Dietary supplements of whole linseed and vitamin E to increase levels of -linolenic acid and vitamin E in bovine milk

Abstract

The potential to increase the concentrations of n-3 polyunsaturated fatty acids (PUFAs) in milk fat was investigated by studying the effects of feeding a xylose-treated, whole cracked linseed supplement (rich in -linolenic acid) to dairy cows. Also the effect of increasing the dietary intake of vitamin E on the vitamin E status of milk was investigated. The effect of pasteurisation on milk fatty acid composition was also examined. Using a 3 2 factorial design, a total of 60 Holstein dairy cows were fed a total mixed ration based on grass silage supplemented with one of three levels of whole cracked linseed (78, 142 or 209 gkg -1 diet dry matter (DM); designated LL, ML or HL, respectively) in combination with one of two levels of additional dietary vitamin E intake (6 or 12 g vitamin Eanimal -1 day -1 ; designated LE or HE, respectively). Increasing lipid supplementation reduced (P < 0.01) diet DM intake and milk yield, and increased (P < 0.001) the overall content of oleic, vaccenic, -linolenic and conjugated linoleic acids, and total PUFAs and monounsaturated fatty acids (MUFA). Myristic and palmitic acids in milk fat were reduced (P < 0.001) through increased lipid supplementation. While -linolenic acid concentrations were substantially increased this acid only accounted for 0.02 of total fatty acids in milk at the highest level of supplementation (630 g -linolenic acidanimal -1 day -1 for HL). Conjugated linoleic acid concentrations in milk fat were almost doubled by increasing the level of lipid supplementation (8.9, 10.4 and 16.1 gkg -1 fatty acids for LL, ML and HL, respectively). Although milk vitamin E contents were generally increased there was no benefit (P > 0.05) of increasing vitamin E intake from 6 to 12 ganimal -1 day -1 . The fatty acid composition of milk was generally not affected by pasteurisation. milk fat / fatty acids / -linolenic acid / vitamin E / pasteurisation Rsum -Augmentation de la concentration en acide -linolnique et en vitamine E dans le lait de vache par complmentation de la ration avec des graines de lin entires et de la vitamine E. La possibilit d'augmenter la concentration en acides gras polyinsaturs n-3 (PUFAs) de la matire grasse du lait a t tudie en suivant les effets de l'addition de graines entires de lin concasses, traites au xylose (riches en acide -linolnique) la ration de vaches laitires. L'effet de l'augmentation de l'ingestion de la vitamine E sur la concentration de la vitamine E dans le lait,