Fetal and placental traits at day 35 of pregnancy in relation to the estrogen receptor genotype in pigs

Fetuses from gilts with estrogen receptor (ESR) genotype AA (AA-AA and AA-AB) and BB (BB-AB and BB-BB) were compared at Day 35/36 of pregnancy, to examine whether fetal ESR genotype nested within maternal ESR genotype would affect fetal traits. Furthermore the relation of fetal body weight and fetal heart weight to various placental traits were evaluated relative to ESR genotype. Fetal and placental weight and length, and implantation surface area were not affected by fetal ESR genotype nested within maternal ESR genotype. Fetal weight was related similarly to placental length, placental weight, and implantation surface area: up to a certain threshold value (40 cm, 40 g and 250 cm2, respectively), an increase in the trait was associated with an increase of fetal weight. Thereafter, fetal weight did not change anymore. Thus, at Day 35/36 of pregnancy porcine fetuses seem to have a maximum growth potential. The percentage of AA-AA fetuses that had not reached this maximum growth potential was larger than of the other three genotype combinations studied, and therefore a higher subsequent fetal mortality may be expected in this group. Hearts of AA-AB fetuses were significantly heavier than those of BB-AB and BB-BB fetuses and tended to be heavier than those of AA-AA fetuses. The reason for this hypertrophy is unclear, but might be related to a difference in placental vascularity. Heart weight of fetuses from BB gilts increased with fetal weight, while heart weights of fetuses from AA gilts did not. Heart weight increased with an increase of placental length and implantation surface area up to 51 cm and 437 cm2, respectively, and thereafter decreased again. For BB-AB fetuses a similar relation was found between heart weight and placental weight, while heart weight of the other three genotype combinations remained unaffected as placental weight increased. The fetus and placenta are continuously changing during early pregnancy, therefore different mechanisms may change the demands for cardiac output. However, keeping in mind that placental size and blood volume are relatively large, placental vascularity and vascular development may play a major role. Therefore, further research on heart size, placental size and vascularity, relative to ESR genotype, is recommended

Parturition in gilts: duration of farrowing, birth intervals and placenta expulsion in relation to maternal, piglet and placental traits

Large White×Meishan F2 crossbred gilts (n=57) were observed continuously during farrowing while the placentae of their offspring were labeled in order to examine the duration of farrowing and placenta expulsion in relation to maternal-, piglet- and placental traits and the duration of birth interval in relation to birth weight, birth order and placental traits. Independently from each other, litter size, gestation length and offspring directed aggression significantly (P0.05) affected duration of farrowing. An increase in litter size was associated with an increase of duration of farrowing and an increase in gestation length was associated with a decrease of duration of farrowing. Aggressive gilts took longer to farrow, compared to non-aggressive ones. After taking into account litter size, gestation length and offspring directed aggression, placental thickness (i.e., placental weight corrected for placental surface area) was significantly (

Critical periods for foetal mortality in gilts identified by analysing the length distribution of mummified foetuses and frequency of non-fresh stillborn piglets

The objective of this study was to investigate the timing of foetal mortality in gilts of a segregating F2 cross of Large White and Meishan pigs on the basis of the length distribution of mummified foetuses and the frequency of non-fresh stillborn piglets in order to establish whether critical periods for foetal mortality exist. All expelled conceptuses and placentae of 192 farrowing gilts with a normal health status were meticulously investigated to recover all mummified foetuses. The length of each mummified foetus was measured. The predicted number of foetuses present per gilt at the early foetal stage of gestation was calculated as the sum of numbers of mummified foetuses and non-fresh stillborn, fresh stillborn and liveborn piglets. Foetal loss was calculated as the sum of mummified foetuses and non-fresh stillborn piglets. The average foetal mortality rate per gilt was 8.7%. In total 162 mummified foetuses were found (average 0.84 per litter), ranging in length from 0.4 to 33.0 cm. This indicates a range in foetal age at death of similar to35-100 days. Although mummified foetuses of all lengths within the above mentioned range were found, relatively many had a length of less than 4 cm or of 10-21 cm. The total number of non-fresh stillborn piglets (i.e. late foetal deaths) was 58 (average 0.30 per litter). It can be concluded that foetal mortality occurred in these gilts throughout the period from day 35 to term, with relatively high incidences at the early foetal stage (days 35-40), shortly after mid-pregnancy (days 55-75) and after similar today 100 of gestation. These three periods coincide with reported periods of change in porcine placental growth. (C) 2002 Elsevier Science B.V. All rights reserved