Uterine Blood Flow and Nutrient Uptake during Late Gestation in Ewes with Different Number of Fetuses

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Abstract
Twenty-three unanesthetized ewes with single, twin or triplet lambs and with indwelling femoral artery and utero-ovarian vein catheters were studied at 105 or 121 days of gestation. Glucose and α-amino acid nitrogen (α-NH2-N) uptake by the gravid uterus was determined from arterial-venous (A-V) differences and utero-ovarian blood flow measurements. Uterine blood flow was determined by p-amino-hippuric acid (PAH) dilution and radioactive microspheres methods and results from the two methods in eight animals were highly correlated (r = .93; P<.01). Arterial blood flow (microsphere method) to the gravid uterus was greater than utero-ovarian vein blood flow (PAH method) by a factor of 1.3 3. Utero-ovarian vein blood flow in ewes with twin fetuses at 105 days of gestation was 958 ± 164 ml/min and was approximately 406 ml/min greater (P<.1) in ewes with triplets at the same stage of gestation. Utero-ovarian vein blood flow increased (P<.1) 400 ml/min as stage of gestation increased from 105 to 121 days of gestation for ewes with twins. Total glucose and α-NH2-N uptake (mg/min) tended to increase with stage of gestation and tended to be greater at 105 days of gestation in ewes with triplets than in ewes with twins. If utero-ovarian vein blood flow and total glucose and α-NH2-N uptake are expressed as ml or mg/kg of fetus/ min, respectively, then there appears to be no increase as stage of gestation increases from 105 to 121 days or as a result of greater fetal number per ewe. This suggests that uterine blood flow and nutrient uptake appear to be closely related to amount of uterine, placental and/or fetal tissue. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.