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Journal of Dairy Science Vol. 49 No. 11 1410-1415
© 1966 by American Dairy Science Association ®
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Effect of Successive Lactations, Gestation, and Season of Calving on Constituents of Cows' Milk

M. R. Parkhie, L. O. Gilmore and N. S. Fechheimer

Department of Dairy Science, Ohio Agricultural Research and Development Center, Wooster

ABSTRACT

Six different least-squares analyses were carried out on 280 records from first through fourth completed lactations on milk yield and the percentages, respectively, of total solids, fat, nonfat-solids (NFS), protein, and pregnancy NFS. These records were from 121 Holstein cows in one herd. Two-factor interactions between laction number, gestation length, and season of calving also were considered.

Milk yield of a cow increased as she advanced successively from one lactation to another, with concomitant decrease in content of total solids. For protein content there was no significant difference among lactations. Cows pregnant for seven months or more produced significantly (P < 0.05) higher protein content in their milk than those pregnant for a shorter time. Cows pregnant for five to seven months and three to five months during their 305-day lactation did not differ significantly in their protein content, although those having gestations of three months or less produced significantly (P < 0.05) less protein. Cows calving during autumn and winter produced milk significantly higher in fat content than those calving during spring and summer. The highest protein content was found in milk from the second lactation of cows calving during spring and summer.

Of the constituents studied, fat was the most variable one, followed by total solids, protein, and NFS.

FOOTNOTES

Journal Article no. 41-66. Ohio Agricultural Research and Development Center, Wooster, Ohio.






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Copyright © 1966 by the American Dairy Science Association ®.