Protein feed stimulates the development of mandibular glands of honey bees (Apis mellifera)

This study assessed the effects of different protein levels on the development of the mandibular gland (MG) in six-day-old worker bees (Apis mellifera) during the dearth period. Twenty colonies were randomly assigned to one of four experimental diets containing 0%, 23%, 25%, or 27% crude protein (CP), with five replicates each. The experimental diets were composed of feed meal and honey sirup. Each colony was provided with 30 g of formulated feed every 3 days over a 36-day period. At the end of the experimental period, ten six-day-old worker bees were collected from each treatment for the morphological analysis of their MGs. The area of the MG was significantly larger in the bees fed protein-enriched feeds than in the controls. The height of the secretory cells in the MG was also significantly greater in all colonies fed protein-enriched feed than in the control group. However, the group that received the feed with 23% CP had significantly taller secretory cells than the other groups. Based on regression analysis, the ideal level of protein in the diet for the development of the MG was 22.2% CP. Thus, the use of protein-enriched feed promotes greater increases in the area and height of secretory MG cells in six-day-old honey bee workers.