▁les ions ▁in ▁the ▁area ▁of ▁the ▁stern um ▁when ▁kept ▁in ▁small ▁c ages , ▁and ▁to ▁b one ▁break age ▁during ▁transport ▁and ▁sla ugh ter . ▁ ▁Where ▁du cks ▁are ▁f atten ed ▁in ▁group ▁pens , ▁it ▁has ▁been ▁suggested ▁that ▁the ▁increased ▁effort ▁required ▁to ▁capture ▁and ▁rest rain ▁du cks ▁in ▁pens ▁might ▁cause ▁them ▁to ▁experience ▁more ▁stress ▁during ▁force ▁feed ing . ▁In j uries ▁and ▁fatal ities ▁during ▁transport ▁and ▁sla ugh ter ▁occur ▁in ▁all ▁types ▁of ▁p oul try ▁production , ▁however , ▁f atten ed ▁du cks ▁are ▁more ▁sus cept ible ▁to ▁conditions ▁such ▁as ▁heat ▁stress . ▁ ▁En larg ed ▁li ver ▁Fo ie ▁gr as ▁production ▁results ▁in ▁the ▁bird ' s ▁li ver ▁being ▁sw ol len . ▁ ▁In ▁some ▁species ▁of ▁du cks , ▁li ver ▁size ▁changes ▁season ally , ▁increasing ▁by ▁as ▁much ▁as ▁ 3 0 ▁to ▁ 5 0 %, ▁with ▁more ▁pron ounced ▁changes ▁in ▁females . ▁However , ▁fo ie ▁gr as ▁production ▁en larg es ▁the ▁li vers ▁up ▁to ▁ 1 0 ▁times ▁( or ▁ 1 , 0 0 0 %) ▁their ▁normal ▁size . ▁This ▁imp airs ▁li ver ▁function ▁due ▁to ▁ob struct ing ▁blood ▁flow , ▁and ▁exp ands ▁the ▁ab d omen ▁making ▁it ▁difficult ▁for ▁the ▁birds ▁to ▁bre at he . ▁Death ▁occurs ▁if ▁the ▁force - feed ing ▁is ▁continued . ▁ ▁Mort ality ▁rates ▁The ▁mort