RELATIONSHIP OF LENGTH OF UTERUS IN PREPUBERTAL PIGS AND NUMBER OF CORPORA-LUTEA AND FETUSES AT 30 DAYS OF GESTATION

Relationships of the length of the uterus at one reproductive stage to the length at other stages and the effect on potential litter size we re determined. In Experiment 1, the length of the uterus was measured in situ at 20, 60, or 100 days of age at laparotomy with 20 gilts in e ach of the three age groups. Forty days after the initial measurement, the uterus was again measured in situ, gilts were ovariectomized and hysterectomized, and associations among uterine measurements at the tw o different stages were determined. Correlations between uterine lengt h in situ and between uterine length and weight 40 days later were all greater than 0.75 (P < 0.001). The length of one uterine horn increas ed from 13.9 cm at 20 days of age to 36.7 cm at 140 days of age (P < 0 .01). In Experiment 2, 66 gilts were unilaterally hysterectomized and ovariectomized (UHOX) at 150 days of age and the ovary was weighed. Le ngth of the one horn was measured in 36 gilts. At 10 days after first estrus, the length of the remaining uterine horn was measured at lapar otomy and corpora lutea were counted in 53 gilts. In 15 of the 53 gilt s the remaining uterine horn was removed to obtain uterine weights. At the second or third estrus, 38 gilts were mated and at Day 30 of gest ation, 31 gilts were pregnant. The gilts were killed, and the length o f the uterus measured and corpora lutea (CL) and fetuses were counted. The length of one uterine horn at 150 days of age was 70 cm with a ra nge of 47-1 10 cm. At 10 days after first estrus, length had increased to a mean of 141 cm with a range of 86-194 cm and at 30 days of gesta tion the mean was 244 cm with a range of 186-311 cm. There were 12.2 C L at first estrus, which was not different from 12.4 CL at the second or third estrus. The mean number of fetuses in one horn at 30 days of gestation was 9.5 with 77% prenatal survival. Length of uterine horn a t 150 days of age was correlated with uterine horn length (r = 0.56, P < 0.001) at 10 days after first estrus and number of live fetuses (r = 0.39, P < 0.05) at 30 days of gestation. At Day 10 after first estru s, uterine length was not correlated with the number of CL, whereas at Day 30 of gestation, the number of CL and uterine length were correla ted with the number of live fetuses in those gilts with below the mean number of live fetuses, but not in those gilts with above the mean of live fetuses. The number of live fetuses (r = 0.66, P < 0.001) and fe tal survival (r = 0.63; P < 0.001) were correlated with uterine horn l ength in pregnant UHOX gilts. Length of the prepubertal uterus gives a n indication of postpubertal length and the potential litter size in p igs.