You are a database consultant. You have been hired by a local dog breeder to develop a database. 
This database will be used to store information about the breeder’s dogs. You create a table named Dogs by using the following script:

CREATE TABLE[dbo].[Dogs]
(
[DogID] [int] NOT NULL,
[BreedID] [int] NOT NULL,
[DateofBirth] [datetime] NOT NULL,
[WeightAtBirth] [decimal] (5, 2) NOT NULL,
[NumberOfSiblings] [int] NULL,
[MotherID] [int] NOT NULL,
[FatherID] [int] NOT NULL
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[Dogs] WITH NOCHECK ADD
CONSTRAINT [PK_Dogs]PRIMARY KEY CLUSTERED
(
[DogID]
) ON [PRIMARY]
GO

You must ensure that each dog has a valid value for the MotherID and FatherID columns. You want to enforce this rule while minimizing disk I/O. 

What should you do?