Low maternal nutrition during pregnancy reduces the number of Sertoli cells in the newborn lamb

The nutritional status of females during pregnancy can play a critical role in the postnatal growth and development of the offspring, often leading to permanent changes ('fetal programming'). The Sertoli cells are a strong candidate for fetal programming of future performance because the number of Sertoli cells is highly correlated with adult testicular size and the maximum rate of sperm production. For Merino ewes, we imposed different levels of metabolizable energy (ME) intake (LowME: 70% of requirements for maintenance of ewe body mass and normal growth of conceptus (n=13); HighME: 110% of those requirements (n=12)) from Week 10 of pregnancy until parturition and then tested for effects on testicular histology in newborn males. Pregnant ewes were weighed weekly and lambs were weighed at birth and 2 days later. Blood was sampled at the same times. LowME ewes did not gain weight, whereas HighME ewes gained 17% over their pretreatment weight. Birthweights were higher in HighME lambs than in LowME lambs. Paired testes tended to be heavier in the HighME group than in the LowME group (P=0.08). The diameter of the testicular cords did not differ. The absolute volume of testicular cords (0.36+/-0.02 v. 0.30+/-0.02 mL for HighME v. LowME, respectively; P=0.03) and the number of Sertoli cells (43.0+/-2.5 v. 34.5+/-2.0x10(8) for HighME v. LowME, respectively; P=0.018) per testis were both greater in the HighME than in the LowME group. Plasma follicle-stimulating hormone concentrations were not significantly affected at birth or 2 days later. We conclude that undernutrition during pregnancy can reduce testicular development in the newborn. Depending on the ability of the Sertoli cell population to recover between birth and puberty, this may limit the ultimate number of Sertoli cells and, hence, the future capacity for sperm production and fertility.