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Principal component analysis of diet-induced changes in milk fat content and fatty acid composition in dairy ewes

AuthorsToral, Pablo G. ; Hervás, Gonzalo ; Belenguer, Álvaro ; Castro Carrera, Tamara ; Carreño, David ; Frutos, Pilar
Fatty acid
Issue DateSep-2014
PublisherAustralian Society of Animal Production
Citation30 th Biennial Conference of the Australian Society of Animal Production: 156 (2014)
First Joint International Symposium on the Nutrition of Herbivores/International Symposium on Ruminant Physiology (ISNH/ISRP)
AbstractIn cows, the relationship between milk fat synthesis and fatty acid (FA) profile and, more specifically, between diet-induced milk fat depression (MFD) and t10c12-18:2 has been investigated using exploratory data analysis approaches, such as principal component analysis (PCA; Kadegowda et al 2008). However, this kind of information is not available in the ovine. Previous studies conducted with dairy sheep suggest that t10c12-18:2 would not be a causative factor for diet-induced MFD in this species (Bichi et al 2013). Therefore, with the aim of identifying the most relevant FA potentially involved in diet-induced MFD in sheep, PCA was used to examine the relationship between milk fat secretion and milk FA profile in ewes subjected to different feeding strategies. A database comprising lot observations from 15 nutritional trials conducted with lactating ewes from the experimental flock of the CSIC (León, Spain) was built. Lots were fed either pasture (n=41) or TMR (n=398) based on alfalfa hay and concentrates, without lipid supplementation (n=183) or supplemented with plant oils (rich in c9-18:1, 18:2n-6 or 18:3n-3; n=145), marine lipids (n=10) or combinations of both (n=60). The loading plot derived from the PCA showed that milk fat content and yield positioned close to the origin of the plot, with no apparent relation to any of the principal components (PC). When the database was split into 2 sub-databases according to trials showing MFD or not (Figure 1), the loading plots obtained were very different. In MFD studies (i.e., those including diets supplemented with marine lipids), PC1 and PC2 described 62.9% of the total variation in milk FA and dairy performance. Milk fat percentage was negatively correlated with PC2 and loaded near 18:0 and c9-18:1 and opposite to a cluster including t10-18:1, 20:5n-3 and 22:6n-3. Although these FA do not have to be necessarily involved in MFD in ewes, their concentration in milk fat could be an indicator of favourable conditions for MFD to occur. In all loading plots (i.e., from the whole database and the sub- databases), the position of t10c12-18:2 (the only FA with unequivocal evidence of milk fat synthesis inhibition) showed no relationship with diet-induced changes in ovine milk fat content...
Description1 página.-- Comunicación presentada al 30th Biennial Conference of the Australian Society of Animal Production y al First Joint International Symposium on the Nutrition of Herbivores/International Symposium on Ruminant Physiology (ISNH/ISRP) (Canberra, Australia, 8-12 de septiembre del 2014).
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