The invention relates to methods for the accumulation and retention of immune-enhancing, bacterial-derived ribonucleotides smaller than 10,000 Daltons (ORN<10 kDa) in bacteria that are produced when bacteria are grown naturally, allowing the pH of the growth medium to become acidic. The immune-enhancing, bacterial-derived ribonucleotides (ORN) and bacteria comprising ORN are useful in the preparation of animal feed or animal drinking water as well as for use in enhancing the immune system of an animal and/or its resistance to infection. The invention also discloses methods of preventing the loss of ORN during bacterial production and storage as well as methods to aid in the release of ORN when consumed by an animal.