About 4 ozs of sodium benzoate per gallon of urine will preserve the urine the same as one cup of pickling salt. However, the sodium benzoate will not serve as an anti-freeze in cold weather so one might need to add glycerine or propylene glycol too if they live in a cold climate. I don't think zinc valerate would be a good idea for urines unless one is wanting to make a lure out of the urine. Zinc Valerate has a distinctive odor that would change the natural urine odor. I should also point out that good quality, clean urine that has been collected properly and strained of food particles should not need a preservative. If stored from season to season urine should be kept in a cool, dark place and stored in glass bottles. Plastic is porous and allows the amonia content of the urine to escape resulting in a flat smelling product. Light is the destroyer of urines and lures as it breaks down and changes their composition. Ace
