You can safely merge chicks under four weeks. After that they are more likely to reject or bully younger chicks or strange chicks.
Try sugar in the water you give the two chicks. It will combat the weakness of this chick. Also, Poultry Nutri-drench is designed to boost such a weak chick. It can be put into the water for the first week.
Try sugar in the water you give the two chicks. It will combat the weakness of this chick. Also, Poultry Nutri-drench is designed to boost such a weak chick. It can be put into the water for the first week.