Nucleotides are continuously synthesized and degraded in tissues, especially in those with faster turnover (immune system, gastro-intestinal mucosa, skin, hemopoietic production, replication of lymphocytes and leukocytes). Nucleotides in the body can derive from 3 pathways:
- de novo synthesis: high demanding metabolic pathway that involve amino acids degradation
- endogenous recovery: in standard condition represent the main source of nucleotides, however endogenous recovery is limited by purine and pirimide availability
- diet: crucial for the aforementioned tissues and in conditions of high growth rate, stress and disease that heavily impairs nucleotides’ synthesis.
Nucleotides content in most of the feed is marginal (Tab. 1), therefore a supplement of nucleotides across critical stages with nucleotides’ rich products, such as weaning of piglets or juvenile stages of fish and shrimps.
Table 1 Nucleotides content in some raw materials (Mateo & Stein 2004; Tonini et al., 2010)
Sows’ milk nucleotide content progressively declines with lactation (Figure 1), thus limiting nucleotides provision in critical period. The addition of nucleotides in the diet of lactating sows improved milk nucleotides content (Vitagliano et al., 2014) and piglets’ growth rate (Hung et al., 2015). In weaned piglets’ nucleotides supplementation limited the morphological alteration consequent to the lower feed intake that occur at weaning (Domeneghini et al., 2004) and improve immune local immune defense at gut level in piglets reared in a challenging environment due to poor hygienic conditions (Waititu et al., 2017).
Nucleotide supplementation is also fundamental in aquaculture. As reviewed by Ringø (2012), nucleotides supplementation reduced mortality and improved immune function in tilapia, carps, trout, Atlantic salmons. Moreover, nucleotides supplementation improved immune response and survival rate of shrimps challenged with white spot syndrome virus (Andrino et al., 2012), Vibrio proteolyticus infections (Madalla et al., 2013) or due to a change in salinity (Hertrampf, 2003).
Feeding nucleotides to stressed animals can therefore improve their resistance, with a beneficial effect on growth performance and reducing disease prevalence.