Intrauterine bacterial inoculation and level of dietary methionine alter amino acid metabolism in nulliparous yearling ewes

Authors: Thelen, Tonya; LOEST, C. - NEW MEXICO STATE UNIV.; Taylor, Joshua - Bret; Wang, Shiquan; Lewis, Gregory

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2007
Publication Date: 9/4/2007
Citation: Thelen, T.M., Loest, C.A., Taylor, J.B., Wang, S., Lewis, G.S. 2007. Intrauterine bacterial inoculation and level of dietary methionine alter amino acid metabolism in nulliparous yearling ewes. Journal of Animal Science. 85:3371-3382.

Interpretive Summary: We measured amino acid metabolism in yearling ewes harboring an acute uterine infection. In response to the infection, the liver tissue released aromatic amino acids, but consumed gluconeogenic amino acids. These activities suggest that the liver is activity synthesizing acute-phase proteins and glutathione to mitigate the infection. We also investigated the effects of feeding diets low or high in metabolizable-methionine on amino acid metabolism in infected ewes. Based on the data, when dietary metabolizable-methionine is sufficient, methionine is not limiting in ewes experiencing an acute infection. Furthermore, supplemental methionine above what is physiologically needed would not necessarily result in a benefit to infected ewes.

Technical Abstract: Using an intrauterine bacterial inoculation method, our objective was to determine the effects of acute sepsis and level of dietary metabolizable-methionine on splanchnic metabolism of amino acids in ewes. Twenty-five nulliparous yearling Rambouillet-cross ewes (initial BW = 65.1 ± 0.6 kg), surgically fitted with chronic-indwelling catheters in hepatic and portal veins, a mesenteric vein and artery, and the uterine lumen, were assigned to a 2 x 2 factorial arrangement of randomized treatments. Factors were intrauterine bacteria inoculation (noninoculated vs. inoculated) and level of metabolizable-methionine (MM; low [2.4 g/d] vs. high [4.0 g/d]). Beginning 12 h before sampling, inoculated and noninoculated ewes received 10-mL intrauterine infusions of Escherichia coli (9.69 x 1011 cfu) + Arcanobacterium pyogenes (2.76 x 1012 cfu) and sterile saline, respectively. Uterine infection was induced in ewes that received intrauterine bacterial inoculations, but not in ewes infused with sterile saline. Inoculation resulted in increased hepatic release and plasma concentrations of aromatic amino acids used for acute-phase protein synthesis, increased hepatic removal and decreased plasma concentrations of amino acids used for glutathione synthesis, and decreased plasma concentrations of some gluconeogenic and acetogenic amino acids use for glucose recycling and anaerobic energy production, respectively (P < 0.05). In ewes fed high-MM diets, compared with low-MM, a consistent net hepatic uptake of phenylalanine occurred throughout the sampling period, more aspartate was released from the portal-drained viscera, and hepatic-vein glucose concentrations were greater (P < 0.05). These data suggests that methionine was limiting in low-MM ewes. Because of the lack of significant interactions between the inoculation and metabolizable-methionine treatments, it was difficult to determine whether greater dietary metabolizable-methionine was beneficial to ewes that received intrauterine bacterial inoculation. The evidence that methionine was limiting in low-MM ewes, would suggest that methionine would continue to be limiting during sepsis. However, based these results, methionine was not the most limiting amino acid in non-fasted ewes experiencing acute sepsis and additional metabolizable-methionine, in excess of the dietary requirement, would not necessarily result in a benefit to ewes experiencing acute sepsis.