▁with ▁wire ▁or ▁pl astic ▁mesh ▁flo ors , ▁or ▁sometimes ▁in ▁small ▁groups ▁on ▁sl atted ▁flo ors . ▁Ind ividual ▁c aging ▁restrict s ▁movements ▁and ▁behav i ours ▁by ▁prevent ing ▁the ▁birds ▁from ▁standing ▁ere ct , ▁turning ▁around , ▁or ▁fla pping ▁their ▁wings . ▁Bird s ▁cannot ▁carry ▁out ▁other ▁natural ▁water f ow l ▁behav i ours , ▁such ▁as ▁bath ing ▁and ▁sw imming . ▁Furthermore , ▁du cks ▁and ▁ge ese ▁are ▁social ▁animals ▁and ▁individual ▁c ages ▁prevent ▁such ▁interactions . ▁ ▁During ▁the ▁force ▁feed ing ▁period , ▁when ▁the ▁birds ▁are ▁not ▁being ▁fed , ▁they ▁are ▁sometimes ▁kept ▁in ▁near ▁darkness ; ▁this ▁prevents ▁normal ▁investig atory ▁behaviour ▁and ▁results ▁in ▁poor ▁w elf are . ▁ ▁In j ury ▁Les ions ▁can ▁occur ▁on ▁the ▁stern um ▁of ▁the ▁birds ▁due ▁to ▁ne c ros is ▁of ▁the ▁skin . ▁ ▁This ▁is ▁observed ▁more ▁frequently ▁in ▁birds ▁re ared ▁in ▁c ages ▁rather ▁than ▁on ▁the ▁floor . ▁The ▁pre val ence ▁is ▁higher ▁in ▁Mul ard ▁du cks ▁( 4 0 – 7 0 %) ▁compared ▁to ▁under ▁ 6 % ▁in ▁Mus c ovy ▁du cks . ▁ ▁This ▁is ▁due ▁to ▁the ▁larger ▁p ector alis ▁prof und us ▁major ▁and ▁minor ▁mus cles ▁in ▁Mus c ovy ▁du cks ▁compared ▁to ▁Mul ards . ▁The ▁relatively ▁new ▁Mul ard ▁bre ed ▁used ▁in ▁fo ie ▁gr as ▁production ▁seems ▁more ▁pr one ▁to ▁developing