Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2014
Publication Date: 6/1/2014
Publication URL: http://handle.nal.usda.gov/10113/59652
Citation: Lents, C.A., Cushman, R.A., Freking, B.A. 2014. Measures of the ovaries and uterus during development of gilts selected for differences in uterine capacity. Journal of Animal Science. 92(6):2433-2439.
Interpretive Summary: Selection for increased litter size has led to the development of hyperprolific pigs, which ovulate more fertilizable eggs than their uterus has capacity to support fetuses. An overcrowded uterine environment increases fetal loss and reduces piglet birth weights, which is associated with decreased postnatal survival. Improvements in uterine capacity of swine can be made through direct selection; however, direct estimates of uterine capacity are difficult to obtain. A method to indirectly estimate uterine capacity in developing females is needed for this trait to be incorporated into commercial selection strategies. Scientists evaluated development of the reproductive tract in unique genetic lines of pigs selected for increased uterine capacity and a control line under random selection. They discovered that females selected for increased uterine capacity developed larger reproductive tracts. Scientists were able to visualize and measure the developing reproductive tract of pigs using an ultrasound machine similar to that used in hospitals to monitor pregnancies in women. Estimating uterine capacity with ultrasound before puberty will allow for more effective selection of females for breeding. This will allow for increased productivity of female pigs and reduce postnatal loss of piglets.
Technical Abstract: Direct selection for uterine capacity (UC) increased the number of live pigs born. A method to indirectly estimate UC in developing gilts is needed for this trait to be incorporated into commercial selection strategies. We tested the hypothesis that selection for UC alters phenotypic characteristics of the reproductive tract of prepubertal gilts and that these changes could be estimated in live animals using transrectal ultrasound (TRU). Gilts from lines selected for UC and a control line (CO) under random selection were submitted for TRU at 130, 150, or 170 d of age and sacrificed 24 h later (n = 10 gilts/line per age). Diameter of the uterine horn was measured (2 to 4 measurements per animal) at TRU. At sacrifice, measurements of the ovary (height, width, length, weight and number of visible follicles > 1 mm) and uterine horn (weight, length, diameter, and endometrial diameter) were taken. There was no line x age interaction for any of the traits. All ovarian traits increased (P < 0.03) with age. Weight and length of the uterine horn was not different at 130 or 150 d, but was increased (P < 0.01) at 170 d of age. Diameter of the uterine horn tended (P = 0.06) to be increased at 170 d compared with 130 or 150 d, but age did not affect (P = 0.38) endometrial diameter. Ovarian weight and width were increased (P < 0.01) and ovarian length and height tended (P = 0.07) to be greater for UC than CO gilts, but the number of visible follicles did not differ. The UC gilts had increased (P < 0.02) weight of uterine horns, which tended (P = 0.09) to be longer than in the CO gilts. Diameter of the uterine horn and the endometrium were greater (P < 0.01) for UC gilts than for CO gilts. Uterine horn diameter measured with TRU was not affected by age or line, and was not highly correlated with any of the measured traits. Selection for increased UC results in larger ovaries and uterine horns, but TRU was not useful for estimating these traits in gilts of the age studied.