Alternative feed additives to help broilers cope with heat stress

With increasing pressure to reduce antibiotic use and rising ambient temperatures, new research from North-West University (NWU) in South Africa highlights a promising nutritional strategy: the combined use of probiotics and stimbiotics in broiler diets to support performance and resilience to heat stress.

The study, conducted by Ramokone Millicent Mokonyama as part of her master’s programme at NWU, evaluated whether this combination could represent an alternative to conventional antibiotic growth promoters (AGP) in broilers. The work examined not only growth and feed conversion, but also meat quality, health indicators, bone characteristics and behavioural responses under cyclic heat stress conditions.

Experimental design and dietary treatments

In total, 600 broiler chicks were assigned to five dietary treatments over a six-week production cycle. The experimental layout included: a negative control without AGP, a positive control with conventional AGP, a diet supplemented with probiotics only, a diet with stimbiotics only and a diet with the combination of probiotics and stimbiotics. Birds were managed under a protocol that included controlled periods of cyclic heat stress to simulate realistic field conditions, allowing researchers to assess the effectiveness of antibiotic-based and antibiotic-free feeding strategies before and during heat stress exposure.

Growth performance and early-stage advantages

In the early rearing phase, broilers fed either probiotics alone or the probiotics–stimbiotics combination showed higher growth rates than the other groups. Importantly, these early advantages did not compromise overall performance: over the full six-week production cycle, the combination of probiotics and stimbiotics maintained overall productivity and feed efficiency comparable to those of birds receiving AGP, even under cyclic heat stress. These findings suggest that this strategy can sustain production while reducing reliance on antibiotic growth promoters.

Meat quality, bone characteristics and blood profile

One of the main concerns when replacing AGP is the potential impact on carcass composition, meat quality and physiological status. In Mokonyama’s work, the inclusion of probiotics and stimbiotics did not adversely affect carcass traits, bone characteristics or blood biochemical parameters. In addition, birds receiving stimbiotics exhibited lower cholesterol and triglyceride levels under thermoneutral sampling conditions than AGP-fed broilers, suggesting favourable effects on lipid metabolism. The dietary treatments also influenced antioxidant characteristics of the meat, with probiotic- and stimbiotic-fed birds showing improved antioxidant capacity in specific assays.

Behaviour and heat adaptation

The diets also influenced bird behaviour during periods of elevated temperature. Broilers fed probiotics and stimbiotics showed differences in certain behaviours, including time spent resting, seeking cooler areas and feeding patterns during the hottest hours of the day. These behavioural changes suggest adaptive responses to cyclic heat stress, while the birds did not exhibit signs of severe thermal distress. Overall, the results indicate that combining the two additives may help support the physiological and behavioural responses of broilers exposed to heat stress.

Towards antibiotic-free and more climate-resilient production

The findings suggest that probiotics and stimbiotics can act in a complementary way within feeding programmes aimed at reducing antimicrobial use while maintaining productive performance under challenging environmental conditions. The absence of adverse effects on growth, health, carcass traits and meat quality, together with favourable changes in lipid profile and antioxidant characteristics, makes this nutritional strategy particularly relevant as heat stress becomes more frequent under changing climatic conditions.

The inclusion of probiotics and stimbiotics in broiler diets may enable producers to maintain production performance, help birds cope with increasingly frequent heat stress events and contribute to more responsible poultry production. This work places Mokonyama and the NWU research team among the groups investigating functional feed additives as potential alternatives to antibiotic growth promoters, with the aim of supporting productivity and physiological adaptation in modern broiler production systems.