title: Within-litter variation in birth weight: impact of nutritional status in the sow.
abstract: Accompanying the beneficial improvement in litter size from genetic selection for high-prolificacy sows, within-litter variation in birth weight has increased with detrimental effects on post-natal growth and survival due to an increase in the proportion of piglets with low birth-weight. Causes of within-litter variation in birth weight include breed characteristics that affect uterine space, ovulation rate, degree of maturation of oocytes, duration of time required for ovulation, interval between ovulation and fertilization, uterine capacity for implantation and placentation, size and efficiency of placental transport of nutrients, communication between conceptus/fetus and maternal systems, as well as nutritional status and environmental influences during gestation. Because these factors contribute to within-litter variation in birth weight, nutritional status of the sow to improve fetal-placental development must focus on the following three important stages in the reproductive cycle: pre-mating or weaning to estrus, early gestation and late gestation. The goal is to increase the homogeneity of development of oocytes and conceptuses, decrease variations in conceptus development during implantation and placentation, and improve birth weights of newborn piglets. Though some progress has been made in nutritional regulation of within-litter variation in the birth weight of piglets, additional studies, with a focus on and insights into molecular mechanisms of reproductive physiology from the aspects of maternal growth and offspring development, as well as their regulation by nutrients provided to the sow, are urgently needed.
authors.affiliation: State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China; Department of Animal Science, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: Tao-lin
authors.initials: TL
authors.lastname: Yuan
authors.forename: Yu-hua
authors.initials: YH
authors.lastname: Zhu
authors.forename: Meng
authors.initials: M
authors.lastname: Shi
authors.forename: Tian-tian
authors.initials: TT
authors.lastname: Li
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.forename: Guo-yao
authors.initials: GY
authors.lastname: Wu
authors.forename: Fuller W
authors.initials: FW
authors.lastname: Bazer
authors.forename: Jian-jun
authors.initials: JJ
authors.lastname: Zang
authors.forename: Feng-lai
authors.initials: FL
authors.lastname: Wang
authors.forename: Jun-jun
authors.initials: JJ
authors.lastname: Wang
mesh_terms: D000818:Animals; D001724:Birth Weight / Q000502:physiology*; D002417:Cattle; D005260:Female; D008098:Litter Size / Q000502:physiology*; D008297:Male; D009752:Nutritional Status / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D039401:Prenatal Nutritional Physiological Phenomena / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine / Q000502:physiology*
keywords: Growth; Morbidity; Mortality; Pig; Sow nutrition; Within-litter variation