There are several reasons why cows were smaller in the 1600s. First, the quality of feed was not as good as it is today. Cows were often fed hay and other low-quality roughage, which did not provide them with the nutrients they needed to reach their full potential. Second, cows were not selectively bred for size and other desirable traits as they are today. As a result, there was more genetic variation in the cow population, and some cows were naturally smaller than others.
Despite their smaller size, cows in the 1600s still provided a valuable source of food and labor for people. They were used to produce milk, meat, and leather. They were also used to pull plows and other farm implements.