Effects of a Streptococcus equi infection--mediated nutritional insult during mid-gestation in primiparous Thoroughbred fillies. Part 1: placental and fetal development.
BACKGROUND
There is a paucity of information on factors that influence placental development in the horse.


OBJECTIVE
Changes in nutrition, particularly around the time of proliferative placental growth, can affect development of the placenta and fetal growth.


OBJECTIVE
To investigate the effects of 2 planes of nutrition and an unforeseen infection-mediated nutritional insult on placental and fetal development in the mare.


METHODS
Twenty maiden Thoroughbred fillies, age 3 or 4 years, mated to one Thoroughbred stallion, were maintained on either High or Moderate food intake throughout pregnancy. In mid-gestation all the mares unexpectedly became infected with Streptococcus equi and suffered varying degrees of weight loss as a consequence. Gross and stereological measurements of the placenta and measurements of foal birthweight, crown-rump length, ponderal index and plasma IGF-1 concentration were made at term.


RESULTS
Gains in bodyweight during gestation were significantly higher in the High vs. the Moderate nutrition groups. Placental and fetal growth parameters were not influenced by the plane of nutrition. However, transient weight loss in mid-gestation from acutely reduced food intake resulted in morphological changes to the allantochorion and decreased foal birthweight.


CONCLUSIONS
Excessive weight gain during gestation in maiden Thoroughbred fillies does not result in nutrient partitioning to the dam at the expense of the fetus. However, sudden weight loss in mid-gestation has detrimental effects on placental development which results in reduced fetal growth.


CONCLUSIONS
Clinicians should appreciate the likely effects of maternal infection and resulting weight loss on pregnancy outcome.
Wilsher
S
S
Department of Veterinary Medicine Equine Fertility Unit, University of Cambridge, Mertoun Paddocks, Woodditton Road, Newmarket, Suffolk CB8 9BH, UK.
Allen
W R
WR
D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000033:anatomy & histology / Q000254:growth & development; D001724:Birth Weight / Q000502:physiology; D047108:Embryonic Development / Q000502:physiology; D002149:Energy Intake / Q000502:physiology; D005260:Female; D005865:Gestational Age; D006734:Horse Diseases / Q000503:physiopathology*; D006736:Horses; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D009929:Organ Size / Q000502:physiology; D010920:Placenta / Q000382:microbiology; D010929:Placentation; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000503:physiopathology / Q000662:veterinary*; D011256:Pregnancy Outcome / Q000662:veterinary; D013290:Streptococcal Infections / Q000503:physiopathology / Q000662:veterinary*; D018502:Streptococcus equi; D015430:Weight Gain / Q000502:physiology*
D007334:Insulin-Like Growth Factor I