|Bequette, Brian - UNIVERSITY OF MARYLAND|
|Oba, Masahito - UNIVERSITY OF MARYLAND|
|Owens, Sandra - UNIVERSITY OF MARYLAND|
Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: September 11, 2004
Publication Date: September 8, 2003
Citation: Baldwin, R.L., Bequette, B.J., Oba, M., Owens, S.L., 2003. Effect of vfa on ammonia utilization for amino acid and urea synthesis by ruminal epithelial and duodenal mucosal cells isolated from growing sheep [abstract]. Journal of Dairy Science 86(Suppl. 1):280. Technical Abstract: The objective was to determine effects of VFA on the extent of assimilation of ammonia N into amino acids and urea by isolated ruminal epithelial (REC) and duodenal mucosal cells (DMC) in short-term incubations. Cells were isolated from growing Polypay ram lambs (n=4) fed a mixed forage-concentrate diet, and incubated for 90 min in media containing [15N]ammonia and glucose plus either acetate or propionate (5 mM each). Production of Ala, Asp, Glu, Arg + citrulline, and urea, and 15N enrichment were determined by gas chromatography-mass spectrometry. Data are presented as a production rate per 106 cells during 90 min incubations. In both cell types, the total release of Ala, Asp, Glu, Arg + citrulline, and urea was not affected VFA. However, for REC, acetate increased net release of Glu (0.51 vs. 0.40 nmol; P < 0.05), and tended to increase that of Asp (0.19 vs. 0.15 nmol; P = 0.07) and Ala (0.64 vs. 0.40 nmol; P = 0.10) compared to propionate treatment. However, ammonia N was not incorporated into Arg + citrulline and urea by REC. For DMC, assimilation of ammonia N into Ala, Asp, and Glu was also greater for acetate (1.57, 0.69, and 2.07 nmol, respectively) compared to propionate treatment (0.86, 0.46, and 1.37 nmol, respectively; all P < 0.05). Use of ammonia N for Arg synthesis tended to be greater for acetate compared to propionate treatment (0.75 vs. 0.49; P = 0.08), but ammonia N was not incorporated into urea. In summary, ruminant gut tissues are capable of assimilating ammonia N into amino acids, and VFA type affect the extent of ammonia N utilization for amino acid synthesis.