Effect of vitamins thiamine and riboflavin on population growth, functional traits, and body fat and protein reserves in Iranian honey bee (Apis mellifera meda) colonies

Introduction: Honey bees need nutrients such as protein, carbohydrates, lipids, minerals, and vitamins. Among nutrients, vitamins are particularly important for their roles in brood rearing, hypopharyngeal gland development, ovary development, longevity, bee immunity, bee weight, and flight muscle development. The vitamins stored in the body of the bees are vitally important in strengthening the immune system, normal growth, and development of broods, producing royal jelly, longevity of bees, and especially wintering quality of honey bees. Among the vitamins required by the honey bees, the most important are thiamine and riboflavin. Pollen quality depends on the supply of vitamins required by honey bees. Most pollen grains are poor and deficient in thiamine and riboflavin. This study aimed to investigate the effect of thiamine and riboflavin on population growth, functional traits, and fat and protein reserves of the bee body in Iranian honey bee colonies. Materials and methods: An experiment was conducted in a completely randomized design with four treatments and seven repetitions from April 2022 to September 2023 in the climatic conditions of Kurdistan province, Iran. Experimental treatments included the sugar syrup (control), thiamine (1500 ppm), riboflavin (1500 ppm), and the combination of thiamine and riboflavin (1500 ppm). From the beginning of 14 April 2023, experimental treatments were fed with the mentioned concentrations of vitamins thiamine, riboflavin, and their combination of 0.5 liters every other day for 45 days and 15 days without feeding. Then, traits such as honey production, pollen collection, population (adults and broods), and protein and fat content of carcass were measured in experimental treatments. Results and discussion: The results of the effect of thiamine, riboflavin, and their combination on the population of adult bees showed that the addition of thiamine and riboflavin in the bees' nutrition was significantly effective in the increase of adult bees' population in the investigated periods as well as the average of the entire period (P<0.05). A comparison of the averages of the experimental treatments revealed that the highest and lowest adult bee populations were associated with the treatments fed the vitamin combination and the control group, respectively. The results of the effect of thiamine, riboflavin, and their combination on the population of broods showed that the addition of thiamine and riboflavin in the diet of bee colonies during the studied periods did not have a significant effect on the increase in the population of newborns, but it showed a significant effect on the average of the entire period (P<0.05). The results of the mean comparison showed that the highest population of broods in the studied honey bee colonies was related to the treatments fed with the combination of thiamine and riboflavin, and the lowest population of broods was related to the control treatment. The results of the effect of thiamine and riboflavin on honey and pollen production traits showed that the use of vitamins and their combination in honey bee nutrition caused a significant increase in honey and pollen production traits of experimental treatments (P<0.05). The results of the mean comparison showed that the highest and lowest amounts of honey and pollen production of the studied honey bee colonies were observed in the treatment fed with the combination of vitamins and the control group, respectively. The effect of thiamine and riboflavin on the carcass protein and fat showed that the use of thiamine, riboflavin, and their combination in feeding the colonies had a significant effect on the amount of carcass protein and fat (P<0.01). A comparison of treatments showed that honey bees in the treatment fed the vitamin combination had the highest carcass protein and fat, and honey bees in the control treatment had the lowest carcass fat and protein. Conclusions: Based on the results of the present experiment, it could be concluded that the use of thiamine and riboflavin, and their combination in feeding honey bees had a positive effect on population growth, functional traits, and fat and protein reserves of the bees' body in the colonies and improved the performance and increased the economic efficiency of the colony.