Effects of Passive Immunization against Peptide Tyrosine Tyrosine on the Growth Performance and Endocrine Hormone Levels in Blood Serum of Rats

The aim of this study was to determine the effects of immunization against Peptide tyrosine tyrosine (PYY) on the growth performance and endocrine hormone levels in the blood serum of rats. Sixty Sprague-Dawley rats were randomly assigned to four treatment groups, with five replicates in each group and three rats for each replicate. The antiserum of PYY was injected into the rats thrice every 8 days at the concentrations of 0 (control), 50, 100 and 200 &muL. Throughout the experimental period, the rats were given free access to food pellets and water. The growth performance of the animals, including their average daily gain, average daily feed intake and feed/gain ratio, was recorded. The blood samples of PYY, Neuropeptide Y (NPY), leptin, gastrin and insulin concentrations were measured. The good effects of PYY antiserum on the growth performance and serum indexes of treat groups were observed in this trial, especially in group 3 rats. The average daily gain recorded for days 8-14 and 15-21 in group 3 increased by 7.23% (p<0.05) and 9.79% (p<0.05) respectively, compared with the control group. The feed intake in group 3 was also higher than that in the control group by 19.73% (p<0.05), 14.47% (p<0.05) and 12.09% (p<0.05) on days 0-7, 814 and 1521, respectively. However, no significant difference in feed/gain ratio between the treatment and control groups was detected. Moreover, the NPY, leptin, insulin and gastrin concentrations in group 3 significantly increased by 34% (p<0.05), 251% (p<0.01), 589% (p<0.01) and 31.93% (p<0.01) respectively, compared with the control group, whereas the level of PYY significantly decreased by 57.82% (p<0.01). In conclusion, the growth, ingestion and some metabolism-related hormones with good effects on the regulation of feed intake and energy metabolism can be improved by passive immunization against PYY rather than by causing immunological stress in animals.