Artificial feeding of honeybees based on an understanding of nutritional principles

Abstract

Artificial pollen substitutes were developed to improve productivity from honeybees during periods of nutrient scarcity. The history of pollen-substitute development is outlined. Although many attempts have been made, no substitute has the same nutritional value as bee-collected pollen. Following a review of honeybee nutrition, Black (2006) described the ingredient and nutrient specifications for a pollen substitute, including the need for attractiveness to honeybees. Protein isolates were recommended to avoid toxicity from carbohydrates found in many ingredients used in previous studies. Twenty-seven plant- and animal-derived oils and a rum supplement, mixed at 2% with a low-lipid irradiated pollen, were evaluated for attractiveness by measuring consumption and bee congregation when placed in dishes within beehives. Coconut, linseed oil and rum were preferred significantly (P < 0.05) to the pollen, whereas pollen was preferred to lavender and sage oils. Almond and evening primrose oils were also highly, but not significantly, preferred compared with pollen and were used in combinations with coconut and linseed oils in subsequent experiments. Eleven predominantly pure protein sources, either singly or in combination, were mixed with 2% or 5% attractive oils and evaluated for attractiveness. Soybean protein isolate was selected, because attractiveness was not significantly different from bee-collected pollen. It was then used with oils in an experiment to evaluate either powdered cellulose or milled oat hulls as a fibre source. There were no significant differences in attractiveness of substitutes with the two fibre sources or pollen, and powdered cellulose was selected for further use on the basis of availability. An experiment with ~1000 newly hatched bees with a fertile queen in cages was undertaken to evaluate the diets when given as the sole nutrient source. Consumption, bee longevity and estimated hypopharyngeal gland development using head weight were measured One artificial diet (PI-5) contained 30% soybean protein isolate, 10% cellulose, 42% icing sugar, 12.5% water, 4.5% mixed oils and 1.3% minerals and vitamin plus cholesterol. Diet (PI-10) was similar, but contained twice as much oil replacing icing sugar. Other treatments were redgum pollen (P), a commercial pollen substitute, Feedbee® and defatted soybean meal. Diet consumption, lifespan and head weights were significantly less for the PI diets than for P, while Feedbee® and defatted soybean-meal diets were generally intermediate. The PI diets were discovered to contain excess sodium, due to the manufacturing process. Bees consuming the PI diets had lower concentrations of magnesium, copper, iron, manganese and zinc in their bodies than did those offered P. The fatty acid content of bee bodies also varied with diet. A revised formulation is recommended with reduced sodium and modified mineral and fatty acid composition.