Investigation on the possibility of reducing protein, phosphorus, and calcium requirements of laying hens by manipulation of time of access to these nutrients.

Experiments (Exp.) were conducted to determine whether the daily requirement of laying hens for protein, P, and Ca can be reduced by providing the hens with adequate levels of these nutrients only during those hours of the day that the physiological need for these nutrients for formation of various components of eggs are increasing. In Exp. 1, birds of the positive control were fed a 16% protein diet and birds of the negative control were fed a 13% protein diet continuously during the light period (0500 to 2100 h). The other groups were fed the 16% protein diet during the morning (0500 to 1300 h) and the 13% protein diet during the afternoon (1300 to 2100 h) or vice versa. The design of Exp. 2 was similar to Exp. 1. The birds of the positive control were fed a 0.4% available P (AP) and the birds of the negative control were fed a 0.2% AP diet, with other groups receiving the high-low AP or the low-high AP diets during the morning and the afternoon, respectively. The birds of the negative controls in these Exp. had almost comparable performance to those fed the other dietary treatments. As a result, these Exp. did not have negative controls for comparison of different dietary treatments. Additionally, regardless of dietary treatments, birds consumed about 40% of their daily feed intake during the morning and about 60% during the afternoon in these Exp. Due to these two shortcomings, it was not possible to reach to a decisive conclusion pertaining to the objectives of the Exp. The results of Exp. 3 indicated that the above pattern of daily feed intake was not due to an increased appetite for Ca during the afternoon hours for shell formation. Various indices of shell quality were not improved when most parts of the daily Ca need was fed during the afternoon and evening and were not reduced when most parts of the daily Ca need was fed during the morning.