PSII-9 - Circulating cytokine profiles of Bos indicus cattle prior to artificial insemination in relation to pregnancy status

Abstract: Cytokines and chemokines (cytokines with chemotactic activity) influence inflammatory responses and can upregulate pro- or anti-inflammatory immune responses and influence fertility. The aim of this study was to characterize the circulating cytokines of Bos indicus females prior to fixed-timed artificial insemination (FTAI). Bos indicus females on operations within a 20-mile radius were subjected to the 7-day CO-Synch + CIDR protocol on day (d)-9 and FTAI on d0. Blood samples were collected on d-9 (CIDR IN), d-2 (CIDR OUT), and d0 (AI). Cattle were body condition scored (BCS) on d0. Pregnancy status was determined by transrectal ultrasonography for resulting non-pregnant females (n=44) and resulting pregnant females (n=34). Cytokine analyses on blood plasma samples were conducted using the RayBiotech Quantibody® Bovine Cytokine Array Q1 kit per manufacturer's instructions. Cytokines and chemokines measured included interferon alpha (IFNa), interferon-gamma (IFNg), interleukin (IL)1a, IL1F5, IL13, IL21, chemokine-ligand (CXCL)9, CXCL10, macrophage inflammatory protein (MIP)1b, and tumor necrosis factor alpha (TNFa). Data were analyzed using PROC GLM in SAS 9.4 with fixed effects for pregnancy status, ranch, day, and parity. Body condition scores did not significantly differ by pregnancy status (P > 0.05). There were no differences in cytokine concentrations by day of the synchronization protocol or between cows and heifers (P > 0.05). There were differences by location (P < 0.05) for most cytokines except MIP1b and TNFa. Circulating concentrations of the pro-inflammatory cytokines IFNg, IL1a, and TNFa were greater (P < 0.05) in resulting non-pregnant females compared to pregnant females (2323.5 ± 260.5 vs. 1502.8 ± 246.8 pg/mL, 894.6 ± 96.8 vs. 598.3 ± 91.7 pg/mL, and 6052.6 ± 627.4 vs. 4156.6 ± 594.3 pg/mL, respectively). Circulating concentrations of the chemokines CXCL9, CXCL10, and MIP1b were also greater (P < 0.05) in resulting non-pregnant females compared to pregnant females (4887.0 ± 538.3 vs. 2905.3 ± 509.8 pg/mL, 12167.3 ± 1496.2 vs. 6295.4 ± 1417.2 pg/mL, 586.4 ± 56.8 vs 324.4 ± 53.8 pg/mL, respectively). Interestingly, circulating concentrations of the anti-inflammatory cytokines IL13, IL1F5, and IL21 were greater (P < 0.05) in resulting non-pregnant females compared to pregnant females (11147.7 ± 1009.9 vs. 6752.1 ± 956.6 pg/mL, 1189.3 ± 111.7 vs. 744.5 ± 105.8 pg/mL, and 11153.6 ± 898.0 vs. 8409.7 ± 850.6 pg/mL, respectively). No differences by pregnancy status were found for concentrations of IFNa (P = 0.13). These results suggest that an elevation in circulating cytokines and chemokines prior to FTAI negatively impacts fertility in Bos indicus cattle. Future research is necessary to determine the threshold of circulating cytokine levels that subsequently impact pregnancy establishment and maintenance.