An energy response curve for a commercial white Leghorn laying-strain cross.

Individually-caged White Leghorn hens, 235-d-old, were given daily metabolisable energy (ME) intakes ranging from 707 to 1321 kJ for 8 two-week periods. Energy was the first limiting nutrient, in those cases where the differences in egg output between treatments were sufficiently large. Body weight, egg number and egg weight all responded (P less than 0.001) to energy intake, and as judged by regression analyses, these responses had stabilised by the fifth period. For a near-maximum egg output of 48 g/bird d, the difference between the ME requirement of the average bird and of the flock, estimated from linear and curvilinear models respectively, was 20.5%. The ME requirement (Y, kJ/bird d) of the average bird for egg production (E, g/bird d) and maintenance of metabolic body size (kg W0.75) corrected to an ambient temperature of 22 degrees C is given by the equation, Y = 440W0.75 + 8.96 E.