Broiler Research: Looking to local antibiotic alternatives

Dr. Deborah Adewole loves “shopping” local for new, innovative ingredients that could replace the use of antibiotics and boost broiler performance and health in the process. Her approach of looking at readily available, natural plant-based compounds started when she was a researcher at Dalhousie University and was approached about adding local seaweed to poultry diets. 

She completed a research project on the potential for brown seaweed meal to help combat the negative effects of heat stress of broilers, along with her PhD student Fisayo Oretomiloye. The pair have now also completed a similar project looking at grape pomace and an extract from red osier dogwood in broiler diets as additional antibiotic alternatives.

“We aren’t going to find one compound to replace antibiotics in broiler production, so we are looking for compounds that help boost animal health,” says Adewole, who is now an assistant professor of non-ruminant nutrition and metabolism at the University of Saskatchewan in Saskatoon.

The other factor driving their work is the impact climate change may have on increasing the occurrence of heat stress in broilers. 

“We know from previous studies that heat stress consistently reduces growth performance, especially feed intake, in broilers,” says Adewole.

Powerful phytochemicals

The novel ingredients Adewole and Oretomiloye explore are phytochemicals – a broad category that refers to naturally-occurring chemicals found in plants. 

The phytochemicals they are most interested in are polyphenols, known for antioxidant properties and beneficial impact on gut health.

“I have used grape pomace and dogwood in other studies that did not involve heat stress, and they helped improve the ability of the gut to absorb nutrients and improve nutrient digestibility in feed ingredients,” says Adewole. “Knowing these products are helpful to the gut, it was a natural extension for this project that if the gut is healthier, maybe the broilers will be better able to handle heat stress.”

The grape pomace was sourced from local wineries in Atlantic Canada but is not yet an approved feed ingredient – something Adewole hopes will change in the near future. The extract from red osier dogwood provides a more concentrated form of polyphenols, is registered as a veterinary health product by Health Canada for poultry and is commercially produced in Manitoba.  Dogwood extract has long been used in traditional medicine. 

Feeding for stress relief

Their research involved raising two groups of broilers for 28 days. One group was housed in a room with normal temperatures and environmental conditions for raising broilers. The other group was in a heat stress room. When birds were 21 days of age in this group, the room temperature was increased by 10°C from 9 am to 5 pm for seven days in a row. 

Each group was further split into four dietary regimes – a control diet, an antibiotic treatment diet, a diet with 2.5 per cent grape pomace and a diet with 0.3 per cent red osier dogwood extract. At day 28, a sample of birds from each room and on each diet were processed. They collected blood samples and tissue samples from various parts of the small intestine to see how nutrients were being absorbed. 

They evaluated the bacteria makeup (microbiota) of the gut, and collected samples and weight of the bird’s immune organs – the spleen and bursa.

Dr. Deborah Adewole explores innovative antibiotic alternatives to boost broiler health and performance.

Dogwood delivers

When they looked at bird performance – body weight gain and feed efficiency – across all diets, it wasn’t surprising that birds on the antibiotic treatment showed the most positive results, regardless of whether they were exposed to heat stress of not. 

But the more interesting result was that broilers fed the diet with red osier dogwood extract performed very similarly to the antibiotic treatment for body weight gain during the growth phase (day 14 to 21) and performed with the same level of feed efficiency as the antibiotic treatment.

For Adewole, these results confirm the opportunities for dogwood in broiler diets.

 “We found that dogwood can offer a similar level of growth performance as antibiotics and could be beneficial for feed efficiency,” the researcher says. 

There was more good news for including dogwood in broiler diets. The researchers found that broilers exposed to heat stress had lower concentrations of an enzyme (creatine kinase) in the blood that helps birds make more energy. 

But the birds receiving dogwood extract in the diet had increased levels of this enzyme, suggesting the extract may help birds deal with the negative effects of heat stress. 

Acting like antibiotics

Both grape pomace and dogwood extract were able to help broilers increase the surface area in all regions of the small intestine, so birds were able to absorb more nutrients from their diet. This is a similar action to antibiotics. 

“Even though we didn’t find significant improvements in growth performance over antibiotics, the ability to absorb more nutrients could mean birds are more resilient to disease, can cope better with stress and have better overall health,” says Adewole. “Plus, having more polyphenols absorbed into their system helps with gut health and overall immune response.”

They also found some benefits with both grape pomace and dogwood extract for the overall bacterial diversity in the gut. Lactobacillus levels increased by similar amounts in both ingredients they tested and increased more than with the antibiotic treatment. “Lactobacillus is well recognized as a potential probiotic that is beneficial to the immune system and overall health,” says Adewole. 

Broiler diet recommendations

“At this point, I would recommend producers consider including 0.3 per cent red osier dogwood extract in the broiler diet to maintain health and reduce the impact of heat stress,” says Adewole. 

Their research shows positive results for grape pomace at a 2.5 per cent inclusion rate, but there is more work to be done. “We have seen beneficial effects of grape pomace in broiler diets to combat heat stress,” she says.

“We will do more studies on a larger scale and also with laying hens, before we can proceed with registering grape pomace as an approved product in Canada.”