A high level of milk and butterfat production indicates generally economy of production" a factor of vital importance. As a consequence of this it is deemed essential at the present time that purebred dairy cattle must be backed by good records. The outcome is that large numbers of cows are tested every year for complete lactations or periods of shorter lengths and the aim in most cases is to get the highest record possible.
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Andrew C. McCandlish (1921) studied this question.
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