altered the natural ecosystem. However, grazing of cattle on rangelands is much the same it was with bison many years ago – the large herbivore functions as an ecosystem engineer to create a variety of plant structures needed by wildlife. A recent analysis of published studies from the Great Plains region by researchers in the Department of Horticulture and Natural Resources and the Beef Cattle Institute at Kansas State University found that grazing overwhelmingly had no effect or a positive effect on several wildlife communities. The one exception being herptile communities, but few studies evaluated herptiles and more research is needed. Generally, grazing had minimal negative effects although specific grazing practices were not evaluated. Many individual wildlife species responded to varying degrees to grazing such that heterogeneous grazing pressure across the landscape provides a diversity of plant communities and structures to satisfy the habitat requirements of many wildlife species. Grazing management practices that create a heterogenous landscape are likely to result in greater wildlife diversity.

Figure 1. Proportion of studies that found negative effect, no effect, or positive effect of cattle or bison grazing on avian, mammal, herptile, or arthropod populations.

Impact of Local Food Purchases Depends upon the Product

Phillip Lancaster, PhD
BCI Nutritionist

Buying local is often touted as being more sustainable, but any improvement in environmental or economic sustainability is highly dependent upon the food product and where you are located. Many food products do not grow well in certain parts of the country. For example, it would be difficult to grow oranges anywhere in the U.S. except southern Florida, Texas, and California. Many of our food production systems revolve around the differences in climate across the U.S. that are optimal for efficient production. In beef industry, cow-calf operations are found in all 50 states because the predominate feed in this sector, grass, grows in all 50 states. However, the growing and finishing operations are concentrated in about 10 states in the center of the U.S., because the majority of feed in this sector, grains and byproducts, grow best in this region of the country. Additionally, the climate in the center of the country is optimal for efficient cattle growth, and efficiency is important for environmental and economic sustainability. Growing and finishing cattle in other regions of the country result in greater environmental impact.

The product being purchased impacts the transportation costs and the carbon emissions from fuel. Estimates of fuel usage and carbon emissions for buying eggs from a local farm are 50 to 60 times greater than buying from a local grocery store. The fuel usage per dozen eggs is significantly increased when the farmer brings a few dozen eggs to the local farmers market each week or each individual consumer travels to the farm each week to buy 1 dozen eggs compared to a semitruck delivery of 23,400 dozen eggs to the grocery store. Contrast that with buying beef locally where the consumer travels once per year to purchase a whole carcass for their freezer. The impact of transportation is much less in the beef scenario than in the egg scenario because the consumer is purchasing so much more food product with each trip, emphasizing the importance of efficiency as pounds of food product per gallon of fuel used.

Another touted benefit of buying local is more money goes to the farmer, but again the impact depends upon the food product being purchased (Figure 1). Purchasing locally produced bread would significantly increase the food dollar going to the farmer, where as purchasing a gallon of milk locally will have less of an impact on the farmer’s share of the food dollar. The difference between the farm share for bread versus milk has to do with the amount of further processing from the raw commodity to the final product. Wheat requires a lot of further processing to produce bread, which results in lots of additional costs that must be accounted for in the price of bread, whereas milk requires little further processing and minimal additional costs. Thus, it is the costs of further processing that really drive the farm share, and so the farmer’s share of the food dollar depends upon how much of the further processing was performed by the farmer.

Figure 1. Retail price, farm value, and farm share for various retail food products in 2019. 

Cattle are Major Recyclers in the Human Food Supply Chain

Phillip Lancaster, PhD
BCI Nutritionist

Food waste accounts for greater than 40% of food production, and food waste disposed of in a landfill contributes to methane emissions. Solid waste in landfills, although not all food waste, accounts for 14% of U.S. greenhouse gas emissions, which is more than agriculture at 9%. Globally, food waste accounts for 6 to 8% of greenhouse gas emissions; about half of the 14% contributed by livestock. However, most food waste could be recycled for a higher purpose. According to the food recovery hierarchy, food waste uses in order from least to greatest benefit are landfill/incineration, composting, industrial uses, animal feed, and donate to food pantries. Thus, animal feed is the most beneficial use of food not fit for human consumption.

Food waste occurs at many places along the food supply chain – food not harvested, lost during handling/transporting, industrial processing and manufacturing, retail groceries and restaurants, and in the home. Unfortunately, food not harvested or lost during handling/transporting has little chance of being recycled. Food waste from industrial processing and manufacturing sector is already highly recycled with only 5% going to landfills, but 45% of food waste from the retail level and 97% from the consumer level are disposed of into landfills. Over all sectors, recycling into animal feed is the largest (57%) destination of food waste followed by disposal in landfills (28%). Recycling into animal feed reduces the amount disposed into landfills.

One major issue with the use of food waste as animal feed is the variation in nutrient content from batch to batch. The unique digestive system of ruminants allows them to effectively utilize these variable feedstuffs with lesser consequences in performance than monogastric animals. Additionally, ruminants can utilize the wide variety of food waste sources produced in the food supply chain. Even though all livestock sectors use food waste derived animal feed, cattle are a major user because of their unique digestive system and large quantity of feed consumed daily. Thus, cattle contribute significantly to the efficiency and sustainability of the food supply chain.

Figure 1. Estimated amount of U.S. food waste destined for different end points. Adapted from Business for Social Responsibility, 2014

Heat Stress and Considerations for Fair and Show Season

Bob L. Larson, DVM, PhD
Beef Cattle Institute
Kansas State University

Fair and show season is a fun time of year that provides a great opportunity to compare breeding strategies, to participate in friendly competition with other producers, and to participate in a family activity. However, heat stress is an important concern for cattle exhibited in the summer time. Planning ahead to assure that cattle have access to plenty of water, shade, and airflow is necessary to reduce the risk of heat stress.

Almost every summer, at least some portion of the U.S. suffers from a period of extreme heat and humidity that can cause problems for cattle. As we move into summer, it is important to be prepared to limit the negative effects of heat stress. Cattle are more susceptible to heat stress than humans and can start to have problems if the temperature-humidity index reaches 80 or higher. Factors other than temperature and humidity are also involved with heat stress. These factors include: high body condition, black hide color, rainfall, lack of wind, lack of night cooling, crowding together to avoid flies or for other reasons, and consumption of endophyte-infected fescue.

Rain and high humidity reduces the ability of cattle to use evaporation to get rid of body heat. Evaporation of sweat is one of the primary means that cattle have to cool themselves at temperatures over 70°F. Hot weather immediately following a rain is often associated with heat stress in cattle. In addition, if winds are calm or cattle congregate behind a windbreak or to fight off biting flies, their ability to be cooled is reduced. Night temperatures that remain above 70°F increase the danger of heat stress because needed night cooling does not occur. Cattle that are not used to hot weather are also a greater risk if weather changes rapidly or they are shipped from a cool environment to a much hotter environment.

Another factor that plays a role in heat stress is hide color, with black-hided cattle at greater risk than cattle with light-colored hides. Breed plays a role in that Bos indicus breeds (Brahman and others) handle heat better than do Bos taurus (European) breeds. Show cattle that are not acclimated to a particular climate or that are nearing finished weight are at higher risk of heat stress. Cattle that have eaten endophyte-infected fescue may have increased body temperature and be predisposed to heat stress. Even following removal from endophyte-infected fescue pastures, cattle may continue to experience severe health problems related to summer toxicosis for several weeks.

During periods of heat stress, it is important to have ample water available. When temperatures reach 80 degrees, cattle need two to three gallons of water per 100 pounds of body weight and they must have access to water throughout the day. If cattle must be handled during hot weather, work them from midnight to 8 AM after at least six hours of night cooling. Providing shade to cattle (including show cattle) has been shown to reduce heat stress and to increase feed intake. Shade reduces the heat gain resulting from direct sunlight even when air temperature is not reduced. In a pasture or drylot setting, cattle seek out the coolest spots during periods of heat stress and are unwilling to leave these areas. Shades should therefore be placed over feed and over areas where the producer

wants the cattle to spend time. Shades should have a north-south orientation to allow drying under the shades as the shaded area moves throughout the day.

Air movement is important to dissipate heat. Fans can provide much-needed air flow in a cattle show setting. In pasture settings, it may be necessary to remove or fence off windbreaks during the summer. For cattle confined in a lot, enhance airflow by providing mounds for cattle to stand on. Move cattle away from windbreaks and wind dead spots in the feedlot. Sprinklers can be also used to combat heat stress. In geographic areas where humidity can be high, a large water droplet is required to wet the skin; fine mists or fog systems are not recommended. Sprinklers reduce heat stress by increasing evaporative losses, by reducing ground temperature and reducing radiant heat gain, and by reducing dust. Sprinkling should be done occasionally throughout the day, otherwise high humidity may result and there may be little opportunity for evaporation.

Attending fairs and exhibitions is very enjoyable and has many benefits to the participants. However, do not forget the risks that are taken anytime cattle are placed in a new environment especially if heat stress is a concern.

Large Herbivores, Whether Bison or Cattle, are Integral Parts of Grassland Ecosystems

Grasslands and rangelands are an important ecosystem providing food, income for rural families and communities, recreation, wildlife habitat, soil carbon sequestration, plant and animal biodiversity, and water filtration. Thus, grasslands and rangelands contribute to all three pillars of sustainability: environmental, social, and economic. Grazing is often assumed to negatively impact the natural ecosystem and that removal of grazing would result in more pristine rangelands. To the contrary, grazing has had minimal effects on plant species richness over long periods of time, e.g., 13 to 65 years. Additionally, lack of grazing created grasslands with greater shrub cover dominated by fewer species. In contrast to plant species, continuous grazing in general has a negative impact on wildlife populations, because different wildlife species require different types of habitat varying widely from tall and dense to short and sparse.

Grassland and rangeland management practices influence the benefits received from these ecosystems. Heavy grazing decreases animal productivity and income for ranchers, increases soil erosion, decreases plant biodiversity which decreases wildlife habitat, and less forage production decreases soil carbon sequestration and water filtration. But, proper grazing management allows forages to store reserves during times of abundant precipitation, increase water-holding capacity, provide wildlife habitat at critical times of rearing young, and create a shifting mosaic with both old and new growth vegetation all the while maintaining animal productivity and income for ranchers. And patch burning regimes can be used to direct cattle grazing to specific sites within rangelands further producing numerous habitat structures for diverse wildlife species.

Prior to European settlement, rangelands were ‘managed’ by periodic fire and grazing by wild ungulates (bison, deer, and elk), which function as ecosystem engineers creating a diversity of plants and vegetation structures promoting wildlife habitat. Today, we have smaller areas of privately-owned rangelands interspersed with towns, cities, and cropland rather than wide open expanses for ungulates and fire to roam. And we generally use cattle rather than bison as the primary grazer. Some differences exist between cattle and bison in grazing behavior and how they utilize the landscape, but many of these differences are more a part of human management (fences, lack of predators, etc.) than inherent differences between bison and cattle. The many ecosystem services of grasslands and rangelands can be achieved by managing smaller privately-owned ranches using proper grazing management and fire regimes that promote all three pillars of sustainability.

Regenerative vs. Sustainable Agriculture: What is the difference?

By Phillip Lancaster

In the last 20 to 30 years, there has been a lot of discussion about sustainable agriculture. ‘Sustainable’ has been a buzzword in many industries for the last 20 years with everybody from farmers and ranchers to multi-billion-dollar corporations trying to find ways to be more sustainable. But what does the word sustainable really mean? If we break down the word, ‘sustain’ means to strengthen or support according to Oxford Dictionary. In the context of agriculture, we generally think of sustainability as the ability to support or maintain food production into the future, which suggests more efficient resource use. Agriculture has made tremendous strides in efficiency of resource use over the last 50 years.

Lately, the term regenerative agriculture has become a new buzz word, but it is really not a new concept. Robert Rodale coined the term ‘regenerative organic agriculture’ in the late 1970s as an approach that encouraged continuous innovation and improvement. Breaking down the word, regenerate means to regrow or replace what is lost. In the context of agriculture, we generally think of regenerative as replacing soil carbon/organic matter that was lost due to soil tillage or overgrazing. Again, agriculture has made tremendous strides in replacing soil carbon with adoption of no-till and cover cropping practices, and management intensive grazing in the last 30 years.

There are other aspects of the ecosystem such as plant and animal biodiversity that also fall under the idea of regenerative agriculture. Researchers are beginning to understand how grassland and rangeland management impacts plant species composition and wildlife populations, and developing novel management strategies to such as patch burning to enhance plant and animal biodiversity.

Many of the agricultural management practices that we considered sustainable are also regenerative. Whether the practice is sustainable or regenerative depends on the context of the situation in which the practice is being used. All soils have a maximum attainable soil organic carbon content based on physical characteristics (clay content, bulk density) and climate (rainfall, temperature). For example, a rancher whose soil has reached its maximum attainable soil organic carbon and practices management intensive grazing is sustaining the level of carbon. A second rancher whose soil has not reached its maximum attainable soil organic carbon and practices management intensive grazing is regenerating the level of carbon. Thus, even though they are using the same management practice, the first rancher is practicing sustainable agriculture whereas the second rancher is practicing regenerative agriculture.

As with soil organic carbon, a maximum attainable level of other aspects of the ecosystem will be achieved with regenerative agriculture.  At this point, we will move from replacing what was lost to maintaining the new level, and from regenerative agriculture to sustainable agriculture.

Intensification of Beef Production Aids in Sustainable Beef Production

Beef production is a significant contributor to global climate change. The source of greenhouse gas emissions is primarily due to inputs into the system such as fertilizer and feed. Estimates of greenhouse gas emissions from beef production are highly variable. Globally, livestock contribute 14% to 18% of total greenhouse gas emissions. Beef production alone accounts for a smaller percentage (6%). In the U.S., beef is an even smaller proportion – only 2%.

So why the discrepancy? Greenhouse gas emissions are highly dependent upon the production system. More intensive systems utilizing highly nutritious feeds, high quality animal genetics, and high levels of management such as the U.S. system produce more beef for each unit of input, which drives down the greenhouse gas intensity. The greenhouse gas intensity is the amount of greenhouse gas emissions per unit of output, in this case carcass weight.

Because of the investment in nutritional quality of feed, animal genetics and management practices, the U.S. system has the lowest greenhouse gas intensity of any major beef producing country (Figure 1). The U.S. produces 18% of the world’s beef and only 8% of the world’s greenhouse gas emissions from beef production. In comparison, Brazil produces 14% of the world’s beef and 19% of the world’s greenhouse gas emissions from beef production. The U.S. system has a ratio of 2.2:1 compared with Brazil’s ratio of 0.75:1 of contribution to beef production relative to contribution to beef greenhouse gas emissions. The U.S. production system has the highest ratio of any of the top 10 beef producing countries with Germany having the next closest at 2.0:1.

Comparisons among greenhouse gas emission intensities of countries (i.e., production systems) indicates that intensifying the system through improving efficiency should be the goal. A global effort to improve nutritional value of feed, increase cattle genetics for growth and yield, and increase producer education of optimum management practices will have the greatest benefit to sustainable beef production. If the other 9 of the top 10 beef producing countries developed beef production systems similar to the U.S., global greenhouse gas emissions from beef production would be reduced by 22%.  

Does beef production really use that much water?

Beef production often gets labeled as unsustainable partly because of its large water footprint. Estimates of the water used to produce one pound of beef are 1,675 gallons compared with 545 gallons to produce one pound of pork and 257 gallons to produce one pound of poultry. However, not all water has the same importance when it comes to sustainability. There are primarily 3 types of water used in the livestock production chain: green, blue and gray water. Green water is rainwater that landed on the field or pasture that required no human intervention to use. Blue water is primarily irrigation water for crops and drinking water for animals. Gray water is water used for cleaning animal facilities, processing plants, etc.

From a water sustainability perspective, blue and gray water are more important than green water because they involve removing water from its natural cycle, and blue and gray water could be used directly by humans. When we compare the water footprint of animal protein sources based on water type, it becomes clear that the important water footprint of beef is much more like poultry and pork (Figure 1). Over 90% of the water footprint for beef production is green water compared with 73% for pork and 79% for poultry. The blue and gray water footprint of beef is 158 gallons per pound compared with 146 gallons per pound for pork and 55 gallons per pound for poultry.

For all species of livestock, the vast majority (> 85%) of water use is to produce feed and the important type of water is blue water used to irrigate crops. Advances in irrigation technology and drought resistant crop varieties will further reduce blue water use for feed production. For example, subsurface drip irrigation can reduce irrigation water use by 45% and variable rate irrigation adjusts the amount of water applied to each square foot of the field based on soil characteristics and plant water needs. Also, in 2016, 40% of corn acreage in Nebraska and Kansas was planted to drought tolerant varieties.

When looking at the water types agriculture can control (blue and gray water), animal proteins are very similar in their water footprints. And technological advances in feed crop production will continue to reduce the blue water footprint of animal proteins.

Cows are not the primary cause of recent increase in methane

Atmospheric methane concentration has reached a record, but the exact reason has been difficult to determine. Atmospheric methane concentration increased 8 ppb per year during the 1980s, 6 ppb per year in the 1990s, then the trend was static from 2000 to 2007, but now increasing at 9 ppm per year since 2007 (Figure 1). The reason for the increased accumulation of methane in recent years is likely due to several factors. The methane budget includes both sources of emissions and sinks that remove methane from the atmosphere. The primary sources include agriculture, natural wetlands, fossil fuels, biomass burning, and other natural sources (oceans, lakes, termites). The primary sinks are chemical reactions in the atmosphere and soils. The increase in atmospheric methane concentrations means that emissions were larger than sinks, but which source has been the cause of the recent increase.

Ruminant animals account for the largest proportion of man-made methane emissions and cattle are by far the largest contributor. Estimated enteric methane emissions have increased since 2000, but the global cattle population has remained constant questioning the reason for the increased enteric methane emissions (Figure 1). Wetlands are the largest natural source of methane emissions and methane emissions from wetlands have also been increasing since 2000. Methane leakage during oil extraction is also a source of methane emissions into the atmosphere and was thought to possibly be the cause of increased methane due to the increase in shale oil extraction.

Based on the change in radio isotope ratio of atmospheric methane, the increase in methane emissions is likely from microbial sources which rules out fossil fuel extraction leaving enteric and wetland methane emissions. The largest increases in atmospheric methane coincide with the largest increases in global temperature. The largest methane growth rates (> 10 ppb) occurred in the tropics and subtropics through 2014 to 2017, which had average temperatures > 1°C warmer than the 1880-1909 baseline. Methane emissions from wetlands increase with increasing temperature because of increased microbial activity, but microbes in the rumen of cattle are at a constant 38°C such that global temperature would not be affecting microbial activity in the rumen. Additionally, the largest increases in methane emissions have come from the tropical and subtropical latitudes, where increased precipitation, flooding and temperature coincided between 2014 – 2017. Wetlands are the largest global source of methane emissions (Figure 2) and are a major driver of atmospheric methane especially with increasing global temperature.

Removal of methane through chemical reactions in the atmosphere can have a dramatic effect on methane lifetime. Hydroxyl, which is the chemical with which methane reacts in the atmosphere, concentrations in the atmosphere increased 10% between the late 1990s and mid-2000s coinciding with the plateau in methane concentrations from 2000 to 2007. But hydroxyl concentrations have decreased approximately 10% from mid-2000s to 2014 coinciding with the renewed increase in atmospheric methane concentrations.

The methane budget is not as simple as once thought and changes in relative amounts of sources and sinks can readily change the atmospheric concentration. Enteric emissions from ruminants is not always the primary driver and is not the largest emissions source. As global temperatures increase, wetland emissions may become a larger proportion of global methane emissions.

Figure 1. Global atmospheric methane (NOAA) and hydroxyl (Rigby et al., 2017) concentration, methane emissions from enteric fermentation (FAO) and wetlands (Zhang et al. 2017), and cattle population (USDA).
Figure 2. Contribution to global methane emissions by various sources. Adapted from the Environmental Change Institute, University of Oxford.

Food, Innovation, Service, & Hospitality Talk

The Association of Healthcare Food Service hosted their first ever Food, Innovation, Service, Hospitality (FISH) Talks – Live Panel at the 2019 national conference.   The broad subject of the panel was to provide healthcare leaders with information surrounding food and climate change that would help them purchase more sustainably.   The below clip shares improvements in ranching and farming over the decades thru the eyes of a dietitian, who was once in their food service shoes trying to make similar thoughtful choices.  

Thinking Beyond Food Waste to Food Recovery

As we listen to conversations about supply issues, food waste and providing food to the hungry, people not familiar with our beef commodity markets have asked why the U.S. exports beef as well as the ethics of feeding human edible beef to our pets. Here are some thoughts and facts to consider. You might think these concepts are common knowledge, and they probably are among your circle of agriculture friends. Sustainable food production questions rarely have simple answers, but try these to help us all have dialogue together and reach the common goal of a more sustainable food supply.

Why do we export beef to other countries?

The majority of beef variety meats are commonly exported as opposed to finding a home in the U.S.  Diets are cultural and ours does not typically include variety meats, but we respect that they are of value to others. In the U.S., they are mainly used as pet food ingredients.

Annual exports are generally 9 to 11 percent of total domestic beef production and are a critically important source of revenue.  U.S. beef producers receive about $300/head in additional premiums as a result of export values in fed cattle according to Oklahoma State University livestock economist, Derrell Peel.  Foreign markets are willing to pay much higher premiums for variety meats than the U.S. consumer and are also purchasing premium cuts as their economies improve.  

Why do we feed edible beef to our pets instead of feeding ourselves?

Twenty-five to 30% of the meat eaten in the U.S. is fed to dogs and cats, according to a recent UCLA study. There are 157+ million pets in the U.S. as of 2014 ,which is triple the number since the 1970’s.  

While it is not recommended that your dog and cat give up meat, it is good to know that the by-products from beef are an important nutritious ingredient as you do your research on the ingredient label. Veterinary nutritionists tell us that feeding by-products to pets not only is safe and healthy, but it is better for the environment and dramatically reduces food waste.  The pet food aisle has seen an influx of brands made with “human-grade” ingredients to lead us to believe they are better than those that contain animal by-products.  

The Environmental Protection Agency has developed the “Food Recovery Hierarchy” that demonstrates the most valuable use of food waste down to the last resort — the landfill. Wholesome, edible food should be kept in the human food supply whenever possible. When food is no longer edible for humans but still safe and wholesome for animals, the hierarchy recommends diverting these food scraps to feed animals, including pets.

Shifting gears, there is renewed interest in feeding food scraps to livestock as a way to reduce organic waste in landfills and the methane gas it generates.  After disease outbreaks were linked to animal feed back in the 1980’s, there are state laws that regulate the process of converting food waste to animal feed.  The Food and Drug Administration’s Bovine Spongiform Encephalopathy/Ruminant Feed Ban Rule also prohibits the use of animal tissue in feeds for ruminant animals such as cattle. Consumers are asking questions about how companies handle their waste, and more research and technology will be needed to overcome some of the barriers of re-feeding people leftovers to food animals. Cattle have demonstrated they can upcycle a variety of products into safe, quality food and can be a part of the environmental solution.   

Mitigating Ruminant Methane Emissions

Last month we evaluated data indicating that only 35% of current methane emissions from domestic ruminants is contributing to increased atmospheric methane. With reductions in methane emissions ranging from 10 to 50%, feed additives could almost eliminate the 35% contributing to atmospheric methane.  Many feed additives have potential adverse effects on the animal, but 3-nitrooxyproponal reduces methane emissions without negatively affecting animal performance and is in the process of commercialization. Furthermore, 3-nitrooxypropanol shifts rumen VFA profile toward higher proportions of propionate making the ruminant animal more feed efficient and the compound very attractive to economically include in livestock rations.

Reassessing Ruminant Methane Contribution

The environmental impact of livestock production, especially ruminants, has received a lot of attention in both the scientific community and popular media. One of the most discussed aspects of ruminants’ environmental impact is the production of the greenhouse gas, methane. Methane is produced as a natural byproduct of fermentation in the ruminant stomach during the process of feed digestion. The production of methane is not a man-made process and occurs naturally in all wild and domestic ruminant animals.

Wild ruminants in North America include deer, moose, elk, big horn sheep, antelope and bison with bison having the largest population. Estimates of the bison population prior to European settlement of North America varies greatly ranging from 21 to 88 million. And estimates of the total wild ruminant population prior to settlement ranges from 83 to 133 million. Due to lots of factors chief among them the growth in human population, the wild ruminant population has decreased to 30.5 million today and have been replaced by 90 million domestic ruminants.

Do domestic ruminants produce more methane than wild ruminants? Methane emissions factors for bison are similar to that of domestic cattle when fed the same diet, and both are greater than deer and elk. However, diets of wild and domestic ruminants are not necessarily similar. Diets of domestic ruminants are managed by humans and are typically of greater nutritive value than wild ruminants consume, especially during the winter months when vegetation is dormant.

Attempting to account for differences in methane emissions from wild and domestic ruminants, recent research compared the amount of methane from wild ruminants prior to European settlement of North America and current wild and domestic ruminant populations (Figure 1). Due to the wide variation in estimates of bison population, results were computed for low, medium and high bison populations. Based on these data, the amount of methane from domestic ruminants contributing to the increase in global atmospheric methane concentration is less than 100% because a fraction of that methane is replacing naturally produced methane from pre-settlement wild ruminant populations. Doing the math, the proportion of methane emissions from domestic ruminants in North America that is contributing to atmospheric methane concentrations ranges from 50 to -19% depending upon the pre-settlement bison population with an average of 35%.

Several feed additives have been investigated for their ability to reduce enteric methane emissions from domestic ruminants; the most effective include methane inhibitors, electron acceptors, hydrogen sinks, and plant extracts. These feed additives can reduce enteric methane emissions from 10 to 50% depending upon domestic ruminant species and diet, indicating that implementation could mitigate the 35% of domestic ruminant methane emissions that is new to North America since the European settlement. Although most of these feed additives have adverse effects that may hinder their use, one, 3-nitrooxyproponal, reduces methane emissions without negatively affecting animal performance and is in the process of commercialization. 3-nitrooxypropanol also shifts rumen VFA profile toward higher proportions of propionate making the ruminant animal more feed efficient, which is very similar to another feed additive, monensin, which has been widely adopted in ruminant livestock production. Thus, the use of 3-nitrooxypropanol looks very attractive for producers to economically include in livestock rations and could significantly mitigate enteric methane emissions from domestic ruminants.

In conclusion, the extent of domestic ruminants’ contribution to greenhouse gas emissions is not as great as once thought, although livestock production has more environmental impact than methane alone. It appears that we are on the verge of balancing the methane scale as far as domestic ruminant emissions are concerned.

Estimated methane emissions from wild ruminants prior to European settlement of North American Continent based on 3 estimates of the American bison herd (30, 50 and 75 million bison) compared with methane emissions from current population of wild and domestic ruminants. Adapted from Hristov, 2012