Written by Dr Vincent Jacquier, Category Specialist Poultry
Maximizing broiler body weight: scientific evidence
In modern poultry production, optimizing body weight (BW) and feed efficiency under diverse environmental, nutritional, and management conditions is essential for securing profitability and sustainability. As the industry moves toward reduced antibiotic usage and greater reliance on natural growth-promoting tools, phytogenic feed ingredients, particularly those containing essential oil compounds (EOC), are attracting considerable attention. Among these solutions, the product called I-prove has been evaluated extensively for its ability to enhance broiler body weight gain (BWG), improve feed conversion ratio (FCR), and support overall gut health.
This article focuses specifically on body weight improvement, using consolidated data from a 15trial meta-analysis and a controlled dose-response study, both of which have demonstrated robust performance benefits. The evidence confirms that efficacious phytogenic compounds not only stimulate growth but do so across a wide range of production contexts.
1. I-prove meta-analysis: +40 g BWG and -1 pts FCR across trials
A consolidated dataset from 15 independent broiler trials conducted under diverse geographic, dietary, and management conditions provides a robust basis for evaluating the effects of I-prove in birds between 35 and 42 days of age. Across these studies, the meta-analysis showed an average of +40 g in body weight gain, with improvements observed in 75% of individual observations and an overall enhancement of the feed conversion ratio by 1 point. These results underline the consistency of the response to I-prove, an essential characteristic for any growth promoting additive, and they demonstrate that achieving an additional 40 g at flock level represents a meaningful biological and economic advantage even under variable production environments.
2. Dose-response trial: Identifying the optimal inclusion level
Controlled dose‑response trials are essential to confirming product efficacy, as they determine whether performance improvements follow a linear, quadratic, or plateau pattern. In the I-prove dataset, broilers were fed diets containing 0, 50, 75, 100, and 200 g/ton of the additive: 100 g/ton was revealed to be the optimal inclusion level, as it delivers the best overall performance. At this dose, broilers showed a +2.3% improvement in BWG at day 21 and +1% at day 35, with clear FCR improvement trends during early- and mid‑cycle. A significant quadratic response for FCR at day 11 (p<0.01) indicates diminishing returns at higher doses, confirming that 100 g/ton is both the technically optimal and economically sound choice.
3. Study case: comparative performance of I-prove and AGP in a Thailand trial
With the progressive restriction and phasing‑out of antibiotic growth promoters (AGPs), poultry producers are increasingly relying on non‑antibiotic solutions to maintain growth performance and feed efficiency. Therefore, it is essential to evaluate alternatives under local production conditions. A study conducted in Thailand (see graph below) compares I-prove at 100 g/ton with both a negative control (NC) and a standard AGP program based on zinc bacitracin, with Ross 308 birds being fed a corn-soy diet from 0-35 days.
I-prove outperformed both control groups across the evaluated performance parameters. Final body weight was +2.4% higher than the negative control and +4.9% higher than the AGP group, while FCR improved to 1.39 compared with 1.43 (NC) and 1.45 (AGP). These results indicate that the phytogenic solution I-prove can provide competitive performance even under AGP-free conditions, an increasingly important requirement in global poultry markets.
4. Understanding how phytogenic compounds boost BW in broilers
Body weight improvement in broilers supplemented with essential oils (EOs) or phytogenic compounds results from a combination of digestive enhancement, gut structural improvements, and microbiome modulation. A substantial body of scientific literature published between 2023 and 2026 confirms that EOs (like thymol and carvacrol) and complex phytogenic blends consistently promote BW gain and feed efficiency across commercial and research environments.
4.1 Digestive Stimulation and Enzymatic Activity
EOs such as thymol and carvacrol stimulate digestive enzyme secretion and bile production, increasing the efficiency of nutrient digestion and energy extraction. In 2026, a study showed that a thymol and carvacrol blend significantly improved average body weight (ABW) and feed intake from 600 to 1200 g/T, driven by enhanced nutrient digestion and improved serum biochemical profiles (Liu et al., 2026). Similarly, another study, published in 2023 (Li et al.), demonstrated that thymol and carvacrol eutectic increased digestive enzyme activity, nutrient transporter expression, and overall digestive efficiency in broilers, resulting in superior growth performance.
4.2 Improved gut health
Other studies have shown that EOs significantly enhance the structural integrity of the gastrointestinal tract. This is the case of a meta-analysis published in 2024 (Rocha et al.) that reported that EO supplements increased ileal villus height by +15.66% and jejunal villus height: crypt depth ratio by +8.26%, changes strongly associated with higher nutrient absorption and greater BW gain. In another study, the couple thymol and carvacrol were tested and showed increased villus height and improved mucosal barrier markers at higher EO inclusion levels (Wei et al., 2020).
4.3 Microbiome Modulation
In addition to the findings described above, essential oils play a key role in modulating the microbiome. A 2024 meta-genomic sequencing study showed that EO mixtures increased ileal microbial diversity and shifted beta‑diversity patterns, altering bacterial biomarkers in ways that reflect improved gut function and pathogen resistance. These effects were observed even under Campylobacter challenge conditions (Girard et al., 2024).
Conclusion
Backed by advanced research and a rigorously optimized formulation of essential oils, I-prove stands out as a high‑performance phytogenic solution for modern poultry production. Its targeted mode of action, including supporting digestive efficiency, gut integrity, and microbial balance, has consistently demonstrated a significant improvement in body weight, delivering an average +40 g gain with an inclusion rate of 100 g/ton of feed.
This combination of efficacy, practicality, and cost‑competitiveness positions I-prove as a valuable tool for producers seeking reliable, consistent enhancement of flock performance. By integrating I‑prove into feeding programs, operations can strengthen overall productivity while leveraging a natural, science‑driven solution tailored to today’s performance and sustainability expectations.