Oyster shells

[raingarden]

They seem to eat the grey oyster shell flakes without hesitation or, perhaps, without knowing it. They seem to eat around the white manufactured stuff. The white stuff I have seems a little large, If you only give a small amount at a time you can judge how well they like it by what is left in the bottom of the bowl.

 

[DucksOhio]

So are the scratch and peck flaked oyster shells good for the ducks? My ducks don't eat the white ones and only like the gray flakes, which are hard to find right now.

They’re the best IMO. Small flaked, white, grayish.

 

[CoriM]

Okay, thanks. That's the kind my ducks like, but they've been hard to find lately - so weird.

 

[Quacking ducks]

Are they Manna pro? My spoiled girls don’t like the rocks, lol. My husband tried to grind them once in my cuisinart, owed me a new cuisnart.

Yes they are.

 

[raingarden]

The manufactured white stuff does not have magnesium. Oyster shell has about 6.3% magnesium. Magnesium is important for growth, egg production and bone density but becomes toxic at levels over about 0.15% of the diet. A very small amount of magnesium supplement is thought to be benificial but is rarely used. The amount of magnesium in the feed+grit will still be well below 0.15%. But I do not know if the amount of extra magnesium in oyster shell versus the white stuff is greater or less than the recomended supplement. I guess it depsnds on how much they eat.
https://www.sciencedirect.com/science/article/pii/S1056617119322858

 

[Crazy Maizie]

From the vendor’ email to me:
We did testing on the clam and coral mixes that are out there. Chickens and ducks cannot absorb any calcium from them, they are very hard and just pass through their system.

I'd like to see the data not just a vendor's word.
Here's a study (in pdf form) regarding 5 different calcium sources including clam shells and oyster: https://www.sciencedirect.com/scien...3323537393131393439373434372d6d61696e2e706466
Within it, the results:
"The mean body weights of the birds receiv-
ing the six supplemental calcium treatments
are presented in Table 3. There were no
significant treatment differences in body
weights at any age measured.
Mean feed efficiency, egg production and
livability are presented in Table 4. Although
numerically superior, the feed efficiency of
the birds receiving clam shell as the source
of supplemental calcium was not statistically
different from the mean feed efficiency of
the birds receiving the other supplemental
calcium sources. There were no statistically
significant differences among treatment
means for hen-housed egg production. The
hen-day production of the birds receiving the
diet adjusted for the protein content of the
egg shell meal or the limestone diet was
significantly greater than that of the birds
receiving the diet containing egg shell meal
but unadjusted for the protein in this supple-
mental calcium source. Differences between
other means for hen-day egg production were
not statistically significant."

 

[Crazy Maizie]

This is so interesting! Thank you for sharing this. I really hope I kept the bag and it states what's actually in the bag. I wonder if that's why I am having so many shell issues with my chickens? My Pekin Duck is having shell quality issues too but she's molting. I have given her calcium citrate + vitamin D3 on a few occasions but it doesn't really change much. I'm going to be looking into this. Thank you so much for bringing it to our attention! I think I'll look into buying some of the flakes either way. Thanks again for everything

I would look into adding calcium gluconate for the duck with issues. If you supplement the calcium citrate, it should be done for weeks on end. The vitamin d that's added is to help with calcium absorption.
Some poultry prefer one type of calcium over another, so I would offer different types. For instance, I don't offer crushed egg shell all of the time, but when I do they select the crushed egg shell over the oyster shell.

 

[Crazy Maizie]

The manufactured white stuff does not have magnesium. Oyster shell has about 6.3% magnesium. Magnesium is important for growth, egg production and bone density but becomes toxic at levels over about 0.15% of the diet. A very small amount of magnesium supplement is thought to be benificial but is rarely used. The amount of magnesium in the feed+grit will still be well below 0.15%. But I do not know if the amount of extra magnesium in oyster shell versus the white stuff is greater or less than the recomended supplement. I guess it depsnds on how much they eat.
https://www.sciencedirect.com/science/article/pii/S1056617119322858

Just for clarification, are you referring to manna pro as the "manufactured white stuff"?
It is oyster shell and coral, both have magnesium content.

https://pubs-test.er.usgs.gov/publication/70030487
http://pubs.sciepub.com/ajfn/5/4/5/index.html

 

[raingarden]

Just for clarification, are you referring to manna pro as the "manufactured white stuff"?
It is oyster shell and coral, both have magnesium content.

I thought it was calcite.

 

[Crazy Maizie]

I thought it was calcite.

Manna pro oyster shell shown above is oyster shell and coral calcium (calcium derived from coral).

GUARANTEED ANALYSIS:
Calcium, min. 33.0%
Calcium, max. 38.0%

INGREDIENTS: Oyster Shell and Coral Calcium

It's not calcite. But, below is some info regarding calcite.

Simple definition of calcite: "Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate."

Info regarding calcite: https://www.minerals.net/mineral/calcite.aspx