The interaction between the embryo and fetus with the maternal environment can have both short- and long-term consequences on health and development after birth. In some cases, these changes may be detrimental to the individual, but in other cases these developmental changes may be beneficial and manipulated to produce desired effects. Our interest is to use this concept of fetal programming to improve skeletal muscle development and meat production in ruminants. To achieve this, we targeted the period of gestation when fetal muscle fiber formation occurs. Primary muscle fibers form during embryonic development, and it is this small number of primary muscle fibers that will serve as templates for secondary fiber formation that occurs in the fetus during mid-gestation. Supplementing amino acids that influence blood flow within the reproductive tract is one potential way to provide fetuses with added nutrients during gestation, and this supplementation strategy may be especially useful when the maternal diet is compromised. L-citrulline was chosen for this work because of its long half-life in maternal circulation.
This work utilized twin-bearing ewes with a moderate dietary energy restriction to assess the effects of mid-gestational L-citrulline supplementation on umbilical blood flow, placental function, neonatal lamb size, and lamb performance. We hypothesize that i.v. administration of L-citrulline will increase uterine and placental blood flow in gestating ewes and this will improve fetal growth, development, and overall postnatal performance. Blood flow parameters were not influenced by treatment (P>0.05). Circulating levels of progesterone and pregnancy-specific protein B (PSPB) were used as indicators of placental function and were unaffected by treatment administration (P>0.05). A treatment by time interaction was detected in both analyses, but no differences between treatments were detected within any time points. There was no effect of treatment on lamb weights or survival to weaning (P>0.05). Lamb sex effects are absent with the exception that body weights were greater in ewe lambs (P>0.05). There was no effect of treatment on any carcass traits or visceral organ weights assessed, though there was an effect of sex on dressing percentage and pancreas weight with wethers having a greater dressing percentage and heavier pancreases per kg body weight than that of ewes (P<0.05). In summary, contrary to our hypothesis L-citrulline supplementation to pregnant ewes under a minor to moderate metabolic challenge had no impact on blood flow and provided no programming benefit to the lambs. / Master of Science / The global population continues to grow, along with the consumption of animal protein. This can be met with increasing the numbers of animals within our food production systems, however, there is also increasing pressure for livestock production systems to produce more while utilizing less space and resources. And simultaneously, we face growing concerns about climate change, its impacts on agriculture, and the role of agriculture in both the cause and any future solution. To combat both these issues, the efficiency of our livestock systems needs to improve with each individual animal becoming much more efficient. This increase in efficiency can occur in many ways including reproductive efficiency, feed efficiency, and in overall producing more meat per individual.
The improvement in efficiency of an animal can begin in the womb. Livestock in meat production spend 35-40% of their life within the uterus being nourished by their mother. The interactions the embryo and fetus have with the maternal environment during this time can have both short- and long-term impacts on health and development after birth. In some cases, these changes may be detrimental to the individual, but in other cases these developmental changes may be beneficial and manipulated to produce the desired effects. Thus, it is important to understand the impact of these fetal-maternal interactions as it directly affects both fetal growth and growth and development after birth. This concept is known as fetal programming.
Our interest is to use this concept to improve skeletal muscle development and meat production in cattle and sheep. To achieve this, we targeted the period of pregnancy when fetal muscle formation occurs. Primary muscle fibers form early in pregnancy, and it is this small number of primary muscle fibers that will serve as templates for secondary fiber formation that occurs in the fetus during mid-pregnancy. Supplementing amino acids that influence blood flow within the reproductive tract is one potential way to provide fetuses with added nutrients during pregnancy, and this supplementation strategy may be especially useful when the maternal diet is compromised. L-citrulline was chosen for this work because of its long half-life in maternal circulation.
This work utilized twin-bearing ewes with a moderate dietary energy restriction to assess the effects of L-citrulline supplementation on blood flow, placental function, newborn lamb size, and lamb performance. We hypothesize that intravenous administration of L-citrulline will increase uterine and placental blood flow in pregnant ewes and this will improve fetal growth, development, and overall postnatal performance. There was no beneficial effect on blood flow to the fetus and on placental function. Additionally, there were very minimal effects on carcass traits or internal organ weights assessed. In summary, contrary to our hypothesis L-citrulline supplementation to pregnant ewes under a moderate metabolic challenge had no impact on blood flow and provided no programming benefit to the lambs. We can conclude that the potential benefit of amino acid supplementation was not realized in our sheep model.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/111128 |
| Date | 11 January 2021 |
| Creators | Kott, Michelle Lynn |
| Contributors | Animal and Poultry Sciences, Ealy, Alan Dale, Stewart, Jamie L., Johnson, Sally E., Rhoads, Michelle |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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