The Influence of Uterine Growth on The Potential Litter Size in Chinese and Occidental Pigs
Wu, Ming-Che
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Permalink
https://hdl.handle.net/2142/70053
Description
Title
The Influence of Uterine Growth on The Potential Litter Size in Chinese and Occidental Pigs
Author(s)
Wu, Ming-Che
Issue Date
1987
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Abstract
Litter size at birth is determined by the number of ovulations, proportion of eggs fertilized and the proportion of embryos and fetuses surviving. Differences in litter size amongst breeds are directly related to the length of the pregnant uterus. Each fetus regardless of breed requires a similar amount of uterine space. The number of live fetuses is limited by the uterine length and the uterine length becomes more important as the number of ovulations increases. The innate length and growth of the uterus in prepubertal gilts may be associated with the potential litter size. The objectives of this thesis were to determine factors that may influence the uterine growth from birth to early pregnancy, and to establish a possible association of the length of the uterus in prepubertal gilts and the potential litter size. Experiments were designed to establish a consistent method of measuring uterine length under several conditions, and to determine the extent that genetic background, the presence of the ovary and embryos influenced the growth of the uterus. Studies were also conducted to establish the extent that the length of the uterus at one reproductive stage was related to the length at other stages and the potential litter size. Uterine capacity was tested by the model of the unilaterally ovariohysterectomized gilt under conditions in which the number of ovulations was not a limiting factor. In total several hundred gilts were examined. To obtain consistent results uterine length must be measured under uniform and standard conditions. The innate length of the uterus was affected by the genetic background. The ovary did not affect uterine growth before occidental gilts were 100 days of age. The presence of embryos is associated with an increased length, weight and diameter of the uterus at day 18 but not before. Length of the uterus before puberty was positively associated with the number of live fetuses at 30 days when a number of potential embryos exceeded 13. These results indicate that selection for uterine length in the prepubertal gilt could have an effect on the potential litter size.
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