Grape Pomace as an Alternative to Antibiotics in Poultry Farming

The use of winemaking by-products, particularly grape pomace, is being considered as a viable replacement for antibiotics in poultry feed. Adding just 0.5% grape pomace to the diet of broilers suffering from chronic intestinal inflammation helped restore their growth, reduce the number of pathogenic bacteria, and improve meat quality. Unlike traditional growth promoters, grape pomace does not contribute to the development of drug-resistant microorganisms, making it an economically advantageous and environmentally safe alternative for the industry.

Phasing Out Antibiotics and Industry Challenges

Agriculture worldwide is gradually reducing the use of antibiotics as growth promoters due to the risk of developing drug-resistant microorganisms. However, eliminating such drugs has led to an increase in chronic intestinal inflammation in poultry, reduced body weight, and inefficient feed conversion. The ideal replacement should address inflammation and support animal growth without negative side effects.

Properties of Grape Pomace

Grape pomace is a by-product of wine and juice production, accounting for up to 20% of the processed grape mass. It is rich in fiber, antioxidants, and polyphenols, yet is most often disposed of in landfills.

Experimental Study

To test the effectiveness of grape pomace, an experiment was conducted on 126 broiler chicks. To simulate poultry farm conditions, the animals were artificially induced with chronic intestinal inflammation using a diet containing 30% rice bran, which is high in non-starch polysaccharides.

The birds were divided into six groups:

• The first group received standard feed,
• The second group was given only the challenging diet,
• The third group received the challenging diet with the feed antibiotic zinc bacitracin,
• The remaining three groups were fed without antibiotics but with 0.5% grape pomace (regular, fermented with lactobacilli, and fermented with yeast).

Over 42 days, weight gain was monitored, and blood composition, cecal microbiome, and gene activity in the intestines were analyzed.

Experimental Results

The challenging diet caused significant inflammation and a 54% reduction in weight gain. Adding grape pomace almost completely compensated for these losses: the growth of birds matched that of broilers receiving antibiotics. Chicks on the grape diet showed reduced expression of inflammation genes (IL-1β and TNF-α), and their intestinal villi, responsible for nutrient absorption, increased in size.

Impact on Microbiome and Antibiotic Resistance

Grape pomace acted as a prebiotic, altering the birds’ microbiome: the number of pathogens (Clostridium and Klebsiella) decreased, while beneficial bacteria (Monoglobus and Lactobacillaceae) increased. Pomace fermented with lactobacilli was especially effective, promoting the production of butyric and propionic acids—key energy sources for intestinal cells and factors that reduce inflammation.

Analysis of manure for antibiotic resistance genes showed a spike in the bcrA resistance gene in the group receiving zinc bacitracin. In birds fed with pomace, such genes were not detected, while their weight gain was comparable to commercial standards.

Economic and Environmental Perspectives

Using biologically active winemaking by-products as a functional feed additive can help improve poultry health and reduce the environmental impact, offering a cost-effective solution to the problem of antibiotic resistance in agribusiness.