It’s no secret that the fertility and egg hatchability of a broiler breeder flock decrease as birds age. But in recent years, there has been a broader, overall decline.
“In 2023 alone, the industry was unable to surpass 81% hatchability for any given week, according to USDA Agrostats,” noted Sophie Chance, graduate student at North Carolina State University, in her presentation at the 2024 International Poultry Scientific Forum.
Many factors impact fertility, egg production and hatchability, such as management, genetics, antibiotic removal and nutrition. While those areas have been researched extensively, the environmental microbiota in the breeder house have received little attention.
“There are abundant opportunistic pathogens and symbiotic bacteria in the bird’s environment that can benefit or harm the hatching egg,” she said.
Chance and her colleagues selected Micrococcus luteus (M. luteus), a gram-positive, aerobic, non-pathogenic bacteria, for their study because it is ubiquitous in the birds’ environment.
They wanted to determine if M. luteus, when applied to the nest-pad surfaces in the broiler breeder house, would impact egg fertility, hatchability and chick quality.
Designing the treatments
Chance conducted the study in a house with 16 pens, eight on each side. Four pens from each side were randomly selected for the M. luteus treatment, with the other four assigned to the control group. All pens contained 60 hens and seven roosters.
The researchers applied a phosphate-buffered saline 108 concentration of M. luteus to the treatment groups’ nest pads and a sterile phosphate-buffered saline to the control groups’ nest pads.
“We gathered 50 eggs per pen over 4 weeks and set those eggs at startup lay, peak lay and post-peak lay to evaluate hatchability and fertility by doing an 11-day candling,” Chance said. “We also followed them all the way through hatch.”
Chance collected individual weights at hatch, then selected 10 chicks from each pen to measure bodyweight gain and 7-day mortality.
The study evaluated M. luteus movement within the pens from the nest pads as well as any cross-contamination to the control groups. They also selected three hens and three roosters from each pen to swab the cloacas for M. luteus transfer.
No significant impact
The research team evaluated differences between the control and treatment groups for each period — start of lay (26 to 29 weeks), peak lay (33 to 36 weeks) and post-peak lay — but not across periods.
There were no significant differences for any of the periods between the M. luteus treatment and control groups for fertility, hatchability or chick weight at hatch, Chance said.
“Results did identify significant differences in average 7-day chick weight and bodyweight gain that favored the control group, but there was no difference in 7-day mortality,” she reported, adding that “there was no detectable M. luteus in our cloacal samples.”
Based on the results, the researchers partially rejected their original hypothesis. For future research, Chance challenges researchers to dig deeper into the potential impact of nest-pad bacteria on fertility and hatchability in late-stage broiler breeder production.
“We should continue to research this space, looking at symbiotic bacteria and consider other environmental options that may be affecting broiler breeder reproduction,” Chance concluded.
