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20/09/2007
Summertime problems
Pale shelled eggs and vitamin D3
In the June issue of the Ranger, I discussed the problem of pale shelled eggs in the summertime. I suggested that
healthy unstressed and well-feathered hens in houses with
no red mite ought not to lay many paler shelled eggs. Since then, useful research by Judy Ryan / University College, Dublin has shown that, almost certainly, sunlight can indeed lead to an increase in the number of pale eggs. However good feathering is still important, because hens that are poorly feathered are likely to be more affected by the ultraviolet rays from the sun than well-feathered ones.
It has been well known for some time that in humans,
sunlight can increase our vitamin D3 (cholecalciferol) status.
Most of us feel healthier and tanned when having sunned
ourselves. What we now learn from the research is that the sunlight on hens, especially bald ones, also results in vitamin D3 metabolism within the hens. So that should be a good thing, shouldn’t it? Well, yes and no! Too high a level of some vitamins within the hens can be a disadvantage because an overdose can be toxic or even antagonistic to vitamins such as D3.
What seems to happen is that the liver has to sort the
balance of vitamins out, as one of its invaluable functions.
This overcomes the toxic effect of too much vitamin D3, but in doing this, it leads to a problem with the pigmentation of the eggs as the cuticle is deposited on the shell. This is likely to be associated with an important role which vitamin D3 has on the utilisation of calcium and phosphorus in the feed and therefore on shell quality.
In practice therefore it is a very awkward problem to rectify. I suspect that for many summers yet on free range egg farms, there will be an increase in the numbers of pale shelled eggs.
Why? The nutritionists have ensured that the balance of
nutrients in the feed that you are using is optimal for hens
that don’t go out into the sunlight. If they hadn’t you would be complaining to them about the hens’ performance. If the vitamin D3 concentration was low, you could have hens with poorer quality eggshells and the possibility of some with rickets would exist. Therefore the vitamin D3 has been included at a concentration in the feed that is correct for hens that don’t top up their vitamin D3 levels by wandering around the range area when the sun is shining.
It is the combination of the vitamin level in the feed with
what the hens metabolise via the sunlight that seems to
lead to the pale shells. So how do we avoid pale shelled
eggs? Do we keep the hens out of the sun? No, that rather
negates what free range egg production is all about!! Do we
reduce the concentration of Vitamin D3 in the feed?
No, the hens that don’t go out onto the range need to get it
from the feed and anyway especially in the 2007 summer, it is not always sunny outside! Too low a concentration of
vitamin D3 can lead to an almost instantaneous loss of shell quality followed by a loss in egg production after about 2 weeks. So what is the answer? I reckon that my
suggestions in the June issue of the Ranger were about right.
"Unstressed, fully feathered and healthy hens should be able to cope with summer sunshine".
Nevertheless, it is still likely that in sunny weather there may be some increase in the number of paler shelled eggs, but console yourself at these times that the worm eggs on the surface of the range are being ’bumped off’ by the ultraviolet rays.
Watery whites
You store your eggs in a cool room. Nevertheless, if your
eggs are sold to a private customer, rather than to a
reputable egg packer, do you give them advice on how they
should store the eggs? If you don’t, you are leaving yourself open to complaints about the whites of the eggs being watery. There are two points to make:
1. The quality of the whites is much better at the beginning of the laying period than towards the end of it. There will have been a progressive deterioration in the quality of the thick white that supports the yolk, in the eggs. The eggs from an older hen are more likely to go ’splat’ in the frying pan. There is not much that you can do to prevent this.
2. During storage, the thin white dilutes the thick whites much quicker when the eggs are kept at warm temperatures.
Therefore if you get a comment from your customer (as one
Ranger reader has just done), that the whites are watery, ask them where they keep the eggs that you have supplied. If necessary, tell them how sensible it would have been if they had been kept at about 12°C. If they were going to use the eggs as soon as they have been taken from cool storage
however, they could, of course, have been kept cooler than that e.g. in their fridge.
It is possible that the watery whites were nothing to do with egg storage and that your hens have had an IB (Infectious Bronchitis) challenge. Here the ball is on the other foot because you may not have been vaccinating the hens during the laying period. Have a chat with your vet, if so.
Pullet liveweights
For pullets that are delivered to you in the summer, it is possible that during the previous few weeks before delivery, it may have been difficult for the rearer to keep the pullets cool enough. Therefore their feed intake would have been reduced and this would result in a poorer liveweight.
You want well-feathered pullets with a liveweight that is up to the breeders’ specification. Underweight pullets, especially in the summertime, can be a problem for you. Peak production may not be maintained and egg weight would probably be too low for optimal profitability. When you go to see your pullets being reared, ask the rearer how he tries to maximise the pullets’ liveweight during the summer. What he should reply is that hens / pullets respond to the average temperature during a 24 hour period.
Therefore during the last week or two on his farm, by allowing temperature to fall slightly below the optimum during the night-time, whilst ensuring that the pullets don’t huddle, and then allowing easy access to ad-libitum feeding before it gets hot, he is actively trying to optimise the liveweights. One sees time and time again, that it is the underweight pullets with a poor appetite, that therefore fail to gain sufficient liveweight whilst coming into lay, that become a problem flock. Vets are using the phrase "running out of steam" for hens that have died.
Often these can be traced back to a flock that was
underweight on delivery to you and remained so thereafter.
Good quality pullets are vitally important for the success of free range egg production.
 |
In the June issue of the Ranger, I discussed the problem of pale shelled eggs in the summertime. I suggested that
healthy unstressed and well-feathered hens in houses with
no red mite ought not to lay many paler shelled eggs. Since then, useful research by Judy Ryan / University College, Dublin has shown that, almost certainly, sunlight can indeed lead to an increase in the number of pale eggs. However good feathering is still important, because hens that are poorly feathered are likely to be more affected by the ultraviolet rays from the sun than well-feathered ones.
It has been well known for some time that in humans,
sunlight can increase our vitamin D3 (cholecalciferol) status.
Most of us feel healthier and tanned when having sunned
ourselves. What we now learn from the research is that the sunlight on hens, especially bald ones, also results in vitamin D3 metabolism within the hens. So that should be a good thing, shouldn’t it? Well, yes and no! Too high a level of some vitamins within the hens can be a disadvantage because an overdose can be toxic or even antagonistic to vitamins such as D3.
What seems to happen is that the liver has to sort the
balance of vitamins out, as one of its invaluable functions.
This overcomes the toxic effect of too much vitamin D3, but in doing this, it leads to a problem with the pigmentation of the eggs as the cuticle is deposited on the shell. This is likely to be associated with an important role which vitamin D3 has on the utilisation of calcium and phosphorus in the feed and therefore on shell quality.
In practice therefore it is a very awkward problem to rectify. I suspect that for many summers yet on free range egg farms, there will be an increase in the numbers of pale shelled eggs.
Why? The nutritionists have ensured that the balance of
nutrients in the feed that you are using is optimal for hens
that don’t go out into the sunlight. If they hadn’t you would be complaining to them about the hens’ performance. If the vitamin D3 concentration was low, you could have hens with poorer quality eggshells and the possibility of some with rickets would exist. Therefore the vitamin D3 has been included at a concentration in the feed that is correct for hens that don’t top up their vitamin D3 levels by wandering around the range area when the sun is shining.
It is the combination of the vitamin level in the feed with
what the hens metabolise via the sunlight that seems to
lead to the pale shells. So how do we avoid pale shelled
eggs? Do we keep the hens out of the sun? No, that rather
negates what free range egg production is all about!! Do we
reduce the concentration of Vitamin D3 in the feed?
No, the hens that don’t go out onto the range need to get it
from the feed and anyway especially in the 2007 summer, it is not always sunny outside! Too low a concentration of
vitamin D3 can lead to an almost instantaneous loss of shell quality followed by a loss in egg production after about 2 weeks. So what is the answer? I reckon that my
suggestions in the June issue of the Ranger were about right.
"Unstressed, fully feathered and healthy hens should be able to cope with summer sunshine".
Nevertheless, it is still likely that in sunny weather there may be some increase in the number of paler shelled eggs, but console yourself at these times that the worm eggs on the surface of the range are being ’bumped off’ by the ultraviolet rays.
Watery whites
You store your eggs in a cool room. Nevertheless, if your
eggs are sold to a private customer, rather than to a
reputable egg packer, do you give them advice on how they
should store the eggs? If you don’t, you are leaving yourself open to complaints about the whites of the eggs being watery. There are two points to make:
1. The quality of the whites is much better at the beginning of the laying period than towards the end of it. There will have been a progressive deterioration in the quality of the thick white that supports the yolk, in the eggs. The eggs from an older hen are more likely to go ’splat’ in the frying pan. There is not much that you can do to prevent this.
2. During storage, the thin white dilutes the thick whites much quicker when the eggs are kept at warm temperatures.
Therefore if you get a comment from your customer (as one
Ranger reader has just done), that the whites are watery, ask them where they keep the eggs that you have supplied. If necessary, tell them how sensible it would have been if they had been kept at about 12°C. If they were going to use the eggs as soon as they have been taken from cool storage
however, they could, of course, have been kept cooler than that e.g. in their fridge.
It is possible that the watery whites were nothing to do with egg storage and that your hens have had an IB (Infectious Bronchitis) challenge. Here the ball is on the other foot because you may not have been vaccinating the hens during the laying period. Have a chat with your vet, if so.
Pullet liveweights
For pullets that are delivered to you in the summer, it is possible that during the previous few weeks before delivery, it may have been difficult for the rearer to keep the pullets cool enough. Therefore their feed intake would have been reduced and this would result in a poorer liveweight.
You want well-feathered pullets with a liveweight that is up to the breeders’ specification. Underweight pullets, especially in the summertime, can be a problem for you. Peak production may not be maintained and egg weight would probably be too low for optimal profitability. When you go to see your pullets being reared, ask the rearer how he tries to maximise the pullets’ liveweight during the summer. What he should reply is that hens / pullets respond to the average temperature during a 24 hour period.
Therefore during the last week or two on his farm, by allowing temperature to fall slightly below the optimum during the night-time, whilst ensuring that the pullets don’t huddle, and then allowing easy access to ad-libitum feeding before it gets hot, he is actively trying to optimise the liveweights. One sees time and time again, that it is the underweight pullets with a poor appetite, that therefore fail to gain sufficient liveweight whilst coming into lay, that become a problem flock. Vets are using the phrase "running out of steam" for hens that have died.
Often these can be traced back to a flock that was
underweight on delivery to you and remained so thereafter.
Good quality pullets are vitally important for the success of free range egg production.
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