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Effects of hindgut acidosis in feed-restricted dairy cows.

M. A. Abeyta




Effects of hindgut acidosis in feed-restricted dairy cows.
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.

Cows experience an increased starch load to the large intestine following parturition, and we hypothesize that the negative consequences of hindgut acidosis (HGA) may be exacerbated by prior periparturient stressors (i.e., reduced feed intake, inflammation). Therefore, objectives were to evaluate the effects of HGA on metabolism and inflammatory biomarkers in feed restricted (FR) cows. Twelve rumen cannulated cows were enrolled in a study with 3 experimental periods (P). During P1 (5d), baseline data were collected. During P2 (2d), all cows were FR to 40% of their ad libitum P1 feed intake. During P3 (4d) cows remained FR and were randomly assigned to 1 of 2 abomasal infusion treatments: 1) control (FRCON; 1.5 L H2O/infusion; n = 6) or 2) starch (FRST; 1 kg corn starch + 1.5 L H2O/infusion; n = 6). Respective treatments were infused 4 � daily. Effects of treatment, time, and treatment � time were assessed using PROC MIXED. Starch infusions markedly decreased fecal pH relative to FRCON during P3 (0.96 pH units; P < 0.01). By design, DMI decreased 60% relative to baseline for both treatments during P2 and P3 (P < 0.01). Milk yield was markedly decreased by FR during P2 and 3 relative to P1 (39%; P < 0.01), but was unaffected by HGA (P > 0.91). Feed restriction altered milk components and variables differently over time with no effect of HGA except on MUN, which decreased (28%; P = 0.01) relative to FRCON during P3. Feed restriction increased NEFA and decreased circulating glucose and insulin for both periods and the most pronounced differences were observed during P2 (3.6-fold, 13 and 74%, respectively; P < 0.01). Starch infusion did not influence circulating NEFA, glucose, and insulin patterns during FR. Relative to FRCON, BHBA concentrations increased (55%; P = 0.04) in FRST cows during P3. Over time, FR decreased BUN for both treatments but starch infusions further exacerbated this response during P3 as BUN levels decreased (31%; P = 0.03) relative to FRCON. No effects of FR or HGA were observed for SAA and LBP. By design, FR caused marked alterations in metabolism, however, no effects of FR or FR in combination with HGA were observed on inflammation.

Keywords: inflammation, starch infusion.

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