Gregarious nesting: "Broiler parents also like to huddle together".

"The strange thing is that the wild ancestor chicken had no need for sociability, she had a nest on her own. Today's hens have a much greater need for what they call 'gregarious nesting', which according to Google Translate is literally 'cosy'. So they like to huddle together."

Anne van den Oever is a researcher at Vencomatic, she recently obtained her PhD on the nesting behaviour of broiler breeders. One of her studies focused on gregarious nesting in broiler breeders, which had already been sufficiently researched in laying hens.

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What is gregarious nesting?

"Laying hens have a preference to go into a nest where there are already hens, why we don't know yet. Sometimes you even see that they like sitting together so much that the nests get overcrowded, especially in certain locations like the corners. Because the nest is too full, laying hens that want to lay an egg can no longer enter it and you get more floor eggs. With broiler breeders, this had not been studied yet."

"I did research on this in 2018, at the same time as my research on leg health. Because it is about different subjects, I wrote two articles. My research showed that 'gregarious nesting' is also common in female broiler breeders. I studied hens from five different genetic lines, from two lines the hens went into the corners and three other lines divided themselves over the nests. I also saw that the groups that spread themselves less even over the nests had more ground eggs, independent of the genetic line."

What else did you investigate?

"I also looked at the number of wounds and the feathering: how neat is the plumage? We were particularly curious about the behaviour of the males, which are more aggressive when mating because they have been bred for meat quality. They damage the hen's feathers and cause injuries, stepping on the hens with their sharp nails. Those matings happen mostly in the litter area, so we suspected that's why the hens avoid the litter area and go onto the slats."

"At the end of the round almost all hens had severe feather damage, they often even started to go bald. One third had injuries at the end of the round, depending on the genetic line. The lines that had more injuries avoided the litter area to avoid the males. They were more often on the slats, mating is apparently not so comfortable."

"I discovered in another study that there is not yet something found to improve the distribution of hens in the nest. A different design of the nest has been tried, for example with partitions, but that did not work. Closing off the nests sometimes works well and sometimes not. That makes it very difficult, you can't steer the hens in that direction apparently. The need for sociability is built into today's chicken, you can hardly change that."