Effects of Dietary Glucose on Serum Estrogen Levels and Onset of Puberty in Gilts

Metabolic signals and the state of energy reserves have been shown to play a crucial role in the regulation of reproductive function. This study was carried out to investigate the effects of dietary glucose levels on puberty onset in gilts. Weight-matched, landrace gilts (n = 36) $162{\pm}3days$ old, weighing about $71.05{\pm}4.53kg$, were randomly assigned to 3 dietary treatment groups of 12 gilts each. The trial lasted until the onset of puberty. Gilts in each group were supplied with diets containing different levels of glucose as follows: i) starch group (SG) was free of glucose, contained 64% corn derived starch; ii) low-dose group (LDG) contained 19.2% glucose and 44.8% corn derived starch; iii) high-dose group (HDG) contained 30% glucose and 30% corn derived starch. Results indicated: i) The growth performance of gilts were not affected by the addition of glucose, but the age of puberty onset was advanced significantly (p<0.05); ii) Compared with the SG, the concentration of insulin significantly increased before puberty in HDG (p<0.05); iii) There was no difference in serum progesterone (P) levels amongst the different feed groups, however, levels of estradiol ($E_2$), luteinizing hormone, and follicle-stimulating hormone were significantly higher at puberty onset in HDG (p<0.05). Overall, our findings indicate that glucose supplementation significantly advances puberty onset, which can have practical purposes for commercial breeding.