| Abstract: | Studies were conducted to determine the relationship of cage size and housing weight to performance of commercial layers. These studies included the influence of cage size, body weight at housing and genetic variability upon the laying hen's ability to adapt to the physical and psychological stresses imposed by multiple-bird caging. The feasibility of increasing the nutrient density of light weight birds was tested by use of a protein phase feeding regime. The influences of cage size and body weight at housing on adrenal weight, serum cholesterol level and atherosclerosis were also studied. Significant strain differences were observed for average body weight, egg production, egg size and feed efficiency. The heavier, early-maturing strain (B) laid at a higher rate and was more efficient. Egg size, however, was greater for the lighter-bodied strain (A). A significant interaction for egg production existed between cage size and strain. Hen-day egg production was higher in the small cages. A 20.3 x 45.7 or 30.5 x 45.7 cm. cage with two to four birds per cage appeared to be optimum for egg production. A significant 22-week body weight x cage size interaction indicated that when housed at a bird density of 464.3 cm² per bird, the threshold cage size for optimum egg production from light weight birds was 30.5 x 45.7 cm. The threshold cage size for medium weight birds was 40.6 x 45.7 cm. Only minor differences existed in egg production of heavy weight birds housed in the six cage sizes varying from 20.3 x 45.7 cm. to 101.6 x 45.7 cm. ... |
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