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Effects of an immunomodulatory feed additive on granulocyte activity in peripheral blood and uterus of early lactating cows.

C. S. Takiya



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Effects of an immunomodulatory feed additive on granulocyte activity in peripheral blood and uterus of early lactating cows.
C. S. Takiya*1, J. L. McGill2, L. K. Mamedova1,3, A. L. A. Scanavez1, R. Rusk1, L. G. D. Mendon�a1, M. Garcia4, D. E. Nuzback4, B. J. Bradford1,3. 1Kansas State University Manhattan, KS, 2Iowa State University Ames, IA, 3Michigan State University East Lansing, MI, 4Phibro Animal Health Teaneck, NJ.

Parturition is a stressful event that causes endometrial damage and facilitates uterine infections. OmniGen-AF (OMN, Phibro Animal Health, Teaneck, NJ) is a feed additive that has improved measurements of cellular immunity and postpartum uterine health of mammals. However, OMN effects on immune cells isolated from endometrium have not been explored. Twenty-eight healthy multiparous cows were blocked by expected calving date and assigned to control or OMN (56 g/d top-dressed) from dry-off (67 � 3.0 d before calving date) until 49 d in milk. Endometrial samples were collected on d 12 � 2, 21 � 3, and 38 � 3 postpartum using the cytobrush technique. Blood samples were also collected after cytobrush sampling. Blood and uterine brush samples were prepared for flow cytometry to measure oxidative burst of granulocytes after phorbol myristate acetate stimulation. Labeled antibodies (CH138a and CD45) and dihydrorhodamine were used to identify granulocytes and quantify oxidative burst, respectively. Granulocyte response (GR) was calculated as stimulated — basal oxidative burst. Data were analyzed using the Mixed procedures of SAS to model the fixed effects of treatment, time, their interaction, and random effects of cow and block; fixed effects of parity group, temperature-humidity index, and all interactions were also tested in a stepwise backward elimination when P > 0.15. Significance was declared at P < 0.05. Granulocyte percentage in uterine samples did not differ between treatment groups (10.7 vs. 9.30 � 2.8% for OMN and control, respectively) but decreased over lactation from 14.4 � 3.7% on d 10 to 2.39 � 4.61% on d 38. Similar GR, both in blood and uterine samples, was observed across treatment groups; however, a treatment � time interaction was observed in uterine GR. Cows fed OMN had lesser uterine GR on d 10 and greater uterine GR on d 38 compared with controls. Furthermore, OMN increased GR in parity 3+ cows but did not influence parity 2 cows. This study demonstrated that OMN did not alter neutrophil infiltration but modulated uterine GR in early lactation, with a greater impact on cows with 3 or more parities.

Keywords: OmniGen-AF, neutrophil, oxidative burst.