How can I get them to eat Oyster Shells

... Even so as i said compound feed contains 4% calcium which is well in excess of even high yeild layers in normal health needs under any management system, including free range, if not heavily fed on scratch feeds....

I disagree with this a little HF as during the longer days of summer my hens hardly eat any layers pellets at all.  They are far more interested in bugs and grass.  I tempt them with some moistened layers mash with a few bits in to tempt them.  If their shells seem to be getting a bit thin I add some limestone flour to their mash until the shells thicken up.

If shells are getting thin the hens bones will be suffering with osteoporosis as calcium is withdrawn from the bones to make shells.

Quote from: hillfooter on March 20, 2011, 17:03

... Even so as i said compound feed contains 4% calcium which is well in excess of even high yeild layers in normal health needs under any management system, including free range, if not heavily fed on scratch feeds....

I disagree with this a little HF as during the longer days of summer my hens hardly eat any layers pellets at all.  They are far more interested in bugs and grass.  I tempt them with some moistened layers mash with a few bits in to tempt them.  If their shells seem to be getting a bit thin I add some limestone flour to their mash until the shells thicken up.

If shells are getting thin the hens bones will be suffering with osteoporosis as calcium is withdrawn from the bones to make shells.

Well let's just say your hens are a special case Aunt Sally.  I suspect your hens are probably older birds and pretty much all the research and nutritional advice is based on birds of less than 80 weeks old. Obviously backyard hens maynot be managed in the same way as commercial layers and you know your hens better than anyone else but the general advice is that hens fed layers rations will receive more than an adequate amount of calcium.  

I think probably what you are saying is that at certain times of the year in fact they are not fed largely on layers but on forage they find for themselves.  Even though they may not be eating bulk calcium there will still be calcium in their diet and if they are free to scratch in the earth they will find a supply in the grit they pick up.  They need about 3.8grams a day so not a lot.  Chx not in lay need about a 0.9gram.

Quote "If shells are getting thin the hens bones will be suffering with osteoporosis as calcium is withdrawn from the bones to make shells."  

This is a condition associated with very high yeilding cage layers I don't think you need worry about this condition with older garden poultry.  It is known as Cage Fatigue and is always associated with cage layers in high production units.  Even then they rapidly recover when moved onto litter or ground.  Chx pick up Ca from eating faeces in litter though I don't recommend this as a source it does illustrate that availability of any Ca source will prevent this condition.

More likely what you are seeing is  "The weaker shells of eggs from older hens are caused by a loss in efficiency by the oviduct shell glands in their production of the shells. "  see the section on mendullary bone in http://www.poultryhub.org/anatomy-and-physiology/skeletal-system/

There's been a reasonable amount of work done on particule size of calcium sources on the basis that smaller particle size (limestone flour for example) is more soluble and so more readily absorbed.  From the reports I've seen this certainly seems to have some validity for younger birds however for birds past their peak egg mass production (phase 2) there seems to be a benefit in feeding part of the calcium requirement as larger particle size such as crushed oystershell.  This is thought to result in some calcium being retained in the gizzard and producing a lower level but extended release of calcium.
 
See this research report done in 2006

http://www.zootecnicainternational.com/article-archive/nutrition/889-calcium-source-particle-size-and-calcium-level-for-laying-hens-.html  

which concluded.

"Laying hens need at least 25% of their calcium from a large particle calcium source. Both oyster shell and large particle limestone can meet that need. Hens do not produce strong shells on a 100% fine limestone diet even when they are young. Not enough data exists at this time to justify increasing large particle to more than 50% of the ration as hen's age. Ground eggshells can be a good source of fine particle size calcium for laying hens."

Which should make Joyful joyful though it does still recommend large particle calcium is still required. The results from trial 1 in this report concluded,

"In summary, calcium from ground eggshells is a highly available calcium source, but it needs to be balanced with a large particle calcium source such as large particle limestone or oyster shell to maintain shell quality in laying hens. Whole eggshells (not ground) can also be used but they are not a clearly defined mixed particle size." 

HF

Sorry HF, I realise you have been doing a lot of research to try to prove me wrong but your answer is far to long for me to read in detail but I'll have a skim through it.

I agree that layers formlations may contain all that young birds up to commercial slaughter age will require if fed only on the formulation.  My birds are older hybrids 4 and 6 years and unlike less well fed hens are still laying 4-5 excellent strong shelled eggs per week each. 

Although living in Kent which some may thing a chalky soil my soil it is, in fact, from the greensand ridge and is poor in calcium.  My hens have removed all the snails from the garden - which as you know are good at concentrating calcium in their shells - so I doubt that my hens get much calcium from a "wild" diet.  They get a little from the grass I would think as all green veg. contains a small amount of calcium (depending on the soil content). 

I do understand the physiology of calcium uptake and utilisation as I studied physiology for two years at college.  I do understand the relationship between calcium, phosphorous, Vit D, and hormonal control and that only 20% of the calcium ingested is taken up in the gut the rest is passed out.  If hens are eating too much meat, e.g. worms, they can have a phosphorous imbalance (too much) which will reduce uptake of calcium too.  Magnesium, copper, boron, zinc, manganese and even strontium all have a part to play in bone health; and as you point out the older a hen gets the more health and egg laying problems can build up if they are not getting the correct balance of nutrients.

I try to keep my advice simple and easy to understand for most hen keepers without a degree in a biological science to follow, so:

If your hens free range a lot of the time offer them extra calcium in the form of oyster shell.  If they are laying thin shelled eggs give them some extra shell building nutrition.  If they are getting on in years be careful to give them a few supliments as and when you judge needed.  There is not a one size fits all for hens or any animals for that matter.

Not wanting to be argumentative HF, but I think everyone should be supplementing with oyster shell anyway.  As you have said many times in the past, it is cheap to buy, and if it is provided ad lib the hens will peck away at it if they need it.

I would also recommend everyone to check the levels of calcium in their compound feed.  For instance Garvo layers only contains 2.5% calcium - not the 4% you profess that chickens need to produce good shells.

I don't think that simply having a alternative view is being argumentative.  I find this discussion of interest so please voice your opinions. 

I absolutely agree I've never said you shouldn't provide OS ad lib and in fact I do myself.  I've been very consistently saying that all the research says hens need 3.5% Calcium in a balance diet.  A balanced compound Layers mash or pellet contains this (or should do if it claims to be a complete feed.  You can check it on the label).   So for pullets there's no need to supplement but providing OS ad lib I don't believe will be harmfull but I wouldn't be concerned if they didn't appear to be eating it.

Garvo is new on the block so I'm not familiar with this brand but I believe it was primarily targeted at fancy breeds and showing and these birds are normall poor layers.  Birds not in lay only need about 1% calcium so maybe Garvo is targeting showing birds.  I've never advocated using this feed but I've always said that whole grain diets need to be supplemented.

I've always said older birds (in their second laying year +) should have oystershell ad lib.

I am opposed to mixing OS or limestone flour in the feed as a routine procedure but as I've said ad lib is fine the birds will take what they need.  If you are trying to treat a particular condition then it's up to you and your vet whether you add LF or OS to the feed but if you do you should also include the balancing  Vit D3 (as bighamd says Cod Liver Oil is a useful source) and ensure that phospherous isn't deficient though this generally isn't a problem.

I'd also suggest that limestone flour shouldn't be your first port of call if poor egg shell quality is indicated multivits and OS particles should be tried first particularly with old hens.  

Calcium supplementing by adding to feed shouldn't be done longterm.

When talking about such fine tuning I'm well aware that the research data is usually obtained from commercial layer trials.  Such birds are the elite performers of the poultry world producing 320+ eggs a year and their feed is finely tuned for optimum thrift (max return) where as backyard poultry aren't in the same league.  A bit like comparing a world class athlete with an amateur club althlete.  So if it recommended that birds need 3.5% Ca you can be pretty sure an average backyard bird producing 240 or less eggs won't need this quantity or the absolute precision of feed ingredient proportions  commercial layers get.  
HF

WOW that is a lot of eggs - how many does she lay at the moment?

I do not know which one's of mine lay which eggs, so do not really know which one is laying the really soft one's, although I have not had one for a couple of days.  Although a couple of the others seem to have quite thin shells.

Sorry HF, I realise you have been doing a lot of research to try to prove me wrong ........................................................................

I try to keep my advice simple and easy to understand for most hen keepers without a degree in a biological science to follow, so:

If your hens free range a lot of the time offer them extra calcium in the form of oyster shell.  If they are laying thin shelled eggs give them some extra shell building nutrition.  If they are getting on in years be careful to give them a few supliments as and when you judge needed.  There is not a one size fits all for hens or any animals for that matter.

Well aunt Sally I'm not trying to do any such thing.  I'm not trying to prove you wrong as you say.  You took issue with what I said on the basis of the special case of your old hens.  I'm just trying to state the facts and put the record straight.

In actually fact I personally do similar things with my hens that you do so I don't actually have an issue with what you do but I try to give advice for chx in general and to people who are in the most case asking about getting new hens.   I do also say that you should supplement OS ad lib for second year+ hens.  I don't expect people to treat their pullets in the same way as I treat my old hens.   That might detract from the simplicity of the advice but it isn't rocket science and I think people can understand that if the facts are given.  

If I've gone over the top with referencing why I give the advice I do it's because I get a little frustrated when people (and I'm not pointing the finger at you) make unsupported statements about compound feeds needing to be supplemented because they don't contain the essential nutrition when actually they do.  Just like older people sometimes needing medication some older hens may need additional supplements.

Well Casey I don't think you are being argumentative just because you have your own views a good debate is much more interesting than if everyone had the same opinons.
HF