Culling makes sense! Just as culling cows for Staph Aureus Mastitis (which is highly contagious by the way and can spread via milkers, employees, and bedding and ruin many good cows) that causes a loss of a lifetime milk production and loss of SCC premiums and income. Culling in this case younger stock which may not have the genetic profit potential of other heifers who also are also consuming your expensive feed.
Genetic testing can show a milk production gap of one and two even 5,000 pounds of milk/lactation or more/lactation, so instead of raising these lower genetic level heifers for approximately two years and hope the figures are wrong. Unfortunately in this late day in history the genetic testing is usually right.
Contact the Holstein Association U.S.A. 1-802-952-5200 for more on genetic testing. Immu-pro helps all hers improve; 1-920-650-1631.