Influence of Constant Elevated Temperature and Diet on Egg Production and Shell Quality'

ABSTRACT A total of 216 individually caged Single Comb White Leghorn pullets were divided into two equal groups and subjected to either a 21 ± 0.75 ° C o r a 32 ± 0.5 ° C. environmental temperature, both with 50 % relative humidity. The birds in each group were fed either a typical corn-soy laying diet (15 % prot., 2.8 % Ca, 0.57 % avail. P, 2,915 cal. M.E./gm. plus vitamins and minerals) or a "High Nutrient Density " (HND) diet (20 % more of all nutrients except energy which was increased only 10%). The data collected during 8 three-week periods indicated that % nitrogen in the shell increased under heat stress, whereas the following parameters decreased: (1) food consumption; (2) egg production; (3) egg weight; (4) specific gravity of eggs; (5) shell thickness; (6) true shell expressed as % of egg weight; (7) plasma calcium; (8) hematocrit values; (9) partial pressure of C0 2 in blood. The use of the "HND " diet partially alleviated the effects of heat stress on egg weight and egg production, and also decreased slightly the amount of nitrogen in the shell; however, this decrease was not accompanied by any significant improvement in specific gravity, and therefore the increase in shell thickness observed with the HND diet appears to be solely due to an increase in egg weight. Diet had little effect on the other parameters listed above with the exception that food consumption was decreased at either temperature by the "HND " diet. Neither the ash nor the calcium content of femurs, removed at the end of the experiment, was affected by environment or diet. Similarly, the calcium content of the shells was not influenced by temperature or diet. Reversal of the environmental temperatures at the end of the sixth period resulted in an inverse response in all parameters measured