Association of DGAT1 genotype, fatty acid composition, and concentration of copper in milk with spontaneous oxidized flavor

Abstract

In 136 cows with altogether 969 milk samples, we investigated the effect of the acyl-coenzyme A:diacylglycerol acyltransferase 1 (DGAT1) K232A polymorphism on milk fatty acid (FA) composition and how, in combination with copper concentration in milk, this influences the occurrence of spontaneous oxidized flavor. All milk samples were analyzed for concentrations of copper and individual FA and subjected to sensory analysis by trained judges. We found an effect of DGAT1 genotype on FA composition where mainly the long-chain FA were affected. The 232A allele was associated with larger proportions of the C18:2 cis-9,trans-11 conjugated linoleic acid and lower proportions of C16:0 FA. Milk concentrations of unsaturated FA and copper showed strong and unfavorable associations with spontaneous oxidized flavor (SOF) development. The interaction between FA and copper indicates that SOF will not develop as easily in milk with high copper content unless the substrate is available (i.e., in addition to the previously shown effect of copper in milk, unsaturated FA are required for the process of oxidation to progress). We observed a marked effect of the DGAT1 genotype on SOF development where the A allele was associated with a higher risk of SOF. Moreover, our results suggest that the effects of the FA C18:3 n-3 and of the polyunsaturated index on SOF development are beyond the effect of the DGAT1 genotype. Breed had an effect on FA composition but not on SOF development. Our results imply that copper, FA composition, and DGAT1 genotype are risk factors for SOF and considerations to these factors might be necessary in future breeding decisions.

Effect of DGAT1 variant (K232A) on milk traits and milk fat composition in outdoor pasture-grazed dairy cattle

“…In general, the associations between DGAT1 K232A and the levels of milk FAs, especially for C16:0, CLA and C18:3 cis-9, 12, 15, were consistent with what has been reported in other breeds, but some exceptions were found. For example, Juhlin, Fikse [18] reported that there were no significant difference on the most milk FAs (except C16:0 and CLA levels) between their AA and AK cows. In addition, Carvajal, Huircan [19] didn't find any associations between K232A and C16:0, C16:1, C18:1, CLA and MUFA levels.…”

Estimation of genetic parameters and detection of quantitative trait loci for minerals in Danish Holstein and Danish Jersey milk

“…The Cu concentration in milk is known to vary between cows and with diet and level of mineral supplementation [ 26 ]. Previously it has been shown that the Cu concentration plays an important role in the spontaneous development of oxidative off-flavor of the milk [ 27 , 28 ]. The mineral contents reported here were based on skimmed milk, which could have affected the reported levels, as small amounts may be associated with the milk fat fraction.…”

“…the LD block was based on the HD SNP markers covering the physical map position of DGAT1 . Juhlin et al [ 28 ] showed that DGAT1 polymorphisms together with the FA composition and Cu concentration were risk factors for the development of spontaneous oxidized flavor. In their study they tested the influence of DGAT1 on different fatty acid groups, however not on the Cu concentration in the milk.…”

Effect of DGAT1 Variant (K232A) on Milk Traits and Milk Fat Composition in Outdoor Pasture-Grazed Dairy Cattle

“…All the cows Carvajal, Huircan [19] investigated were fed predominantly pasture (supplemented with conserved forage such as silage, hay, and maize during autumn and winter). One possible reason to explain the inconsistency with the results of Carvajal, Huircan [19] and Juhlin, Fikse [18], was that the samples they investigated were collected from over a whole lactation period (about 1 year), when the effects of K232A on milk FAs identified by Duchemin, Bovenhuis [14], Tabaran,…”