Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2001
Publication Date: December 20, 2001
Citation: Christenson, R.K., Leymaster, K.A. 2001. Fetal mortality as influenced by ovulation rate and uterine capacity in three selected lines of pigs [abstract]. Journal of Animal Science. 79 (Supplement 2):93. (Abstract #275) Technical Abstract: Uterine capacity as a component trait of litter size is responsive to selection [J Anim Sci 78(Suppl 1):68, 2000]. Embryonic mortality that occurs before d 30 of gestation has been studied extensively, while fetal mortality (after d 30 of gestation) has not been well characterized. The objective was to examine fetal mortality in unilaterally hysterectomized- ovariectomized (UHO) gilts of control (CO), ovulation rate (OR) and uterin capacity (UC) selected lines. Gilts were UHO at 160 days of age, mated to boars of the same lines at 2nd or 3rd estrus and slaughtered at 105 days of gestation. Number and total weight (combined fetal and placental necrotic tissues) of all mummified fetuses were recorded. In total, 148 CO, 153 OR and 121 UC litters produced 2923 live and 547 mummified fetuses. Ovulation rate (# of CL) and uterine capacity (live fetuses) for the CO, OR and UC lines were 14.8 and 6.8, 17.9 and 6.3 and 15.0 and 7.8, respectively. The total number and litter avg of mummified fetuses for CO, OR and UC lines were 193 and 1.3, 250 and 1.6 and 104 and 0.9, respectively. Mummified fetuses were grouped by weight ranging from 0 to 499 g in 50-g increments and ò 500 g to calculate the frequency of mummified fetuses in each weight class. Across all lines, the lowest weight class (0-49 g) had the greatest frequency of mummies. Chi-square analysis indicated that the frequency of mummified fetuses was greatest in OR, intermediate in CO and lowest for UC gilts (P<0.01). In conclusion, results suggest that fetal mortality occurs throughout gestation for all three lines but occurs during early gestation as indicated by the high frequency of mummified fetuses in the lowest wt class. Thus under crowded uterine conditions, selection for ovulation rate increased and selection for uterine capacity decreased fetal mortality.