Zinc nutrition increases the antioxidant defenses of honey bees

Is the typical zinc (Zn) content of honey and pollen sufficient to meet the nutritional requirements of honey bees? To answer this question, and find the optimal dietary Zn levels for honey bees, we investigated the effects of varying dietary Zn levels on both captive worker bees and free-flying honey bees, Apis mellifera ligustica Spinola (Hymenoptera: Apidae). We fed captive workers and free-flying honey bees with 50% (wt/wt) sucrose solutions with Zn levels of either 0, 15, 30, 45, 60, or 75 mg kg(-1) diet and measured their Cu/Zn-SOD activity, the mean survival time of captive bees, the Cu/Zn-SOD activity of larvae, and the Zn concentration of royal jelly. Captive workers provided with 30 mg kg(-1) dietary Zn had higher Cu/Zn-SOD activity and mean survival time than the control. Dietary Zn levels from 60 to 75 mg kg(-1) significantly increased the Zn content of royal jelly provided by colonies and the Cu/Zn-SOD activity of larvae. Honey or pollen with a Zn content of <30 mg kg(-1) was insufficient to satisfy the maintenance nutritional requirements of bees that were not raising larvae. It therefore seems advisable to supply supplementary Zn to non-brooding colonies when the Zn content of honey or pollen is <30 mg kg(-1). Honey or pollen with a Zn content of 60 mg kg(-1) was sufficient to satisfy the nutritional requirements for royal jelly production and to improve the health of larvae. It may therefore also be advisable to provide supplementary Zn to colonies with larvae when the Zn content of honey or pollen is <60 mg kg(-1).