Do you feed limestone grit? Article of the day

[Farrier1987]

Effect of limestone particle size on performance, eggshell quality, bone strength, and in vitro/in vivo solubility in laying hens: a meta-analysis approach
https://www.sciencedirect.com/science/a ... via%3Dihub
Authors: F.Hervo, A.Narcy, Y.Nys, M.-P.Létourneau-Montminy
First three researchers at INRAE, Université de Tours, Nouzilly, France
Fourth at Département des sciences animales Université Laval,



I read this paper, and it is very interesting, but for a layman like me, somewhat difficult, It took me quite a while to read and digest. I have written a more readable sort of summary/book report thing which follows. I hope it properly reflects their research. If not, the fault is mine.

Limestone Grit writeup, By Colin Reid

I expect most of us know that chickens don't have teeth, that they swallow their food whole and it goes to the crop for storage and then to the gizzard to be ground up and on through the GI track. And they eat small rocks that work with the gizzard to grind and break up what they eat.

If your birds free range as mine do, the chickens have their choice of what they want for grit. Small pieces of gravel and sand and such. In winter, I will buy a bag of limestone grit. I don't feed oyster shell.

The limestone is beneficial in two ways. The stones help grind the food, and the calcium in the stone contributes to stronger egg shells and bones.

Another point in the paper makes sense, which I didn't know before. A chicken deposits calcium in a certain type of bones called medullary bone which develops in the female at puberty. The hen deposits calcium in these bones, then draws on it to make egg shell. This is a daily cycle. About 70% of the egg shell comes directly from the diet, but about 30% is drawn out of the bones, which replenishes itself mostly over the night perching. So if they aren't getting enough usable calcium, they will have weakened bones as well as thin shelled eggs.

I had never considered that the size of the limestone might make a difference to how well the chicken functions. Limestone in the diet is limestone in the diet? Not so, as the researchers for this article studied and demonstrated.

This has been studied ib nabt papers before, and the results show that courser limestone is better than finer. Those are relative terms, but overall 1.5 to 4 mm is best. (To us old codgers, about 1/16 to 1/8 inch.) Larger than that can be a problem for their bodies to handle, and smaller tend to pass through too quickly.

They found that the courser limestone stayed longer in the crop and gizzard, prompting the body to produce more stomach acids which then metabolized more of the limestone and food rather than passing through unused. This resulted in better egg shells and stronger bones.

This was more a side note in the discussion, but I found it interesting. Just as the larger limestone particles stimulate stomach acid production and higher calcium uptake, so does feeding whole or course grain. I only feed whole grains, no mash or pellets. I might be doing something right.

Within the paper there were many equations and graphs and calculations to justify how they came to therr results, but the following is the last paragraph of the paper, and it sums it up rather nicely.

"The aim of this meta-analysis was to quantify the effect of LmPS on the digestive availability and metabolic utilization of Ca by the laying hen. Current results show that coarse limestone particles improve eggshell quality, most likely by increasing mean retention time of Ca in the gizzard and increasing Ca absorption during the night. It also showed that coarse limestone particles improve eggshell quality regardless of age while its effect on bone strength is age dependent. Thus, coarse limestone particles help prevent bone weakness in layer flocks."

[TomK]

@Farrier1987 ..awesome piece of info..thanks a bunch