I used it on my Ybs a few seasons ago when I had them on the darkness, and they definately looked as if they benefitted from using it as I also had improved results during racing and had the best season I ever had. Directions on the tub say to add 1 teaspoon onto the damp feed daily (I only used it 3 days per week). Specially recommended for improving all round condition and performance and acts as a nutritional supplement when birds are moulting. I just realised it has a good shelf life too as the tub I have I bought in 2011 and just noticed that the expirery date is Jan2016