Reproductive Physiology in Chinese Meishan Pigs

Abstract

Experiments were designed to examine: 1) age at puberty in Chinese Meishan (Ms) and Yorkshire (Y) gilts, 2) litter size in Ms and Y gilts and 3) ejaculate characteristics in Ms and Y boars. Ms gilts reached sexual maturity 105 da earlier than Y gilts and Ms gilts were in estrus almost 1 da longer than Y gilts for their first, second and third estrus. No differences were detected between breeds for cycle length on the first or second estrous cycle. Validation of the Coat A Count Progesterone RIA procedure resulted in an accurate, rapid and efficient method for quantification of porcine serum progesterone and has extended to swine a reliable, repeatable methodology to confirm visual estrous detection which allows for accurate prediction of first ovulation at puberty. Luteal phase concentrations of progesterone are greater in Meishan gilts than Y control gilts during the first 2 estrous cycles. Reciprocal cross females (Ms × Y and Y × Ms) had higher ovulation rates and numbers of fetuses than Ms and Y females, possibly due to hybrid vigor. However, length of the uterus was not influenced by their larger litter sizes suggesting that uterine capacity was not challenged at this reproductive age. It appears there is a key point for Ms females where physiological and reproductive age must coincide to maintain improved prolificacy over domestic breeds of females. Further, the mechanism of fetal survival may be different in crossbred Ms females than in purebred Ms females. Therefore, of ovulation rate, uterine and embryonic interactions, including uterine capacity, and reproductive age are all important in the greater prolificacy of Ms females over occidental breeds of females. There were higher concentrations of estradiol-17β (E2) and testosterone in the seminal plasma from Ms boars compared to seminal plasma from Y boars.