No abstract

Using historic lactation records for Ayrshire cattle, we report a gradual increase in the production of milk, butter fat and protein levels across four decades. This was generally at the extent of attaining a level of increase per decade which was similar to the increase seen between animals during their first and second lactations in the previous decade. However these increases were achieved without significantly affecting the percentage of butter fat or protein throughout the time examined, and also without changing the heifer: second lactation ratios