Hmm....unrelated blood. Traditionally, before the days of commercial hatcheries to supply laying/meat stock, poultry farms had to build self sufficient flocks in order to be success. They would usually start with stock from two lines and cross them so that their flock would start with out any inbreeding. They then would line breed to select the best breeding stock and maintain a healthy line by only breeding the top 10% of everything they hatch. By only breeding the top 10% they would get the healthiest, most vigorous, and most hardy stock breeding forward. That would help counter the effect of in breeding.
The effects of inbreeding are low disease resistance, low fertility, low hatchability, birth defects (missing toes is the most common), low vigor (this is seen by sunken eye, under weight birds, low activity during the day, etc.).
If you are line breeding for color or show points then your line will decrease is vigor very rapidly. Line breeding only works if you are selecting your top 10% based on health and vigor. You will know your most vigorous birds because they will be the first off the perch in the morning and the last to roost at night. The vigorous cockerels will always walk on the ends of his toes in a cocky strut. The most vigorous will the top of the pecking and crowing order, etc.
So...do you need to start will unrelated blood? It depends on how inbreed your original stock is and what type of breeding program you are going to set up. Healthy stock should be able take 3-5 generations of inbreeding with out showing any ill signs of inbreeding. If you are seeing signs of inbreeding in your first generation, then your original stock was oviously already inbred. Also, are you going to breed one pen, two pen, three pens, more? If you rotation breeding stock systematically with multiple pens you can breed a lot longer with out showing signs of inbreeding than if you just keep one. I recently ready a paper on line breeding white Plymouth Rocks and it said with line breeding one pen you will run out of gene pool in 5 year, two pens in 8 years, three pens was something like 17 year (time?) and four pens was something like 25 years (time). That was assuming that your start with out any inbreeding.
If you have strong stock you can start without getting stock from multiple sources. If not you will need to find another source to cross lines. If you are planning on one pen plan on bringing in new blood in 3-5 years. If you are setting up multipl pens you can start you own breeding. Most line breeding with 3+ pens still bring in new blood about every 8 years.
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