Seasonal Variations in Milk and Fat Production

In a previous paper (1) the seasonal variations of the percent of fat in cow's milk was presented.The object of this paper is to present the results of a study of the seasonal variations in milk and fat production using the records of the same cows.The decrease in production due to the advance of the stage of lactation has been shown by Cooke (2), Linfield (3), Woll (4), and Grady (5).Cooke found that cows calving in the fall were more persistent than those calving in the spring.WoU concluded that there was little difference in the rate of decline of the various breeds.Ectdes ( 6), studied the rate of decline of cows freshening every twelve months.Haecker (7) and Gavin (8) made studies to determine the length of time after calving that maximum production was attained.The favorable influence of spring pasture on milk production has been shown by Cooke (2), Linfield (3), Grady (5), Hills (9), Otis (10), and Humphrey and Woll (11).The effect on milk and fat production of spring and fall freshening has been shown by McCandlish (12), McDowell (13) and Moore ( 14).Fall freshening in each case favored increased milk and fat production.The records of each breed 1 were divided into groups according to the month during which the lactation began, i.e., all cows calving in January were placed together, those in February together, etc. Records made during parts of two lactation 1 The data for the Guernsey cows were obtained from 3215 Advanced Registry records from eastern and middle western states with a sprinkling from the Pacific Coast states.Values for the Jersey cows were obtained on 305 Register of Merit animals in Missouri.The Holstein data were compiled from 95 Advanced Registry records on animals in the University of Missouri dairy herd.