The purpose of this research was to further test a stable isotope based approach as a more reliable in vivo method to determine amino acid bioavailability from a variety of ingredients. The method was used to assess feather meal (FM), blood meal (BM), soybean meal (SBM), and a rumen protected amino acid (RPAA). An abomasal infusion of raw EAAs (isoleucine, leucine and methionine) and an abomasal infusion of sodium caseinate were used as control treatments to test the accuracy of the technique. The isotope-based results were then compared to in situ, in vitro and in vivo test results. The isotope-based technique provided AA bioavailability values for five non-essential AA and seven essential AA. The raw EAA infusion had the greatest AA recovery in plasma with an estimated absorbed RUP value of 93.4± 7.35% followed by the casein infusion (86.7 ± 4.81%), SBM (54.8 ± 5.19%), FM (52.7 ± 4.81%) and BM (47.5 ± 4.81%). The RPAA treatment had the lowest bioavailability at 9.9 ± 12.73%. Numerically, SBM supplied the most absorbable EAA of the 4 feed ingredients, but was not significantly different from that of BM and FM. Simply based on the control treatments in this research (raw EAA and casein), this isotope method was a more accurate method in determining AA bioavailability values with relatively low standard errors. Ingredients are exposed to all aspects of natural digestive processes and the method is able to determine AA appearance in the blood with no use of in situ or in vitro measurements. / Master of Science / Balancing rations for essential amino acids has beneficial effects on milk production and milk protein synthesis. However, to have predictable results, accurate knowledge of essential amino acid supply deriving from ingredient rumen undegradable protein and microbial crude protein flows is required. Methods used to assess essential amino acid supply include in vivo, in vitro and in situ methods; however these methods often generate conflicting results and have significant deficiencies that have hampered development of robust, accurate predictions of essential amino acid supply to the animal. This research tested a non-steady state, stable isotope based approach as a more reliable in vivo method to determine amino acid bioavailability for feed ingredients. Two control treatments (abomasally infused casein and raw essential amino acid) and four ingredients (feather meal, blood meal, soybean meal, and a rumen protected amino acid) were tested. Based on the control treatments, the method provided a reliable assessment of amino acid bioavailability values with relatively low standard errors. This method has the advantage of assessing essential amino acid bioavailabilities in a natural state where the ingredients of interest are components of a relatively normal diet exposed to all of the natural digestive processes. Thus values derived from this approach can be expected to be representative of most normal industry diets. With some further refinement, this method can help to create a library of true values for a variety of feed ingredients, leading to more accurately balanced diets and increased milk production. More accurate values of amino acid digestibility and rumen undegradable protein measurements for ingredients will also help to better determine their fair market value.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/84352 |
| Date | 30 January 2017 |
| Creators | Estes, Kari Ann |
| Contributors | Dairy Science, Hanigan, Mark D., Cockrum, Rebecca R., Lapierre, Helene |
| 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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