Uterine health and fertility of timed AI postpartum Nelore beef cows raised in the Amazon biome

Abstract

This study evaluated the effect of uterine health on the fertility of postpartum beef cows. Multiparous lactating Nelore cows (Bos indicus; n = 155) were subjected to a timed artificial insemination (TAI) protocol. Cows were included in a progesterone-estradiol based TAI protocol. On Day 0, before the beginning of the protocol, cows were subjected to evaluation of purulent vaginal discharge (PVD) and collection of uterine tissue using the cytobrush technique. Slides for polymorphonuclear (PMN) cells counting were prepared before the same cytobrush was used for RNA extraction and analysis of IL-1β, IL-6, IL-8, TNFα, GAPDH, and βactin gene transcription. Cows were separated into 4 categories according to the proportion of PMN and PVD: 1) Healthy (HE; n = 87), cows with ≤ 4.75% PMN and PVD of 0; 2) Positive Purulent Vaginal Discharge (PVD+; n = 24), cows with ≤ 4.75% PMN and PVD ≥ 1; 3) Subclinical Endometritis (SCE; n = 29), cows with > 4.75% PMN and PVD of 0, and; 4) Subclinical Endometritis + PVD+ (SCEP; n = 15), cows with > 4.75% PMN and PVD ≥ 1. Cows in the HE group had a greater (P < 0.05) pregnancy per AI (P/IA) than cows in SCE and SCEP groups. However, P/AI in cows from the PVD+ group was not different in comparison to HE and SCE groups (P > 0.05). Cows from the SCE and SCEP groups had a higher (P < 0.001) proportion of PMN cells in the uterus than HE and PVD+ groups. Relative transcription of IL-6 and TNFα did not change among groups (P > 0.05). In contrast, transcription of IL-8 was greater (P = 0.02) in SCEP than HE and SCE groups. The relative transcription IL-1β was greater (P < 0.05) in SCEP than in PVD+, but the cows in the HE and SCE groups were not different from the other groups (P = 0.08). Our results demonstrate that postpartum beef cows, raised in the Amazon biome, with a higher proportion of PMN cells have lower fertility. Moreover, ~ 40% of the postpartum cows included in TAI programs early postpartum had suboptimal uterine conditions (subclinical endometritis, purulent vaginal discharge, or both).