Earlier this month, a beef-type cow in Florida was identified as having bovine spongiform encephalopathy (BSE), also called mad cow disease. For those old enough to remember, BSE was the cause of death (by disease and culling) of many thousands of cattle—most heavily in the United Kingdom—in the late 1980s through early 2000s.  Worse yet, it caused the deaths of a couple hundred people who had consumed beef from infected cattle (in humans, this is called variant Creutzfeld-Jakob disease).

The “bad” prion protein (PrPSc) converts normal PrP proteins.

The caused-many-deaths BSE is referred to as classical BSE, where the route of infection was due to ingestion by cattle of the infectious agent: a nasty little misfolded protein called a prion, specifically a prion designated PrPSc. Infection with PrPSc came from affected animals that were recycled into meat and bone meal and fed to other cattle. When the molecules of PrPSc get into the body, they go around refolding the native, normal PrPC proteins into the abnormal PrPSc proteins (see figure). As the disease progresses (over years), normal brain tissue becomes decidedly abnormal, and the animal’s behavior follows suit. Key symptoms of BSE include nervousness or aggression, abnormal posture, and lack of coordination. Cattle exhibiting such behaviors are not allowed in the food chain and are automatically tested for BSE.

Due to bans on the recycling of higher-risk tissues into feed, identified cases of classical BSE have fallen to essentially zero worldwide. What surveillance programs have picked up are a very few cases of what is called atypical BSE. The prions detected in these cases are slightly different at the molecular level from that in classical BSE. Atypical BSE arises from a spontaneous mutation in the gene that encodes the native PrP protein with the result that they start to misfold into a PrPSc-like shape. Like the atypical BSE-affected cow recently identified in Florida, these cases are not caused by infection from the outside.

Discovery of this “mad” cow (and the five others over the last 28 years) demonstrates that the surveillance procedures conducted by USDA are effective. At this point, USDA is testing about 25,000 cattle a year, and those are largely sampled from older or ill animals. USDA estimates the prevalence of BSE in the US at 1 in 1 million cattle.

Bottom line: we will occasionally see cases of atypical BSE pop up due to nature (mutations happen!) and our well-functioning surveillance system, but risk to the health of people and other cattle is exceedingly low.

Additional information:

on this recent case (August 2018; USDA)

USDA’s general information on BSE

CDC’s information on BSE

It is estimated that the world’s population is around 7.4 billion people. The US population recently climbed past 300 million people, as we continue to add a new person every 7 seconds. The United Nations projects that the world population will increase to 7.9 billion people by 2020. The huge majority of this growth (95%) will be in developing countries, where 77 percent of the world’s population already lives. These developing countries are also increasing their per capita consumption of meat, milk, and eggs.  Thus, the demand for animal products is expected to increase more rapidly than the total population.

I have listened to people debate the issue of feeding this ever increasing population and have wondered what needs to be done to continue to provide nourishment for all these people. Many argue we have no food shortage currently; we just have populations that are too poor to grow or purchase food. Regardless, I think feeding the world’s residents is a major challenge in years to come. I am convinced ruminant animals have a significant role to play in the solution.

I know my children have questioned for years why I get so excited about cattle and grass. I have tried to explain the unique role ruminants play in our lives, but I still am not sure they are excited as I am. Globally, around 55% of the world’s land is classified as pasture, grasslands, meadows, or forest-pastures that have the potential to produce 5.8 trillion Mcal of metabolizable energy. Around 50% of the 1.9 billion acres in the US is classified as range or pastureland. This is an extremely large resource that already is or can be used for food production.

Grazing ruminant animals is an efficient way to produce food for humans. Grazing animals on land that is unsuitable for crop production more than doubles the land area in this country that can be used to produce food. Ruminant animals can use plant cell walls as a major source of dietary fiber and energy. The polysaccharides in plant cell walls cannot be degraded by mammalian enzymes, which is why humans cannot effectively use grass as food.  However, ruminants are uniquely adapted mammals that depend on microbial fermentation in one of their stomachs, the rumen. With this adaptation, ruminants are especially capable at using plant fiber for energy. Fiber, measured as neutral detergent fiber (NDF), usually accounts for 30-80% of the organic matter in forage crops. The remaining organic matter is almost completely digestible by a ruminant’s own enzymes. It is this unique digestive system that allows ruminant animals to consume poor quality forages and transform them into high quality meat and milk. And because so much of the world is covered with range and pasture lands, it only makes sense that sustainable communities and sustainable agriculture include grazing animals.

Over the years, critics of animal production have argued we should be feeding human-edible foodstuffs (grains, protein sources, etc.) to only humans and not include these in ruminant diets. Too often the opponents of animal agriculture evaluate the desirability of animal production on gross calorie or protein intake/output values, with an assumption that all animal feed could or would be eaten by people. However, in many cases the feeds used in animal production are not consumed nor consumable by humans, and in order to properly evaluate animal production, only human-edible consumable energy and protein intake should be used for efficiency comparisons.

Many studies and evaluations have been conducted looking at the efficiency of livestock in converting plant based protein and energy into animal products. Non-ruminant animals like swine and poultry, cannot utilize low quality forages like ruminants can, but they are really efficient in their ability to gain weight eating grains. Ruminants, on the other hand, are less efficient in converting grains to animal protein. However, they can maintain and produce on a diet of 100% forage or by-product feeds if necessary. In fact, dairy cattle and goats are quite exceptional in being extremely efficient in converting plant-based protein/energy sources into high-quality animal fats and proteins. I believe the evidence that ruminant livestock belong in sustainable livestock production systems is convincing.

Ruminants have served and will continue to serve a valuable role in sustainable agricultural systems. They are particularly useful in converting vast renewable resources from rangeland, pasture, and crop residues or other by-products into food readily eaten by humans. With ruminants, land that is too poor or too erodible to cultivate becomes productive. Nutrients in all kinds of by-products are utilized and do not become a waste-disposal problem. In Oregon, waste products from the grass seed, vegetable, nut, tree fruit, and berry industries as well as brewing wastes are being fed to livestock.  It is clear to me ruminants are essential components in food production systems now and in the future.