Urolithiasis (stones in the urinary tract) is caused by an imbalance of calcium and phosphorus in the diet. Calcium in the diet should be 2.5 times more than phosphorus. Alfalfa hay is high in calcium and grains are high in phosphorus. When lambs are eating 3-4 lbs of grain per day and a pound or less of alfalfa, the phosphorus is too high for the amount of calcium. The excess phosphorus which is absorbed into the blood stream from the intestine, is thrown away in the urine. Unfortunately when the phosphorus gets too high in the urine, it forms crystals. The crystals have very sharp edges and look like tiny grains of sand. These bits of sand will pack into stones and plug up the tube that take the urine from the bladder to the outside (the urethra). Since this tube is much smaller in males than females, this disease is seen only in the wethers and rams.
When the tube becomes plugged, the urine often leaks out into the tissues, or the bladder ruptures. Since urine is toxic to the animal, the lamb will die of urea toxicity.
If the diet is imbalanced, often the “sand” will collect on the hair of the prepuce (the skin covering the penis or the end of the sheath). You can run your hand along the prepuce and feel the gritty crystals that are collecting on the hair. If so, its time to change the diet.
If the stones have already formed, the lamb will act depressed and stop eating. He will stand with his hind legs stretched out behind him. He may walk stiffly and reluctantly. Sometimes a swelling will be apparent in the sheath area. He will strain to urinate. If the plug has not completely obstructed the tube, he’ll dribble urine and urination may take a long time; however, if this is the case, he will probably still eat and not appear particularly depressed.