These proteins are broken down by the animal to form urea, which upon excretion is broken down to ammonia which can then volatilize. As ammonia is derived from excesses in dietary protein feed formulation can greatly affect ammonia emission. Technically, this is certainly true. Practically, though, only small decreases in the protein content of a pig s diet are possible without increasing production costs. Another means to reduce ammonia emission is to alter the pH of excreta.
Ammonia emission is very sensitive to pH, with a lower pH resulting in lowered ammonia emission.
Nutritionally, urine pH is easy to affect. For example, for cat nutrition feed additives are commonly added such that urine pH is around 5, preventing urinary tract problems. For pigs, similar strategies are possible. Thus, removing this from the diet and adding an acidifying calcium source back to the feed would be of interest. Both these compounds are approved for use in animal nutrition and are acidifying compounds, thus lowering urine pH. However, both affect feed intake and can cause intestinal upset in animals, and feeding experiments have demonstrated that they are not desirable as sole replacements of limestone.