Farm animals were smaller in the past.

In 1860, in Lublin (southeastern Poland), the Agricultural Society organized an Exhibition of Farm Animals.  The following were average weights of cattle at the show, according to their country of origin:

Dutch cows - 246 kg (600 pounds)
Swiss cows - 287 kg (700 pounds)
Polish cows - 164 kg (400 pounds).

Almost 100 years later in the 1950s, the weight of typical Polish dairy cows had increased to 400-550 kg, and their current weight is about 600-650.

The sheep were also much smaller: In 1840, the typical Polish Merino ram weighed around 43-48 kg (104-116 pounds and ewes weighed 33-36 kg (80-87 pounds). Now, the average weight of rams is around 100 kg and for ewes about 60 kg.

Cold-blood horses were also smaller. In the 1950s, a coldblooded Sokolski stallion reached a maximum weight of 550-700 kg and about 150 cm height at withers with a bone circumference of 22.8 cm. To date, the mean withers’ height is 161 cm and the average bone circumference 26.9 cm.