PS3-6. Effects of Dietary Supplementation with Dried Seaweed, Micro-Fused Essential Oils, and Lactobacillus reuteri on Pregnancy Rates in Ewes Following Natural Breeding.

Abstract Natural feed additives, including micro fused essential oils (MEO), probiotics (e.g., Lactobacillus reuteri; LR), and plant-derived supplements such as seaweed, are increasingly explored as alternatives to antibiotics in ruminant production. These additives have been associated with improvements in growth performance, gut microbiota balance, immune function, and antioxidant status. However, despite these benefits, their effects on reproductive performance and growth outcomes in livestock remain unclear. This study evaluates the effects of dietary supplementation with LR, dried seaweed meal (DSM), and MEO on pregnancy rates following natural breeding in ewes. A total of 36 crossbred ewes (1 year old) were stratified by body weight and randomly assigned to four dietary treatments (n = 9 per group): (1) control (basal diet), (2) basal diet + 5 g/head/day DSM, (3) basal diet + 4g/head/day MEO (1.3% Origanum vulgare subsp. hirtum), and (4) basal diet + 10 g/head/day lyophilized LR (2 × 10⁹ CFU/g). Ewes were individually housed and managed under uniform conditions throughout the experimental period. Ewes were synchronized for estrus using CIDR inserts for 11 days, with a PGF₂α injection (dinoprost, 10 mg/ml/female) on day 10. Females were bred 24-72 h post-CIDR removal using two mature adult rams (2-3 years). Pregnancy was diagnosed using transabdominal ultrasonography on day 28 post-breeding (PB) and females’ body weights were also recorded at the same time. Fisher exact test and one-way ANOVA were used to analyze pregnancy outcomes and body weight data, respectively. No significant differences were observed in pregnancy rates (ranged from 77.8% to 88.9%) and body weights (109lb to 120lb) among the control and treatment groups. In conclusion, dietary supplementation with DSM, MEO, and LR had no effects on pregnancy rates or body weights of pregnant ewes. Further studies are in progress to evaluate the levels of reproductive hormones, blood metabolomics, and vaginal microbiome in relation to feed supplements.