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Effect of empty uterine space on birth intervals and fetal and placental development in pigs.
Anim Reprod Sci. 2011 May; 125(1-4):158-64.AR

Abstract

A substantial loss of embryos occurs between Days 30 and 40 of pregnancy in the pig under crowded intrauterine conditions, but it is not clear whether this loss affects the growth of adjacent conceptuses. Birth intervals are known to increase with decreasing litter size, but the factors responsible are unknown. Two possibilities are that increased birth weight associated with reduced litter size and the empty uterine space and resulting constricted uterine regions that occur in pigs with small litters may impair piglet delivery. To address these, pregnant gilts were laparotomized on Day 35 of pregnancy and one or two fetuses were manually crushed through the uterine wall on the ovarian or cervical end of each uterine horn to create an empty uterine space behind or in front of the litter of piglets, respectively, in relation to the route of delivery from the uterus. A subset of gilts was slaughtered at 105 days of gestation to confirm that the empty uterine spaces were successfully created and to determine their effects on placental and fetal weights of adjacent conceptuses. At slaughter, the lengths of all externally visible empty constricted regions of the uterus were measured. The uterine horns were opened and the lengths of each placenta were measured from the umbilicus toward the ovary and toward the cervix to assess whether placentas developed symmetrically, and then each fetus and placenta was weighed. Fetal crushing successfully created constricted empty uterine regions on the ovarian and cervical ends of the uterine horns. Ovarian-side placental lengths were greater than cervical-side for conceptuses adjacent to fetuses crushed on the ovarian end of the horn. Cervical-side placental lengths were greater than ovarian-side for conceptuses adjacent to fetuses crushed on the cervical end. Both placental and fetal weights were greater (10% and 6%, respectively, P<0.05) for conceptuses adjacent to crushed fetuses compared to nonadjacent conceptuses. Remaining gilts were farrowed to determine the effect of litter size, average birth weights, and treatment on birth intervals of piglets, which were monitored using 24-h video surveillance. The negative association between number of piglets born alive and average birth interval was confirmed and was not explained by litter size-induced reduction in litter average birth weights. Birth intervals and stillbirth rate did not differ between cervically- and ovarian-treated gilts. These results indicate that conceptus loss on Day 35 of gestation can benefit the growth of adjacent placentas and fetuses, but the benefit is small. Increased average birth weight and the presence of empty uterine space that occurs when litter size is reduced does not fully explain the effect of litter size on birth intervals.

Authors+Show Affiliations

USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933-0166, United States. jeff.vallet@ars.usda.govNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

21550736

Citation

Vallet, J L., et al. "Effect of Empty Uterine Space On Birth Intervals and Fetal and Placental Development in Pigs." Animal Reproduction Science, vol. 125, no. 1-4, 2011, pp. 158-64.
Vallet JL, Freking BA, Miles JR. Effect of empty uterine space on birth intervals and fetal and placental development in pigs. Anim Reprod Sci. 2011;125(1-4):158-64.
Vallet, J. L., Freking, B. A., & Miles, J. R. (2011). Effect of empty uterine space on birth intervals and fetal and placental development in pigs. Animal Reproduction Science, 125(1-4), 158-64. https://doi.org/10.1016/j.anireprosci.2011.03.006
Vallet JL, Freking BA, Miles JR. Effect of Empty Uterine Space On Birth Intervals and Fetal and Placental Development in Pigs. Anim Reprod Sci. 2011;125(1-4):158-64. PubMed PMID: 21550736.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of empty uterine space on birth intervals and fetal and placental development in pigs. AU - Vallet,J L, AU - Freking,B A, AU - Miles,J R, Y1 - 2011/03/23/ PY - 2010/04/23/received PY - 2011/02/23/revised PY - 2011/03/15/accepted PY - 2011/5/10/entrez PY - 2011/5/10/pubmed PY - 2011/10/15/medline SP - 158 EP - 64 JF - Animal reproduction science JO - Anim Reprod Sci VL - 125 IS - 1-4 N2 - A substantial loss of embryos occurs between Days 30 and 40 of pregnancy in the pig under crowded intrauterine conditions, but it is not clear whether this loss affects the growth of adjacent conceptuses. Birth intervals are known to increase with decreasing litter size, but the factors responsible are unknown. Two possibilities are that increased birth weight associated with reduced litter size and the empty uterine space and resulting constricted uterine regions that occur in pigs with small litters may impair piglet delivery. To address these, pregnant gilts were laparotomized on Day 35 of pregnancy and one or two fetuses were manually crushed through the uterine wall on the ovarian or cervical end of each uterine horn to create an empty uterine space behind or in front of the litter of piglets, respectively, in relation to the route of delivery from the uterus. A subset of gilts was slaughtered at 105 days of gestation to confirm that the empty uterine spaces were successfully created and to determine their effects on placental and fetal weights of adjacent conceptuses. At slaughter, the lengths of all externally visible empty constricted regions of the uterus were measured. The uterine horns were opened and the lengths of each placenta were measured from the umbilicus toward the ovary and toward the cervix to assess whether placentas developed symmetrically, and then each fetus and placenta was weighed. Fetal crushing successfully created constricted empty uterine regions on the ovarian and cervical ends of the uterine horns. Ovarian-side placental lengths were greater than cervical-side for conceptuses adjacent to fetuses crushed on the ovarian end of the horn. Cervical-side placental lengths were greater than ovarian-side for conceptuses adjacent to fetuses crushed on the cervical end. Both placental and fetal weights were greater (10% and 6%, respectively, P<0.05) for conceptuses adjacent to crushed fetuses compared to nonadjacent conceptuses. Remaining gilts were farrowed to determine the effect of litter size, average birth weights, and treatment on birth intervals of piglets, which were monitored using 24-h video surveillance. The negative association between number of piglets born alive and average birth interval was confirmed and was not explained by litter size-induced reduction in litter average birth weights. Birth intervals and stillbirth rate did not differ between cervically- and ovarian-treated gilts. These results indicate that conceptus loss on Day 35 of gestation can benefit the growth of adjacent placentas and fetuses, but the benefit is small. Increased average birth weight and the presence of empty uterine space that occurs when litter size is reduced does not fully explain the effect of litter size on birth intervals. SN - 1873-2232 UR - https://www.unboundmedicine.com/medline/citation/21550736/Effect_of_empty_uterine_space_on_birth_intervals_and_fetal_and_placental_development_in_pigs_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0378-4320(11)00085-6 DB - PRIME DP - Unbound Medicine ER -