Cattle occasionally develop urinary calculi — kidney stones or bladder stones that are mineralized clumps in the urinary tract. In cattle, bladder stones are more common than kidney stones.
Smaller stones usually pass out with the urine but sometimes become caught and create a blockage. This happens more frequently in males, and rarely in females due to their larger and shorter urethra. Blockages are also more common in steers than bulls, because an intact male’s urethra is slightly larger that of a steer’s.
Andrew Niehaus, Ohio State University assistant professor of farm animal surgery, says one of the biggest risk factors for urinary calculi is diet, specifically grain, which is high in phosphorus.
“We often see struvite stones, made up of magnesium ammonium phosphate, when animals are fed cereal grains. We see calcium carbonate stones when animals are on a high-calcium diet, like alfalfa and clovers.” A balanced diet is important, says Niehaus, who strives for a calcium-to-phosphorus ratio of about 2 to 1 in cattle diets.
Body pH is another factor. “Struvite stones tend to form in alkaline urine. Herbivores tend to have alkaline urine, whereas carnivores tend to have acidic urine,” he explains.
Matt Miesner, Kansas State University associate professor, says most animal species are susceptible to urinary calculi under the right conditions, but some animals are more prone to developing stones.
Cattle on feed, small ruminants eating grain and show cattle eating lots of carbohydrates are most at risk to develop struvite stones, but pasture animals can develop a silicate type of stone, he says.
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In addition to diet, dehydration is another risk factor, Niehaus adds.
“If the animal isn’t drinking enough water, urine becomes concentrated,” he says.
“If the diet leads to high mineral content in the urine, this makes a double problem. Mineralized salts may crystallize or clump together into stones. The animal needs plenty of water to keep the urine diluted and to help flush out any stones that start to form before they get very large. Reduced water consumption due to cold weather, frozen water or a shortage of water is always a risk,” he says.
Look for clues
The common signs of bladder stones include difficult urination or a lack of urine, Miesner says. “Healthy ruminants are frequently passing manure and urinating. If an animal is lethargic or off by itself, we first check to see if it’s urinating or defecating. We need to know if the animal is passing urine, especially in a feedlot situation,” he says.
Clinical signs in early stages of blockage are going off feed, a hunched back, obvious discomfort, straining to urinate, and a stretched-out stance with the tail waving or switching due to irritation, and sometimes urine dribbling. If the animal seems a bit off, make sure it’s able to urinate, he advises.
Miesner suggests checking the end of the animal’s sheath to see if it’s wet. Since cattle urinate often, it should always be moist. If you suspect a problem, observe the animal long enough to see if it can urinate normally.
After a couple days of not releasing urine, an animal’s bladder can burst or the urethra tear, he says. “If the bladder bursts, the animal often feels better for a while because pressure is relieved. If the urethra breaks, we generally see a bulge where urine is accumulating under the skin, under the belly,” Miesner adds. A rectal examination can determine if the bladder is enlarged.
Water belly vs. urethral rupture
Water belly is so named because the bladder continues to enlarge until it bursts, with the urine then accumulating in the abdomen. “In some cases, I’ve drained off 20 gallons of urine,” Miesner reports.
Even if a distended bladder doesn’t rupture, it can become leaky. As the bladder wall gets thinner with stretching, urine begins to seep through, with droplets forming on the outside, he says.
“The bladder is a remarkable organ and can generally heal, even if it ruptures. Sometimes by the time these animals are brought to the clinic, their bladder has healed and becomes large again if the blockage is still there. We can surgically repair a bladder because it heals so readily. The bigger issue is electrolyte imbalance [which can be fatal] when urine goes out into the tissues,” Niehaus says.
If the urethra ruptures, urine flows into the surrounding tissues. “The location has more to do with where the stone lodges rather than pressure. The bladder ruptures due to pressure when overly distended, but the urethra can withstand a lot of pressure before it ruptures. But if a stone lodges tightly, such as where the urethra makes a sharp bend at the sigmoid flexure, it may cause damage and necrosis, creating a weak spot. The wall basically rots out and ruptures,” he explains.
“Signs of urethra rupture are different from bladder rupture. Instead of accumulating in the abdomen, urine seeps through subcutaneous tissues in the ventral abdominal area [underline of the belly]. There is swelling from the scrotum all the way down the lower abdomen — a huge plaque of edema. It’s a firm swelling, but if you push it with your finger, it will leave a dent, like pressing into dough,” Niehaus says.
“In steers, we often do surgery to dissect down to the penis and urethra, and redirect the penis [to avoid the blocked area] and bring it out the back,” Miesner says. “This rerouting [urethrostomy] is often called a ‘high heifer’ or ‘low heifer,’ depending on where it comes out. If the obstruction is at the distal sigmoid flexure [the most common location], we redirect the penis above that,” he explains.
The urine then has an outlet. It may just dribble through that opening, but the animal may also be able to forcibly urinate. “These animals will posture to urinate, and you don’t want to be behind them when they do!”
Niehaus says that if surgery can provide an exit for urine, the animal generally survives, with a good prognosis. Even if the bladder has burst, sometimes this surgery allows it to heal, providing an outlet above the blockage to take the pressure off.
Urethra surgery to repair a rupture, however, has less chance of success. “There is usually so much scar tissue at the rupture site that it tends to close off again. The best option is to reroute the penis to the rear. They then urinate like a female, below the rectum,” Niehaus explains.
“Surgery to reroute the urethra will get these animals past the crisis of blockage and may last about six months, which is enough to get the animal to slaughter. It allows time for healing and clearing of the urine products from the body. Just like drug withdrawal, the animal needs adequate time to get rid of all these toxins before he can be taken to slaughter,” Niehaus says.
Of course, if the urethra is rerouted in a bull, that animal no longer can breed. “If it’s a valuable bull, we may try a different surgery, called tube cystostomy,” Miesner says.
“We lay them down, open the abdomen, find the bladder and insert a tube. We redirect that tube out another hole we create from the surgery site on the lower abdomen. This allows the bladder to drain while it heals, and we hope that the animal will pass the stone, after which we remove the tube. In some instances, we just dissect down and try to find the stone and remove it, and hope the urethra will heal,” he explains.
The prognoses on these options are guarded, however. “You may spend thousands of dollars and still fail to have a breeding animal,” Niehaus says. “But we can put a tube into the bladder for a short period to provide an outflow for urine and avoid a distension or rupture.
“We medically manage these animals, giving them ammonium chloride and a lot of water to try to dilute the urine and dissolve the stones that are present. We hope the stones will dissolve or the urethra will relax enough that the stones will pass,” he says.
After a time, the tube is clamped off to determine if the animal can urinate normally through the urethra. If he can, the tube is removed. The average cost of this procedure is about $1,500, compared to about $200 for a urethrostomy, Niehaus says.
“Another option for a valuable breeding animal would be to put a scope up the urethra to find the stone, try to grab it with a little basket, and pull it out. The method chosen depends on the animal’s value and use, how long it’s been blocked, and whether the bladder or urethra has ruptured,” he explains.
Ruminants are tough and have an amazing ability to withstand a ruptured bladder or urethra (and can survive the aftermath of urine in the abdomen and body tissues) and then heal. “They seem to be able to metabolize urea and don’t get as sick as a horse or dog,” Miesner says. “We put them on antibiotics, however, especially if the urine has seeped under the skin,” he says.
Broad-spectrum antibiotics are administered, as well as anti-inflammatory drugs, to help them feel better and keep eating. Urine in the tissues is very irritating. Regarding drug withdrawal time, it always needs to be extended because of uremia from accumulation of urine in the tissues.
“In this situation, you should discuss with your veterinarian what the withdrawal time might be and how soon the animal could be sent to slaughter,” says Miesner. The earlier the problem is recognized, the quicker it can be resolved, which means a better chance for the animal and a shorter withdrawal time.
The pH of the urine can be a factor in stone formation. “If animals are having problems, we check the urine,” Miesner says.
“Since struvite stones tend to form more readily in alkaline urine, we try to acidify the urine with ammonium chloride. This, and other urine acidifiers, may be included in feedlot rations to try to prevent stone formation.”
Other methods include changing the electrolytes in the feed by adding ions to reduce or keep pH to a minimum, and change some of the electrolytes that go through the urine, he adds. This is sometimes an option in treatment as well as prevention.
“If the animal is dribbling [not totally blocked], we may try to acidify the urine. This may help prevent more stone formation and, additionally, makes the animal want to drink more water. If we can dilute and acidify the urine, we might be able to break down the stones.”
This could be a treatment and prevention if the animal has small stones.
Niehaus sometimes recommends adding salt (sodium chloride) to the diet. “This will increase water consumption and help keep the urine more dilute,” he explains.
“If one animal in the group has symptoms, and you recognize this as bladder stones, you could try these options to prevent this in the others,” Miesner adds.
More risk for young castrates?
Niehaus, Ohio State University assistant professor of farm animal surgery, says most of the animals he sees with urinary obstructions are castrated males, which tend to have a smaller-diameter urethra than bulls. He says age at castration can also be a factor.
“Some folks recommend waiting until 6 months or so of age to allow the animal’s urethra to become bigger before castration. Some sources claim the urethra can be up to 50% bigger in intact animals or animals castrated at a later age,” he says.
But that’s more of an issue with longer-lived animals such as goats or pets, he adds. Most cattle veterinarians recommend early castration for steers, which generally are harvested before two years of age because early castration is easier on them at a young age, with fewer health risks and complications.
“We still see urinary stones in intact males as well as steers, so there’s no guarantee that castrating late prevents blockage. But testosterone, as the male animal grows, influences urethral diameter, and this plays a role in whether these animals will become obstructed or not,” he says.
Niehaus believes that genetics may also play a role. “Some cattle never have a problem even if castrated at a day of age and fed a diet of grain or clover and become dehydrated; they still won’t get blocked. Other animals, even if you do everything right, become blocked,” he says.
“I think genetics plays a role. For instance, blockage occurs more frequently in some types of goats. I also wonder if there’s a genetic component in cattle, though I don’t know what breeds or bloodlines might be more predisposed. Perhaps certain animals have smaller-diameter urethras,” Niehaus adds.
Heather Smith Thomas is a rancher and freelance writer based in Salmon, Idaho.
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