Monthly Variations in Gross Composition of California Herd Milks

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Abstract
Data on the gross composition of herd milks were collected over 14 mo.; 15 herds (5 Jersey, 4 Guernsey, 5 Holstein and 1 Shorthorn) from California''s San Joaquin Valley [USA] were studied. An IR milk analyzer was used to determine fat, protein, lactose and solids-not-fat in samples collected daily from farm tanks. Monthly variations were parallel for fat and protein concentrations in the milk from all breeds, winter milk containing more than summer milk. Monthly variations for lactose concentration were not as great as for fat and protein, with winter milk containing less than summer milk. Annual means for each component by breed did not differ from Illinois [USA] data collected 30 yr ago over 12 mo. except for fat in Guernsey milk, which was .5% lower. Monthly variations in gross composition was the same in California as in Illinois. There appear to be differences from gross composition in 12 mo. studies in South Dakota and North Carolina and for a shorter study in Pennsylvania [USA].