Document Detail

Effects of week of lactation and genetic selection for milk yield on milk fatty acid composition in Holstein cows.
MedLine Citation:
PMID:  16230694     Owner:  NLM     Status:  MEDLINE    
Control (CL) and select line (SL) dairy cows (n = 22) managed identically but differing in milk yield (>4100 kg/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. 31.2 kg/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 Delta(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. 5.4 mg/g, or 31 and 76%, respectively) and were correlated strongly among wk 1, 8, and 16 of lactation. Temporal changes in the Delta(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.
J K Kay; W J Weber; C E Moore; D E Bauman; L B Hansen; H Chester-Jones; B A Crooker; L H Baumgard
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of dairy science     Volume:  88     ISSN:  1525-3198     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2005 Nov 
Date Detail:
Created Date:  2005-10-18     Completed Date:  2006-03-02     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3886-93     Citation Subset:  IM    
Department of Animal Sciences, The University of Arizona, Tucson 85721, USA.
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MeSH Terms
Cattle / genetics*,  physiology
Cell Count
Fats / analysis
Fatty Acids / analysis*
Lactation / genetics*,  physiology*
Lactose / analysis
Linoleic Acids, Conjugated / analysis
Milk / chemistry*,  cytology
Milk Proteins / analysis
Postpartum Period
Selection, Genetic*
Stearoyl-CoA Desaturase / metabolism
Time Factors
Reg. No./Substance:
0/Fats; 0/Fatty Acids; 0/Linoleic Acids, Conjugated; 0/Milk Proteins; 63-42-3/Lactose; EC Desaturase

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