By Ashen Epa Arachchi, University of Arkansas
Modern broiler production faces the dual challenge of sustaining high growth efficiency while reducing reliance on antibiotic growth promoters. Although genetic selection has accelerated growth rates, it has also increased susceptibility to gut dysfunction, skeletal weakness, and welfare concerns. Consequently, feed additives that enhance intestinal integrity and skeletal development, without negatively affecting performance, are of growing importance to the poultry industry.
Synbiotics, which combine prebiotics and probiotics, are designed to support beneficial gut microbiota while improving intestinal structure and function. However, their commercial adoption depends on consistent responses across broiler strains and measurable benefits under practical rearing conditions. In a recent study published in European Poultry Science, researchers evaluated the effects of a synbiotic containing fructooligosaccharides (FOS) and multiple probiotic strains (Enterococcus, Bifidobacterium, Pediococcus, and Lactobacillus spp.) on growth performance, intestinal morphology, tibia characteristics, and caecal microbiota in Cobb 500 and Ross 308 broilers.
Six hundred male broilers were fed a basal diet, an antibiotic-supplemented diet, or a synbiotic-supplemented diet (0.5 g/kg) for 35 days. Importantly, both genetic strain and diet were considered, providing results that are directly relevant to integrators using different commercial broiler lines.
The study showed that synbiotic supplementation had no negative effects on overall weight gain, feed intake, and feed conversion ratio (p > 0.05) in either strain. However, Cobb 500 broilers consumed more feed (p < 0.0001) and achieved greater body weight gain over the full rearing period (p < 0.01) than Ross 308 birds, confirming known strain-related performance differences. The absence of negative performance effects from synbiotic supplementation is notable, as it indicates that replacing or reducing antibiotics did not compromise productivity under thermoneutral conditions.
While growth performance remained unchanged, synbiotic supplementation significantly improved indicators of gut health. Broilers fed the synbiotic exhibited greater duodenal villus height compared with control and antibiotic-fed birds (p < 0.01), alongside reduced villus width (p < 0.05). These structural changes reflect enhanced intestinal absorptive surface area and improved epithelial efficiency, outcomes that may not immediately translate into higher body weight but are critical for nutrient utilization, disease resilience, and long-term flock stability.
From an industry standpoint, skeletal health findings were particularly relevant. Synbiotic-fed birds showed higher tibia weight (p = 0.02) and increased tibia dry matter content (p = 0.008) compared with birds receiving antibiotics, despite no differences in bone-breaking strength (p > 0.05). Given the economic and welfare costs associated with leg disorders in fast-growing broilers, improvements in bone mineral characteristics may contribute to better skeletal robustness under commercial stressors such as high stocking density or heat stress.
Caecal bacterial populations, including Lactobacillus spp., Clostridium spp., and E. coli, were not significantly altered by diet or strain (p > 0.05), and Salmonella was not detected in any group. This suggests that synbiotic supplementation was microbiologically safe and did not disrupt intestinal microbial balance.
Why is this study important for the producers?
- Synbiotics provided measurable gut and bone benefits without compromising growth performance, supporting antibiotic-reduction strategies.
- Positive responses were consistent across Cobb 500 and Ross 308, increasing confidence in broad commercial application.
- Improvements in intestinal architecture and tibia quality may enhance bird resilience, reducing welfare issues and long-term production losses.
Overall, this study highlights that synbiotics can deliver valuable physiological advantages that support sustainable, antibiotic-conscious broiler production even when short-term performance gains are not immediately evident.
The full paper can be found in Volume 90, Issue 1-2 of European Poultry Science and is available online at https://doi.org/10.1016/j.eups.2025.100012.
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