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Effects of hindgut acidosis in lactating dairy cows already experiencing systemic inflammation.

M. A. Abeyta




Effects of hindgut acidosis in lactating dairy cows already experiencing systemic inflammation.
M. A. Abeyta*, E. A. Horst, E. J. Mayorga, B. M. Goetz, S. J. Rodriguez-Jimenez, M. F. Caratzu, L. H. Baumgard. Department of Animal Science, Iowa State University Ames, IA.

Following parturition cows experience an increased starch load to the large intestine, and we hypothesize that the negative consequences of hindgut acidosis are exacerbated by prior periparturient immunoactivation. Therefore, objectives were to evaluate the effects of hindgut acidosis on metabolism and inflammation in cows previously infused i.v. with lipopolysaccharide (LPS). Twelve rumen cannulated cows were enrolled in a study with 3 experimental periods (P). Baseline data were collected during P1 (5d). Beginning on d1 of P2 (2d), all cows received an i.v. LPS bolus (0.2 �g LPS/kg BW). During P3 (4d), cows were randomly assigned to 1 of 2 abomasal infusion treatments: 1) control (LPSCON; 1.5 L H2O/infusion; n = 6) or 2) starch infused (LPSST; 1 kg corn starch + 1.5 L H2O/infusion; n = 6) 4 times daily. Additionally, both treatments received an LPS bolus on d1 and 3 of P3 (0.8 and 1.6 �g LPS/kg BW, respectively). Effects of treatment, time, and treatment � time were assessed using PROC MIXED. During P3, starch infusion markedly decreased fecal pH relative to controls (0.82 pH units; P < 0.01). Relative to P1, administering LPS decreased production metrics during both periods, and the most pronounced effects were observed on d1 of P2 and d1 and 3 of P3 for milk yield (54, 45, and 37%) and DMI (49, 43, and 40%) respectively (all P < 0.01); However, starch infusion did not exacerbate effects of LPS on either parameter. Regardless of starch infusion, administering LPS markedly altered milk components and somatic cell counts. During P3, hindgut acidosis had no effect on circulating glucose, insulin, NEFA, or BHBA (P > 0.35), but decreased BUN (17%; P = 0.07) relative to LPSCON cows. Relative to P1, LPS administration markedly increased SAA and LBP during P2 (3.3-fold and 51%) and P3 (2.7-fold and 48%; all P < 0.01), however there were no additional effects of starch administration during P3 on acute phase proteins. By design, LPS administration initiated marked changes in metabolism and inflammation, however, hindgut acidosis did not exacerbate the inflammatory response.

Keywords: inflammation, starch infusion, LPS.

Biography: Megan is a PhD student under the direction of Dr. Lance Baumgard.