You can find a wealth of knowledge by going to the ADGA website. To make it easier, type what you are looking for into the search bar by clicking on the eyeglass icon in the upper right-hand corner and the site will narrow it down. ADGA is the most widely used registration for Nigerian Dwarf goats.
The NDGA also contains valuable information when researching and learning about the breed. You can become a member of the NDGA for a very reasonable fee. The NDGA also has a very unique Master Wether Program for those that only own wethers.
AGS is another great source for finding more information on the breed, show ring details, and was the first organization to register purebred goats exclusively. Nigerian Dwarf goats may also be registered through this organization. If you have a goat that is registered with ADGA, but has parents that were registered with AGS only, the ADGA registration paperwork will show the parentage as starting with "AGS" and should contain a corresponding registration number similar to this: D-55735. You can find a great example of this shown under our "Does" tab for Farm Swiftwind Mia.
This link is one of the best and most useful in my personal opinion. Once you learn to navigate through it, you can really learn a lot about the genetics behind the breed and what all is involved when it comes to selective breeding. To learn more about what the values PTI/ETA really mean and not just the numbers as shown on this site, go to ADGA's website and type PTI or ETA in the search bar.
You can find this calculator within the AGS website link I have provided above. However, I am including this direct link as it is frequently used and extremely helpful.
This is a very useful link, especially for those that are new to the breed. Although, even if you have been breeding goats for some time its a great reference to many of the terms used in the goat world, so I wanted to make this easy to access for all. The information in this link is supported by New Technologies for Agriculture Extension through grant no. 2015-41595-24254 from the USDA National Institute of Food and Agriculture.
This article I found online from the website Better Hens & Gardens of Bramblestone Farm, provides an excellent overview of how to understand dairy goat linear appraisals. The letters and numbers you may see behind the name of a goat such as VEEE 90 or EEE 91 or +VV+ 84, for example, are all based on the linear appraisal process and are an indication of how that particular goat excels or where it may need improvement. These values also give a indication of how future offspring may perform.