The experimental study was conducted at the apiary laboratory of Bangladesh Sugarcrop Research Institute (BSRI), located in Ishurdi, Pabna, Bangladesh, during the dearth period of July to September 2021–2022 and 2022–2023. The climate of the experimental site is classified under the Köppen climate classification system as having a predominantly tropical monsoon climate, specifically designated as Am (Farukh et al., 2023). This classification indicates a region with a hot, dry, and humid climate, where there is heavy rainfall during the rainy season from July to September. The average rainfall is 17.94 mm (avg.), and the temperature is 31.44°C (avg.) (BSRI weather station). Bangladesh boasts a rich variety of local flora, including thriving forests, mangrove swamps, and extensive wetlands. However, during the dearth period from July to September, honeybees in Bangladesh encounter considerable difficulties due to food shortages. This period aligns with the monsoon season, characterized by a decrease in floral resources caused by heavy rainfall. There were seasonal gaps in food availability for honeybees during this time, and they faced challenges when it comes to finding enough food. These challenges include diminished flowering of plant species, damage to flowers and loss of nectar and pollen due to flooding, limited floral diversity in agricultural areas, and loss of habitat due to deforestation and urbanization. In order to tackle these challenges, beekeepers might have to consider providing supplementary food.

The experiment was conducted on the honeybee species Apis mellifera. The experimental design chosen was a randomized complete block design (RCBD) with five replicates for each treatment, as shown in Table 1 , where sugar syrup was used as a control treatment. The honeybees of A. mellifera colonies were taken for treatment from the BSRI apiary, Ishurdi, Pabna.

An assortment of food supplements was developed and supplied to honeybee colonies, with subsequent monitoring of their growth and consumption of food. Various syrups have been developed using sugar, banana, pumpkin, maize flour, and rice flour to provide an alternate food source for honeybees during a dearth period. The following outlines the preparation techniques for these food substitutes:

The nutritional data of the supplementary food were typically measured by laboratory analysis of representative samples of the food supplements. This analysis includes measuring macronutrients (such as carbohydrates, proteins, and fats) and other components like fiber and moisture. A bomb calorimeter was used to measure the heat of combustion of the used food supplements, providing information on the total caloric content, where the specific bomb calorimeter calibration method (i.e., benzoic acid) was used (Hopper et al., 2023). Proximate analysis is a set of procedures to determine a food material’s approximate or proximate chemical composition—the components typically analyzed include moisture, ash (minerals), lipids (fats), proteins, and carbohydrates. In order to measure the moisture content, the gravimetric method involves drying the sample and measuring the weight loss (Farias et al., 2022). The method of incineration of the food sample to combust organic matter, leaving behind the inorganic ash, the muffle furnace (PCMF-1) instrument, was used to determine the ash content of food materials (PACORR, 2023). The instrument solvent extractor was used to measure the lipid (fat) content by using the solvent extraction method (Hewavitharana et al., 2020). The Kjeldahl method was introduced to determine the protein content, which involves the digestion of food supplementation with a strong acid so that nitrogen can be released, the quantification of the protein by a titration procedure, and the multiplication of total nitrogen in the food supplementation with a traditional conversion factor of 6.25 for brown sugar, banana, and pumpkin and a species-specific conversion factor of 5.4 for maize and rice flours, as described elsewhere (Mæhre et al., 2018). The indirect method was employed to measure the carbohydrate content by calculating the difference (100% − sum of moisture, ash, lipids, and protein) of the specific food materials. Following the homogenized sample’s water extraction, sugars (mono- and disaccharides: fructose, glucose, sucrose, and maltose) were measured using liquid chromatography (AOAC 980.13) (AOAC, 2005; Phillips et al., 2021). These methods are standard procedures and have variations based on the specific requirements of the analysis and the characteristics of the food materials. The choice of method depends on factors such as the nature of the food, the precision required, and the available resources in a laboratory setting. The accuracy of the labels depends on various factors, including the accuracy of the laboratory analysis, the manufacturing process, and the regulations in place. However, there can still be variations in the actual nutritional content of individual items due to factors like natural variation in agricultural products and manufacturing processes (Chen and Antonelli, 2020). Table 2 shows the nutritional contents of the different feeding materials used in this study.

The total quantity of food consumed by honeybees was quantified to determine the preferred food supplements for honeybees. The remaining supplies were counted the day after providing the food (24 h later). Food consumption was determined by subtracting the initial food supply from the remaining food. Three boxes for each treatment containing bee colonies were put together, each equipped with queens of similar levels. Each of these three treatment colonies was allocated to a specific feeding treatment using the same feeder. Every box contained 300 ml of food substitutes. Data collection involved extracting two sides of a single frame from each box. The first data were collected before the feeding material was provided. Additional data were obtained every second day to evaluate the influence of honeybee colonies on these food sources during a week. Pictures of bee frames were captured, and the number of brood, honey, and pollen cells was determined by counting the images with the naked eye.

Statistical analysis of various treatments was conducted using the ‘R’ Studio (Team, R.D.C, 2019). Analysis of variance (ANOVA) tests were used to detect significant differences (at a significance level of α = 0.05) within treatments. The means were compared using the least significant difference (LSD) test at a significance threshold of 5%. Cost analysis involves calculating the expenses associated with acquiring various food supplements, comparing the result benefits in terms of productivity, and identifying the most economical option. This assessment considers factors such as the cost per unit of each supplement, its effectiveness in supporting colony growth, and potential long-term cost-effective savings in honeybee maintenance.

Table 3 shows the comparative assessment of daily supplementary food consumption in honeybee colonies during the dearth period. Without question, sugar is the preferred food in the diet of honeybees. The results show that the brown sugar syrup used in this experiment contains 97 g sugar out of 100 g, whereas the honeybee colonies consumed 100% sugar syrup. One hundred grams of banana syrup has 12.2 g of sugar, whereas pumpkin contains 2.8 g of sugar. That is why honeybees have a higher preference for consuming banana syrup (93.96%) than pumpkin syrup (88.30%) in food consumption competition, as shown in Table 3 . It can be seen from Table 2 that maize and rice have a minimal sugar content of 0.6 g and 0.1 g, respectively. Therefore, the food consumption ratio of these two items is lower than that of the other three items, which are 85.07% and 78.41%, respectively. Based on the findings in Table 3 , it appears that honeybees have a clear preference for banana, pumpkin, maize flour, and rice flour syrup, in that particular order. The amount of syrup consumed by honeybee colonies can vary depending on the type of syrup provided. For example, researchers presented that honeybees might have a preference for banana and pumpkin syrups because of the natural sugars and unique flavors they make available, resulting in honeybees consuming more of these syrups compared to rice and maize flour syrups (Neupane and Thapa, 2005). Nevertheless, honeybees might still consume rice and maize flour syrups, particularly when it is fermented.

Fermentation can improve the taste by improving flavor quality and nutritional content although the amount consumed could differ. It was observed from the study that the fermentation process of rice and maize flour syrups began approximately 24 h after feeding, while the fermentation of banana and pumpkin syrups started approximately 36–48 h after feeding. It was also noted that the supplement syrups were consumed within 48 h, which counted for the analysis. When the honeybees consume supplementary food, they introduce it into their hives, which undergo a natural fermentation process due to the enzymes and microorganisms in the hive environment. It is interesting to note that bees prefer fermented foods over fresh foods due to their higher energy value and the aromatic compounds that they produce that could attract bees to the syrup. In addition, fermentation duration may extend beyond 24 h, particularly in situations where conditions are conducive to microbiological activity. However, availability, colony health, and environmental conditions all contribute to the variations in supplementary syrup consumption among honeybee colonies (Margaoan et al., 2020; Camacho-Bernal et al., 2021). It is essential to acknowledge that the exact time and duration of fermentation may exhibit variability dependent upon various environmental factors, including temperature, humidity, pH level, specific strains of microorganisms, and the specific composition of the supplement flours. For this study, warmer temperatures and higher humidity levels during the dearth period could enhance fermentation.

The number of pollen cell development in honeybee colonies during the dearth period was measured while providing various supplementary foods, as shown in Table 4 . According to the findings, the number of cells covered with pollen after each treatment decreased, except for the pumpkin syrup. The colony was provided with pumpkin syrup, resulting in a significant increase in the number of pollen cells (58.73%). On the other hand, the consumption of sugar syrup resulted in a decline of 21.97% in pollen cells. In the same way, the consumption of maize syrup led to a 53.25% reduction in pollen cells, whereas rice syrup caused an even more significant decrease of 73.61%. The colony which consumed banana syrup exhibited the most significant decrease (81.98%) in pollen cells.

The supplementary foods could have an impact on the pollen cell development in honeybee colonies by providing additional nutrients necessary for pollen collection and storage. Pollen serves as a crucial protein source for developing brood and the overall health of the colony. Protein and carbs are the primary constituents for developing honeybee pollen cells (Khalifa et al., 2021). According to the findings, pumpkin has an ideal protein and carbs ratio conducive to pollen growth ( Table 2 ), and consuming pumpkin syrup leads to a rise in pollen cells. However, pumpkin syrup, which is rich in sugars and micronutrients, has the potential to attract bees to forage more actively, resulting in an increased pollen collection that aids in the growth of pollen cells. Pollen cell development ensures the availability of sufficient pollen resources within the hive, promoting the growth and vitality of the colony’s production.

The study investigates the variation in the number of brood cell development in honeybee colonies when provided with different food substitutes during a dearth period ( Table 5 ). The findings indicate that the number of brood cell development varied after feeding several types of food substitutes. It was observed that bee colonies that received pumpkin syrup showed a significant increase of 71.36% in the number of brood cells. Colony growth was observed as brood cells developed, with a notable increase of 37.58% in colonies fed with banana syrup. Conversely, colonies fed with rice syrup showed a slight loss of 0.33% in brood cells, while those fed with maize syrup had a more significant decrease of 49.66%. The sugar syrup exhibited the lowest number of brood cells, with a drop of 69.48% compared to other conditions, as seen in Table 5 . Researchers find that feeding a protein-rich diet significantly positively affects the number of bees present on frames (Ricigliano et al., 2022).

The impact of supplementary food with banana, pumpkin, maize flour, and rice flour syrups on the growth of brood cells in honeybee colonies could vary based on the specific nutrient composition of each syrup. Carbohydrates, protein, and fat are essential components for optimal brood cell growth of honeybee colonies. The banana and pumpkin syrups are known for their high levels of natural sugars and nutrients. The study revealed that both bananas and pumpkins are good sources of protein and carb ratios ( Table 2 ). These syrups have been found to positively impact brood cell development, resulting in higher brood production and faster development. Although the maize and rice flour syrups do provide more carbohydrates, the food consumption rate of these syrups was lower, resulting in these syrups not having all the essential nutrients needed for optimal growth. Therefore, it is crucial to carefully consider the food consumption of each syrup, ensuring proper nutrition and effectively managing supplementary food in order to promote brood cell development and maintain the sustainable health growth of the colony.

Supplementary food such as banana, pumpkin, maize flour, and rice flour syrups during the dearth period significantly impacts honey cell development in honeybee colonies. Table 6 shows the development of honey cells in honeybee colonies when provided with different supplementary food alternatives during the dearth periods. The honey cell numbers exhibited a somewhat uniform appearance at the start of the experiment and then varied after providing various types of food substitutes. Upon concluding the experiment, it was noted that the bee colonies that were given pumpkin syrup displayed the highest number of honey cells, showing a significant increase of 108.36%. Next, colonies were given sugar syrup as supplementary food, resulting in a 5.37% increase. Conversely, colonies fed with banana syrup experienced a decrease of 4.18% in honey cells, while those fed with maize syrup showed a decrease of 8.96%. The lowest number of honey cells was found in colonies fed with rice syrup, with a decline of 48.69%, as shown in Table 6 .

Banana and pumpkin syrups, being naturally rich in sugar, water and potentially other nutrients, can provide a boost to honey cell development, promoting increased honey storage within the hive. However, primarily, carbohydrate sources, maize flour, and rice flour syrups can also contribute to honey cell development by providing energy for wax production and maintenance of hive infrastructure. However, the decrease in honey cells, even with the addition of maize flour and rice flour syrups to honeybee colonies, may be due to a deficiency in essential nutrients and an unbalanced carbohydrate composition in these syrups (Samukelisiwe, 2023). Maize flour and rice flour syrups mainly offer carbohydrates but may not contain the wide range of sugar and water needed for optimal honey cell development to reach their full potential.

Figure 2 shows the comparative analysis of the brood, honey, and pollen cell numbers before and after the consumption of supplementary food in the dearth period from honeybee colonies. The development of brood cell numbers is increased only for the banana and pumpkin syrups. On the other hand, brood cell numbers are decreased for the other three syrups. Honeybee colonies that were given pumpkin syrup experienced a greater rise in brood and bee populations than those that were given banana, maize, or rice flour syrup. Thus, pumpkin and banana syrups surpass rice flour in terms of quality. Additionally, maize flour can be a cost-effective alternative for feeding bee colonies during the off-season, enhancing their viability. The results reveal that pumpkin supplementary food increased the population density compared to all supplemented foods. Honey and pollen cells also increased significantly in those bee colonies fed on supplemental pumpkin syrup. The figures also underline that all supplemental food tests here were not equally effective in stimulating the various biological activities of honeybee colonies. This analysis allows for a comprehensive assessment of how the introduction of supplemental food influences the development and resource allocation within honeybee colonies over time.

Figure 3 shows the comparative percentage of pollen, honey, and brood cell numbers after taking the supplementary food in the dearth period. The figure underlines that brood, honey, and pollen cell percentages are increased only for the pumpkin syrup. It can be noted that wherever the feeding supplementary foods contain low carbs and high sugar, the honeybee most likely prefers to consume those supplementary foods in the dearth period, resulting in an increase in the development of brood, honey, and pollen cells in arid or semi-arid hot climate environment during the dearth period. The sugar and water are essential components for forming honeybee honey cells ( Table 2 ). Pumpkin syrup has these components in an optimal amount. Therefore, consumption of pumpkin syrup leads to an increase in honey cell numbers. Due to the lower water content in banana syrup compared to pumpkin, the honey cell experiences a minor drop in size after its uptake. Due to the low sugar content in maize and rice syrups, the intake of these syrups in honeybees decreased. Consequently, there is a decrease in the production of brood, pollen, and honey cells.

The nutrition of honeybees encompasses a diverse array of chemical compounds, including carbohydrates, lipids (fat), proteins, minerals, and vitamins. During the dearth period, there is a wide availability of fruits, vegetables, and cereals in the market that are abundant in carbs, proteins, vitamins, and minerals. These nutritious options may be obtained at a lower cost and can serve as suitable alternatives for feeding bees during this period. Among these, banana and pumpkin are both the most affordable and the most nutritious fruits compared to others ( Table 2 ). Feeding bees with banana and pumpkin syrups offers energy and provides protein, vitamins, minerals, and sugar in a certain amount, resulting in increased tissue growth. Similarly, rice flour and maize flour syrups, readily accessible during the dearth period, are likewise more affordable and abundant in nutrients. The research has also shown that honeybees are capable of using the intricate carbohydrate that is the basis of their crucial functions as food processors within the honeybee colonies but not significantly developed in their brood, pollen, and honey cells (Hrassnigg et al., 2003). Hence, providing bees with carbohydrates, protein, mineral, and fat-rich fruits, vegetables, or cereals may serve as a cost-effective substitute for costly cane sugar.

The experiment revealed that the honeybee colonies flourished when fed with pumpkin and banana syrups, leading to an increase in brood and honey cells. Moreover, feeding pumpkin and banana syrups helped sustain the viability of honeybees during the off-season. Conversely, honeybees exhibited a drop in brood and bee populations when provided with a diet of maize and rice flour syrups. Nevertheless, the quantity of honey stored in the experimental bee colonies that were provided with rice and maize flour syrups was inadequate to meet the bees’ needs. The number of cells containing honey in the pumpkin- and banana-feeding colonies was sufficient alone to sustain the viability of the bees. No traces of toxicity were detected in any of the syrup samples tested on bees. Furthermore, none of the experimental bee colonies had any occurrence of pests or illnesses affecting the bees.

The comparative cost analysis of various supplementary food materials can be seen in Table 7 . The costs of various food substitutes utilized for feeding the colonies vary. The highest-cost food substitute was found to be sugar syrup. A 900-ml supplementary food was provided to feed each colony. Preparing 900 ml of sugar syrup costs 1.89 dollars. The cost of banana, pumpkin, maize flour, and rice flour syrups was 0.91, 0.83, 0.53, and 0.53 dollars, respectively. Feeding honeybees with pumpkin syrup during the dearth period could decrease the cost of sugar feeding by 50%, as shown in Table 7 .

The cost analysis of supplement foods during dearth periods for honeybee colonies is essential for beekeepers to ensure optimal colony health and productivity. Evaluating the expenses associated with supplementary foods helps beekeepers make informed decisions about their feeding strategies. By assessing the cost-effectiveness of each supplement option, beekeepers can optimize their resource allocation and budget management, ultimately enhancing the sustainability and profitability of their apiaries. Moreover, understanding the cost implications enables beekeepers to balance nutritional needs with economic considerations, fostering efficient hive management practices and supporting the long-term viability of beekeeping operations. This supplement also contains nutrients that are necessary for honeybee’s proper growth and development, as well as for brood production. This technique is a cheaper feeding material to reduce the feeding cost during the dearth period.