Effect of Zearalenone on Days 7 to 10 Post-mating on Blastocyst Development and Endometrial Morphology in Sows

First litter sows in naturally occurring post-weaning estrus were hand mated to proven boars and were fed a diet supplemented with zearalenone, an estrogenic mycotoxin (I mg zearalenone/kg body weight), or a control diet on days 7 through 10 after mating. Embryos (blastocysts) and endometrial biopsies were collected from control and treated sows on days 9, II, and 13 after mating. All blastocysts harvested on day 9 were spherical; treatment ofsows with zearalenone had no effect on blastocyst development. Blastocysts collected from treated sows on day II were in stages of elongation comparable to those of blastocysts from control sows but had mild degenerative changes in the embryonic disks, characterized by slightly retarded development and an increase in the number of necrotic cells. Blastocysts collected from treated sows on day 13 were in an advanced stage of degeneration, characterized by circumferential constrictive division, fragmentation, and degeneration and disorganization of the embryonic disk. Feeding zearalenone to pregnant sows had no effect on the normal decrease in height of the endometrial luminal epithelium on days 9 through 13 after mating and no effect on morphologic appearance of secretory vesicles in the endometrial glandular epithelium. The dosage scheme of zearalenone used in this study did not cause any morphologic changes in the endometrium that could be associated with hyperestrogenism. Zearalenone is an estrogenic mycotoxin produced by ofearly pregnancy by accelerating changes in the uter­ the grain mold Fusarium roseum (graminearum). 3 This ine environment that are associated with the estab­ fungal contaminant of corn occurs in the midwestern Iishrnent of pregnancy in the pig.!' In the sow, at II United States and is associated with toxicosis ofswine. to 12 days after mating, marked changes occur, both Signs of hyperestrogenism are evident in prepuberal in endometrial secretions and in the structure and se­ gilts consuming zearalenone.v'? Consumption of zear- cretory function ofthe blastocysts.' One ofthese changes alenone by sexually mature sows results in nympho- is the secretion of estrogens by developing blastocysts mania, anestrus, ovarian atrophy, pseudopregnancy, that, in turn, affects changes in endometrial function. and alterations in endometrial morphology.v-v-" The Treatment with exogenous estrogens before this period specific manifestations are dependent upon the relative accelerates changes in characteristics ofthe uterine en­ dose of zearalenone and the stage of the estrous cycle vironment such as the concentration of Ca' ' and the or pregnancy during which zearalenone was consumed. types of proteins present. 14.19 Blastocyst elongation oc- Consumption of zearalenone by sows during early curs in estrogen-treated sows, but the blastocysts ap­ pregnancy results in loss of embryos but retention of pear incapable offurther development and degenerate corpora Iutea."'? The timing ofthe exposure is critical, by day 16 after mating.'> because a dose of zearalenone that causes loss of em- Treatment with zearalenone on days 7 to 10 after bryos when administered on days 7 to 10 after mating mating also causes changes in the intrauterine envi­ does not disrupt pregnancy when administered on days ronment, such as alterations in Ca' ' concentration in 2 to 6 or II to 15 after mating." These effects are similar the uterine lumen." Estradiol 17-(3 concentration in the to those of other exogenous estrogens on pregnancy; uterine lumen of zearalenone-treated sows on days 9, estradiol 17-(3 is more potent (on a dosage basis) for II, and 13 after mating did not differ from that of disrupting pregnancywhen administered on days 9 and controls, suggesting that the ability ofblas tocysts from 10 after mating compared with administration on days zearalenone-treated sows to secrete estrogen was not 12 and 13 after mating. 17 inhibited. Migration of blastocysts within the uterus Exogenous estradiol is presumed to cause disruption was also unaffected by treatment. The purpose of the