BLOG & ARTICLES

Ruminations Blog

For the average person who would like to be more informed about ruminants and agriculture in general. 

Bison vs. Cattle: Neither are Better nor Worse than the Other

Feb 12, 2019

Don’t get me wrong, I like bison near as much as the next person does. They’re admirable creatures, symbolic of the Old West, and rulers of the North American grasslands. They’re such large and placid-seeming creatures, yet they’re remarkably graceful and fast. We can’t also forget they’re wild animals. Unfortunately, there’s too much romanticizing that goes on. In my personal opinion, I feel too that they’re held at too high a standard; so much that the misinformation gets delved out there is rather questionable. 

A while ago I had a run-in with one individual who was adamant that bison were the best thing overall. So good, in fact, that nothing could compare, not even cattle. No matter what anyone would tell her, she wouldn’t hear anything different. Well, she won’t, but I’m hoping you will. This is why I can write what I do here!

Here is the comment I’ll be debunking today, which was left by a misinformed, well-meaning commenter on TreeHugger.com’s In Defence of the Cow: How Eating Meat Could Help Slow Climate Change

Some things that should be obvious but, to my utter amazement apparently are not, to the author and those commenting…. BISON… (Bison bison bison AND Bison bison athabascae) are NOTHING like cows. These are WILD herds that evolved over millions of years of natural selection, weeding out the weaker scions and leaving only individuals with strong genetic adaptation to the pathogens, parasites, prevailing climatic factors and predators of their ecosystem. CATTLE (Bos taurus), on the other hand, are a wholly artificial species, bred from the giant auroch (Bos primigenus) during the Neolithic (or Anatolian) Revolution that developed the beginnings of agriculture. As most artificial (or “domestic”) breeds, modern cattle was bred for its commercial aspects… either milk production, for dairy cattle, or meat. They are often prone to parasitic infestations, pathogens, (fungal, viral and bacterial) and would probably adapt, if left to survive in the wild, but millions of them would die in the process, leaving only the few scions that overcame all infections, infestations, freezing winters and stifling, arid summers, until their resilience had been tested and they had successfully bred over a few generations. So, to compare Bison (which, incidentally is much more efficient in its ability to extract nutrients even from relatively poor pasture, unlike Bos taurus, that needs good, clean, rich pasture). FFS Bos taurus can’t even tolerate RAGWORT, one of the most common weeds here in the UK… where the [sic] cattle has [sic] been around for thousands of years, but still does not know better than to avoid the bloody plants! Cows have birthing problems, because so many have been bred out of proportions, too fat, or pelvis too small, because the pressure on their selection has been meat or milk, not good calf-bearing. As to the environmental impacts… The issue is the NUMBERS of cows. This may come as a shock to you all, but actually America is NOT the world and the WORLD has a lot more cows than you can count! 😂 And each one of them generates so mush Methane you could rename them CH4OWS! Here is some info for those interested…

I’d like to take the time to tear apart this big comment piece by piece to discuss why and how this person is wrong in most of her assertions. 

BISON… (Bison bison bison AND Bison bison athabascae) are NOTHING like cows.

This is more of a half-truth than anything. There are quite a few similarities that bison share with cattle. Both species:

  • Are large, mammalian, ruminant animals, capable of emitting plenty of methane (more on this later);
  • Have a diet that is comprised of at least 95% grass;
  • Are cloven-hoofed, providing the same amount and type of hoof impact and trampling on vegetation, for better or for worse;
  • Are prey animals, and will run yet have an affinity to fight for their lives when cornered; 
  • Are social, herd-oriented animals, and both tend to divide themselves (in a natural environment with very minimal to no human interaction) into smaller herds of family or friend groups, bachelor groups, cows with calves, etc. 
  • Often have a single calf at birth and have the same gestation period length;
  • Are just as prone to parasites, disease, and predation as the other, and this affinity is more of a difference between individuals than, as with cattle, between breeds or types.
  • Belong to the same taxonomic family which is Bovidae. This makes them closely related in terms of the genetics that either species share. 
  • Can interbreed to give relatively fertile offspring; such crosses are usually known as Beefalo. In fact, a large number of bison (estimated at under 40,000) do have some Bos genetics in them from past inter-breedings in the early 1900s. 
  • Are primarily managed and raised by people for meat. There are more bison raised on ranches and farms today than there are out in the wild snd free-roaming, as in national/state/provincial parks, forest reserves, protected areas, etc.
  • Will avoid eating plants that are unpalatable. Bison tend to avoid eating far more forbs than cattle do, leading to a greater likelihood for weeds to infest a bison pasture with poor management practices (i.e., allowing overgrazing to occur) than cattle are. 

Because these are certainly two different species that don’t originate from the same historical lands, and certainly don’t look like each other, it’s also worth acknowledging that cattle and bison do have their differences. That still doesn’t give a person reason to believe that “bison are nothing like cows,” when the opposite is more true. Here are some differences between bison and cattle (you may be also interested in some of the things that Western Watershed Project have to say about differences and similarities between bison and cattle, as well as this fascinating study on comparing the grazing and land-use behaviours between bison and cattle in different locations): 

  • Structurally, bison have a large boney crest above the shoulders and a sloping top-line down to the rump. These animals don’t look it, but they’re built to run for long distances. Their build is advantageous for the efficiency of movement with a rolling, cantering gait.  
  • Cattle are built for walking, and for shorter distances, due to their bone and muscle structure. They only run when they absolutely must, unlike with bison, but for short bursts of speed and for short distances. Domestication has bred many of these animals to be more muscular or with larger udders (cows) which sacrifices the ancestral ability (from the Aurochs) to be more efficient at travel.  
  • Bison tend to travel a lot more than cattle do, and cover twice the distance in a day. This makes them less likely to continue to return to the same area that has been grazed as cattle will, on a free-will basis. This makes cattle more likely to contribute to over-grazing issues in a continuous grazing system than with bison.
  • Because cattle tend to travel less often and at fewer distances, often they’ll stick around a watering area more often than not. Bison also tend to prefer forages close to water sources, but will still venture further than cattle may; the study showed that bison tend to travel about three times the distance from water that cattle normally would.
  • Bison prefer more perennial grasses and coarse forage than cattle do. (More on this below.) 
  • Historically, the North American Plains bison have evolved on drier open steppe grasslands and savannahs, whereas cattle have been more adapted to the higher-moisture savannah and woodland areas. Drier and more open lands get animals to be much more nomadic, larger-grouped, seasonal, and less “territorial” than their woodland cousins.  

These are WILD herds that evolved over millions of years of natural selection, weeding out the weaker scions and leaving only individuals with strong genetic adaptation to the pathogens, parasites, prevailing climatic factors and predators of their ecosystem.

Only partly right. While there still are wild herds existing in the United States, Canada, and parts of the European Union, there is still a huge majority that is raised commercially on farms and ranches. In Canada, 250,000 are raised this wayand in the US, 500,000 bison are also raised on ranches and reserves, all for the purpose of meat production.

Arguably too, a large number of bison have been interbred with cattle to create more docile animals, and this started in the early 1900s when some ranchers took on the opportunity to protect and ensure the remaining bison did not go extinct. I don’t think the interbreeding was done on purpose, though today it’s really hard to tell.

Beefalo is also a breed of this successful interbreeding with bison and cattle.

There are still bison that are prone to the effects of pathogens and parasites. Tuberculosis, BSE, Anthrax, Brucellosis, and other diseases have plagued bison herds in the recent past. Parasites will affect bison just as readily as they will cattle. It’s not uncommon to see face flies or other insects bothering bison in the summer. Just like with cattle, disease and parasitic resistance differs greatly between individuals, as you can get individuals that are more disease- and parasite-resistant than others. 

Bison are also still seriously affected by climatic factors in their biome. Calf mortality is determined by harsh winters and available feed. If there is not enough grass available for their mothers to eat, then the calves suffer as well because their mothers are unable to produce enough milk for their calves, and the calves themselves cannot get sufficient forage to eat. Deep snow or freeze-thaw cycles that forms a hard crust over the snow surface making it more difficult for bison to nose their way into the snow to dig for the grass underneath can make life more difficult for them in the winter. 

Bison can and will die. It’s never a matter of if but rather when (and how). While it’s true that the sick, weak, old, or young are likely to be “weeded out,” sometimes it’s the strong and healthy that may not survive for whatever reason, be it a freak incident, predators got a lucky break, a fatal mistake made, whatever. We humans also play a role in the process of selection for the survivability of the herd through hunting. It’s not always the young bulls that get the bullet. (Often it’s the young bulls or steers with domestic bovines that are harvested for meat in the commercial meat industry.) Occasionally it’ll be a cow that will need to go down to fill someone’s freezer. A mature bull that has done his job in siring a number of calves will get his time to move on and let his sons carry on. It certainly is true that through natural selection the strongest survive, but there’s always going to be animals that will die. This leaves the next generation to take their place, replacing those that must become sustenance for others, including humans. 

Indeed it has taken millions of years of evolution to get the bison to where they are now. But know that just because they’re where they’re at now doesn’t mean that process still isn’t continuing onward into the future, hopefully into the next several million years. Nature has never made any species perfect so that they’ve gotten to the point where no disease, parasite, predator or injury can kill them. That can and will never happen. Instead, these animals have been made with the ecosystem function and role they play in mind, to be grass eaters and to feed those who prey upon them (including us humans). 

CATTLE (Bos taurus), on the other hand, are a wholly artificial species, bred from the giant auroch (Bos primigenus) during the Neolithic (or Anatolian) Revolution that developed the beginnings of agriculture. As most artificial (or “domestic”) breeds, modern cattle was bred for its commercial aspects… either milk production, for dairy cattle, or meat. They are often prone to parasitic infestations, pathogens, (fungal, viral and bacterial) and would probably adapt, if left to survive in the wild, but millions of them would die in the process, leaving only the few scions that overcame all infections, infestations, freezing winters and stifling, arid summers, until their resilience had been tested and they had successfully bred over a few generations.

First correction: The updated and proper species name of all cattle is Bos primigenius, with subspecies, Bos primigenius taurus (European-type cattle) and Bos primigenius indicus (Indo-Asia/Africaaner Zebu-type cattle).

Second correction: Cattle are not a “wholly artificial” species. Allow me to explain. 

While it is correct that the ancestral roots of today’s cattle can be traced back to the ancient Aurochs, many cattle had actually started out as cattle, along with their old auroch ancestor, long before the Neolithic Revolution (or 10,000 years ago). Many breeds started out well before they were even recognized as breeds; They were merely indigenous bovines of the homeland from where their later-identified “breed” has been identified to have come from. 

For example, Piedmontese (long before they were selected to have double muscling, which began in the late 19th century) are derived from the 25,000-year-old evolution and integration of the Pakistani Zebu cattle, which made their migration north and west into the boxed-in mountain valleys of Piedmont, with indigenous cattle of that area which had resided there for many years before. Galloway and the Scottish Highland had been living and evolving in their areas of northern Scotland even before the Neolithic period.  

There is still a lot of half-wild or feral cattle in Europe and Asia, and plenty still as wild as the old extinct Aurochs, such as the wild Chillingham cattle, and the pre-Second World War attempt made by the Heck brothers, a couple of Nazi-party zoologists, to bring back the ancient, extinct Aurochs: the half-feral and very dangerous Heck Cattle. Many of these cattle have long since adapted to their environment through natural selection; very, very much like the bison have done here in most of North America. As a matter of fact, many of the breeds that are deemed as quite old may have been living alongside their old Aurochs ancestors, before these truly wild bovids were hunted to extinction. 

The old breeds like Hereford, Galloway, Tarentaise, Marchigiana, Piedmontese, and Scottish Highland cattle have survived for this long thanks in part to natural selection to resist climatic extremes (including harsh, cold winters and hot summers), parasites, pathogens, as well as being very adaptable to rugged terrain, and foraging without requiring extra grains, among other things, has made them some of the healthiest, toughest and most rugged cattle breeds known to mankind, not to mention Nature. 

These cattle are in no way “artificial”; of course, they’ve been domesticated over time, but for many breeds even still today, the traits that many of these cattle have exhibited for thousands of years, before the advent of agriculture, have remained favourable and desirable to those people who care for them, to the point that it is quite ignorant to call all cattle in general “artificial.”  

The only time the term “artificial” may apply is if the commentator has only known cows as those infamous black-and-white bovine milking machines called Holsteins… 

Many breeds started out as multi-purpose animals; for milk, meat, and draft power (something which the commenter above failed to recognize). Some breeds were selected for use for work and meat, others for meat and milk. It’s only been in the last 100 years that certain breeds have well and truly diverged into two distinct types of cattle.

The popularity of few breeds for their specialized purpose of either milk (dominated by Holstein-Friesians, Jerseys and Brown Swiss), or beef (Angus, which is very popular in the United States, and the few dominating breeds well known for leaner beef and large sizes like Charolais, Simmental, Limousin, and Gelbvieh) has certainly skyrocketed. Breeds that were once very popular for draft work, such as Chianina and old Durham-Shorthorns have given away to a greater selection for meat since their jobs as oxen were replaced by motorized, fossil-fuel consuming vehicles (like tractors).  

Yet, many breeds are still raised to be dual-purpose and highly adaptable to the area they must live in. They may not be able to compete in the dairy-only or beef-only classes, but they can excel at being a part of an operation where they’re expected to be more than mere cogs in the commercial milk or meat industry machine. 

The resiliency of cattle is thanks to the recognition of their natural ability to require little to no assistance in raising their young and to perform well on forages alone. It may take a few generations for cattle to become adjusted to a particularly rough locale. This is nothing new to producers.

Generations of ranchers and cattlemen understand that they have two choices. In order to have good cattle for their area, they must financially invest in making those cattle work for them by pouring tons of mineral and grain in them (whilst running a risk of bankruptcy or getting so burned out that they decide to go into crops instead). Or, significantly reduce costs by letting Mother Nature help them select the best cattle for their climate. (There is a third option: liquidate the entire herd, and start again with genetics proven to be adapted to the area!) I love this phrase that producers often use: “Let the cows weed themselves out.” In other words, those cows that look worse than the other cows, with you doing everything right by them, need to be culled.

I speak primarily on beef cattle plus most dual/multi-purpose cattle. These animals are allowed to become well-adapted to their particular area, to develop pathogen and parasite resistance through some form of natural selection, and to be raised where they don’t require much additional TLC. When we look at commercially-raised dairy cows, like Holsteins, which spend most of their lives in a barn, they aren’t given the chance to become as hardy, tough, and adapted to their area. They are bred to produce more milk than what’s “natural,” and given feeds and forages suited for their production needs. 

I strongly suspect that the commenter here is confused about all cattle in general. They may be thinking that “all cattle” refers to those Holstein dairy cows. Such cows would indeed have trouble adapting to a harsh environment and have issues with various pathogens and parasites. No doubt this particular breed would experience heavy death loss over several generations than with tough beef breeds like Galloway, Hereford, Angus, Scottish Highland, Dexter or Devon. 

Realistically, Holsteins aren’t all breeds of cattle! They don’t represent the incredible capability of survival that many other breeds have when left to their own devices.  That’s not to say that some beef cattle fall into this harsh level of expectation. However, the fact is that there’s more variability within individuals than within breeds. Just like with bison, some animals are more susceptible to illness than others. Those individuals get weeded out the soonest.

So, to compare Bison (which, incidentally is much more efficient in its ability to extract nutrients even from relatively poor pasture, unlike Bos taurus, that needs good, clean, rich pasture).

As far as being ruminant grazing herbivores, bison really aren’t much different from cattle in that a large part of their diet is grass. However, there are some key missing components that don’t make bison “better” in every way than cattle. 

Studies (such as THIS one from the University of Arizona) show that bison tend to select for much more grass and sedges than forbs (or your broad-leaved plants), making forbs less than 2% (some earlier studies cite less than 10% such as THIS one) of their diet. Cattle are considered quite a bit less selective in their grazing habits. They eat more forbs and shrubs that bison prefer to leave behind. This harkens back to the age-old woodland/savannah habitat cattle originally came from that contains a higher forb component, unlike the prairie grasslands bison are adapted to. 

Cattle do very well on pasture with a large-legume-component (60% or higher). They can also be successfully trained to eat broad-leaf weeds like Canada thistle, and leafy spurge. Cattle will also strip leaves off of deciduous trees and shrubs when there’s plenty of grass to eat. You don’t see bison doing that; very, very rarely would you catch a bison stripping leaves off a willow tree compared to a cow! 

A study was done (from the February 2000 edition of the Tallgrass Gazette: How Bison Grazing Habits Affect Plant Composition) where researchers compared the effects of bison versus cattle on plant species composition (grasses vs. forbs) after several seasons of grazing. The results were surprising: The bison pasture had higher forb biomass. Bison were deliberately selecting for grasses, but not the forbs. They severely overgrazed their pasture in their search for grass. They refused to eat most of the forbs that took over.  In the cattle pasture, the plant composition was still largely grass with few forb species because cattle were consuming both grasses and forbs. While there was greater plant diversity in the bison pasture, most of these were annual forbs (“weeds”). Perennial plants, such as big bluestem, were few and far between. 

Thus, is it really true that cattle require “cleaner” pastures than bison? From the studies shown here, the obvious answer is NO. “Good, clean, rich” pastures aren’t enough for cattle; they will do more than fine on pastures with a high diversity of plant species–more than just grasses and sedges–to meet their nutritional needs. In other words, if a pasture has a whole host of edible, nutritious forbs that cattle can latch onto eating (like dandelion, thistle, lamb’s quarters, chickweed, hawkweed, willow herb, pigweed, kochia, and many others), so much the better! It looks like bison need cleaner, low-biodiverse pastures to get any nutritional value from. Picky eaters!

In addition, cattle are also better suited for grazing in smaller, fragmented parcels of grassland because they are able to uniformly grazing in smaller patches on top of not being such picky eaters. They also don’t have the sudden urge to travel for miles. Their domestication makes them easier to handle and move. (Generally speaking, as human training to stockmanship practices helps a great bunch too.) It helps when they’re regularly moved from paddock to paddock.  Bison, on the other hand, prefer vast open landscapes they can roam freely on, and eat all the grass they desire.

Here is another similar study that looked at grazing habits of cattle versus bison. Part of the abstract reads, “Cattle include more forbs in their diet, and they use wooded areas and riparian zones more intensively. At similar annual stocking rates, the amount of grass remaining at the start of the dormant season is higher under year-long bison grazing compared to growing season cattle grazing. There are inherent differences between bison and cattle, suggesting that they be managed differently. Under our respective management regimes, bison are less productive than cattle, but they require less processed feed and labor inputs.

It’s very true that bison can use coarser plant material than cattle. But it’s very wrong to think that means “poorer pasture.” Understanding the meaning of words and phrases is important here. Remember the mention above about cattle being less picky eaters than bison are.

When talking about “poor pasture,” one needs to tread very carefully. Unfortunately, the commenter was swinging her “facts” around like a pissed-off bull in a china shop. “Poor pasture” is full of unpalatable, undesirable plant species has soil compaction issues, has very few “desirable” species (or has little in the way of stuff animals would like to eat), is severely overgrazed, and is prone to erosion. Poor pasture is created by mismanagement, not by a particular grazing species! It doesn’t matter whether you have sheep or cows or pigs or bison or llamas or horses, it’s the human element that is responsible. The human element determines, by way of management, whether a pasture is either “excellent” or “poor.”

Let this be a lesson to you: NEVER confuse “poor pasture” with the presence of coarser, harder-to-digest plants like sedges or “hard” grasses. 

This is why I hate it when someone scoffs at management practices being nothing more than “PR campaigns” and uses that to justify the “fact” that cattle are poorer-doing on native pastures–all because they can’t eat ragwort. Yes, I just rolled my eyes. 

!! 

Speaking of which:

FFS Bos taurus can’t even tolerate RAGWORT, one of the most common weeds here in the UK… where the cattle has been around for thousands of years, but still does not know better than to avoid the bloody plants! ​

You know what? I’ll bet you a million bucks on a chocolate-glazed Boston cream donut that bison don’t dare touch ragwort (Jacobaea vulgaris syn. Senecio jacobaea) either.

Ragwort is a horrid-tasting, alkaloid-poisoning (compounds that are toxic to cattle, horses, pigs, and poultry) weed. The only other animals that have almost no problem eating this plant are sheep, goats, and deer. Like bison, they’re picky eaters (somewhat; goats will eat pretty well anything). Unlike bison or cattle, though, they prefer a diet comprised of mostly forbs and shrubs. 

In my previous blog post (see Pasture Weed Management Solutions vs. Going Vegetarian) I talked about ragwort and why it’s become a noxious weed in New Zealand (and the United Kingdom). What’s clear is that mismanagement is why ragwort is so prolific. It loves overgrazed pastures and lack of plant cover. It is highly opportunistic and will grow on bare ground and where other plants won’t compete with it for sunlight and water. 

Cows have birthing problems, because so many have been bred out of proportions, too fat, or pelvis too small, because the pressure on their selection has been meat or milk, not good calf-bearing.

At this point, it’s safe to assume that she’s trying to further justify her position of being strongly anti-cattle by putting down these last couple of points for good measure. While they’re unrelated to where we started with, they’re still worth debunking. 

The problem with this comment is that it’s a half-truth, and jutting out in the extreme. This comment on calving issues assumes that beef and dairy production is focused on selecting cattle for only milk (or muscle) and nothing else; a.k.a “single-trait selection.” This is a terribly one-sided and naive point of view. It doesn’t tell the whole truth; only the “truth” that she’s created inside her head. 

There’s no denying that calving issues (a.k.a “dystocia”) don’t happen because they do. Whether it happens because of single-trait selection is possible, but I’m no genetics expert to tell. That said, dairy cows are primarily selected for milk production. Maternal abilities and good body conformation kind of takes a back seat in the realm of milk production. I could be wrong. With beef breeds, I’ve heard plenty of horror stories with cowherds where a producer was trying to put more focus on growth and feed conversion rather than the more feminine side of things. Ick. I’ve also heard of horror stories where “the wrong bull” was used… yikes! Yes, the bull will take a large part of the blame for problems in the calving department.

Birthing problems will also occur due to severe weather, or hormone imbalances because a feeding program wasn’t planned correctly. Other stressful factors can cause the calf to present in weird positions in the birth canal.

Not only that, cows don’t have to be too fat to have a hard time pushing out a calf. They can also be much too thin and be presented with a tough delivery.

Generally, though, at least in North America, beef cattle are expected to be good mothers and calve with minimal or no assistance. It’s fairly easy to select for cows with good maternal capabilities. As I mentioned above, the ones who just can’t hold their own show up quite readily. Too, it’s a matter of selecting the right bull. He’s either going to put stronger maternal characteristics into the herd or sire smaller calves that grow like weeds. 

As to the environmental impacts… The issue is the NUMBERS of cows. This may come as a shock to you all, but actually America is NOT the world and the WORLD has a lot more cows than you can count! 😂 And each one of them generates so mush [sic] Methane you could rename them CH4OWS!

This particular statement is very loaded. It may require an entirely different article to debunk. But I can summarize my points well enough here.

The first major, major misunderstanding is her belief that there are too many cows in the world. This couldn’t be farther from the truth. Actually, we need more ruminants, not less. 

The evidence is from the mismanagement of the Earth’s landscape. More areas don’t get enough ruminant attention; a few get too much. It’s not their fault that this happens. It’s the human element as discussed above. So yes, it really does come down to one thing: Management. 

And yes, the number of cows can be counted; I may not be able to count them, but there are others out there who will do it for me, and make it so easy to find via Google. So, according to Beef2Live, there are just under 1 billion head of cattle in the world (2020 statistics). 

Of course, America isn’t the world! But just for shits and giggles, let’s look at cattle population by country (via Beef2Live). The country with the most number of cows in the world, is India, with 30.7% of the world’s bovine population (at over 303 million head). The United States has only 9.56% of the world’s population at around 94.4 million head. And Canada, my favourite country, sits at 11.09 million cattle, which has just 1.12% of the world’s bovine population. 

But again, numbers are irrelevant. The HOW that cattle are raised and managed creates the most problems in regards to environmental impacts. Methane output is just a tiny symptom and a symptom that has largely been taken out of context in more ways than one. 

Cattle are not the only species that produce a lot of methane. Bison are notorious for producing a lot of methane as well, as are sheep, goats, water buffalo, deer, caribou, and many others. It’s really not fair to point to cows alone as the sole blame for methane output.

Besides, around pre-settlement, bison represented between 84 and 93% of all emissions from wild ruminant animals. Today, because the bison population is far smaller than that of domestic bovine (and deer today take a larger chunk of the pie for being the highest number of wild ruminants producing methane), their methane emissions don’t amount to as much as they did pre-settlement. And it’s because of that that cattle get pointed at for being the largest source of methane.

Not only that but what most people don’t seem to understand is that methane is just part of the carbon cycle. Methane was never a significant issue in the pre-settlement, pre-Industrial Revolution era from the billions of ruminants that were running amok all over the world (Africa, Eurasia, North America, South America). There were intact grasslands and other biomes (forests, savannahs) that functioned well to help oxidize most methane before it reached the upper atmospheric echelons. Methanotrophs and hydroxyl radicals from intact soil microbial communities and perennial, green photosynthetic vegetation, respectively all work[ed] together to destabilize methane and reduce its potential to create the well-known heating effect it has in the atmosphere. 

If you want to read more detail into the methane crux of bovines, I suggest you check out Ruminations: Methane Math and Context by Post-Vegan, and WilderCulture’s Flatulence, Wildfires, and Bogs: The Madness of Measuring Methane.

Overall, from staying with me through all this mess, the question to ask is: Are bison really better than cattle? Yes, and no. Bison are no better nor no worse than cattle are. Bison have attributes that make them better at other situations and locations than cattle, and cattle have attributes that make them more favourable in situations and areas that bison would produce disappointing results with.

Here are a few good sources and posts on the bison vs. cattle debate that will give some wider perspective, which you may find interesting. 

Bison Good, Cattle Bad?? –  The Prairie Ecologist (This is a very good article to read.)
Bison Versus Cattle: Are They Ecologically Synonymous?
Are cows just domestic bison? Behavioral and habitat use differences between cattle and bison – Western Watersheds Project (Note: I’m not in agreement with a large part of what this organization represents, however this particular article they wrote makes some interesting points. But do take this with a grain of salt, as this group is quite anti-cattle grazing.)