GROWTH OF THE REPRODUCTIVE TRACT OF THE GILT FROM BIRTH TO PUBERTY

Abstract

Growth of the ovaries, uterus and oviducts was determined in groups of four gilts on the day of birth and at 2-wk intervals from 42 to 168 days of age, and in six gilts on the day after puberty. Ovarian and uterine growth from birth to 168 days was described by cubic regressions (R2 = 0.841 and 0.772, respectively). Changes in the growth pattern occurred after 70 days. Ovarian weight increased up to 112 days and then remained constant until puberty. The number of small (1- to 3-mm diam.) and large (> 3-mm diam.) vesicular follicles reached constant levels by 140 days. At puberty there was a decline in the number of small and large follicles. Oviduct weight and length increased between 70 and 112 days and then remained constant until puberty when a further increase in weight and length occurred. The rate of uterine weight and length increase changed between 70 and 84 days, followed by a continual gradual increase in weight to day 168, while uterine length remained relatively constant. At puberty there was a further increase in weight and length. From birth to puberty the pituitary and adrenal glands had linear increases in weight while the thyroid gland weight changes were described by a cubic regression (R2 = 0.733) with an increase in weight between 70 and 112 days and a constant weight to 168 days. These results indicate that there are four stages of development: from birth to 70 days; 70 days to 140 days; a variable time interval to just before puberty; and the changes associated with puberty. Key words: Puberty, reproductive tract, growth, swine, gilts