The short answer is that most of our breeds will start to lay at around 5 to 7 months. For example, our Black Australorps layed their first egg when they were 26 weeks old (6 months) and were laying very well by 7 to 7 1/2 months.
Though you can buy hybrid layers from various sources that will start laying earlier than that, some as early as 4 1/2 months, early laying is not one of the traits that we select for. I’ll explain why.
It’s important to realize that as soon as your hen starts to lay, she will cease to grow. So, if she starts to lay at a very young age, she will not get very large. All of our breeds are dual-purpose, developed for both meat and egg production. We want both roosters and retired hens to be large enough for table use. If we were to select for early laying, our birds’ average sizes and weights would start to decrease in each successive generation, making these birds less “dual purpose” and less useful to our customers and to us. For this reason, we don’t select for earliness of lay. Instead, we select our breeders based on the breed standard and based on production traits.