Malt bill directly affects attenuation!?

[sbaclimber]

I have a feeling that this is a stupid question, but I haven't yet found a satisfactory answer by searching the interwebs....
Can the type of malt I use directly affect the attenuation I get?

I have been often brewing the same basic recipe for quite a while now (only change from brew to brew is the hop bill), with consistent results.
+ 6.0 kg Pale Ale
+ 0.5 kg CaraFoam(Pils)
+ consistent mash and single sparge volumes and temp
+ consistent boil time
+ consistent pitching rate
+ temperature control
=> attenuation always 87 - 87.5% !

2 brews ago I wanted to brew a SMaSH, so I replaced the CaraFoam with 0.5 kg more of the Pale Ale.
Everything else stayed the same, and low-and-behold, I ended up with an attenuation of 90% :shock:

Should I chalk the 2.5% increase in attenuation up to the 0.5 kg of Pale Ale vs. CaraFoam, or is this just some fluke that probably occured due to some other facton I haven't accounted for?

 

[sbaclimber]

PS, never mind!
I just realised that I had completely over-read this, which directly answered my question. :roll:

- grain bill composition (base malt): mashes rich in enzymes, i.e. high diastatic power, (Pilsner malt, Pale malt) will produce more fermentable worts since they contain a lager amount of beta-amylase and limit dextrinase which can produce more maltose than mashes with lower diastatic power (Munich malt or large amounts of unmalted grains) assuming the same saccharification rest temperature.

- grain bill composition (specialty malts): crystal and roasted malts add mostly unfermentable sugars to the wort which lowers its overall fermentability.

Source: http://braukaiser.com/wiki/index.php?title=Understanding_Attenuation

 

[The Brew Mentor]

SBA,
That's a good source. 1# of Carafoam could certainly lower your attenuation.

Brian