The six bacteriophages were highly susceptible to acidity at pH 2 and susceptible to varying degrees to overnight exposure to pH 3 to 4 and ability to survive well over the pH range between 5 to 9 is a common feature in bacteriophages. JH4 and JH6 bacteriophage were susceptible to low pH while bacteriophage JH5 was susceptible than the others. Hazem (2002) had reported that bacteriophages are often quite sensitive to protein denaturation in an acidic environment, which may result in a loss of viability of the bacteriophages. He found that many bacteriophages are stable at pH 3 or 4. The pH in the stomach of weaned pigs may be as low as one to two before a meal and may rise quickly to four to five after the meal, depending on the diet and the feeding regime (Snoeck et al., 2004). The six bacteriophages will likely undergo a marked reduction in titer following oral administration to pigs unless steps are taken to reduce their exposure to low pH in the stomach and upper small intestine (Jamalludeen et al., 2007).