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The effect of dietary lipid content and composition on the milk fat iodine value of dairy cows

  • E. Magowan (a1) (a2), A. M. Fearon (a3) (a2), D. C. Patterson (a1), D. J. Kilpatrick (a3) and J. A. M. Beattie (a3)...


Iodine value (IV) indicates the degree of unsaturation of milk fat, thus reflecting the presence of long chain unsaturated fatty acids (LCUFA), especially C18:1c. The higher the IV the greater the degree of unsaturation. Changes in dietary lipid content and composition can have a major effect on the IV of milk fat. The principal fatty acid in the forage component of the diet, namely grass or grass silage, is C18:3 (Murphy, 2000) while concentrate supplements contain varying proportions of C18:1 or C18:2 fatty acids. LCUFA undergo hydrolysis and biohydrogenation in the cow’s rumen producing mainly C18:0, the majority of which is converted to C18:1c by the desaturase enzyme systems, mainly in the mammary gland (Murphy, 2000). This experiment aimed to examine the relationship between milk fat IV and dietary lipid content, composition and diet type.


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Fearon, A. M., Charlton, C. T. and Kilpatrick, D. J. (1994). A further investigation of the influence of dietary protected lipid supplements on the characteristics of cows’ milk fat. Journal of Science, Food and Agriculture 66: 247 – 256.
Murphy, J. J. (2000). Synthesis of milk fat and opportunities for nutritional manipulation. Milk Composition Occasional publication No. 25, BSAS 2000 (ed. Agnew, R. E., Agnew, K. W. and Fearon, A. M.).


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