The effect of perch availability during pullet rearing and egg laying on musculoskeletal health of caged White Leghorn hens
A major skeletal problem of conventional- ly caged hens is increased susceptibility to osteoporosis mainly due to lack of exercise. Osteoporosis is charac- terized by a progressive decrease in mineralized struc- tural bone. Whereas considerable attention has been given to enriching laying cages, little research has been conducted on providing caged pullets with furnish- ments, in particular perches. The objective of the cur- rent study was to determine if metal perches during all or part of the life cycle of White Leghorns affected hen musculoskeletal health, especially at end of lay. Treat- ments during the pullet phase (hatch to 16.9 wk) en- tailed cages with and without perches. Four treatments were used during the laying phase (17 to 71 wk of age). Treatment 1 chickens never had access to perches at any point during their life cycle, typical of egg industry practices in the United States for conventional cages. Treatment 2 chickens had access to perches only during the egg-laying phase, which was from 17 to 71 wk of age. Treatment 3 chickens had access to perches only during the pullet phase (0 to 16.9 wk of age). Treatment 4 chickens had perch access throughout their entire life cycle (0 to 71 wk of age). Musculoskeletal health was assessed by measuring muscle weights, bone mineraliza- tion, bone fracture incidence, and keel bone deviations. Muscle deposition of 71-wk-old hens increased when given access to perches as pullets. Bone mineralization of 71-wk-old hens also increased if given perch access as adults. However, the disadvantage of the adult perch was the higher incidence of keel deviations and keel fractures at end of lay. The increase in bone mineraliza- tion of the keel bone as a result of perch access during the pullet and laying phases was not great enough to prevent a higher incidence of keel bone fractures at end of lay. Perch redesign and placement of perches within the cage to minimize keel fractures and deviations are possible solutions.