Calcium Carbonate vs Oyster Shell

Discussion in 'Ducks' started by AlohaDuck, Nov 15, 2014.

  1. AlohaDuck

    AlohaDuck In the Brooder

    May 29, 2014
    I'm debating whether I should get 50lbs. of Calcium Carbonate Grit made by MICRONA.

    Here is the product description:
    "MICRONA[​IMG] Poultry Grit is derived from calcium carbonate. As a grit source, it is superior to oyster shell – shell is not hard enough to do the digesting task grit will.
    Most laying poultry will benefit from MICRONA[​IMG] being offered free choice. Because of it’s pH adjusting qualities, MICRONA[​IMG] will also keep coops and runs hygienic and clean. Just sprinkle a handful per square foot, then spread your bedding material.
    MICRONA Poultry Grit 6 x 10"

    My ducks are at 20 weeks now and I will be switching them over to layer feed this week.

    Is Calcium Carbonate safe for ducks? (I don't see why not...but...just checking....)

  2. IMO grit and calcium supplement should not be "2 for 1" product like this, you simply don't get the best of both worlds instead you honestly compromise both worlds...

    Consider this, your birds area already getting what should be sufficient levels of calcium from their layer feed, but now if they choose or need to eat some grit you are forcing them to ingest 'excess' calcium...

    And on the grit side calcium carbonate is a far inferior grit substance, it's honestly a really soft mineral compared to the alternatives like say granite...

    For what it cost IMO a bag of granite grit and a bag of oyster shells is a far better option...

    Also I'm not buying their sales pitch one bit, IMO it's one big fib...

    They state "As a grit source, it is superior to oyster shell – shell is not hard enough to do the digesting task grit will."

    Oyster shell that is 95% calcium carbonate and they claim it isn't a good grit (I agree) but their own calcium carbonate grit is somehow good? Their MSDS says their grit is 99% limestone, and limestone is any rock with at least 50% calcium carbonate...

    So I'm not sold when they say calcium carbonate (oyster shell) isn't a good grit but that calcium carbonate (limestone) is a good grit... Seems like double talk to me...
    Last edited: Nov 15, 2014
    gilbert2 likes this.
  3. AlohaDuck

    AlohaDuck In the Brooder

    May 29, 2014
    Thanks for your input! I was tempted because I can get this 50lbs bag for only $20! Hmmm.....

    Also, I thought lime (mineral) wasn't good for ducks?

    What size grit is safe for ducks at 20
  4. At my local feed store, 50lbs of granite grit (Gran-I-Grit brand) is only $7 and 50lbs of crushed oyster is $9... Those prices are give or take, I have not purchased any for about 6 months now...

    As for your other questions I'll let someone else that is more knowledgeable on duck need answer that...
  5. AlohaDuck

    AlohaDuck In the Brooder

    May 29, 2014
  6. Amiga

    Amiga Overrun with Runners

    Jan 3, 2010
    Southern New England
    Apparently calcium carbonate is one of the ways to give extra calcium to layers (this is about chickens )

    And I think I read in Storey's Guide to Raising Ducks that this is an option. But I cannot find my copy of that book right now. sigh.

    If the ducks have access to the outdoors, they will likely get enough grit on their own just from foraging around. Mine do, during the warmer months. I will sometimes add granite grit on the side for them during the winter when the ground is frozen. I also offer them free choice oyster shell on the side.

    By the way, some of my ducks have a hard time even on layer pellets, producing shells. I have read, and read, and read, and asked and listened, all about this topic. Seems that some ducks just need more calcium.
  7. AlohaDuck

    AlohaDuck In the Brooder

    May 29, 2014
    Sometimes I wonder how the ducks can put down that sharp piece of oyster shell LOL. I see a lot of it in the layer feed I've switched them to. The pieces are razor sharp! Wouldn't that cut up the inside? They must have some thick lining with strong acids in the gizzard to break this down.

    Very amusing.
  8. Gursula

    Gursula Hatching

    Jan 31, 2015
    I have taken the time to design and research poultry grits made from calcium carbonate sources.
    It is written in the MICRONA Poultry Grit flyer :
    that A. Bruce Webster, Extension Poultry Scientist, University of Georgia researched this and he explained about calcium carbonate grit as a suitable source of calcium for chicken. While we must offer chicken and other birds hard pieces for their crop - we can use granite as a digestion aid. But oyster shell is a calcium source. We now know that the mineral calcium carbonate in grit form at various sizes is well accepted for chicken and other foul. It is used as a single grit and calcium source but sometimes also used in combination with granite and oyster.

    Ideally, we would really like to keep our chickens and ducks truly 'free range' so that they can find enough of their own rock grit and calcium sources such as dark green leaves and vegetables, bugs and worms. However, I struggle for space to be able to do this and I think most of you do as well. We have lost too many chicken to neighbors dogs, coyotes, and eagles. Flint grit, oyster shell and MICRONA Poultry Grit Calcium Carbonate is really not expensive. Our modern birds require a lot of calcium that even a large back yard cannot supply. One hen requires 8 lbs of Poultry Grit per year - and they will "recyle" the particles as well. A 50 lbs bag will last a long time so it's a good idea to provide this for hens, especially because most of the birds have lost their freedom to roam for their own safety.

    Another way to see the viability and usefulness of poultry grit came when my friend noticed that song birds would pick through the MICRONA Poultry Grit for smaller calcium particles. Obviously, they need this too to stay healthy when making eggs in Spring.

    Referring again to the need of calcium carbonate Poultry Grit, read the research article at : I don't think it is "double talk" to have the dual benefits of calcium carbonate grit.

    "Calcium provided as coarse particles can improve egg shell quality and bone strength (Scott et al., 1982; Fleming et al., 1998; Scheideler, 1998; Whitehead and Fleming, 2000). The coarse-Ca particles are solubilized more slowly from the gizzard than fine-Ca particles which allows the hen to absorb dietary Ca at night during egg shell formation. This absorption can result in less Ca mobilized from bone stores (Scott et al., 1971; Zhang and Coon, 1997; Whitehead, 2004). Calcium is also necessary for the release of gonadotrophic hormones, including the surge in luteinizing hormone that results in ovulation necessary for egg production (Luck and Scanes, 1979, 1980; Johnson, 2000)."

    Larger size calcium carbonate chicken grits such as the MICRONA Poultry Grit 6x10 are found to be especially beneficial for older hens. The calcium particle remains in their digestive system over night and helps pull calcium form the mineral instead of the bones and joints of the chicken. If you have those treasured hens that are laying large but often soft shelled eggs, poultry grit on calcium basis can be a good supplement; in research it performed better than oyster shell and granite grit for mature layers.
    Hens sometimes need a bit of time to adjust to a new grit source and require transitions to get used to calcium carbonate type grit. Our oyster shell consumption went down drastically after a few days of adjustment and we only need a potion of the quantity of total oyster shell used before.

    The MICRONA Poultry Grit is available in local farm stores in Eugene, OR for about $10 for a 50 lb bag. It probably is higher in cost if it is mailed out or shipped.

    To support our feathered friends with added health and good digestion including getting them sources of available calcium from oyster shell and limestone calcium carbonate (other than drawing from their own bones), many recommend to add a squirt of apple cider vinegar to the drinking water on occasion (once per week) that is what we have been doing.

    AlohaDuck was looking for calcium source for egg laying ducks. This is unfortunately not well researched in our country. I love to eat and cook with duck eggs! Duck eggs are a cherished source of food in many Asian Nations and they have a huge requirement of calcium to lay good eggs and not become ill due to malnourishment.
    Extension bulletins are a great resource:

    A ground, round high purity calcium carbonate limestone grit, given free choice in a feed dish, on the stall floor or in the outside run, is a vital part of our birds life. But in my perfect world they should have enough space to run (where any grit and particles can be picked up), good clean (vinegary) water, good food from a reputable feed mill and access to fresh greens.
    gilbert2 and Miss Lydia like this.
  9. Miss Lydia

    Miss Lydia Loving this country life

    Thank you so much for all your work in putting this info together ,I agree it's very important out egg layers get the best feed we can buy and offer Oyster shell along with it. separate from food. I find it amazing how the girls know what they need and eat it as needed. Even when mine are out on a half acre foraging they still seek out the oyster shell when laying. Good info you have provided.


    Jun 22, 2016
    i had a problem with thin shells .... let me explain . when i first got my chickens i literally only fed them solely on corn and what ever they could free range .... they were laying but nothing wonderful but the egg shells were thin ...didn't take much to crush them. so i got some agricultural lime (grit) ... and left it one side for them ... really didn't make that much of a difference .. still didn't help that much .... anyway I produce household chemicals for a living and one of the ingredients i stock for my company is calcium carbonate ... got the jig the one day and took a table spoon of the really fine stuff and added it to a 20 litre bucket of feed .... Boom ...over night the shells became tough as nails ... so that got me thinking ... what else are they not getting ??? .... got some alfalfa pellets (which i ground up).. added that in the mix together with sunflower seeds ..and also decided to give them vit and mineral supplements in their water once a week ... also started growing cabbage and carrots and feed that to them once a day .. they kill for cabbage .... its like they are different chickens ... eggs are flowing like honey .... taking of which ...getting my hives setup this spring .... gonna add it to the mix and see if they go turbo winter time !

    glad i started with only the bare essentials and built up from there ... if only to observe the effects of better nutrition. They seem happy and that makes me happy
    gilbert2 likes this.

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