J. Anim Sci., doi: 10.2527/jas.2007-0624
©Copyright, 2007, The American Society of Animal Science
Baggs ewes adapt to maternal undernutrition and maintain conceptus growth by maintaining fetal plasma concentrations of amino acids
W. S. Jobgen 1,
S. P. Ford 2,
S. C. Jobgen 1,
C. P. Feng 3,
B. W. Hess 2,
P. W. Nathanielsz 4,
P. Li 1,
G. Wu 1*
1 Department of Animal Science and Faculty of Nutrition, Texas A&M University, College Station, TX 77843
2 Department of Animal Science and Center for the Study of Fetal Programming, University of Wyoming, Laramie, WY 82071
3 Department of Animal Science and Faculty of Nutrition, Texas A&M University, College Station, TX 77843; Department of Obstetrics and Gynecology, China-Japan Friendship Hospital, Beijing, China 100029
4 Department of Obstetrics and Gynecology, University of Texas Health Sciences Center, San Antonio, TX 78299
* To whom correspondence should be addressed. E-mail: g-wu{at}tamu.edu.
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Abstract |
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Adequate delivery of amino acids (AA) is essential for normal fetal growth and development. Recently, we reported that when ewes from the University of Wyoming flock (UW ewes; farm flock with adequate nutrition) were fed 50% (nutrient-restricted) or 100% (control-fed) of National Research Council (NRC)-recommended nutrient requirements between d 28 and 78 of gestation, fetal weights as well as concentrations of most AA in maternal and fetal blood were substantially reduced in nutrient-restricted versus control-fed pregnancies. The present study utilized Baggs ewes, which were selected under a markedly different production system (range flock with limited nutrition), to test the hypothesis that adaptation of ewes to nutritional and environmental changes may alter placental efficiency and conceptus nutrient availability in the face of maternal nutrient restriction. Baggs ewes received 50% or 100% NRC nutrient requirements between d 28 and 78 of pregnancy. On d 78, maternal uterine arterial and fetal umbilical venous blood samples were obtained and ewes euthanized. Amino acids and their metabolites (ammonia, urea and polyamines) in plasma were analyzed using enzymatic and HPLC methods. The results showed that maternal plasma concentrations of 9 AA (asparagine, isoleucine, leucine, lysine, ornithine, phenylalanine, threonine, tryptophan, and valine) as well as maternal and fetal plasma concentrations of ammonia, urea, and polyamines were reduced (P < 0.05) in nutrient-restricted, compared with control-fed Baggs ewes. However, fetal plasma concentrations of all AA did not differ (P = 0.842) between these two groups of ewes. Collectively, these findings suggest that Baggs ewes, by adapting to the harsh conditions and limited nutrition under which they were selected, were able to maintain fetal concentrations of AA in the face of a maternal nutrient restriction through augmenting placental efficiency.
Key Words:
fetal growth, fetal programming, fetal intrauterine growth restriction, nutrition, pregnancy
