Benefits of probiotics in chicks explored

With antimicrobial resistance and the use of antimicrobials in livestock feed a major concern over the spread of resistance to many other drugs, researchers at Penn State University in the US conducted a study of natural feed additives, seen as promising alternatives to substitute for antimicrobial growth promoters.

In findings to be published in the May edition of Poultry Science, the researchers characterised the effects of a probiotic and a blend of essential oils on broilers’ growth and gut health. Led by Erika Ganda, assistant professor of food animal microbiomes, the research team involved a total of 320 day-old chicks, which were raised for 21 days in 32 randomly allocated cages.

Ganda said: “Because the elimination of antimicrobial growth promoters use is associated with increases in disease and a decrease in growth performance in chicks, antibiotic-free alternative approaches to enhance intestinal health and improve growth performance are of great interest to the poultry industry. The claim that a product is “natural” does not make it necessarily more beneficial than antibiotics, so we conducted this experiment to answer this question.”

Treatments consisted of 4 experimental diets: a standard diet; a standard diet mixed with the antibiotic bacitracin methylene disalicylate; a standard diet with an essential oils blend of oregano oil, rosemary and red pepper, or the probiotic Bacillus subtilis.

Antioxidant, immune-modulating, antimicrobial properties

Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host by supporting a more diverse range of beneficial bacteria in the digestive tract. Essential oils are plant-derived extracts that possess various antioxidant, immune-modulating, antimicrobial properties and the ability to change the microbiome.

The researchers individually weighed all broiler chickens on day 1 and then at the end of each dietary phase on day 10 and day 21. The feed consumed per pen was monitored at the end of each growth phase. The team also calculated the daily bodyweight gain average, feed intake and feed conversion rate of feed consumed divided by weight gain at 3 periods: the starter phase up to day 10; the grower phase of 11-21 days, and the total period of 1 to 21 days.

The relative abundance of bacterial strains

They also collected excreta samples daily during the experimental period and analysed DNA to identify bacteria present. Across all 9 points, supplementing chicken diets with the probiotic or the antibiotic significantly changed the relative abundance of bacterial strains compared to the standard diet. There were, however, no microorganisms affected by essential oils compared to the standard diet.

Surprising results

Graduate student Ana Fonseca said some of the results were surprising: “We were somewhat surprised by the results of the essential oils; we were expecting them not only to have some effects on the microbiome, but also on the performance side. We still think essential oils may present a promising alternative to antimicrobial growth promoters, but their effectiveness can be influenced by various factors.

“We only observed these animals for 21 days, and maybe the essential oils would have more significant effect when they are older and their microbiome gets more stable. The benefits of essential oils in this context deserves more research,” she added.