The objective ofthis work was to evaluate the effects of levels of nucleotides in diets forweanling pigs on performance, organs morphometry and histology of intestinalepithelium. One hundred and forty-four pigs weaned at 21 days of age and with5.80 ± 0.16 kg initial live weight were used in a completely randomizedexperimental design with six diets, six replications per diet and four animalsper pen (experimental unit). Diets were: Am _ antimicrobial: basal diet with40 ppm of colistin sulfate and basal diet with 0, 150, 300, 450 and 600 ppmof nucleotides. At the end of the experimental period, one animal of each penwas slaughtered to evaluate morphometry of the organs and intestinal epitheliumhistology. From day 1 to day 14 of the experimental period, performance traitsworsened linearly and for the total experimental period of 34 days, a linearreduction of final live weight was observed when levels of dietary nucleotideswere increased. Pigs fed diet with colistin showed greater length of small intestineand lower villus height:crypt depth ratio (AV:PC) of duodenum when compard tothose fed nucleotides. Also, a linear increase of relative weight of spleen,as well as a linear increase of AV:PC and linear reduction of crypt depth ofduodenum were observed with the addition of nucleotides in the diet. Therefore,although the addition up to 600 ppm of nucleotides in complex diets did notimprove performance, it improves morphometry of the organs and intestinal epitheliumhistology of weanling pigs.
