Response of Layer Breeders to Dietary Acetylsalicylic Acid.

Acetylsalicylic acid (ASA, aspirin) is an inhibitor of prostaglandin (PG) synthesis and an antipyretic drug. Because PG may be involved in the premature oviposition of some soft-shelled (SS) and shell-less (SL) eggs, the objective of the present study was to determine whether dietary ASA, as an inhibitor of PG synthesis, would convert SS and SL eggs to hard-shelled (HS) eggs, thus increasing total salable egg output and improving feed efficiency. White Leghorn layer breeders were fed 0, .025, .05, .10, .20, and .40% ASA for the first 13 mo of egg production. When averaged over 13 mo, hens fed .40% dietary ASA laid fewer HS eggs (P < .002), had poorer feed efficiency (P < .03), had increased mortality (P < .0001), and laid smaller eggs (P < .01). All levels of dietary ASA resulted in significant decreases in specific gravity (P < .0001), shell thickness (P < .0001), shell weight (P < .0001), and percentage shell (P < .0001). During Month 1 of production, mortality was greatly increased for hens fed .20 and .40% ASA as compared with hens receiving 0, .025, .05, or .10% ASA (diet by month interaction, P < .0001). However, during the other 12 mo of production, only hens receiving .40% dietary ASA experienced a slight increase in mortality. Also during Month 1 of production, hens fed .20% ASA laid fewer SL eggs, whereas hens fed .05 and .40% ASA laid more SL eggs than birds receiving the control diet (diet by month interaction, P < .0007). In conclusion, chronic feeding of ASA did not improve egg production or feed efficiency. In addition, long-term feeding of ASA to layer breeders proved to be detrimental with respect to early hen livability and eggshell quality.