IMPROVING EGGSHELL QUALITY AT HIGH-TEMPERATURES WITH DIETARY-SODIUM BICARBONATE

Two experiments were conducted that confirmed the hypothesis that a di etary bicarbonate supplement will improve eggshell quality in hens at high temperatures as long as feed is consumed during the period of egg shell formation. End-of-lay hens were maintained on continuous light a t temperatures of 30 and 35 C. Individual egg weights and shell qualit y measures for each hen were calculated as a proportion of the initial values determined during an acclimatization period at 25 C. Improveme nts in shell breaking strength in both experiments were observed as a result of supplementing control diets with 1% sodium bicarbonate (NaHC O3). This response to NaHCO3 was not a reflection of a reduced rate of lay or egg mass output, as these were similar or inferior on the cont rol diets. Similar feed intakes on the control and NaHCO3 diets indica ted that the response was not related to differences in calcium intake s. Supplements of zinc methionine and ascorbic acid proved to be infer ior to NaHCO3. Improvements in egg weight were associated with the int roduction of continuous lighting.