Wilson — The Variations of Milk Yield toith the Cow's Age. 101 



Nor can much more be said as to the jdelds of cows over eight years old. 

 Dr. Pearl and Mr. Miner's figures indicate that the cow comes to her maximum when 

 she is somewhere between ten and thirteen years old, Dr. Tocher's when she is 

 about ten or eleven, Mr. Speir's when she is ten or eleven ; while the figures for 

 1913 indicate ten, those for 1919 nine to eleven, and those for 1920 eight years. 



\00 



6o 



C(fw5: 1 i U 5 6 7 



Fig. 1. — Relative yields of cows of different ages at different periods. 



yux^ 



It is very doubtful, however, whether the Ayrshire records can be used to say when 

 the cow comes to her maximum yield, for, when cows no longer young have to be 

 discarded for age, the poor ones are likely to be discarded first, the best ones last : 

 and the older age records become loaded with those of cows which are above the 

 average. Mr. Gavin, though his materials were excellent and his eight-year-old 

 cows actually gave more milk than his seven-year-olds, did not insist that the 

 maximum is reached at eight years rather than at seven. He had fewer cows after 



