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 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 d 5, 10, and 15 of a synchronized follicular wave. Ewes were subsequently placed with a raddle-painted ram on d 16 for a 35-d breeding season. On treatment d 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 d 5 and 15. Endotoxin increased circulating plasma concentration of the acute phase protein, haptoglobin by greater than 15%, in both LPS-treated groups on d 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 d 5. However, ewes challenged with LPS on d 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 = 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.

Growth, carcass characteristics, cut yields and meat quality of lambs finished with zilpaterol hydrochloride and steroid implant.

Forty hairbreed male lambs were used to evaluate the effects of zilpaterol hydrochloride (ZH, 0 and 0.15 mg/kg BW) and steroid implant (SI, without and with 52.5 mg trenbolone acetate and 7.5 mg 17ß-estradiol) on feedlot performance, carcass characteristics, non-carcass components, wholesale cut yield, and meat quality. Supplemental ZH increased growth rate, feed efficiency, carcass weight, and dressing percentage, with no effect on wholesale cut yields. Feeding ZH increased muscle pH at 24 h. Supplemental ZH increased meat shear force, but decreased lightness, redness, and yellowness after frozen storage followed by a 14-day aging period. The SI administration increased dressing percentage and neck yield, but decreased testicle weight and meat redness, without affecting other variables. The LT area was greater with ZH + SI administration than with individual application of ZH or SI. Compared to individual administration, simultaneous application of ZH and SI did not result in improved growth performance, carcass traits and wholesale cut yields in hairbreed male lambs.