Genetic correlations of milk fatty acid contents predicted from milk mid-infrared spectra in New Zealand dairy cattle

Abstract

The objective of this study was to estimate genetic correlations among milk fatty acid (FA) concentrations in New Zealand dairy cattle. Concentrations of each of the most common FA, expressed as a percentage of the total FA, were determined by gas chromatography on a specific cohort of animals. Using this data set, prediction equations were derived using mid-infrared (MIR) spectroscopy data collected from the same samples. These prediction equations were applied to a large data set of MIR measurements in 34,141 milk samples from 3,445 Holstein-Friesian, 2,935 Jersey, and 3,609 crossbred Holstein-Friesian × Jersey cows, sampled an average of 3.42 times during the 2007-2008 season. Data were analyzed using univariate and bivariate repeatability animal models. Heritability of predicted FA concentration in milk fat ranged from 0.21 to 0.42, indicating that genetic selection could be used to change the FA composition of milk. The de novo synthesized FA (C6:0, C8:0, C10:0, C12:0, and C14:0) showed strong positive genetic correlations with each other, ranging from 0.24 to 0.99. Saturated FA were negatively correlated with unsaturated (−0.93) and polyunsaturated (−0.84) FA. The saturated FA were positively correlated with milk fat yield and fat percentage, whereas the unsaturated FA were negatively associated with fat yield and fat percentage. Our results indicate that bovine milk FA composition can be changed through genetic selection using MIR as a phenotypic proxy.

Genetic Parameters of Bovine Milk Fatty Acid Profile, Yield, Composition, Total and Differential Somatic Cell Count

“…Although low, such correlations were not null as standard errors of estimates were ≤0.01. Overall, weak correlations of SCS with FA were observed also by Lopez-Villalobos et al [9], except for moderate negative associations with C4:0 (−0.25), C6:0 (−0.21) and SCFA (−0.26). Genetic correlations between SCS and FA were estimated also by Petrini et al [30], who reported weak negative correlations with SFA, C16:0 and C18:0, and weak positive correlations with UFA, MUFA, PUFA, and C18:1.…”

“…Nevertheless, those authors [6] reported approximate genetic correlations among traits as correlations among daily breeding values, possibly without fully representing the genetic relationships between traits. Although positive genetic correlations between SFA, MUFA, and PUFA have been reported in literature [19,26], some authors [9,27,28] reported strong negative genetic correlations. As explained by Lopez-Villalobos et al [9], this discrepancy is due to the different expression of concentration of FA: as grams per 100 g of milk (positive correlation) or grams per 100 g of total FA (negative correlation).…”

“…Although positive genetic correlations between SFA, MUFA, and PUFA have been reported in literature [19,26], some authors [9,27,28] reported strong negative genetic correlations. As explained by Lopez-Villalobos et al [9], this discrepancy is due to the different expression of concentration of FA: as grams per 100 g of milk (positive correlation) or grams per 100 g of total FA (negative correlation). Considering the classification based on the length of the FA chain, medium to strong genetic correlations were estimated, with the strongest genetic and phenotypic associations between SCFA and MCFA (0.87 ± 0.01 and 0.81, respectively).…”

“…Indeed, lower genetic correlations can be found between LCFA and both SCFA and MCFA, indicating different provenance of the FA groups. Lopez-Villalobos et al [9], who expressed FA as % of total FA, observed a positive association between SCFA and MCFA (0.18) and negative association of LCFA with SCFA (−0.55) and MCFA (−0.09). Among individual FA, genetic correlations were in the range from 0.58 ± 0.05 (C16:0 and C18:1) to 0.79 ± 0.03 (C16:0 and C18:0), with the exception of a very strong genetic (and phenotypic) correlation of 0.94 ± 0.01 (0.92) between C14:0 and C16:0.…”

“…Nevertheless, correlations with other milk traits should be taken into account to use FA profile for genetic purposes. For this reason, several studies have explored the phenotypic and genetic relationships of milk FA with yield and composition [6,8,9]. In addition, the genetic aspects of FA and their possible use in genomic selection have been investigated also in sheep [10,11] and goat [12,13] milk.…”