Kausar Shaikh: Ideally, the higher concentration means better efficacy for all products (including Sodium Butyrate), however, there are various factors that may have a say in the performance. Few of the important parameters are below:
1) Coating system - This is important because with pKa value of 4.82, Sodium Butyrate will get converted into Butyric acid in the Foregut (if coating material or quality of coating is not appropriate) , and we will encounter loss of concentration ( partial or total) of Sodium Butyrate in this area of the GIT of the bird - and may result in low availability of butyric acid in midgut and hind gut which is the site of action for the molecule.
2) Expanding on point number 1, please look into the coating material used. If the melting point, elasticity, spread-ability, mechanical strength etc. is not reasonably good, there could be damage in the coating of Sodium Butyrate, then during blending (feed mixing) and pelleting process the the coating may get damaged resulting of release of Sodium Butyrate in the fore gut (instead of reaching the mid gut and hind gut where it is required most)
3) Sodium Butyrate is also very hygroscopic, and higher the concentration, lower is the percentage of coating material (or sometimes no coating). This may result in formation of lumps in the product itself leading to uneven distribution of the product in feed mixing/blending. In such case some of the birds may receive high quantity of Sodium Butyrate, while others in the flock may receive low or no Sodium Butyrate.
There could be various more factors which may have an impact on the efficacy - however, as you may see, the above could have a direct impact on the dose/MT of feed.
For ethical reasons, It may not be appropriate for myself to pin-point further on your query in this forum. Such discussions may happen on one to one interactions only.