The effect of repeated lipopolysaccharide endotoxin challenge on immune response of breeding ewes and subsequent lamb performance.

Infectious disease caused by exposure to Gram-negative bacterial endotoxin lipopolysaccharide (LPS) is recognized to suppress female fertility. However, the effect of varying low-dose endotoxin exposure during distinct stages of follicle development on immune response, reproductive performance, and lamb performance has yet to be elucidated. Therefore, the objective of this study was to evaluate acute phase response, mRNA abundance of inflammatory markers, reproductive performance and lamb growth characteristics of ewes challenged with subclinical doses of LPS. Rambouillet ewes (n = 36; 68.2 ± 1.1 kg; age 3 to 7 yr) stratified by body weight (BW) and age were assigned to treatment groups. Ewes received subcutaneous injections of saline (CON, n = 12), 1.5 µg/kg BW LPS (LOW, n = 12), or 3.0 µg/kg BW LPS (HIGH, n = 12) on days 5, 10, and 15 of a synchronized follicular wave. Ewes were subsequently placed with a raddle-painted ram on day 16 for a 35-d breeding season. On treatment days 5 and 15, blood samples, peripheral blood leukocytes, and rectal temperature were collected before and at regular intervals for 12 h after LPS challenge. Immune response to LPS was confirmed by increased temperature and serum cortisol concentrations on days 5 and 15. Endotoxin increased circulating plasma concentration of the acute phase protein, haptoglobin by greater than 15%, in both LPS-treated groups on days 5 and 15 at 12 h compared with control (P≤ 0.05). Pro- and anti-inflammatory mRNA gene expression demonstrated no differences in expression for tumor necrosis factor-α or peroxisome proliferator-activated receptor gamma among treatment groups (P > 0.10). Likewise, Toll-like receptor 4 (TLR4), interleukin-8 (IL-8), and superoxide dismutase 2 (SOD2) expression was similar among treatment groups on day 5. However, ewes challenged with LPS on day 15 displayed greater mRNA expression for TLR4 from 2 to 6 h (P < 0.05), a 7-fold increase for IL-8 from 1.5 to 2.5 h (P < 0.05), and 8-fold induction for SOD2 from 2 to 6 h (P < 0.05) as compared with controls. First service conception rates were 90% for control ewes and 75% for both treated groups (P â€…= 0.84). Treated ewes demonstrated a reduction in lamb birth weight compared with controls (P ≤ 0.05) and a tendency for reduction of 60-d adjusted weaning weight (P = 0.09). Data suggest that subacute endotoxin exposure aligning with key follicle and oocyte maturation events results in detrimental growth performance of the subsequent lamb.

During disease states, bacterial endotoxins act locally and systemically, negatively impacting reproductive capacity and economic productivity. The present study investigated the impacts of repeated low-dose endotoxin exposure during follicular development on the immune response and subsequent reproductive and lamb growth variables. Results indicate that bacterial endotoxin challenge during follicular development and oocyte maturation leads to reduced lamb birth weight and 60-d adjusted weaning weight.

A Case Study Using Accelerometers to Identify Illness in Ewes following Unintentional Exposure to Mold-Contaminated Feed.

Sensor technologies can identify modified animal activity indicating changes in health status. This study investigated sheep behavior before and after illness caused by mold-contaminated feed using tri-axial accelerometers. Ten ewes were fitted with HerdDogg biometric accelerometers. Five ewes were concurrently fitted with Axivity AX3 accelerometers. The flock was exposed to mold-contaminated feed following an unexpected ration change, and observed symptomatic ewes were treated with a veterinarian-directed protocol. Accelerometer data were evaluated 4 days before exposure (d -4 to -1); the day of ration change (d 0); and 4 days post exposure (d 1 to 4). Herddogg activity index correlated to the variability of minimum and standard deviation of motion intensity monitored by the Axivity accelerometer. Herddogg activity index was lower (p < 0.05) during the mornings (0800 to 1100 h) of days 2 to 4 and the evening of day 1 than days -4 to 0. Symptomatic ewes had lower activity levels in the morning and higher levels at night. After accounting for symptoms, activity levels during days 1 to 4 were lower (p < 0.05) than days -4 to 0 the morning after exposure. Results suggest real-time or near-real time accelerometers have potential to detect illness in ewes.