My second post on the Federation of Middlesex Beekeepers’ Associations annual ‘Federation Day‘. Below are my notes from the second speaker, Pam Hunter.
Pam is a Master Beekeeper who has been keeping bees for over 25 years. She is now Chairman of the BBKA Examinations Board, sets and marks module exams and is an assessor for the Basic, the General Husbandry and the Advanced Husbandry exams. She has a particular interest in the interaction of plants, bees and the environment as well as the more biological/scientific aspects of bees and historical aspects of beekeeping.
Pam Hunter, How nutrition affects colony health
Pam explained in detail the different substances contained in nectar and pollen. She recommended an Australian government publication with the cute name ‘Fat bees, skinny bees‘, the pdf of which is free to download. This goes into the chemical composition of nectar and pollen and explains the nutritional requirements of honey bees.
Pollen is very precious, providing bees with protein, fats, minerals, organic acids and vitamins.
It is needed in large quantities when raising brood – partly because some is directly fed to the brood, but mainly because young nurse bees need to eat lots of pollen to produce ‘brood food’.
[After Pam’s talk I investigated exactly what’s contained in brood food – this special food for the growing larvae contains a mix of white food (from workers’ mandibular glands), clear food (from the hypopharyngeal glands in workers’ foreheads) and yellow food (from pollen). For workers the mix is on average white:clear:yellow in ratio 2:9:3 (ref. Mid Bucks Association Module 5 study notes, p.29).]
Nurse bees feed on pollen so that their hypo pharyngeal glands develop. The young nurse bees have puffed up, fat hypopharyngeal glands, full of enzymes busy turning pollen into brood food. In contrast, the glands of older foragers no longer producing brood food are all shrivelled up.
Most of us beekeepers know that the queen is not really in charge of the colony, but Pam went one step further by telling us that the older foragers are dominated by the young nurse bees. In her view, it is the nurse bees who are really in charge – they are at home keeping an eye on brood, pollen, honey, water and propolis levels, so know what the colony needs.
Not all pollen is equal
Pollen can have widely varying crude protein levels of between 2.3 – 67%, with at least 20-30% protein being desirable. Pam said it is highly likely that some pollens are lacking ‘essential amino acids’ like Isoleucine. Certain amino acids are ‘essential’ because they can’t be made by the bees themselves but have to be consumed through food.
In 2014 I went to a Middlesex Federation Day talk by Dr David Aston, who at the time was President of the British Beekeepers Association (BBKA). He showed us the below chart of the percentage of crude protein in various pollens, which I jotted down hurriedly (so any mistakes are mine). As you can see, he has blueberry, weeping willow and sunflower listed as particularly poor for bees.
|% of crude protein in pollen (source David Aston)|
|Above average/excellent pollens|
Fresh is best
Research suggests that bees need a great variety of pollen and that it is not wise to stockpile pollen frames because its nutritional value deceases rapidly after collection – by about 75% after a year. This makes late pollen sources like Michaelmas daisies, sedums and ivy and early sources like hazel important, so that the bees can get fresh pollen with greater nutritional value.
The fats provided by pollen also play an important part in metabolism. Some fats are metabolised to fatty acids and glycerol, providing energy for muscle contractions in flight or when clustering. Fat is also needed for proper larval development. Experiments have found that honey bee larvae deprived of fat are more likely to die early on. Both humans and bees do need some cholesterol! The audience looked cheerful when Pam told us this.
Pollen is also needed so that the bees can store food reserves in their bodies, in the form of “magic stuff” called vitellogenin. It’s a ‘glycolipoprotein’ – a complex molecule containing protein, fat and sugar. It’s very important for building fat stores in winter bees. Winter bees are stuffed full of fatty deposits, including these vitellogenins. Pam mentioned that Randy Oliver has a lot of information on vitellogenin on his website and indeed he does:
- Fat Bees – part 1 – Randy talks about brood food, the benefits of vitellogenin for larvae and nurse bees, how it helps bees overwinter and how vitellogenin levels influence foraging and swarming behaviour.
Nectar mainly provides the bees with carbohydrates, in the form of sugar. Nectars contain different combinations of sucrose, glucose and fructose. Foragers add the enzyme sucrase (contained in their saliva) to the nectar they collect, which breaks down sucrose to produce glucose and fructose.
A honey which contains a high amount of sucrose can be a sign that it’s been produced by feeding the bees sugar syrup – but not always. A Yorkshire beekeeper was once accused of feeding his bees sugar before it was discovered that borage is an unusually high sucrose nectar. The England Honey Regulations 2015 make allowances for this, requiring that honey has a sucrose content of not more than 5g/100g, with a few exceptions for certain honeys, including borage, which can have up to 15g/100g (see page 10 of the regs).
In this August 2010 Statford-upon-Avon & District Beekeepers’ Association newsletter, Peter Edwards writes “This high sucrose level combined with low glucose results in a honey that will not set – so this makes it popular with the packers as it can be used to produce clear honey with an almost indefinite shelf life. The next problem with borage honey is its total lack of flavour unless mixed with something else. Pure borage honey is completely white and looks, and tastes, like sugar syrup with maybe just a hint of cucumber skin – yuck!”
Factors affecting nectar flow
Pam talked about some of the difficulties bees face in collecting nectar. There are all sorts of factors which affect how much nectar flowers provide:
- The moisture & PH of soil
- Sunshine – it’s said that dandelions only produce nectar if they’ve been in sunshine for two hours. Many plants – oil seed rape for example – don’t produce nectar in cold temperatures. Pollen availability is much less affected by the weather.
- Time of day – bees go to apple blossom for pollen in the morning and nectar in the afternoon.
- Age & vigour of the plant – young blackberry plants produce more nectar.
What makes a good colony?
Pam concluded that a healthy colony needs a steady supply of nutrients. She gave us a couple of quotes she likes:
“The very best queens will not be produced except under the best conditions!” (A.L.Gregg)
“If queens were not well fed in the early larval stage, they will be superseded early” (A.I.Root, The ABC of Bee Culture)
Without protein, a colony can survive on pure sugars for some time, but the bees will not be able to develop their hypopharyngeal glands and rear brood. If pollen being collected has a low protein content, nurse bees can feed fewer larvae. During protein shortages brood may be eaten by the adult bees.
There is also evidence that a lack of pollen can reduce the immunocompetence of bees. In controlled trials by DeGrandi-Hoffman et al (2010), a reduction in virus levels was seen in bees fed good pollen supplies.
As discussed earlier on by Pam, not all pollen is equal – she quoted a study by Schmidt et al (1995), which involved feeding colonies either rape, sunflower or sesame pollens. The bees fed sesame or sunflower pollen lived shorter lives (31 days on average for the bees fed sunflower pollen, compared to 51 days for the bees fed rape pollen). The authors suggested that honey bees used to pollinate monocrops of sunflower or sesame flowers should be provided alternate floral or nutritional supplements to maintain colony health. This will have particular relevance to beekeepers in France, which has vast sunflower fields.
My hive partner Emma’s write-up of Pam’s talk: Federation of Middlesex Beekeepers Day 2016.
Pam mentioned that Professor Geraldine Wright‘s lab in Newcastle is doing the first new work on honey bee nutrition for many years. There is still lots we don’t know.
And a lot of Pam’s talk overlapped with the content of the BBKA Module 2 (Honey bee Products and Forage) and Module 5 (Honey bee Biology) exams, which the Mid Bucks Association have produced excellent study notes for: Module 2 study notes and Module 5 study notes.