EFFECT OF ZINC SUPPLEMENTATION ON HYPOTHALAMIC? PITUITARY?GONADAL AXIS IN GROWER PIGS

Zinc (Zn) has a wide spectrum of biological activities and its deficiency has been related to various dysfunctions and alterations of normal cell metabolism. The effect of dietary supplementation Zn on Hypothalamic?pituitary?gonadal axis was investigated in the present study. Gilts (24; average body weight 20.65±1.72 kg and age 3 months) were randomly assigned into 3 groups (8 animals / group) receiving a basal diet supplemented with (i) 100 mg/kg of Zn (CON-fed); (ii) 100 mg/kg of Zn along with calcium carbonate (1.5% of dry matter of diet, to induce Zn deficiency) (DEF-fed), or (iii) 500 mg/kg of Zn (FOR-fed) for 120 days of experimental period. Estimation of serum estradiol 17β (E3) and progesterone (P4) through “COAT-A-COUNT” method of RIA were considered as the marker for activity of hypothalamic?pituitary? gonadal axis of the pigs. Serum E3 level maintain a basal concentration up to day 75 of experiment in all the groups however, in FOR-fed group the concentration of E3 was highest (P<0.05) on day 105 of experiment (age 225days) compared to CON pigs. The P4 concentration in FOR-fed group was highest on day 105 of experiment. However, the E3 and P4 level was steady in DEF-fed animals up to 120 days of treatment. The higher (P<0.05) values observed in respect of E3 and P4 concentration on day 105 of experiment (at the age of 225) might be due to stimulatory effect of higher dietary Zn level on hypothalamic?pituitary?gonadal axis. The present study suggested that dietary supplementation of Zn at 500 mg/kg level in grower pigs might stimulate Hypothalamic?pituitary?gonadal axis for early attainment of puberty in crossbred pigs.