I just pulled up all the growth data from my first NN flock. At week 13, my flocks' average growth rate was only 11%, and the cockerel who was lowest on the pecking order had the slowest growth rate beginning at week 14. Truth be told, overall growth rates dropped for the entire flock around week 9 with occasional spikes up to around 20%, but usually stayed between 10% and 15%. Again...those are averages including both males and females. If you like I can do a quick calculation a little later today after I finish my chores to track the males exclusively. (I love Excel!)
As far as reasons for an actual drop-off....barring any indications of illness, stress and/or bullying would be my first guess. Even among some of my other flocks I will often notice that the cockerel lowest in the pecking order gets chased away from the food dish even by the pullets. I have one very sweet EE cockerel who's been the slowest to really mature and for weeks the rest of the flock refused to let him eat. I actually began feeding him separately from them just so he wouldn't waste away. After doing this for a few weeks, his weight began to climb along with his confidence. He's no longer the lowest in the pecking order and eats with the rest of the flock now. He even has his own little harem now.
That is very helpful. I have two quite large hanging feeders in their tractor with lots of room for everyone, but it is certainly possible that he's being bullied. I'll look into adding a range feeder or two outside as well.
- Ant Farm