I was racking to secondary yesterday and I even drank a good portion of the gunk at the bottom of the primary. Didn't want to dump it all! It was like drinking a chocolate milk shake. It was a porter btw.
My first beer had great head while the second and third had none. I tried to figure out why this happened. I had put brown sugar in my 2nd and 3rd but not my 1st and attributed it to that.
Also keep in mind that there are different regulations on food meant for people and food okay to feed to animals. You might have a higher percentage of mouse droppings or something.