Supplementation with a blend based on micro-encapsulated carvacrol, thymol, and cinnamaldehyde in lambs feed inhibits immune cells and improves growth performance

Highlights

• Supplementation with the phytogenic product in lamb feed increased the weight gain.

• Phytogenic improved the antioxidant response without change the levels of free radicals and lipid peroxidation in serum.

• Phytogenic product in lamb feed exerted anti-inflammatory effects.

• Consumption of phytogenics did not compromise lamb health.

Abstract

The objective of this study was to determine whether supplementation with a blend based on micro-encapsulated carvacrol, thymol, and cinnamaldehyde added to concentrate in growing lamb feed would affect performance or produce antioxidant and immunological responses. In our study, the blend mixed with concentrate was technically defined as a phytogenic. Thirty female animals were randomly distributed in three groups with five repetitions and two animals per repetition, as follows: Control (basal feed), T500 (basal feed supplemented with 500 mg phytogenic/kg of concentrate) and T1000 (basal feed with 1000 mg phytogenic/kg of concentrate). Weights were measured and blood was collected on days 0, 15, 30 and 40 of the study. The T1000 animals had greater weight gain during the experimental period (0 to 40) as well as from day 30–40 of the experiment compared to the Control group. The T500 and T1000 lambs had greater weight gain on the 15^th to 40^th day when compared to Control. T1000 lambs had lower numbers of leukocytes and lymphocytes on days 30 and 40 compared to Control. Cholesterol levels were greater on day 30 in the T500 group than in the Control group. Levels of reactive oxygen species, lipid peroxidation and glutathione S-transferase did not differ between treatments. The activities of glutathione peroxidase (GPx) and glutathione reductase were lower in the T1000 animals than in the Control at day 30; this was different from what was observed on day 40, when GPx showed a significant increase in T1000. We conclude that supplementation with this phytogenic product in lamb feed stimulated antioxidant and anti-inflammatory responses and consequently increased weight gain in lambs. In practical situations, we expect that the inclusion of this additive in the diet of female lambs will produce more healthy and heavier ewes that achieve the reproductive life earlier.

Introduction

In Brazil, the first sheep that produced milk were introduced around 1992; these were derived from the Lacaune breed from France, and they demonstrated excellent adaptation to Brazilian feed and climate (Brito et al., 2006). A major challenge with raising ruminants is their high mortality in the post-weaning period, especially among dairy animals (Budzynska and Weary 2008). This is because the lambs are removed from their mothers (i.e., weaned) very early and the digestive system is not completely adapted to receive solid food only. Until they adapt to the new feed, young animals lose weight, their growth is delayed, and they become more susceptible to diseases; this is directly reflected in their productive capacity. For these reasons, many ranchers seek commercially available immune stimulant products that can minimize these negative effects of the feed transition period.

The use of additives of plant origin in the post-weaning or weaning period can minimize productive losses resulting from the adaptation of the animals when their diets are altered. The use of phytogenics (plant-derived products such as essential oils used as additives) is a compelling alternative to bolster animal health; many of these additives stimulate biological functions in animals (Karásková et al., 2015; Volpato et al., 2019), thereby enhancing growth performance. Essential oils in ruminant feed can help improve the use of nutrients, in addition to reducing the impact on the environment (Benchaar et al., 2007); some researchers claim that the addition of phytogenics in the feed of adult goats improves the utilization of nutrients, in addition to stimulating antioxidant responses (Choubey et al., 2015). The putative mechanism involves protection of cells and tissues from excess free radicals produced in physiological or pathological reactions, including cellular respiration. The use of a phytogenic based on thymol, cinnamaldehyde, and carvacrol had potent anti-inflammatory effects, combined with better weight gain in broiler chickens (Reis et al., 2018; Galli et al., 2020). There is a strong correlation between productive performance and inflammatory responses; that is, greater inflammatory responses correlate with lower weight gain. During inflammatory responses, there is high consumption/expenditure of ATP, a molecule no more utilized to produce meat and milk. Supplements with antioxidant and anti-inflammatory properties are therefore potentially desirable in animal feed.

We tested a blend based on carvacrol, thymol, and cinnamaldehyde in micro-encapsulated form. This formulation is important for ruminants because it passes in inert form through the rumen and reaches the intestine to be absorbed, thereby improving bioavailability. It is worth mentioning that the herbal components present in this product have antimicrobial activity. Since antiquity, properties of essential oils have been used; it is now recognized that these have antiviral, antibacterial, antifungal, and anti-inflammatory effects (Acamovic and Brooker, 2005). Among the activities of essential oils, their antimicrobial effects have been demonstrated in a wide variety of microorganisms, including gram-positive and gram-negative bacteria (Benchaar et al, 2008). It is not desirable that the product be released in the rumen, where there are protozoa and bacteria that could be negatively affected by the herbal components. Recently, a study conducted by Chapman et al. (2019) revealed that addition of 2 and 4 mg cinnamaldehyde/kg diet of dairy cows exerted antimicrobial effect in the rumen, but did not alter feed intake, milk yield or milk components. On the other hand, Chapman et al. (2017) revealed that inclusion of 1 and 2 mg cinnamaldehyde/kg diet not exert performance or coccidia control benefits for weaned heifers, suggesting that it is dose dependent. Carvacrol is a phenolic monoterpenoid. It positions itself in bacterial cytoplasmic membranes and increases permeability and fluidity, thereby allowing passive transport of ions through the membrane (Hyldgaard et al., 2012). Lambert et al. (2001) reported that the mixture of carvacrol and thymol caused total inhibition of Pseudomonas aeruginosa and Staphylococcus aureus, mediated by damage caused to the integrity of the membrane, affecting pH homeostasis and the balance of inorganic ions.

Therefore, the hypothesis in the present study was that the use of a phytogenic additive in the diet would improve growth performance, and antioxidant and immune responses in lambs. The objective of the current study was to determine whether supplementation with a micro-encapsulated commercial product (a phytogenic) formulated with carvacrol, thymol, and cinnamaldehyde in lamb feed would improve performance, as well as antioxidant and immune responses.