Document Detail

Fatty acid composition of milk from multiparous Holstein cows treated with bovine somatotropin and fed n-3 fatty acids in early lactation.
MedLine Citation:
PMID:  19762802     Owner:  NLM     Status:  MEDLINE    
Multiparous cows (n = 59) were blocked by expected calving date and previous milk yield and assigned randomly to treatments to determine effects of bovine somatotropin (bST; Posilac, Monsanto Animal Agricultural Group, St. Louis, MO) and source of dietary fat on milk fatty acid composition during the first 140 d in milk. Diets were provided from calving and included whole, high-oil sunflower seeds (SS; 10% of dietary dry matter; n-6/n-3 ratio of 4.6) as a source of linoleic acid or a mixture of Alifet-High Energy and Alifet-Repro (AF; Alifet USA, Cincinnati, OH; 3.5 and 1.5% of dietary dry matter, respectively; n-6/n-3 ratio of 2.6) as a source of protected n-3 fatty acids (15.7% 18:3, 1.3% 20:5, and 1.3% 22:6). Treatments were derived from a 2 x 2 combination of supplemental fat source (SS, AF) and with 0 (SSN, AFN) or 500 (SSY, AFY) mg of bST administered every 10 d from 12 to 70 d in milk and at 14-d intervals thereafter. Milk fatty acid composition was determined in samples collected from 32 cows (8 complete blocks) during wk 2, 8, and 20 of lactation. Data were analyzed as repeated measures using mixed model procedures to determine the effects of diet, bST, week of lactation, and their interactions. Proportions of 18:3 (4.02 vs. 3.59 +/- 0.16%), 20:5 (0.52 vs. 0.41 +/- 0.02%), and 22:6 (0.11 vs. 0.02 +/- 0.02%) were greater and the n-6/n-3 fatty acid ratio (7.40 vs. 8.80 +/- 0.30) was reduced in milk from cows fed AF compared with SS. Proportions of de novo-synthesized fatty acids increased and preformed fatty acids decreased as lactation progressed, but bST administration delayed this shift in origin of milk fatty acids. Transfer efficiency of 18:3, 20:5, and 22:6 from AF to milk fat averaged 36.2, 4.9, and 5.2%, respectively. These efficiencies increased as lactation progressed, but were delayed by bST. Apparent mammary Delta(9)-desaturase activity and milk conjugated linoleic acid (cis-9, trans-11 conjugated linoleic acid) content increased through the first 8 wk of lactation. Based on the product-to-substrate ratio of 14:1/14:0 fatty acids in milk, there was an interaction of diet and bST because bST decreased apparent Delta(9)-desaturase activity in SSY cows but increased it in AFY cows (0.10, 0.09, 0.08, and 0.09 +/- 0.01 for SSN, SSY, AFN, and AFY, respectively). Feeding Alifet-Repro increased n-3 fatty acids in milk and bST prolonged the partitioning of dietary fatty acids into milk fat.
M Carriquiry; W J Weber; C R Dahlen; G C Lamb; L H Baumgard; B A Crooker
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of dairy science     Volume:  92     ISSN:  1525-3198     ISO Abbreviation:  J. Dairy Sci.     Publication Date:  2009 Oct 
Date Detail:
Created Date:  2009-09-18     Completed Date:  2009-12-11     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985126R     Medline TA:  J Dairy Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  4865-75     Citation Subset:  IM    
Department of Animal Science, University of Minnesota, St Paul 55108-6118, USA.
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MeSH Terms
Cattle / metabolism*
Dietary Fats, Unsaturated / administration & dosage
Fatty Acids / analysis*
Fatty Acids, Omega-3 / administration & dosage*
Fatty Acids, Omega-6 / administration & dosage
Growth Hormone / administration & dosage*
Lactation / physiology*
Linoleic Acids, Conjugated / analysis
Mammary Glands, Animal / enzymology
Milk / chemistry*
Stearoyl-CoA Desaturase / metabolism
Reg. No./Substance:
0/Dietary Fats, Unsaturated; 0/Fatty Acids; 0/Fatty Acids, Omega-3; 0/Fatty Acids, Omega-6; 0/Linoleic Acids, Conjugated; 89383-13-1/growth hormone, bovine; 9002-72-6/Growth Hormone; EC Desaturase

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