Experimental Design
Animal care procedures used in the current study
were evaluated and approved by the Animal Care
and Use Committee for Livestock at the University of
Alberta. Nonlinear regression was conducted to establish
temperature-dependent maintenance ME requirements
using individually housed broiler breeder hens exposed
to a range of environmental temperature and fed 2 dietary
ME levels (2 dietary treatments). From 25 to 41 wk of
age, the hens were fed either a low ME (LE; 2,790 kcal/
kg and 16.1% CP) or a high ME (HE; 2,912 kcal/kg and
16.4% CP) breeder laying diet in mash form (Table 1).
During the same time frame, each of 6 environmental
chambers were subjected to 4 target set temperatures
(15°C, 19°C, 23°C, and 27°C), which were randomly assigned
to each chamber with the following constraints:
during each 2-wk period each temperature set point
was applied to at least 1 but no more than 2 chambers
(Table 2). Temperature treatments were assigned randomly
to prevent bias in MEm estimates. Temperatures
were therefore replicated both within each time period
and across time periods. The rationale for this approach