Heavier-milking, bigger cows are more efficient in some situations, while moderate,
lighter-milking cows are more efficient in others

Marketing cows because they are open, calved late or their conformation is breaking down are easy decisions. Marketing cows or retaining heifers based on productive efficiency definitely requires more thought. Biological efficiency is not always the same as economic efficiency. In a cattle production system, efficiency is often a combination of those two. How we