South Dakota cattle are dying from eating plastic hay bale netting. Here's how to prevent it.

Dominik Dausch
Farm Forum
A large wad of plastic lies where the stomach of a partially decomposed skeleton of a cow would be. Recently, livestock veterinarians have noticed a trend in which cattle, killed by an unknown or misdiagnosed illness, also contain softball- and basketball-sized clumps of net wrap, a popular hay bale binding material, in their digestive system.

Few things are more frustrating for a cattle rancher than losing livestock to disease.

But it's double the headache when a cow dies for reasons unknown. Unfortunately for producers and their veterinarians, mysterious deaths seem more common lately.

That's according to Russ Daly, state public health veterinarian with South Dakota State University. He told Farm Forum in a phone interview that livestock vets are noticing more cows coming to their clinics with symptoms similar to the often-fatal Johne's disease, an infection often found in the small intestine.

On the surface, that seems simple enough. But once those cattle end up on the operating table, some veterinarians are finding an entirely different — and disturbing — issue: plastic.

Bale net wrap can be deadly to cows

Some vets are finding wads, clumps and globs of plastic in the stomachs of cattle, Daly said. The foreign bodies vary in shape and size: some are stringy strands of ground plastic as long as 12 inches, while others are large wads about the size of a basketball and weigh around 1 to 2 pounds.

A large clump of plastic net wrap removed from a cow's stomach lies on the ground. Russ Daly, state public health veterinarian with South Dakota State University, said he has noticed more producers taking their sick livestock to diagnostic labs over the years, and cases in which significant amounts of plastic are found in their digestive systems are becoming more common.

According to Olivia Amundson, cow/calf field specialist with SDSU Extension, the problem stems from net wrap, a plastic covering that farmers use to organize piles of hay. The material is literally wrapped around the feed using a baler, which is what gives hay bales their iconic circular-shape. 

"The big thing is guys just don't remove net wrap," Amundson said.

"Leave net wrap on a bale and the cows will get into it because cows get curious and will eat anything. I've seen cows munching on net wrap. You just know that's probably not the best for them," she said.

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The cow specialist calls the problem "software disease," a reference to the more commonly known "hardware disease" (medically diagnosed as bovine traumatic reticuloperitonitis), or the ingestion of inedible items like nails, screws and cut-up metal fencing.

Cattle can't digest plastic around hay bales

Similarly to hardware disease, the ingestion of plastic can disrupt the appetite of cattle and cause them to lose weight over time. Daly said that in most cases, loss of appetite and the resulting weight loss are the lone indicators of plastic-related illness, which can lead a veterinarian to misdiagnose the condition.

When cows ingest something, it accumulates in the rumen, the first of four stomachs in cattle that stores feed and sustains bacteria that aid in digestion. Plastic, Daly said, cannot be digested by the cow's stomach and will gradually ball-up if enough is ingested, potentially wrapping around internal organs, cutting the intestines of cattle and causing an infection.

Because of the lack of outward symptoms, the problem can be a slow-yet-silent killer.

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"If it gets big enough, it's going to block the esophagus. It just kind of plugs up the way for digestion to take place. So, it would be something that causes long-term chronic kind of problems rather than an acute death," Daly said.

However, while hardware disease can be treated, there are no treatments for plastic ingestion.

"There's nothing that can screen out on a particular cow that (indicates) yes, this cow is having problems because of an accumulation of net wrap. It can look like so many other things. So, in that regard, you'd have to assume that problem is sort of underestimated," Daly said.

While other hay binding materials exist, Adele Harty, another field specialist with SDSU, said net wrap is currently the most popular material to bind hay. That can be attributed to time and money, Harty said. Plastic netting is quicker and easier to wrap around hay and often cheaper than twine.

Additionally, Harty said net-wrapped bales often hold a tighter and rounder shape better than those wrapped in twine. A tighter bale better prevents snow and rain from building up on top of the hay and consequently prevents mold from developing.

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Harty speculated about 75% of all hay bales in South Dakota are wrapped with the plastic, and an SDSU survey conducted in 2017 found that 67% of farmers and ranchers preferred net wrap, 26% preferred twine and 6% used both for binding feed.

"The equipment is being built around it, so most of the new balers are just using net wrap," Harty said.

Removing wrap is helpful, but takes time

Midwestern farmers typically unroll hay bales between December and April to keep cattle fed during the winter months, but Harty said some farmers are not removing net wrap from their bales.

The problem with net wrap removal, Harty said, is that it takes time and manpower to fully remove the plastic from the hay, which ultimately costs producers money. Unwrapping one bale usually requires between 45 seconds and a minute, but can take longer in the cold. Depending on the size of the herd, one farm might unwrap more than 100 bales in a day, which can take hours to complete and pull attention away from other important tasks.

Net wrap removal step: 1. Remove top one-third of bale. 2. Wrap around body of bale, make loop knot. 3. Once secured, take remaining net wrap off of bale. 4. Remove rest of net wrap.

Additionally, Harty said net wrap removal is best done with at least two people, which may force producers to hire extra hands specifically to unwrap the bales.

"It really is a two-person job to really be efficient. If you're by yourself, you're going to have to be really efficient since there's going to be a lot of jumping in and out of a tractor," Harty said.

With that in mind, Amundson said some producers opt to simply shred the plastic-wrapped hay bales prior to feeding in hopes that the smaller pieces, despite still being consumed by the cattle, will eventually and more easily pass through their systems. However, in a study led by Harty, SDSU researchers found that even shredded plastic will continue to clump together inside the rumen of cattle when ingested.

"I think the idea of, 'Oh, we're just grinding it up. It's just gonna pass through,' is prevalent," Amundson said. "It does become an invisible issue. Out of sight, out of mind, right?"

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Either way, she said ingesting plastic can prove deadly for cattle and also hurt farmers financially.

"(Cows) could potentially die even though they have a few more productive years on them … It takes seven to nine calves to make a cow worth it, so if they're dying before that, they're costing more than they're worth," Amundson said.

Study shows cattle accumulate plastic in stomach

In order to understand the scope of the issue, Harty wanted to examine how quickly net wrap would accumulate in a cow's digestive system during a standard five-month feeding period.

As part of the SDSU study, Harty's research team placed six cows on a diet of grass hay bales wrapped in net wrap and ground in a 5-inch screen in order to examine whether cattle with plastic already in their system would accumulate more plastic. Three cows had net wrap surgically placed in their rumens and three did not.

An SDSU researcher pulls out a large clump of net wrap plastic directly from one of the stomachs of a cow. An SDSU study, "Evaluation of ruminal net wrap accumulation in cows fed ground hay," mimicked the process of feeding cattle shredded hay bales and measured significant amounts of plastic in their systems within a standard feeding period of 140 days. A cannula — the circular porthole-like opening in the cow's side — is used by animal scientists to study the digestive system of cattle.

Harty said the study could not prove whether cows already exposed to plastic would accumulate more than others, but added all cows exhibited consistent accumulation of net wrap in their rumen.

"Just in one five-month feeding period, what we collected was over a gallon of wrap, which I know doesn't sound like a lot," Harty said. "But if you feed them for five winters and plastic's taking up five to six gallons of rumen, that's when you might start seeing those impacts. The total capacity of a rumen of a cow is 30 to 50 gallons, so my question was, 'How much net wrap can you see in the stomach before you start seeing negative effects?' We didn't answer that question. That will take more research."

"That plastic is not digestible. For the mort part, that plastic stays in one of the cow's stomachs. Some might pass, but that's a really small percentage of it," Daly said.

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Because the study was just a snapshot of the issue of plastic accumulation, a bigger question still remains: just how many cattle have plastic in their stomachs?

Harty said that, unfortunately, there isn't a convenient method of measuring or finding evidence of plastic in cattle. Some that ingest a small amount of net wrap will easily survive. It's the gradual intake of plastic that kills, she said.

In most cases vets are not called to do postmortem exam

And not every mysterious death is being looked into. According to the 2017 survey, only 26% of producers had a veterinarian conduct a postmortem examination following the death of a cow, even though 30% of those exams discovered net wrap in their systems.

"In prior years, nobody was using this product, so not as many animals were brought into the lab." Daly said. "The question of prevalence is hard to wrap our heads around, pardon the pun, because it doesn't impact every cow out on a farm. Some cows will get on just fine. But we are seeing more cows come in with large wads in their stomach."

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He said that net wrap-related deaths, inconvenient to the bottom line and time of farmers, can be prevented by simply unwrapping the hay.

"Because we don't really know the numbers of how prevalent this is … I fear that it gives our producers a free pass," Daly said. "I think of it as another thing we can do to protect the health of our cows."

Dominik Dausch is the agriculture and environment reporter for the Argus Leader and editor of Farm Forum. Follow him on Twitter and Facebook @DomDNP and send news tips to