Cattle can die from eating twine or net wrap left on big bales or put through the bale processor. And Dr. John Campbell, head at the Western College of Veterinary Medicine, in Saskatoon thinks it happens more often than we think.
“I don’t have a lot of data, unfortunately, but I’m starting to believe this is a bigger problem than we give it credit for. I recently did a herd investigation in which a fairly well-managed cow-calf herd had six cows die over a period of two days. The local veterinarian asked me to stop by and I was able to necropsy two cows that had recently died. The cows were close to calving and in reasonable body condition,” Campbell says.
“The rumens were very large and full of feed and I found large amounts of plastic net wrap occluding the outflow in both rumens. The producer had used a bale processor but did not remove net wrap when processing bales. I believe the cows ingested these large pieces of net wrap and it was probably not an issue until they became heavily pregnant. Once the fetus got large enough to restrict abdominal space, the rumen became occluded and huge, and the cows died of what appeared to be suffocation. Lying down on a hillside may have played a role as well.”
This scenario is becoming more and more common, but unless the unfortunate animal is cut open to determine the cause of the problem many producers never know what happened. Necropsy may reveal wads of net wrap or baling twine. The cow may ingest these when they are left on the bales, or consume rebaled twines or bale wrap that were out in the field and ended up in the next crop of hay.
- More on ‘twine’ from the Canadian Cattlemen: Bale grazing on the Niagara Escarpment
The most common symptoms are poor appetite (some cows stop eating entirely), weight loss, diarrhea, or sometimes a too-full rumen and suffocation. The producer may do nothing to try to save the cow because of the high cost of surgery, and because the symptoms are vague. People might suspect BVD, hardware, Johne’s disease, salmonella, E. coli, liver flukes, coccidiosis or internal parasites.
“The herd I investigated had multiple cows that all died within a few days of each other, possibly because they were heavily pregnant. The full rumen and large uterus may have put too much pressure on the lungs. In other instances the net wrap may become entangled with all the food material and create blockage at the exit into the intestine. This creates a slower demise, with the cow losing weight for a period of time.”
The ingested material may be small amounts of chopped-up net wrap, or a large piece that was left on a bale — or was not chopped up by the processor. “Perhaps the blades are dull, or the net wrap gets wound around them, or for whatever reason sometimes the processor just shoots that wrap out in one big piece and doesn’t chop it up. In this particular instance it was pretty obvious that the processor was not chopping up the wrap,” says Campbell.
- More from the Canadian Cattlemen: Bale grazing
“One of my colleagues thought maybe the cows ate it because they’d run out of feed; some people wait until the cows clean up the previous feed before feeding them again. I’m not sure if that’s a reason or not, however, because cows will eat all sorts of things even if they have a lot of feed. Once they start chewing on something like baling twine or net wrap they tend to keep wadding it into the mouth and usually swallow it,” he says.
“I think that sometimes the ingested pieces don’t affect them much when they are not pregnant. There is enough room in the rumen for a fair amount of foreign matter to roll around in there without obstructing anything. But once a cow gets heavily pregnant with a big fetus pushing up against the rumen, this makes it more difficult for that foreign material to move around in there. It may get wedged in the wrong spot. It might suddenly obstruct the outflow of the rumen. In some cases it might completely block the outlet and the food can’t go on through the tract.”
The cow can’t eat much because the rumen is full and unable to empty itself. She loses weight because she’s not eating enough, and not much material is going through the tract. These cows waste away and may have diarrhea because only the fluid contents of the rumen can make it past the obstruction.
“The pregnant cows I observed were in good shape, however, and dying suddenly. Their rumens were full of feed, and they had a big calf in them, and when they lay down on a slight hillside with pressure on their lungs, they essentially suffocated. One of the cows I opened up had just started to calve. The calf’s legs were entering the birth canal. She may have laid down to calve and couldn’t breathe adequately because of the full rumen,” says Campbell.
“These cows died so quickly that they didn’t lose weight. But in a cow that isn’t heavily pregnant you might see the opposite scenario — with cows losing weight over a period of time, and poor appetite. The net wrap could cause an obstruction to where they are basically impacted and not much solid feed going through,” he says.
“The rumens of the cows I opened up were gigantic. It took a lot of time to wade through all the feed material in the rumen to find the net wrap. It would be easy to miss if you weren’t looking for it, even though these were really big wads,” he says.
“I don’t have any idea how common this problem is, or how often we’re missing it. For that producer who lost the six cows, you wouldn’t know whether he’d have 10 more cows die, or no more cows die. Certainly you could look for and diagnosis this condition in the heavily pregnant cow if you saw a cow that was really full on the left side and you palpated her rumen and it was hard and impacted, rather than full of gas,” says Campbell.
“You could do a rumenotomy — open up the rumen and search for the foreign material. It wouldn’t be an easy job, with all the food material in there, but it would be something a person could try. That’s what I told the farmer — that if he had any more cases and suspected a problem he could palpate the left side of the abdomen. If it’s big and hard this would be something we could try.” It might be a chance to save the cow.
“It would be an extensive surgery because you’d be pulling material out of that rumen for quite a while before you could get it all out. A lot of that stuff was hard and dry, and packed in there pretty tightly, in the cows I opened up. It would take some time, but a person could do it,” he says.
The plastic material doesn’t seem to break down, so it could potentially stay in the rumen forever. “Small pieces might pass on through, but big chunks would probably stay in the rumen and roll around in there indefinitely, and might cause problems.”
In this particular instance the bale processor had not chopped the net wrap up into little pieces like you’d expect it to. “It seemed to wrap around and then shoot it out in a big wad now and then,” he says. You often see big pieces lying out in the field after the cows have eaten the hay. Some people gather it up afterward, but some don’t. It might be a good idea to gather it up or take it off the bales before feeding them, but that can be a challenge at times — if there has been moisture that’s frozen the net wrap to the bales. It can be almost impossible to get it all off.