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The Relation Between Age and Fat Production in Dairy Cows

Department of Dairy Husbandry, University of Missouri, Columbia, Missouri

ABSTRACT

Data was presented showing the relation between age and yearly production of over 46,000 cows of the Jersey, Guernsey, Holstein-Friesian, Ayrshire and Dairy Shorthorn breeds and over 104,000 Holstein-Friesian seven-day records.

It was shown that fat production gradually increases up to between seven and eight years of age on the average, and then gradually decreases with the onset of old age.

No significant difference between the breeds in the time of maturity was noted.

The close relation between an increase in body weight and milk secretion with age is interpreted as indicating that the upward trend of the milk secretion curve with age is due to growth while the descending segment of the curve is due to senescence or the physiological changes due to old age.

A method of converting the fat production records of dairy cows made at any age to the "mature equivalent" was presented as an aid in making studies of the transmitting ability of dairy sires.