Effects of Week of Lactation and Genetic Selection for Milk Yield on Milk Fatty Acid Composition in Holstein Cows

• Published in: Journal of dairy science Vol. 88; no. 11; pp. 3886 - 3893
• Main Authors: Kay, J. K, Weber, W. J, Moore, C. E, Bauman, D. E, Hansen, L. B, Chester-Jones, H, Crooker, B. A, Baumgard, L. H
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.11.2005; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: Animal productions; Animals; Biological and medical sciences; Cattle - genetics; Cattle - physiology; Cell Count; conjugated linoleic acid; dairy cow; Diet; Fats - analysis; fatty acid composition; Fatty Acids - analysis; Female; Food industries; Fundamental and applied biological sciences. Psychology; genetic selection; Lactation - genetics; Lactation - physiology; lactation curve; lactation stage; Lactose - analysis; line differences; Linoleic Acids, Conjugated - analysis; Milk - chemistry; Milk - cytology; Milk and cheese industries. Ice creams; milk fat; Milk Proteins - analysis; Postpartum Period; selection response; Selection, Genetic; stearoyl-CoA desaturase; Stearoyl-CoA Desaturase - metabolism; Terrestrial animal productions; Time Factors; Vertebrates; conjugated linoleic acid; dairy cow; genetic selection; WOL; milk fat; CL; CLA; SL; VA; Genetic selection; Farming animal; Lactation; Dairy cattle; Polyunsaturated fatty acid; Lipids; Fatty acids; Milk production; Linoleic acid; Vertebrata; n-6 fatty acid; Mammalia; Dairy industry; Chemical composition; Artiodactyla; Milk fat; Ungulata
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(05)73074-5

Control (CL) and select line (SL) dairy cows (n=22) managed identically but differing in milk yield (>4100kg/305 d) were used to determine differences in milk fatty acid profile as lactation progressed. Milk yield was recorded daily and milk samples were collected during wk 1, 4, 8, 12, and 16 postpartum for milk composition analysis. Milk samples from wk 1, 8, and 16 were also analyzed for fatty acid composition. Select-line cows produced more milk (44.4 vs. 31.2kg/d) and milk components than CL cows during the 16-wk period. There was no difference in rate of milk yield increase, but peak milk yield for SL cows was greater and occurred later in lactation. There were no differences in milk SCC or milk fat, protein, or lactose content. Selection for milk yield did not affect the content of most individual milk fatty acids; however, compared with CL, SL cows had a reduced ▵9-desaturase system and tended to produce milk with lower monounsaturated fatty acid content. Selection for milk yield did not affect milk fatty acid origin but the percentage of de novo fatty acids increased and preformed fatty acids decreased as lactation progressed. Milk fat trans-11 18:1 and cis-9,trans-11 conjugated linoleic acid increased with progressing lactation (10.7 vs. 14.1 and 3.1 vs. 5.4mg/g, or 31 and 76%, respectively) and were correlated strongly among wk 1, 8, and 16 of lactation. Temporal changes in the ▵9-desaturase system occurred during lactation but these changes were not correlated with milk fat cis-9,trans-11 conjugated linoleic acid content. Results indicate prolonged genetic selection for milk yield had little effect on milk fatty acid composition, but milk fatty acid profiles varied markedly by week of lactation.