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Effects of antioxidant supplementation on metabolism and inflammatory biomarkers in heat-stressed dairy cows.

M. A. Abeyta




Effects of antioxidant supplementation on metabolism and inflammatory biomarkers in heat-stressed dairy cows.
M. A. Abeyta*1, M. Al-Qaisi1, E. A. Horst1, E. J. Mayorga1, S. J. Rodriguez-Jimenez1, B. M. Goetz1, S. Carta1, H. Tucker2, L. H. Baumgard1. 1Department of Animal Science, Iowa State University Ames, IA, 2Novus International St. Charles, MO.

Study objectives were to evaluate if antioxidant supplementation (AP; AGRADO Plus 2.0; Novus International, St. Charles, Missouri) affects metabolism and inflammatory biomarkers in hyperthermic lactating dairy cows. Thirty-two cows were randomly assigned to 1 of 4 dietary-environmental treatments: 1) thermoneutral (TN) conditions and control (TNCON; n = 8), 2) TN conditions and AP (TNAP; n = 8), 3) heat stress (HS) and control (HSCON; n = 8), or 4) HS and AP (HSAP; n = 8). Before study initiation, cows were fed their respective diets for 30d and dietary treatments were top-dressed once daily. The trial consisted of 2 experimental periods (P); during P1 (4d) baseline data were collected. During P2 (7d) HS was artificially induced using an electric heat blanket (Thermotex Therapy Systems Ltd., Calgary, Canada). Effects of treatment, day, and treatment � day interaction were assessed using PROC MIXED. HS increased (P < 0.01) rectal, vaginal, and skin temperatures relative to TN controls and the largest differences were detected on d3—7 (1.2, 1.1, and 1.9�C, respectfully). On d2 of HS, AP supplementation decreased respiration rate (15%; P = 0.01) relative to HSCON. As expected, HS decreased (P < 0.01) milk yield and DMI during P2 and this was most pronounced on d4—7 (28, and 33%, relative to TN). Feed efficiency was increased by AP supplementation on d4—7 of HS relative to HSCON (15%; P = 0.06). DMI from HSAP cows tended to be decreased relative to HSCON cows during P2 (10%; P = 0.06). Circulating insulin and NEFA did not differ across environmental treatments, however, AP supplementation decreased insulin (37%; P = 0.01) and increased NEFA (68%; P = 0.03) during HS relative to HSCON cows. HS decreased circulating glucagon (26%; P < 0.01) relative to TN cows. Throughout P2, BUN from HS cows increased (21%; P < 0.01) relative to TN, and on d3 AP supplementation decreased BUN relative to HS controls (15%; P < 0.01). HS increased SAA and LBP relative to TN cows (78 and 59%, P = 0.08 and < 0.01) but neither variable was influenced by AP. Overall, AP supplementation appeared to alter metabolism but not inflammation during heat stress.

Keywords: heat stress, antioxidant, inflammation.

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