Progress 07/01/12 to 06/30/16
Outputs
Target Audience:The target audience for this research is primarily the scientific community, particularly those studying non-ruminant and equine nutrition, and the feed industry. Eventually, once more research in this area has been accomplished, we will focus our efforts on increasing the knowledge of the individual horse owners regarding amino acid metabolism, but as this type of research is still in its early stages, we have focused on these two entities. Additionally, some data from this study were presented to the feed industry at sales representative training programs (Southern States- November 2015). Two manuscripts have been published in The Veterinary Journal and an additional 2 manuscripts are expected within the next year. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Overall, three graduate students were trained during this research. Sara Tanner (Mastellar) completed her PhD in Summer 2014 (splanchnic extraction research), ChanHee Mok completed her MS in Fall 2015 (Mature horse threonine requirements) and Kelsey Smith completed her MS in Spring 2016 (Yearling horse threonine requirements). Additionally, several undergraduate interns also contributed to this research and received training in animal sampling and laboratory analysis techniques. The graduate students that completed this research were mentored throughout the projectabout how to design and conduct animal research, including learning all of the sample collection techniques, how to perform laboratory and statistical analyses and how to write a scientific manuscript describing the findings from this research. All were able to attend scientific meetings (Equine Science Society, American Society for Animal Science, Experimental Biology), to network with other scientists in related areas of research. All three of these graduate students are currently employed in areas directly related to the training received as a part of this grant: Sara Mastellar is a Lecturer in equine science at South Dakota State University, ChanHee Mok is completing her PhD in the Department of Veterinary Sciences at the University of Kentucky and Kelsey Smith is a Senior Laboratory Technician at Dairy One. How have the results been disseminated to communities of interest?Throughout the course of this grant, the results of this study have been diseminated in several manners. First, data related to this research was presented in poster form at the 2014 ASAS/ADSA Joint Annual meeting and as a presentation at the 2015 Equine Science Society meetings. This was the innitial dissemintation of this material to the scientific community. Other ways that the material has been diseminated to the scientific community is through two peer reviewed publications, and it is anticipated that an additional 2 peer reviewed publications will result within the next year. Two MS theses and 1 PhD dissertation were also published. Disemination to the feed industry was through presentations at the two scientific meetings listed above, as well as through the presentation of data to sales representatives for Cargill Animal Nutrition (Spring 2014) and Southern States (Fall 2015) as a part of their sales representative training meetings. Disemination to horse owners was through presenting portions of the data at the 2015 University of Kentucky Equine Research Showcase. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
All of the major goals of the project were addressed throughout the four year period of funding. Three studies were conducted. In the first, horses were studied while receiving a basal diet and a threonine excess diet (threonine was supplemented at a level equivalent to the estimate of the threonine requirement for mature horses in the NRC), and whole-body phenylalanine kinetics were assessed twice for each diet: once while the isotope was administered intravenously and a second time when the isotope was administered orally by being top-dressed on the feed. Administering the phenylalanine isotope through two routes allowed for the calculation of phenylalanine splanchnic extraction, which was found to be 26.5% for both levels of threonine intake, which is needed for the formulas used in thewhole-body phenylalanine kinetics formula to calculate the amount of phenylalanine intake that reaches the circulatory system. It was also of interest that the splanchnic extraction of the phenylalanine isotope was not affected by the rate of threonine intake, and this allowed us to administer the isotope orally (rather than intravenously) for the remainder of the studies in this grant. These findings have been published. The second study aimed to determine threonine requirements in mature horses and whether they were influenced by the amount of forage in the diet. There were two phases to this study: the high forage phase (80:20 forage:concentrate)and the high concentrate phase (1:1 forage: concentrate). Within each phase, 6 different levels of threonine were provided, for a total of 12 (6 high forage, 6 high concentrate) different treatments. Withineach diet composition, as threonine intake increased, there was an increase in plasma threonine and methionine concentrations, but no effect on either plasma urea nitrogen concentrations or any measure of whole-body phenylalanine kinetics. Therefore, the threonine requirement was either below the lowest level of threonine provided by each diet composition, 41 and 45 mg/kg/d for the high forage and high concentrate diets, respectively, or there was another amino acid more limiting than threonine in the diets. One manuscript is expected from this study. The third study was similar in design to the second study, but used horses that were ~9-14 months of age. The high forage treatments provided a forage:concentrate ratio of 75:25 and the high concentrate treatments provided a forage:concentrate ratio of 60:40. Similar to the study in mature horses, increasing levels of threonine intake resulted in increasing plasma threonine and methionine concentrations, but no evidence that there was an increase in whole-body protein synthesis in response to threonine addition to the diet. Therefore, the threonine requirement of yearling horses was less than 109 mg/kg/d and 98 mg/kg/d for the high forage and high concentrate diets, respectively. Interestingly, although the range of treatment intakes of threonine was similar across both diet compositions, the plasma urea nitrogen concentrations were consistently higher and the plasma threonine concentrations were consistently lower when horses received the high forage treatments. This suggests that there is significantly less dietary threonine reaching the plasma pool when horses received the high forage diet, compared to the high concentrate diet, and even still there were no differences in whole-body protein kinetics. One manuscript is expected from this study. The overall take home message from our studies is that inboth growing horses and mature horses, threonine does not appear to be a limiting amino acid when a reasonable quality of forage is provided (ie. one that is typically used in the equine industry), regardless of whether a high forage or high concentrate diet is fed. There is still much to learn regarding threonine nutrition in horses, including the effects of diet composition and threonine intake on mucin output and determining why threonine supplementation has consistently resulted in increasing plasma methioninne concentrations. There is also a need to determine whether there are other potentially limiting amino acids, such as histidine, in diets that are typically fed to horses.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Mastellar SL*, Brewster-Barnes T, Cybulak K and Urschel KL. Splanchnic extraction of phenylalanine in mature mares was not affected by threonine supplementation. Vet J, 207: 190-192, 2016.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2016
Citation:
Mastellar SL*, Moffett A, Harris PA and Urschel KL. Effects of threonine supplementation on whole-body protein synthesis and plasma metabolites in growing and mature horses. Vet J, 207: 147-153, 2016.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2014
Citation:
Tanner SL. Evaluating dietary amino acid adequacy in horses using isotopic techniques. University of Kentucky. 2014.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2015
Citation:
Mok, C. Using the indicator amino acid oxidation technique to study threonine requirements in horses fed different feed compositions. University of Kentucky. 2015.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2016
Citation:
Smith, KM. Towards determination of the threonine requirement of yearling horses fed varying dietary compositions using the indicator amino acid oxidation method. University of Kentucky. 2016.
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Progress 07/01/14 to 06/30/15
Outputs
Target Audience:The target audience for this research is the scientific community, particularly those studying non-ruminant and equine nutrition, and the feed industry. Eventually, once more research in this area has been accomplished, we will focus our efforts on increasing the knowledge of the individual horse owners regarding amino acid metabolism, but as this type of research is still in its early stages, we have focused on these two entities. Data was presented in oral presentation form to the scientific community at the 2015 Equine Science Society meeting in St. Pete's Beach, Florida. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The research conducted this year provides the data for 2 MS thesis: Chan Hee Mok (to complete September 2015) and Kelsey Smith (expected completion Summer 2016). Throughout this project Kelsey and ChanHee were mentored about how to design and conduct animal research, including learning all of the sample collection techniques, how to perform laboratory and statistical analyses and how to write a scientific manuscript describing the findings from this research. Additionally, several other graduate and undergraduate students participated in this research, both during the sample collection and sample analysis phases and also received training in these methods. How have the results been disseminated to communities of interest?Results were presented at the 2015 Equine Science Society meeting and 2 manuscripts relating to the pilot studyhave been submitted to The Veterinary Journal. What do you plan to do during the next reporting period to accomplish the goals?We will complete the final sample analysis and statistical analysis for the growing horse study. Two MS thesis will be defended. An abstract pertaining to the growing horse study will be submitted. We intend to submit the manuscripts pertaining to each of the mature horse and growing horse studies.
Impacts
What was accomplished under these goals?
The mature horse study was completed. These results have been compiled into an MS thesis for Chan Hee Mok, which will be defended on September 29, 2015. We were unable to determine a requirement for threonine under high forage (80% of diet) or equal forage and concentrate conditions (50% forage), suggesting that threonine may not be a limiting amino acid in mature, idle horses receiving a good quality forage in their diet. This is the first evidence to dispute the claim that threonine is a key limiting amino acid for horses. The sample collection phase of the growing horse study was completed, and sample analysis is currently underway. In the growing horse study, horses received both the high forage (75% forage) and high concentrate (40% forage), with graded amounts of threonine provided to each treatment. This study is the first time that threonine has been studied independently as a potential limiting amino acid in growing horses using well accepted measures of whole-body protein metabolism.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Mok CH*, Brewster-Barnes T, and Urschel KL. Using the indicator amino acid oxidation technique to study threonine requirements in horses. Journal of Equine Veterinary Science, 35(5): 403, 2015.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2015
Citation:
Mastellar SL*, Moffett A, Harris PA and Urschel KL. Effects of threonine supplementation on whole-body protein synthesis and plasma metabolites in growing and mature horses. Submitted to Vet J on January 13, 2015 (YTVJL-D-15-00059).
- Type:
Journal Articles
Status:
Under Review
Year Published:
2015
Citation:
Mastellar SL*, Brewster-Barnes T, Cybulak K and Urschel KL. Splanchnic extraction of phenylalanine in mature mares was not affected by threonine supplementation. Submitted to Vet J on January 12, 2015 (YTVJL-D-15-00051).
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Progress 07/01/13 to 06/30/14
Outputs
Target Audience: The target audience for this research is the scientific community, particularly those studying non-ruminant and equine nutrition, and the feed industry. Eventually, once more research in this area has been accomplished, we will focus our efforts on increasing the knowledge of the individual horse owners regarding amino acid metabolism, but as this type of research is still in its early stages, we have focused on these two entities. Some preliminary data was presented in poster form to the scientific community at the 2014 Joint Annual Meeting of ASAS, ADSA and CSAS in Kansas City MO. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This research was a portion of the PhD dissertation research for Sara Tanner (completed in July 2014) and will also form the basis of a MS thesis research for 1-2 other students (including ChanHee Mok). Throughout this project Sara and ChanHee were mentored about how to design and conduct animal research, including learning all of the sample collection techniques, how to perform laboratory and statistical analyses and how to write a scientific manuscript describing the findings from this research. Additionally, several other graduate and undergraduate stude How have the results been disseminated to communities of interest? To date, the results have been presented at the 2014 Joint Annual Meeting of ASAS, ADSA and CSAS in Kansas City MO. What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period, we will complete the sample collection and analysis and begin manuscript preparation for the mature horse component of the study. We will also complete the growing horse portion of this study (the horses are currently ~6 months old).
Impacts
What was accomplished under these goals?
During this period we completed the sample analysis for the preliminary study in mature horses. We found that the lowest level of dietary threonine did not result in differences in whole-body protein metabolism when compared to a supplemental threonine diet, when horses consumed a diet with approximately 40% concentrate and 60% forage. Therefore, in future studies we will attempt to formulate diets with even less threonine for our basal diet. We did find that supplementing threonine to the diet results in alterations in the plasma concentrations of amino acids that share degradative pathways with threonine, such as methionine, serine and glycine. The plasma threonine concentrations were very high when horses were supplemented with threonine, suggesting limitations in the threonine catabolic pathways. Therefore, in our future studies we planned to reduce the total amount of supplemental threonine. We were also able to validate that the phenylalanine isotope can be delivered orally. We are currently in the process of completing the sampling on the mature horse portion of the study. To date, we have completed the sample collection from 3 horses in each of the high forage (20% concentrate) and high concentrate (40% concentrate) portions of the study and the remaining 3 horses for each of these portions are currently on study. Sample collection will be finished in November 2014 and we anticipate that sample analysis will be completed in the Spring of 2015.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
2. Tanner S*, Barnes T, Cybulak K* and Urschel KL. Splanchnic extraction of phenylalanine in adult Thoroughbred mares fed two different levels of threonine. Joint Annual Meeting ADSA-ASAS-CSAS 2014, Kansas City MO, July 20 24, 2014. Abstract #1199.
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Progress 07/01/12 to 06/30/13
Outputs
Target Audience: The target audience for this research is the scientific community, particularly those studying non-ruminant and equine nutrition, and the feed industry. Eventually, once more research in this area has been accomplished, we will focus our efforts on increasing the knowledge of the individual horse owners regarding amino acid metabolism, but as this type of research is still in its early stages, we have focused on these two entities. This project has just started and as data is not yet available, it has not been presented at this time. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This research was a portion of the PhD dissertation research for Sara Tanner and will also form the basis of a MS thesis research for 1-2 other students. Throughout this project Sara was mentored about how to design and conduct animal research, including learning all of the sample collection techniques, how to perform laboratory and statistical analyses and how to write a scientific manuscript describing the findings from this research. Additionally, several other graduate and undergraduate students participated in this study and it is expected that more undergraduate students will be involved in this study in the future. How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period, we will continue with the sample analysis from the pilot study (confirming that a deficient threonine diet was formulated) and then the first study (looking at threonine requirements in mature horses) will begin in early Spring 2014. This initial study will be completed by the end of the summer and sample analysis procedures will be conducted.
Impacts
What was accomplished under these goals?
At this time, we have only begun to collect data. We were able to formulate a low threonine diet (providing 48 mg/kg/d), and have conducted a pilot study to confirm that it is in fact deficient in threonine, in comparison to a diet that is top dressed with additional threonine. Additionally, we also conducted the work to validate the oral delivery of the phenylalanine isotope, rather than the intravenous administration, to make this procedure less invasive for the horses on study (as only a single catheter will be required on each study day). We were able to measure sufficient isotope label in the breath when the isotope was delivered orally, and although the samples are still being analyzed, it does appear as though our low threonine diet was in fact providing a deficient level of this nutrient. Sample analysis for this study is currently underway.
Publications
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