Data for cows can be evaluated many ways. The data reported in fig. This method was selected to eliminate some management differences between herds. This value was calculated for each of the DHI herds in the study. The herds were then grouped by average age in months at first calving.
Some differences appear in the data.
The lowest percent occurred in herds with less than 24 months at first calving. The accuracy of this figure is ques- tionable since only 10 herds are represented. If a 15,000-pound mature cow average is used for a reference point, then each 1 percent represents 150 pounds of milk. Additional production data are available from DHI records on a national basis. Larger difference can be expected in ages less than 23 months at first calving.