Animal have a continuous requirement for nucleotides (puri- nes and pyrimidines), especially for systems that present a high rate of cell turnover, like the immune system. Nucleotides may become semi-essential nutrients under certain circumstances (e.g. weaning period) because endogenous synthesis may be insufficient to sustain normal function. In this case the immune function depends upon dietary nucleotide sources.

The aim of the present study was to test the impact of a nucleotide supplement specifically designed to mimic nucleotides in bitch’s milk (Nucleoactive, Bioiberica, Spain) on the immune function of weaned puppies.

A total of 21 beagle male and female puppies weaned at 8 weeks of age were allocated to 3 balanced groups and fed during 35 d with 3 different diets: 1) a standard commercial diet for puppies (control diet, group C); 2) a control diet supplemented with 900 ppm of nucleotides (group A); or, 3) a control diet with 1350 ppm of nucleotides (group B). One week after weaning, puppies were vac-cinated against parvovirus with a heptavalent vaccine (Vanguard-7, Pfizer, Spain). Blood samples were taken after 24-h, 21- and 35-d post-vaccination. At these time points, plasmatic concentrations of C reactive protein (CRP), non specific immunoglobulins (IgG, IgM, and IgA) and antibody titre against parvovirus were analyzed. On d 35 peripheral blood mono-nuclear cells (PBMC) were isolated and cultured in the presence or absence of phytohaemagglutinin mitogen (PHA). Net stimulation of PBMC was measured and expressed as optical density. The level of CRP peaked in all groups 24 h after vaccination. As shown in table 1, increments from basal values were higher in group A than B and C (40.0a ± 7.6; 10.3b ± 9.9; 2.7b ± 3.7 mg/l for A, B and C groups respectively; P<0.05). Higher increments of antibody parvovirus titres (P<0.05), 21 d after vaccination, were detected in groups A (1334a ± 165) and B (855a ± 175) than in C (573b ±173). No differences in parvovirus titres were detected 35 d post-vaccination. However, plasmatic increments of IgG, IgM and IgA with respect to basal values were greater in B than in groups A and C (P<0.05).