Studies On The Early Sexual Development Of JiangQuHai Meat-type Line Gilts

The experiment was conducted to study the early sexual organ development and reproductive hormone secretion, and how they interact each other in the JiangQuHai meat-type line gilts and the parental DFJ(Duroc x FengJing x JiangQuHai) gilts from birth to 75 days of age.24 gilts were selected within each breed, and 4 gilts of each group were slaughtered every 15 days from birth to 75 day. Before slaughter, blood samples were collected 4 times from precava at 30 minutes interval. Also, another test was conducted to compare the hormonal fluctuation of the two groups gilts. Within one oestrus cycle, blood samples were collected from 1 day to the end of the oestrus cycle (21 days) at 2 days interval.The results showed that:1) High reproductive hormone levels were observed at birth time. Serum concentration of LH (luteinizing hormone), FSH (follicle-stimulating hormone) and E2 (estrodiol) were significantly lower (P<0.01) in the meat-type line gilts than in DFJ gilts. While no significant differences were seen in P (progesterone) and T (testosterone). The concentrations of LH, FSH and E2 experienced an apparent rise before 75 days of age, which coincided with the gradual growth of ovisacs.2) During the first oestrus cycle, LH level was much higher (P<0.01) in themeat-type line gilts than in DFJ gilts, but no significant differences (P>0.05) were seen in FSH or E2. The peaks of LH and E2 appeared at the same day in both groups. P level differed significantly between the two groups, and their peaks appeared at the 11th and 13th day respectively (20.259?.984ng/ml, 50.539?.968ng/ml; P<0.01). T concentration in the meat-type line gilts was much lower than that in the DFJ gilts (P<0.01).3) Reproductive organs grew rapidly at 60 day, close correlating with the changing of high concentrations of LH, FSH and E2 at this phase. It suggested these three hormones' ascents accelerated the growth of the sexual organs, especially the ovary. At the age of 75 days, tertiary follicles were observed in the meat-type line gilts, and graafian follicles were observed in DFJ gilts. Follicle development was little later in the meat-type line gilts than in DFJ gilts. To a large extent, the advantage of precocious puberty was maintained in the meat-type line gilts...