Dietary Self-Selection by Layers

Individually caged, 27-week old Single Comb White Leghorn birds of a commercial strain were offered either 1) a conventional diet providing 2794 kcal ME/kg, 17.1% CP and 3% Ca or 2) simultaneously, two “split-diets” containing a) high energy (3065 kcal/kg) and protein (19.1%) but low calcium (.47%), and b) a second diet providing low energy (1740 kcal/kg) and protein (10.7%), but high calcium (13.1%). The split- and control diets were provided ad lib in two troughs. Sixteen replicate groups of 4 consecutively caged birds were used for each treatment. Feed intake, egg production, egg size, and egg shell deformation were measured at 4 week intervals throughout a 40-week laying cycle. Birds offered the split-diets consumed significantly (P<.01) less feed than did control birds, while producing the same quantity of eggs, although these were of larger size (P<.01) and of superior shell deformation value (P<.05). In selecting their own nutrients, birds consumed less energy and protein, but more calcium (P<.01). Feed and calcium intake differentials were most pronounced during the initial stages of production; these results are discussed in relation to calcium utilization. These results confirm that birds are able to select diets based on an appetite for calcium, and in so doing reduce overall intake by some 7%.