Comparative feeding experiments
In 1997 and 1998, the Bavarian Institute for Apiculture in Erlangen /Germany conducted comprehensive experiments in Erlangen and Kringell to investigate the effects of winter feeding with sucrose-based and starch-based feeds. Roughly 100 bee colonies were used for the experiments, the aim of which was to determine whether the composition of the bee feed influences the following:
All the colonies fed with Apiinvert survived at both locations. In some of the colonies fed with starch-conversion products losses were high. This was especially the case in Kringell, which has a harsher climate. A possible explanation for these results is that oligosaccharides (complex sugars) are broken down only partially or not at all by the bees' enzymes. This is harmful to the intestine and can lead to diarrhea. The high ash and colour contents of some starch-conversion products make this effect even more pronounced.
Changes undergone by the sugar between
the time of feeding and deposition in the hive
Bees have various enzymes, of which invertase is the most important for the digestion of carbohydrates. It breaks down the disaccharide sucrose into its component monosaccharides, fructose and glucose. These monosaccharides are available to the bees as nutrients relatively quickly. The disaccharide maltose contained in starch-conversion products is broken down much more slowly into glucose, and is thus less readily available to the bees as a nutrient. In some cases, the proportion of maltose in the feed deposited in the hive had increased by the end of the winter, which is an indication of further reactions. The resulting oligosaccharides either cannot be assimilated at all by the bees, or only poorly.
Tendency of the feed to granulate in the comb
The tendency of the feed to granulate was determined at the time of deposition and at the end of the winter. It was found that feed syrups rich in glucose and maltose had a higher tendency to granulate. In some cases, no syrup could be isolated from the cells because the entire cell content had granulated.
In the combs of colonies fed with Apiinvert, only a slight tendency to granulate was observed. The bees thus had sufficient supplies of readily-available food.