Tanniniferous oak (quercus hartwissiana) leaves do not affect plasma levels of leptin, IGF-I and LH in lambs

The aim of the current study, was to evaluate the effects of diets containing different levels of tanniniferous oak (Quercus hartwissiana) leaves in the absence and presence of a tannin binding substance, polyethylene glycol, on plasma leptin, IGF-I and LH levels in ewe-lambs. Lambs (n = 42) were kept in individual metabolism cages and a total of 7 groups (n = 6 per group) were formed (Group I, control; Group II, 185 g leaf; Group III, 370 g leaf; Group IV, 185 g leaf plus 10 g PEG; Group V, 185 g leaf plus 20 g PEG; Group VI, 370 g leaf plus 20 g PEG; Group VII as 370 g leaf plus 40 g PEG). All groups were given 272 g concentrate and varying amounts of hay in a way that the amount of roughage was equal to 645 g. The diets were isonitrogenous and isoenergetical and the experiment continued for 60 days. Blood samples were collected fortnightly for the measurement of leptin and IFG-I. Additionally, on day 55 post-prandial rhythm of leptin was assessed with 30 min intervals for 8 h and LH response to naloxone was assessed for 2 h with 15 min intervals. For the determination of LH pulsatility, blood samples were collected on day 45 of the experiment with 15 min intervals for 6 h. IGF-I levels, fortnigtly leptin secretion, LH pulsatility and LH response to naloxone did not differ among the groups. Post-prandial leptin secretion appeared to be episodic but it was not affected by dietary treatments (p>0.05). Both leptin and IGF-I concentrations were positively correlated to LH pulse frequency (R2 = 0.235, p = 0.027 and R2 = 0.248, p = 0.006, respectively). In conclusion, the results suggest that tanniniferous Q. hartwissiana leaves do not have any effect on leptin, IGF-I and LH secretion and that leptin secretion appears to be in episodic manner and that leptin and IGF-I secretions appear to signal reproductive axis in ewe-lambs.