Justification of Unilateral Hysterectomy-Ovariectomy as a Model to Evaluate Uterine Capacity in Swine

Abstract

Experimental objectives were to measure the effect of ovulation rate on litter size at 86 d of gestation and at farrowing in 110 unilaterally hysterectomized-ovariectomized (UHO) gilts and in 142 intact, control gilts and to evaluate postnatal survival and development of progeny. Surgery (UHO) was performed on gilts 8 to 12 d following first estrus. Control and UHO gilts were mated and then randomly assigned to be slaughtered at d 86 of gestation or allowed to farrow. Gilts scheduled to farrow were observed by laparoscopy on d 40 of gestation to count corpora lutea (CL). Ovulation rate (number of CL) was similar for control (12.1 CL) and UHO (11.9 CL) gilts, thus indicating that compensatory ovarian hypertrophy had occurred in UHO gilts and resulted in a near doubling of ova per uterine horn relative to control gilts. Average litter size at 86 d of gestation and farrowing was greater (P less than .01) for control than UHO gilts. At farrowing, litter size for control and UHO gilts was 9.0 +/- .3 and 5.7 +/- .3 pigs, respectively. Fetal losses were greater and pig weights at birth were less in litters by UHO gilts. Postnatal pig survival, growth rate to 14 d of age and 14-d individual pig weight did not differ for progeny of control and UHO gilts, and performance of UHO pogeny did not appear to compromise the usefulness of this animal model. Regression of litter size on ovulation rate was .41 +/- .15 pigs/CL for UHO and .60 +/- .12 pigs/CL for control gilts at d 86 of gestation. Regression was .07 +/- .17 pigs/CL for UHO and .42 +/- .14 pigs/CL for control gilts at farrowing.(ABSTRACT TRUNCATED AT 250 WORDS)

Index Selection for Components of Litter Size in Swine: Response to Five Generations of Selection

“…The observed change in litter size was .20 • .20 at 50 d of gestation and .19 +_ .14 at birth. The agreement between these values indicates a fairly high genetic correlation between litter size at the two stages even though a sizeable loss in number of fetuses occurs late in gestation (Christenson et al, 1987).…”

“…Therefore, the rate of decline in embryo (fetal) survival rate did not completely offset the increase in ovulation rate. Christenson et al (1987) reported that fetal loss is sizeable late in gestation. If some of the variation in this loss is genetic, selection for an index as in this experiment probably would be more effective if fetuses or piglets could be counted closer to or at farrowing time.…”

Intrauterine crowding impairs formation and growth of secondary myofibers in pigs

“…However, only Town et al (2004) and studied the effects of intrauterine crowding on muscle development using these experimental approaches. Compared with OL sows, HO sows have only half the uterine space, whereas the overall ovulation rate is similar for both experimental models (Christenson et al, 1987). Therefore, combining the HO and OL experimental model makes uterine conditions regarding space and nutrient availability per fetus even more divergent and allows to better determine the effects of intrauterine crowding on fetal development and myogenesis.…”

Genetic variability of age and weight at puberty, ovulation rate and embryo survival in gilts and relations with production traits

“…This may be due to differences in the populations studied, but may also indicate that uterine competition tends to increase throughout gestation. This increased competition has been evidenced by superovulation and embryo transfer experiments (Dziuk, 1968;Pope et al, 1972;Webel and Dziuk, 1974) or more recently by experiments on unilaterally hystero-ovariectomized females (Christenson et al, 1987;Legault et al, 1995). Bennett and Leymaster (1989) (Santacreu et al, 1990).…”