If I put only layer pellets in a feeder and offer grower feed and fowl grain in a separate feeder, will the laying hens be smart enough to eat the layer pellets while the cockerel and other non-layers donāt eat the pellets?
No.
Or is it better to just offer plain oyster shells? I struggle to find the oyster shells here, which is why I ask. But I can use Amazon USA it just takes a long time (6-8 weeks) to deliver.
They need calcium for the eggshells. It does not have to be oyster shell. They can get calcium from some of the plants and some of the creepy crawlies they eat. If your native stone is limestone they can get calcium from that. For some of us they get so much calcium from those sources that they hardly ever touch the oyster shell. Some flocks don't need any supplemental calcium. Your eggshells will tell you how you are doing with that. If your eggshells are firm you are golden. If they are thin or soft you need more calcium.
Many people feed their eggshells back to them. Eggshells alone are a losing proposition, they are not going to supply enough calcium for body function as well as eggshells, plus not all calcium is digested. Some goes on out of the back end. Still, a lot of people get enough calcium from other sources that feeding them their eggshells is sufficient.
Can you get crushed limestone about the size of a green pea or smaller? Some feed companies crush limestone and add it to their feed to supply calcium instead of using oyster shell.
Pretoria is a distance from the ocean but can you get hard shells you can crush? It does not have to be oyster or from the sea. There are two types of shell. The soft flexible parts that do not have significant calcium in it and the hard ones. The hard parts are hard because they are made from calcium. Snails, mussels, clams, lobster, crabs and such have shells that can work.
Also, Iāve been mixing equal parts 1:1:1 mixed fowl grain, layer mash/pellets, and grower mash for 2-3 weeks nowā¦. Oops! Will that be enough to cause kidney damage? Or are they okay if I stop immediately?
Good question. You are probably fine. The tests that have proven that excess calcium can lead to internal organ damage are run assuming the level of calcium is the same as is in Layer. One bite will not kill them. It is eating excess calcium over a time period that causes the problem. Like many things on this forum dosage plays a part. High concentrates can cause problems. Low concentrate is much less dangerous. A certain dosage of a poison can kill you. A lower dosage can make you sick. A low enough dosage and your body won't even notice it. I know of no studies that studied any dosage other than the amount of calcium in Layer food and those assumed that layer food was all they eat.
The level of calcium that is dangerous is different for each chick. Not all chicks in those studies had any problems but enough did to show that excess calcium can be dangerous to them. I think you will be fine removing the Layer from the mix. Besides, what are your other options? I can't think of a better way forward.