Nectar and pollen resources are not sustainable year-round in most parts of the world, and the lack of either results in reduced colony productivity. To address this challenge, we investigated the effects of a high-protein pollen substitute diet on honey bee (Apis mellifera L.) colony performance over a one-year period. Ten colonies were fed a diet (50 g/colony, twice weekly) comprising 15 g defatted soybean flour + 15 g brewer's yeast + 5 g sugar powder + 5 g skimmed milk + 10 g cotton honey. Another ten colonies served as a control group without protein supplementation. Colony performance metrics including foraging activity, stored pollen area, worker and drone brood production, and overall colony strength were monitored and compared. Additionally, monthly surveys identified the dominant nectar and pollen sources in the Kafrelsheikh district. Faba bean, Egyptian clover, sunflower, eucalyptus, and sesame were the dominant sources of nectar and pollen. Maize was the main pollen source, and cotton was a major nectar source in the Kafrelsheikh district. Compared with the unfed colonies, the fed colonies showed significant superiority in colony activity and productivity. The highest values of the number of forager bees, pollen forager, stored pollen area, worker sealed brood area, and colony population size were recorded during May, followed by August, then March, while the lowest values were recorded during December. The highest values of drone sealed brood area were recorded during March, followed by May, then August, while no drone broods were reared from October to January. Honey yield from fed colonies increased by 36.62% and 35.10% more than honey from unfed colonies for Egyptian clover and cotton honey, respectively. Supplementing honey bee colonies with a high-protein diet during periods of natural pollen scarcity significantly enhances colony performance, strength, and honey production. We recommend protein supplementation during scarcity periods and between major nectar flows to sustain colony health and maximize productivity.
Pollen and nectar are the major natural protein, carbohydrate, and lipid sources of honey bee colonies. They are essential for brood production, growth, and health of the honey bee colony (Taha et al., 2019a; Al-Kahtani et al., 2021). There is a positive relationship between the low seasons of nectar and pollen and all honey bee activities and their products under suitable environmental conditions, according to the rule that states 'no pollen, no bees' (Taha and Al-Kahtani, 2019; Shawer et al., 2021). Development, reproduction, colony population size, and food reserves are among the criteria used to determine whether honey bee colonies are successful in a region (Helal et al., 2003; Shawer et al., 2003; Elwakeil et al., 2025; Taha et al., 2025a).
Providing honey bee colonies with supplemental pollen feed is critical to their health and productivity. Honey bees need nectar and pollen to generate heat for thermo-regulation within their nests and to rear their brood (Degrandi-Hoffman et al., 2008). The production of a colony depends on the availability of high-quality nutritional sources. When natural pollen sources are not available, artificial pollen diets can be used to supplement honey bee colonies, which is essential for the development of young bees, reproduction, brood rearing, honey production, and colony maintenance (Taha, 2015b; Elwakeil et al., 2025). Bees in their developing stages and nurse bees require pollen supplements that are abundant and diverse in amino acids, fatty acids, and mineral elements, since certain pollens may lack essential amino acids they cannot synthesize for themselves (Al-Kahtani and Taha, 2020; Taha and Al-Kahtani, 2020b).
Colony performance is influenced by environmental factors, which in turn impact colony productivity. The beekeeper feeds supplementary pollen or pollen substitutes to colonies during times of pollen dearth to maintain colony strength (Morais et al., 2013; Taha, 2015b; Elwakeil et al., 2025). Bee diets often contain protein-rich substances such as soy, pea, yeast, casein, etc. (Ricigliano et al., 2022; Elwakeil et al., 2025). Pollen substitutes should meet the nutritional needs of honey bees throughout the year, be cost-effective, and provide comprehensive nutrition (Elwakeil et al., 2025). A pollen substitute diet should contain protein, lipids, and other nutritional sources (Brodschneider and Crailsheim, 2010; Taha et al., 2025a). A consistent supply of pollen or a protein-supplemented diet can encourage brood rearing and promote colony expansion (Morais et al., 2013; Elwakeil et al., 2025). However, adult workers who are nutritionally stressed, such as larvae, might experience weight loss, shorter survival, less foraging activity, and more aggressive dance behavior (Noordyke et al., 2021). Most beekeepers commonly use commercial or artificial diets to avoid apparent nutritional deficiencies (Taha, 2015b; Elwakeil et al., 2025).
Colony growth and maintenance are limited by the amount of protein available typically found in pollen. Protein is an essential nutrient for honey bee larvae, and a shortage will greatly affect brood production (Brodschneider and Crailshein, 2010; Taha et al., 2019a; Al-Kahtani et al., 2020). During the first 3 days of larval age, bee larvae feed on royal jelly produced by nurse bees. Nurse bees feed on pollen to develop their hypopharyngeal glands and mandibular glands, which release royal jelly. Therefore, colonies that have no access to protein during the active season have a reduced capacity to rear new bees to replace the old ones when they die, resulting in a quick decline in population and potential death (Shawer et al., 2021). The wintering ability, brood areas, colony population size, and adult survival rates are positively influenced by feeding (Elwakeil et al., 2025; Taha et al., 2025a). The evaluation of pollen substitutes should include their attractiveness to bee workers, and their effects on brood area, survival of bees, and colony development (Taha, 2015b; Lamontagne-Drolet et al., 2019; Elwakeil et al., 2025).
Colony strength before the nectar flow is a critical factor for honey production and yield, allowing effective use of early flow seasons. Pollen supplements or substitutes may accelerate colony growth and improve colony performance by stimulating brood rearing during scarcity periods (Mattila and Otis, 2006; Elwakeil et al., 2025). While adult bees can survive on carbohydrates alone, access to pollen significantly extends worker longevity (Manning et al., 2007); this can be seen in the colony population size and can have effects on colony performance and productivity.
In most regions, seasonal fluctuations in nectar and pollen availability lead to weakened colonies, reduced productivity, and potential colony decline. To address this issue, this study investigates the effects of a high-protein diet on honey bee colony performance, with particular focus on: foraging activity (monthly variations), stored pollen reserves, worker and drone brood production, colony population dynamics, and honey yield. By evaluating these key metrics, we assess how protein supplementation sustains colony strength and productivity during resource-limited periods.
MATERIALS AND METHODS
Apiary Location and Experimental Colonies
Experiments were conducted at the Faculty of Agriculture apiary (31° 5′ 54″ N, 30° 57′0″ E) at Kafrelsheikh University, Kafrelsheikh, Egypt, during the period extended from October 2022 to September 2023. The oxalic acid vaporization method was used to control Varroa mite (Varroa destractor) in experimental colonies in mid-September 2022. By the beginning of October 2022, 20 Carniolan hybrid honey bee (Apis mellifera carnica Pollmann × A. m. lamarkii Cockerell) colonies (14000 bees for each) headed by sister open-mated queens and having relatively similar brood area, and storage food were prepared for the experiments. The colonies were divided into 2 groups, each 10 colonies. The 1st group was fed a diet of Taha et al. (2025a). The diet (50.00 g/colony) comprises 15 g brewer's yeast (Saccharomyces cerevisiae) + 15 g defatted soybean (Glycine max) flour + 5 g skimmed milk + 10 g cotton (Gossypium barbadense) honey + 5 g sugar powder. The diet was introduced fresh to the colonies as a paste placed on waxed paper directly above the brood nest at a rate of 50 g/colony twice a week. The proximate analysis of the experimental diet has been determined (Taha et al., 2025a). The 2nd group was left without proteinaceous feeding (control). Sugar feed was provided equally to all colonies as needed during periods of scarcity.
Colony Performance
Colony performance was determined over one year. The number of incoming workers without and with pollen loads to a colony within one minute at the flight activity peak was counted monthly, once a week. The counts were taken at 09.00–10.00 hrs during June–September and at 12.00–13.00 hrs during October–May. A plastic sheet divided into square inches was utilized to measure the areas (square inches) of stored pollen and worker and drone sealed broods at 12-day intervals, and the monthly areas were counted. The number of combs covered with bees/hive was calculated monthly to determine the number of bees (colony population size), as the bees covering one comb equal 2000 bees (Taha, 2007). The Egyptian clover (Trifolium alexandrinum L.) honey yield was harvested by the beginning of June and cotton (Gossypium herbaceum L.) honey was harvested by the end of August. The honey yield of each colony was determined by calculating the difference between the weight of honeycombs before and after extraction. The monthly increments due to feeding in the previous aspects were calculated (Eq. 1)
Survey of Major Bee Plants
The most important nectar and/or pollen-producing plant species in the experimental area were recorded throughout the year. The scientific name, common name, and plant family were identified for each plant. The flowering date of each plant and its value to bees as a source of nectar and/or pollen were recorded.
Meteorological Factors
The mean values of maximum and minimum air temperature, rainfall, wind velocity, and relative humidity in Kafrelsheikh district, Egypt during experimental months (Table 1) were obtained from the meteorological station of Rice Research and Training Center, Sakha, Kafrelsheikh, Egypt.
Table 1.
The mean values of some meteorological factors in Kafrelsheikh district, Egypt during experimental months in 2022/2023.
Statistical Analysis
The two-way analysis of variance was used to test the differences between the fed and unfed colonies for foraging activity, stored pollen area, worker and drone sealed brood areas, colony population size, and honey yield via the PROC GLM function in SAS version 9.1 (SAS Institute, 2003). The treatment means were compared by using Tukey's HSD post-hoc test.
RESULTS
Data presented in Table 1 show that the maximum air temperatures were above 32 °C during June to September, above 25 °C during April, May, October, and November, and above 20 °C during March and December. The minimum air temperature declined under 10°C only in January and under 15 °C during December, February, and March. The relative humidity values were above 65% during October, November, and January, above 60% during February, July, and August, above 55% during March, June, and September, and above 50% during April and May. Wind velocity was above 4 km/hr from March to May.
Data listed in Table 2 show the most important nectar and/or pollen flora for honey bees in the Kafrelsheikh district during the experimental year. Faba bean (Vicia faba L.) was the predominant source of nectar and pollen from January to March. Egyptian clover (Trifolium alexandrinum L.) was the major source of nectar and pollen during May and June. Maize (Zea mays L.) was the main source of pollen for honey bees from June to November. Sunflower (Helianthus annuus L.), cotton (Gossypium herbaceum L.), and sesame (Sesamum indicum L.) were the dominant sources of nectar; sunflower and sesame were the major sources of pollen during July and August. Eucalyptus (Eucalyptus globulus Labill) was the predominant source of nectar and pollen from October to April.
Table 2.
Major nectar and pollen floral resources in the Kafrelsheikh district in 2022/2023.
Data presented in Figs (1-7) show the impact of proteinaceous feeding on the monthly changes in colony performance. The monthly variations in the number of forager bees, pollen foragers, stored pollen area, worker sealed brood area, and number of bees per colony (colony population size) showed the highest values during May, followed by August, then March, while the lowest values were recorded during December. The highest significant (P < 0.01) values of drone sealed brood area were recorded during March, followed by May, then August, while no drone brood was reared from October to January. Compared with the unfed colonies, the fed colonies showed significant (P < 0.01) superiority in all colony activities and honey yield. Honey yield in fed colonies was significantly larger than honey yield in unfed colonies (7.35 vs 5.38 kg/colony) in the Egyptian clover flowering season, and (5.35 vs 3.96 kg/colony) in the cotton flowering season.
Figure 1.
Monthly fluctuation of the number of forager bees/colony/min in fed and unfed Carniolan hybrid honey bee colonies in Kafrelsheikh district during 2022/2023.
Figure 2.
Monthly fluctuation of the number of pollen foragers/colony/min in fed and unfed Carniolan hybrid honey bee colonies in Kafrelsheikh district during 2022/2023.
Figure 3.
Monthly fluctuation of stored pollen in fed and unfed Carniolan hybrid honey bee colonies in Kafrelsheikh district during 2022/2023.
Figure 4.
Monthly fluctuation of worker sealed brood area in fed and unfed Carniolan hybrid honey bee colonies in Kafrelsheikh district during 2022/2023.
Figure 5.
Monthly fluctuation of drone sealed brood area in fed and unfed Carniolan hybrid honey bee colonies in Kafrelsheikh district during 2022/2023.
DISCUSSION
Honey bees primarily get carbohydrates from nectar, while pollen provides them with protein, fats, minerals, vitamins, and other nutrients. For honey bees, Taha et al. (2019b) have recorded 15 major sources of pollen and/or nectar, in addition to 95 minor sources in Kafrelsheikh province. In the current study, 7 major bee plants were recorded in the study area. The most important pollen resources for honey bees were faba bean (January–March), Egyptian clover (May and June), maize (June–November), sunflower and sesame (July and August), and eucalyptus (October–April), and the most important nectar resources were sunflower and cotton (July and August), sesame, Egyptian clover, eucalyptus, and faba bean. Besides, there were a large number of secondary sources of pollen and/or nectar that contributed to maintaining colony growth throughout the year. From the 6 major nectar sources, only Egyptian clover honey and cotton honey were harvested. The previous plants have been recorded as important sources of nectar and/or pollen for honey bees in Kafrelsheikh province; similar results have been recorded by Taha et al. (2019b). The major and minor nectar and/or pollen sources play a vital role in honey bee colony growth and colony strength maintenance (Shawer et al., 2003; Taha and Al-Kahtani, 2013; Shawer et al., 2021).
Foraging for food was fluctuated throughout the months of the year and affected by the availability of nectar and/or pollen flora (Taha et al., 2006; Seitz et al., 2020; Sponsler et al., 2020; Verweij et al., 2025), weather and environmental factors (Taha and Al-Kahtani, 2019; Taha et al., 2025b), colony population size (Taha and Al-Kahtani, 2013), comb age (Taha and Al-Kahtani, 2020), and presence of bee enemies like birds of migratory bee-eater, Merops spp. (Ali and Taha, 2012). Three peaks of flight activity were noticed; the biggest was during May (the flow season of Egyptian clover), followed by August when cotton, sunflower, maize, and sesame bloomed, and then March the flowering period of faba bean and eucalyptus. These results confirmed the findings of Helal et al. (2003) and Shawer et al. (2021) who have recorded the highest numbers of incoming bees and incoming bees with pollen loads during May, followed by July and August the blooming season of cotton, maize, and sunflower. In the current study, a decline in the numbers of forager bees was observed during October to December, and after flow seasons. Flight activity decreased during October–December, April, and June due to a shortage of pollen and nectar flora. Relatively similar results have been reported by Taha (2005) and Shawer et al. (2021). However, a decrease in air temperature during January caused a decline in foraging activity. Compared with the unfed colonies, the number of incoming workers in fed colonies increased by 0.58, 17.17, 18.09, 27.41, 12.29, 20.53, 24.40, 23.57, .71, 26.04, 26.90, and 22.17% during the months from October 2022 to September 2023, respectively. A similar trend was observed with the number of incoming workers carrying pollen. The impact of feeding colonies with a rich-protein diet became very clear. The fed colonies outperformed the unfed colonies in the number of incoming workers carrying pollen by 8.14, 50.00, 51.79, 30.23, 22.89, 14.94, 36.00, 50.54, 54.55, 15.39, 21.36, and 32.50% during the months from October 2022 to September 2023, respectively. The positive effect of feeding colonies on foraging activity has been confirmed (Elwakeil et al., 2025; Taha et al., 2025a).
The stored pollen area reflects pollen-gathering activity in a colony, as mentioned in different studies by Pankiw and Page (2000); Döke et al. (2015); Taha and Al-Kahtani (2020a); Taha et al. (2021); Elwakeil et al. (2025). The stored pollen area reflects pollen-gathering activity in a colony (Taha and Al-Kahtani, 2020a; Taha et al., 2021; Elwakeil et al., 2025). The stored pollen area displayed three peaks; the biggest during May (the flow season of Egyptian clover), followed by March, the flowering period of faba bean, and then August when sunflower, maize, and sesame bloomed. Similar peaks in pollen collection have been observed in Kafrelsheikh province (Taha et al., 2019b; Taha et al., 2021), and in Saudi Arabia (Taha, 2015a; Taha and Al-Kahtani, 2019). There was a significant increase in the area of stored pollen due to feeding colonies a protein-rich diet. Compared with the unfed colonies, the stored pollen area in fed colonies increased by 2.95, 26.60, 48.98, 27.59, 24.65, 23.97, 56.68, 62.92, 76.29, 63.13, 55.50, and 71.51% during the months from October 2022 to September 2023, respectively. These results emphasize the findings of Taha (2015b), Amera et al. (2024), Elwakeil et al. (2025), and Taha et al. (2025a). The above ratios reveal that feeding colonies a high-protein diet was most effective during periods of scarcity.
Beekeepers give pollen or pollen substitutes to colonies to encourage them to build. In addition to the colony strength, bee race, and environmental factors, brood rearing and colony growth in a colony are affected by nutritional factors (Taha and Al-Kahtani, 2019; Kavitha et al., 2021; Elwakeil et al., 2025). At the beginning of the experiment, all colonies were headed by openly mated young sister queens, colony population, and brood areas were similar, so the effects should have been the same, except for nutritional factors. The fed colonies showed superiority in the worker sealed brood area by 2.15, 7.19, 22.19, 25.66, 30.41, 31.84, 34.80, 31.86, 35.71, 22.59, 25.58, and 37.03% more than the unfed colonies during the months from October 2022 to September 2023, respectively. These results are endorsed by the findings of Mattila and Otis (2006), Kumar et al. (2013), Topal et al. (2019), Elwakeil et al. (2025), García-Vicente et al. (2025), and Taha et al. (2025a). Three peaks of worker sealed brood area occurred; the biggest was during May, followed by August, and then March. These results are emphasized by the findings of Shawer et al. (2021) and Taha et al. (2021). The peaks of worker sealed brood area coincided with the peaks of foraging activity and stored pollen area. Significant positive correlations have been found between worker sealed brood area, stored pollen area, and the number of pollen foragers (Taha and Al-Kahtani, 2019; Elwakeil et al., 2025; Taha et al., 2025a). Three peaks of drone sealed brood area occurred; the biggest was during March, followed by May, and then August, Meanwhile, no drone broods were reared during the period from October to January. Similar results have been reported by Taha et al. (2021). However, providing colonies with pollen substitutes encouraged drone brood rearing since the fed colonies outperformed unfed colonies in drone brood production by 58.82%, 39.10%, 71.13%, 41.67%, 48.84%, 36.05%, 80.85%, and 62.07% during the months of February 2023 to September 2023, respectively.
The colony population size results from the difference between eggs produced by the queen that emerge as adult workers and the old workers that died. The fed colonies displayed significant superiority in population size during all months. Compared with the unfed colonies, the colony size in fed colonies increased by 2.11, 2.62, 9.17, 9.63, 13.38, 18.19, 16.60, 20.42, 17.49, 21.38, 20.35, and 20.97% during the months from October 2022 to September 2023, respectively. These results confirm those obtained by Topal et al. (2019), Amera et al. (2024), Elwakeil et al. (2025), García-Vicente et al. (2025), and Taha et al. (2025a). Three peaks of colony population size occurred; the biggest was during May, followed by August, and then March. These peaks coincided with the peaks of stored pollen and worker sealed brood areas. Taha and Al-Kahtani (2019), Elwakeil et al. (2025), Taha et al. (2025a) have found significant positive correlations between colony size, worker sealed brood area, stored pollen area, and the number of pollen foragers.
The production of honey yield is affected by several factors, including the honey bee race (Al-Ghamdi et al., 2017; Taha and Al-Kahtani, 2019), availability of nectar and/or pollen flora (Taha et al., 2006; Seitz et al., 2020; Sponsler et al., 2020; Verweij et al., 2025), colony population size (Taha and Al-Kahtani, 2013; Brar et al., 2018), feeding of colony (Amera et al., 2024; García-Vicente et al., 2025), comb age (Taha and El-Sanat, 2007; Taha and Al-Kahtani, 2020a; Taha et al., 2021), and queen status (Shawer et al., 2021). Here, the fed colonies outperformed the unfed colonies in honey production by 36.62% and 35.10% for Egyptian clover honey and cotton honey, respectively. The superiority of fed colonies in honey production was related to the superiority in foraging activity, brood rearing, and colony population size. Significant positive correlations have been found between honey yield, worker sealed brood area, stored pollen area, and the number of pollen foragers (Taha and Al-Kahtani, 2013; Elwakeil et al., 2025; Taha et al., 2025a).
ACKNOWLEDGMENTS
The authors extend their appreciation to the Deanship of Scientific Research at King Faisal University for funding the Project number (KFU 252554), King Faisal University, Al-Ahsa, Saudi Arabia.
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