Abstract
BackgroundFatty acids (FA) in bovine milk derive through body mobilization, de novo synthesis or from the feed via the blood stream. To be able to digest feedstuff, the cow depends on its rumen microbiome. The relative abundance of the microbes has been shown to differ between cows. To date, there is little information on the impact of the microbiome on the formation of specific milk FA. Therefore, in this study, our aim was to investigate the impact of the rumen bacterial microbiome on milk FA composition. Furthermore, we evaluated the predictive value of the rumen microbiome and the host genetics on the composition of individual FA in milk.ResultsOur results show that the proportion of variance explained by the rumen bacteria composition (termed microbiability or h_{B}^{2}) was generally smaller than that of the genetic component (heritability), and that rumen bacteria influenced most C15:0, C17:0, C18:2 n-6, C18:3 n-3 and CLA cis-9, trans-11 with estimated h_{B}^{2} ranging from 0.26 to 0.42. For C6:0, C8:0, C10:0, C12:0, C16:0, C16:1 cis-9 and C18:1 cis-9, the variance explained by the rumen bacteria component was close to 0. In general, both the rumen microbiome and the host genetics had little value for predicting FA phenotype. Compared to genetic information only, adding rumen bacteria information resulted in a significant improvement of the predictive value for C15:0 from 0.22 to 0.38 (P = 9.50e−07) and C18:3 n-3 from 0 to 0.29 (P = 8.81e−18).ConclusionsThe rumen microbiome has a pronounced influence on the content of odd chain FA and polyunsaturated C18 FA, and to a lesser extent, on the content of the short- and medium-chain FA in the milk of Holstein cattle. The accuracy of prediction of FA phenotypes in milk based on information from either the animal’s genotypes or rumen bacteria composition was very low.
Highlights
Fatty acids (FA) in bovine milk derive through body mobilization, de novo synthesis or from the feed via the blood stream
Studies have focused on the genetic factors that affect the synthesis of FA in the milk and have shown that they are the main factors that influence the synthesis of saturated FA, whereas feed is more important for the synthesis of unsaturated FA [9,10,11]
Proportions in milk FA varied with the highest proportions being in C14:0 (11.60%), C18:1 cis-9 (20.27%) and C16:0 (31.24%), and the lowest in C13:0 (0.14%), conjugated linoleic acid (CLA) cis-9, trans-11 (0.48%) and C18:3 n-3 (0.53%)
Summary
Fatty acids (FA) in bovine milk derive through body mobilization, de novo synthesis or from the feed via the blood stream. The relative abundance of the microbes has been shown to differ between cows. The relative microbiome composition may differ between cows [2]. The long chain FA derive mainly from the feed but can be modified in the rumen and the mammary gland [8]. C16:0 can be derived both from feed and de novo synthesis in the mammary gland. Studies have focused on the genetic factors that affect the synthesis of FA in the milk and have shown that they are the main factors that influence the synthesis of saturated FA, whereas feed is more important for the synthesis of unsaturated FA [9,10,11]. Within the context of the digestion of feed by the microbial community in the rumen, it is interesting to investigate how much of the variation in milk FA can be explained by variation in the rumen microbiome
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