Abstract
Honey bees obtain lipids from pollen or commercial supplements. These supplements do not fully support colony health. We tested the hypothesis that supplements are deficient because they lack essential fatty acids (EFAs). The five supplements we tested had low linolenic (⍵3) acid and were unbalanced (⍵6:⍵3 > 6) compared to natural pollen. We selected two of these supplements for further study because they had different levels of individual EFAs and different ⍵6:⍵3 ratios. Bees from hives fed these different supplements had equivalent tissue EFA levels. In choice assays, hives fed these different supplements were presented with flours with various absolute and relative levels of EFAs. We saw no difference in foraging preference. Rather, all hives preferred flours with small grain size and high protein to lipid ratios. We conclude that bees balance their internal EFAs and that differential colony nutrition does not affect foraging preference. The data also argue for more linolenic (⍵3) acid in commercial supplements.
Highlights
Honey bees exploit a range of floral resources to meet their protein, lipid, carbohydrate, and micronutrient needs
Nutrients that bees obtain from their diet and cannot synthesize are termed “essential” and include the essential fatty acids (EFAs) linoleic (18:2n-6, ⍵6) and α-linolenic acid (18:3n-3, ⍵3)
These EFAs make up ~43% of the total fatty acids (TFAs) measured in pollen (Online Resource Table I; (Arien et al 2015; Avni et al 2014; Corby-Harris et al 2018; DeGrandi-Hoffman et al 2021, 2018; Manning 2001; Robinson and Nation 1970; Saa-Otero et al 2000))
Summary
Nutrients that bees obtain from their diet and cannot synthesize are termed “essential” and include the essential fatty acids (EFAs) linoleic (18:2n-6, ⍵6) and α-linolenic acid (18:3n-3, ⍵3) On average, these EFAs make up ~43% of the total fatty acids (TFAs) measured in pollen (Online Resource Table I; (Arien et al 2015; Avni et al 2014; Corby-Harris et al 2018; DeGrandi-Hoffman et al 2021, 2018; Manning 2001; Robinson and Nation 1970; Saa-Otero et al 2000)). Given previous research suggesting that colonies forage for diets that rescue previous fatty acid deficiencies (Zarchin et al 2017) and the benefits of a balanced diet to honey bee health (Arien et al 2018, 2020), we assessed the foraging behavior of hives fed low- or high-EFA supplements. If hives forage in a way that balances their EFA intake towards an ⍵6:⍵3 ratio of one, we hypothesized that hives fed the more unbalanced low-EFA supplement would make more visits to choice flours with more linolenic (⍵3) acid and with lower ⍵6:⍵3 ratios compared to the high-EFA hives
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