Comparative aspects of placental efficiency.

摘要: Litter size is often proposed as the trait that could have greatest impact in improving reproductive efficiency of pigs. Efforts to select directly for increased litter generally been unsuccessful and highly variable. As a result, several attempts made identify critical physiological components control size, with underlying assumption augmenting these would improve this important trait. One attempt at has involved selection animals uterine capacity, measured by number fetuses or piglets female can carry successfully term. Recent evidence indicates one component capacity pigs placental efficiency, body weight piglet divided mass its placenta. It easy determine average litter, but variation among conceptuses within be substantial, leading conclusion an individual conceptus suggested limited success results, least part, from misguided view 'uterine capacity' strictly maternal Uterine better defined tissue pregnant support term, involves phenotypic both dam her offspring. This definition allows maximization future increase