Effects of dietary feed additives on the performance and gastrointestinal health of broilers exposed with coccidial spores and varying litter conditions

Abstract

Coccidiosis is a prevalent parasitic disease in broiler chickens, caused by protozoa of the genus Eimeria. Birds become infected by ingesting sporulated oocysts from contaminated litter, resulting in intestinal damage, impaired nutrient absorption, and reduced growth performance, which contribute to economic losses for poultry producers. Conventional control methods, including vaccines, ionophores, and other anticoccidials, have limitations, prompting the need for alternative strategies. This dissertation investigates the effectiveness of dietary feed additives, essential oils (garlic and cinnamon), betaine, butyrate, and benzoic acid, on broilers raised under coccidial challenges and varying litter conditions such as differences in moisture content and reuse of litter, focusing on their potential to improve performance, gastrointestinal health, and sustainability while reducing antimicrobial reliance. The second chapter provides an in-depth literature review on coccidiosis, alternative feed additives, and factors influencing litter quality. In the third chapter, the combination of essential oils and betaine was effective in mitigating the effects of coccidiosis. Broilers supplemented with 500 ppm of essential oils and 250 ppm of betaine and raised on used litter seeded with coccidia increased BWG and reduced FCR over multiple time periods (P ≤ 0.05). Oocyst counts were reduced in treated birds compared to the PC, validating the efficacy of this treatment in mitigating the adverse effects of coccidiosis. The fourth chapter evaluated butyrate supplementation in broilers raised on used litter without antibiotics, examining its effects on growth performance, nutrient digestibility, and intestinal health. The supplementation of butyrate in the broiler diet resulted in improved performance over the starter phase of broiler production. Broilers fed 500 ppm butyrate from days 0–8 exhibited a 7% improvement in BWG and a 5% reduction in FCR compared to the PC (P ≤ 0.05). However, these advantages diminished by day 42. Additionally, butyrate improved apparent ileal digestibility of dry matter and energy during the starter phase (P ≤ 0.05) but did not significantly reduce oocyst shedding. Benzoic acid was investigated in pure (PBA) and enteric released (EBA) forms in the fifth chapter. Over the 0–42-day period, EBA supplementation (330 ppm) improved BWG by 5.1% and decreased FCR by 4.6% compared to the control group, which consisted of broilers fed a basal diet without benzoic acid supplementation (P ≤ 0.05). Additionally, enteric-released benzoic acid led to significant improvements in intestinal morphology, specifically reducing crypt depth and increasing the villus height-to-crypt depth ratio in the jejunum and ileum. In the sixth chapter, the combination of betaine and butyrate (B+B) was evaluated under varying litter moisture conditions. B+B supplementation increased energy (4.0%) and dry matter digestibility (4.5%) on day 17 (P ≤ 0.05) but did not improve performance over a 0–42-day broiler grows out period. The increased litter moisture generated by the addition of 2,000 mL of water/day (over the first 21 d) resulted in decreased broiler BWG over the starter phase in comparison to the broilers raised on litter without water addition (P ≤ 0.05). The seventh chapter builds a tool to allow the use of Near-Infrared (NIR) spectroscopy for real-time litter moisture monitoring. To achieve this, 1,455 litter samples across five trials were modeled for NIR spectrum and litter dry matter. Calibration models exhibited high predictive accuracy, characterized by improved R-squared values and reduced standard errors of prediction. These findings highlight the promise of NIR spectroscopy as a tool for precision litter management, particularly with continued advancements and updates to on-farm technology. Overall, this dissertation defines the potential of feed additives in broiler production and the importance of managing environmental conditions, particularly litter quality to maximize performance and efficiency. These findings provide potential and practical insights into reducing reliance on antibiotics while maintaining broiler performance and health, aligning with industry demands for sustainable broiler production.