by Sam Shafer
Poultry scientists show that floor eggs are less likely to be fertilized—and much more likely to be contaminated than previously thought
Some hens like to lay in nest boxes. Others not so much. Where hens lay their eggs can make a big difference in egg viability. “Floor eggs” tend to be cracked, contaminated with bacteria, and much less likely to hatch.
A new study in The Journal of Applied Poultry Research, sheds light on how flock age and place of oviposition (egg laying) affect hatching. The researchers also investigated how cleaning floor eggs may improve hatchability. Their findings may help boost productivity at hatcheries in broiler/breeder systems.
The scientists examined 4,950 eggs collected from two commercial (Cobb 500 parent stock) flocks aged 29 weeks (3,600 eggs) and 64 weeks (1,350 eggs) in two experiments. Nest eggs from the flocks were divided into four groups: Intact eggs (not washed or brushed), washed eggs, brushed eggs, and nest eggs placed onto the floor. Floor eggs were split into four more groups: Clean eggs with no visible stains or manure, intact dirty floor eggs, washed dirty floor eggs, and brushed dirty floor eggs.
Once the groups were divided up, eggs were weighed, candled for viability, and viable eggs were further incubated. Once the eggs hatched, the researchers tracked chick weight and mortality.
The researchers pinpointed several reasons why floor eggs are less likely to hatch. First, floor eggs were less likely to be fertilized. Floor eggs also lost more weight than nest eggs. This weight loss was most pronounced from eggs from the older flock. The researchers think this may be due to declining shell thickness and quality in the older hens. The floor eggs were also much more likely to have hairline fractures that would let moisture out.
No matter the age of the hens, even seemingly clean floor eggs had far greater contamination than nest eggs. This contamination took a toll on hatchability and was associated with a significantly higher percentage of culled chicks in the group hatched from floor eggs.
Brushing, but not washing, the dirty floor eggs did make a difference—but only for the eggs from the younger birds. Their brushed eggs showed lower early embryo mortality, though this did not translate to higher hatching rates later on.
The researchers also examined an additional group of eggs that were laid in the nest, cooled in the nest, and then placed on the floor in a contaminated environment. They found that if eggs have already cooled, exposure to a dirty environment does not pose a threat. “The fact that there were no differences in hatching parameters between the nest eggs and nest eggs placed on the floor, emphasized the importance of the place where the eggs were cooled,” write study authors L. Peric, et al.
“If the eggs are cooled in a clean environment, they will not be subsequently contaminated in a dirty environment,” they add. “These results confirmed that the place of egg cooling is a critical point for contamination because the egg is wet and warm when laid and prone to microbial transferring into the shell.”
Overall, as many studies have shown, eggs from younger birds are more likely to be fertile. Together with the new findings, it’s clear that nest eggs are best—but clean, brushed floor eggs from young birds may be worth the effort of hatching when producers are in a pinch.
What does this study mean for producers?
- Even clean-looking “floor eggs” are more contaminated than nest eggs.
- If a clean nest egg spends time on the floor after cooling, it can still be thought of as a clean nest egg.
- Brushing floor eggs clean may improve embryo survival, but more research needs to be done to determine if this can aid hatchability
The full paper, titled “Effects of flock age, place of oviposition and cleaning treatments of hatching eggs on hatchability in broiler breeders,” can be found in The Journal of Applied Poultry Research and online here.