This is the result of a recently published study conducted by researchers from China Agricultural University. To their knowledge, studies investigating the effects of capsicum extract alone as an antibiotic substitute on growth performance and health status of broilers are limited, as is the mechanism of action of the extract in broiler chickens. This was the basis of their investigative study which explores the mechanism of action of the extract.
The application of growth promoting antibiotics (AGP) in animal feed has been banned in several countries due to the risk of bacterial drug resistance and residues of bacteria and antibiotics in animal products. Due to their bioactive compounds, plant extracts are considered potential alternatives to AGPs.
Pepper (Annual capsicum) is widely planted around the world and applied in food and traditional medicine. Capsaicin, which is responsible for the spicy taste of chili peppers, has been shown to play an important role in improving antioxidant capacity and anti-inflammatory activity, relieving pain and modulating the metabolism of lipids and the intestinal microbial community. Thus, the natural extract of capsicum, whose main component is capsaicin, could have a positive impact on poultry production.
In their research, scientists determined the effects of natural capsaicin extract as an alternative to the antibiotic chlortetracycline on growth performance, antioxidant capacity, immune function and meat quality in broiler chickens. A total of 168 day-old broiler chickens were randomly assigned to 3 dietary treatments.
The 3 dietary treatments included:
- a corn-soya meal base diet (control diet),
- a basal diet + 75 mg/kg chlortetracycline, and
- a basic diet + 80 mg/kg of natural capsicum extract.
The experimental period was from day 1 to day 42.
Overall weight gain for the total period was 5% and 8% higher in the extract group compared to the control and antibiotic group, respectively. Food intake also followed a similar pattern. The food conversion rate for the extract was 1.46, for the antibiotic 1.48 and for the control 1.50.
Improved growth performance has been attributed to the antioxidant capabilities and anti-inflammatory activities of capsaicin which results in a healthier GIT system. The researchers also pointed to similar studies that proved the effectiveness of the extract; for example, a study in broilers shows that 100 mg/kg of plant extract (including 1.98% capsaicin) decreases the abundance of E.coli and Clostridium perfringens in the rectum, while a study in laying hens shows that natural capsaicin supplementation significantly decreases the abundance of pathogenic bacteria when attacked by Salmonella enteritidis.
The digestibility of OM, CP and EE in chickens fed the capsicum extract was higher than for the antibiotic and control groups. Capsicum supplementation also improved dietary N-corrected apparent metabolisable energy (AMEn) compared to unsupplemented or chlortetracycline-supplemented diets. According to the researchers, improved nutrient digestibility is linked to increased activity of digestive enzymes. In their study, lipase and trypsin enzyme activity was higher in the capsicum extract diet than in the control and chlortetracycline groups. “The possible underlying mechanism for increased digestive enzyme activities may be related to increased levels of endogenous cholecystokinin (CCK). Chronic stimulation of CCK may improve pancreatic functions, and it has been shown that capsaicin could increase CCK concentration by stimulating the capsaicin-sensitive afferent vagal pathway,” the researchers said.
Furthermore, they hypothesized that higher CP digestibility was also associated with lower serum urea-N concentration in broilers. A high level of serum urea-N is considered to have adverse effects on the growth performance of broilers as a stress factor.
It has been reported that intensive broiler farming could lead to excessive production of reactive oxygen species (ROS) or free radicals; excessive production of ROS could lead to damage to lipids, proteins and DNA. Antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase play an important role in protecting against oxidative damage. The current study showed increased serum total antioxidant capacity, superoxide dismutase and glutathione peroxidase concentrations in broilers fed the capsicum diet. Liver catalase levels were higher in broilers fed the extract than in the control and antibiotic diets. Moreover, the addition of capsicum extract decreased the serum concentration of MDA, a product of lipid peroxidation; MDA reflects the level of oxidative stress. Overall, the extract improved the antioxidant capacity of broilers. It was concluded that “the phenolic hydroxyl group of capsaicin can transfer hydrogen atoms from free radicals, thereby effectively reducing their activities”.
Capsicum extract had positive effects on the immune function of broilers. For broilers in the capsicum extract group, an increase in the weight of the bursa of Fabricius relative to body weight was found compared to broilers in the antibiotic and control groups. The bursa of Fabricius is an essential immune organ in broilers, and its relative weight is a key indicator of health status. Additionally, lower concentrations of pro-inflammatory cytokines TNF-α and IL-1β were observed in broilers fed the extract, showing the anti-inflammatory effects of the extract in broilers. Thus, the anti-inflammatory effects of capsaicin have been attributed to its effective regulation of pro-inflammatory factors.
In this study, the meat quality of the breast muscle of broilers fed the capsicum diet was significantly improved compared to the control group. At day 42, breast muscle samples from extract-fed broilers showed lower drip loss and luminosity values than the control and chlortetracycline groups. Additionally, samples from chickens fed the antibiotic diet had a higher pH value at 24 h compared to chickens fed either the control diet or the extract diet. The reason for the improved meat quality was related to the antioxidant and anti-inflammatory properties of capsaicin.
The researchers concluded that capsicum extract alone can act as an antibiotic substitute without compromising the growth performance and health status of broilers.
References are available on request