Layer Cage Depth Effects on Nervousness, Feathering, Shell Breakage, Performance, and Net Egg Returns

The effects of deep and shallow laying cages upon nervousness, feathering, shell breakage, and performance were each measured in three populations of 3, 6, and 12 birds, each with 310, 387, and 464 cm2 of space per bird. In depth, deep cages varied between 30.5 and 45.7 cm and shallow cages, 20.3 and 30.5 cm. Feed trough space was 10.2 and 15.2 cm for deep and shallow cages, respectively. A total of 3840 commercial strain White Leghorns were tested for 60 weeks in two tests. In shallow cages, annual average egg weight, body weight, feed per bird, and end of year back feathering were significantly (P<.01) greater. Conversely, feed conversion and relative freedom from soft shelled and broken eggs were significantly (P<.01) superior for the deep cages. Mortality, eggs per bird, egg mass, shell thickness, specific gravity, total egg cracking losses, Haugh units, percent eggs Grade A, net egg income, nervousness, and neck, wing, tail, and underside feathering were unaffected. Interactions between the main effects were rare. In the specific case of 3 birds at 464 cm2/bird, where the dimensions of the deep and shallow cages were exactly reversed, those in shallow cages were significantly less nervous (P<.01), had more feathers and egg cracking losses, and had significantly inferior egg production (P<.01), feed conversion (P<.01), and net egg income (P<.05). These last three effects were primarily attributed to the excessive feed consumption of the birds in shallow cages. It was concluded that for the 9 population-density combinations tested, birds in deep cages had superior feed conversion and were at least as profitable as those in shallow cages. In the specific case of 3 birds at 464 cm2/bird, the reversal to shallow cages caused a significant loss in eggs and net egg income. There was no evidence that layers could better withstand the added stress of decreased space and increased population number in shallow cages.