Propolis Spray on Hatching Eggs Boosts Early Broiler Growth Without Harming Hatchability

Spraying hatching eggs with a diluted propolis solution during incubation improved early growth in broiler chicks without undermining hatchability, according to a study on Ross 308 broiler breeder eggs. Researchers divided 270 eggs from 32-week-old breeders into three groups: eggs left unsprayed, eggs sprayed with distilled water, and eggs sprayed with a propolis solution. The spraying was repeated daily between embryonic days 0 and 17, and the birds were followed through hatching and the first ten days after hatching. The propolis-sprayed group showed the heaviest chicks and the best feed conversion ratio at seven days of age, while hatchability of fertile eggs, hatchability of set eggs, embryonic mortality, chick yield, and chick weight at hatch all remained statistically similar across the three groups.

Previous work on in-ovo spray application of propolis had not examined embryonic development in detail, so the team measured egg weight, egg weight loss, embryo morphology at embryonic days 14 and 18, hatching traits, chick quality scores, growth performance, and carcass and organ traits at ten days of age. The birds were raised in chick cages with three replicate groups of twenty chicks each, fed a diet containing 22 percent crude protein and 3000 kilocalories per kilogram of metabolizable energy, and given feed and water ad libitum under a 21-hour light and 3-hour dark photoperiod.

The propolis solution was prepared by mixing five milliliters of a 33 percent enriched water-based propolis with 100 milliliters of distilled water at 30 degrees Celsius, shaken by hand for about a minute to ensure homogeneity. Eggs in the sprayed groups were removed from the incubator each day and sprayed for five minutes between 10:00 and 10:05 in the morning, while the unsprayed eggs were also removed and handled to ensure that the only factor differing among the groups was the spray itself. Incubation ran under standard conditions of 37.8 degrees Celsius and 65 percent humidity until embryonic day 18, when fertile eggs were moved to a hatcher set at 37.5 degrees Celsius and 70 percent humidity.

Egg weight itself was largely unaffected. Weights before incubation and at embryonic days 7, 14, and 18 did not differ significantly among the groups, and neither did cumulative egg weight loss across the full 0 to 18 day window. However, egg weight loss during the earlier intervals, embryonic days 0 to 7 and 0 to 14, was significantly lower in the unsprayed eggs than in both sprayed groups. Consistent with this, eggshell thickness measured at hatch, across the broad end, equator, and narrow end, was similar among all groups, indicating no severe structural degradation of the shell itself.

Embryonic development showed selective rather than uniform responses. At embryonic day 14, yolk weight and yolk yield were lowest in unsprayed embryos and highest in water-sprayed embryos, while a dozen other traits, including yolk-free body mass, embryo length and width, embryo plus yolk weight, tibia, thigh, wing, and beak lengths, and eye width, were statistically similar. At embryonic day 18, yolk-free body mass was highest in unsprayed embryos and lowest in propolis-sprayed embryos, and embryo width was highest in unsprayed and lowest in water-sprayed embryos, while the remaining measured traits again did not differ.

Hatching outcomes were reassuring for the technique. Embryonic mortality, hatchability of set eggs, hatchability of fertile eggs, chick yield, and chick weight at hatch showed no significant differences among treatments. Eggshell thickness at hatch was also unchanged. Chick quality assessments, based on scoring systems for legs, appearance, navel, activity, and eyes, revealed that chick length at hatch was highest in the water-sprayed group, and appearance scores were better in both sprayed groups than in unsprayed chicks. Activity, navel, eye, and leg scores were similar across treatments. A total of 76, 72, and 77 chicks from the unsprayed, water-sprayed, and propolis-sprayed groups, respectively, were used for these quality evaluations.

The clearest performance benefit appeared in the first week after hatching. At seven days of age, body weight was lowest in water-sprayed chicks and highest in propolis-sprayed chicks, and the feed conversion ratio was better in the propolis group and poorest in the water-sprayed group. Body weight gain and feed intake at seven days did not differ significantly. The authors speculate that propolis spraying might have improved intestinal development and lowered post-hatch intestinal pH, inhibiting pathogenic bacteria and increasing beneficial microbes involved in nutrient digestion and absorption.

By ten days of age, the growth advantage had faded. Body weight, body weight gain, feed intake, and feed conversion ratio were all statistically similar among the groups, suggesting the propolis effect was not strong enough to persist beyond the first week. Rectal temperature and body length at ten days also did not differ. Carcass and organ measurements told a more nuanced story. Slaughter weight, breast weight, liver weight, and intestinal yield were lowest in water-sprayed chicks, which the authors suggest may reflect that group's poorer early growth performance. Thigh weight was highest in propolis-sprayed chicks, and breast weight was lowest in water-sprayed and highest in unsprayed chicks. Liver yield nearly reached significance, highest in the propolis group, while proventriculus weight and yield and intestinal weight approached significance, highest in unsprayed and lowest in water-sprayed chicks. Heart, gizzard, back, and thigh yields, along with rectal temperature and body length, remained similar.

The study’s authors frame the findings within a broader challenge for the poultry industry. In-ovo application techniques, including injecting, dipping, washing, and spraying eggs with natural or inorganic plant-based solutions, have been explored as ways to supply nutrients, reduce stress during incubation, and disinfect eggs. Propolis, a resinous mixture produced by honeybees, contains bioactive compounds with antibacterial, antiviral, anti-inflammatory, antioxidant, and immunostimulant properties, attributed largely to its phenolic compounds.

The authors conclude that spraying hatching eggs with propolis may improve chick appearance at hatch, early post-hatch performance, and some carcass traits, without any negative effect on hatchability or embryonic mortality. They caution that differences in propolis type and concentration, the timing of application during incubation, and the species of hatching eggs used likely explain why results vary across studies, and performance traits at ten days of age were similar among the groups, indicating the effect influencing growth and development up to seven days of age was not effective enough to exert a profound lasting effect beyond seven days.

Subject of Research: Effects of in-ovo propolis spraying of hatching eggs on embryonic development, hatchability, chick quality, and post-hatch performance in broiler chickens

Article Title: Effect of in-ovo spray application of propolis on embryonic development, hatchability, chick quality, and post-hatch performance in broiler chickens

Article References: Gumustas, Y., Abdallah, N., Kursun, K., Baylan, M., Ssempuma, H. W., & Tainika, B. (2026). Effect of in-ovo spray application of propolis on embryonic development, hatchability, chick quality, and post-hatch performance in broiler chickens. Discover Animals, 3(1), Article 109. https://doi.org/10.1007/s44338-026-00269-w

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00269-w

Keywords: propolis, in ovo, hatching eggs, broiler chickens, embryonic development, hatchability, chick quality, feed conversion ratio, carcass traits, poultry incubation, Ross 308, post-hatch growth