ademic research facilities. Heat stress, for instance, has been shown to compromise gut health, an effect that can be com- pensated, at least partly, by the addition of plant-based products. In a recent study, the introduction of heat stress re- sulted in increased markers of oxidative stress and inflamma- tion as well as loss of gut integrity, leading to impaired broil- er performance (Table 1). The data show changes of parameters in heat-stressed birds fed plant-based isoquino- line alkaloids (IQs) compared to heat-stressed control birds. With IQ supplementation, broilers were able to better cope with heat stress. Levels of thiobarbituric acid-reactive sub- stances (TBARS) as well as the mRNA expression of inducible nitric oxide synthase (iNOS) were significantly reduced (Fig- ure 1). TBARS can be used to quantify lipid peroxidation products, which indicate membrane damage resulting from oxidative stress. On the other hand, iNOS is an enzyme whose expression in macrophages and enterocytes is trig- gered by inflammatory cytokines. iNOS increases the pro- duction of nitric oxide (NO) to damage the membrane of pathogens or infected host cells. However, large amounts of NO also damage healthy cells, forming part of a vicious cycle of inflammation and oxidative stress. This results in impaired gut integrity, which can be assessed with FITC-dextran. The transfer of FITC-dextran from the intestine into the blood in- creases with decreased gut tissue integrity. When supple- menting heat-stressed broilers with IQs, the serum-levels of FITC-dextran were significantly lower than in the non-sup- plemented control group.
Conclusion
Robust gut health is fundamental for efficient, sustainable animal production, health and well-being. Plant-based feed
additives have gained much attention in science and in prac- tice due to their beneficial impacts on gut health. However, including plant-based products in the feeding program comes with a cost. Economically, this cost must recompense the producer by increasing their profitability. Profitability is improved either by generating more output (meat, eggs, milk) through enhanced performance or livability, or by re- ducing inputs (feed, time to market, medicinal interventions) through higher feed efficiency, faster growth or reduced morbidity. For example, a reduction in FCR by just 0.023 to 0.025 points can compensate an inclusion cost in feed of € 3.00 per tonne of a gut health product in broiler production, depending on feed cost and live weight price. In conclusion, plant-based feed additives such as IQ can help animals cope with common challenges of commercial production condi- tions, thus improving performance and finally creating an economic benefit for the user.
The commercial efficacy of plant- based feed addi- tives depends on several fac- tors such as housing, diet, animal health and general performance level.
Table 1 – Performance of broilers under thermoneutral versus heat stressed conditions.
Parameters 15-42 days of age BW (g)
BWG (g) FI (g)
Thermoneutral conditions Control 3,031a 2,510a 4.726
IQ FCR (g/g) 1.88b,c
3,114a 2,606a 4.846 1.86c
Heat stress conditions Control 2,428c 1,889c 3.777 2.00a
IQ
2,647b 2,121b 4.008 1.89b
Different superscripts within a row indicate a significant difference (a,b,c P < 0.05). Adapted from Kikusato et al., 2021
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