1. What is the best age to switch my young chicks to laying crumbles?
After you see the first egg or 20 weeks of age.
2. Will a hen let a Roo mate with her if she is not yet ready to lay eggs or will she try and fight him off?
It depends on the pullet and the rooster. I had one 14 week old that willingly squatted for a young rooster. She did not start to lay until she was 19 weeks old. But that is extremely rare. Practically all my pullets try to get away from the rooster when he starts getting amorous if they are not of laying age. I seldom see pullets actually trying to fight off a rooster over mating behavior. They always try to run away if they are not interested in his advances. He is bigger than them so they know he will win. They just run. I've seen mature hens beat the stuffings out of a young amorous rooster, even if he is bigger than them, but not young pullets. If young pullets are fighting with a young rooster, they are both immature and it is a pecking order thing more than a mating thing.
or will he even attempt it?
Some roosters will and some won't. As Fred said, the young ones are much more likely to try. They are immature adolescents with their hormones running wild. They can tell the pullets are female but not whether they are ready or not. Their hormones are just out of control. Most mature roosters have control of themselves and will wait until she is ready, but then some roosters never seem to leave that adolescence phase and actually grow up.
But it is also a dominance thing. I've seen a mature hen mount an adolescent pullet in an all-female flock to show her dominance. Mounting and mating is how a dominant rooster accepts a new hen into his flock and establishes dominance over her. When adolescent roosters especially are trying to position themselves to take over the flock, they will try to mount pullets that are not ready to establish dominance. It's not just a mating thing. It's as if a rooster that has enough self-confidence in himself to dominate by the pure magnificence of his personality does not have anything to prove, but an immature adolescent is unsure of himself and has to get physical.
There is another side to this. Unless a rooster can dominate the hen with the sheer magnificence of his glory and personality, even mature egg laying hens will try to run away from some mature roosters. It varies among individuals, but many females, especially the ones past their just-starting-to-lay phase, expect a rooster to find them food, protect them, and keep order in his flock. A rooster that cannot perform his flock responsibilities will find himself rejected by some of his ladies. So a hen's or pullet's response depends not only on her maturity, but on the maturity of the rooster. I've seen 15 week old roosters that mature hens would willingly squat for, but I've also seen much older roosters that got no respect.
Probably a lot more than you wanted, but a simple, "Sometimes" seemed an insufficient answer. But when they start not running away, it is usually a sign they are getting ready to lay. Not always, but almost always.
I see you added a bit of information since I started typing. Ill post my response anyway.
so I'm hoping thats a sign they are ready to join my WL in paying the rent!!!
