Phenotypic and genetic relationships of residual feed intake measures and their component traits with fatty acid composition in subcutaneous adipose of beef cattle1

Abstract

Feed efficiency is of particular interest to the beef industry because feed is the largest variable cost in production and fatty acid composition is emerging as an important trait, both economically and socially, due to the potential implications of dietary fatty acids on human health. Quantifying correlations between feed efficiency and fatty acid composition will contribute to construction of optimal multiple-trait selection indexes to maximize beef production profitability. In the present study, we estimated phenotypic and genetic correlations of feed efficiency measures including residual feed intake (RFI), RFI adjusted for final ultrasound backfat thickness (RFIf); their component traits ADG, DMI, and metabolic BW; and final ultrasound backfat thickness measured at the end of feedlot test with 25 major fatty acids in the subcutaneous adipose tissues of 1,366 finishing steers and heifers using bivariate animal models. The phenotypic correlations of RFI and RFIf with the 25 individual and grouped fatty acid traits were generally low (<0.25 in magnitude). However, relatively stronger genetic correlation coefficients of RFI and RFIf with PUFA traits including the -6:-3 ratio (0.52 ± 0.29 and 0.45 ± 0.31, respectively), 18:2-6 (0.45 ± 0.18 and 0.40 ± 0.19, respectively), -6 (0.43 ± 0.18 and 0.38 ± 0.19, respectively), PUFA (0.42 ± 0.18 and 0.36 ± 0.20, respectively), and 9-16:1 (-0.43 ± 0.20 and -0.33 ± 0.22, respectively) were observed. Hence, selection for low-RFI or more efficient beef cattle will improve fatty acid profiles by lowering the content of -6 PUFA, thus reducing the ratio of -6 to -3 along with increasing the amount of 9-16:1. Moderate to moderately high genetic correlations were also observed for DMI with 9-14:1 (-0.32 ± 0.17) and the sum of CLA analyzed (SumCLA; -0.45 ± 0.21), suggesting that selection of beef cattle with lower DMI will lead to an increase amount of 9-14:1 and SumCLA in the subcutaneous adipose tissue. However, unfavorable genetic correlations were detected for ADG with 11-18:1 (-0.38 ± 0.23) and SumCLA (-0.73 ± 0.26), implying that selection of beef cattle with a better growth rate will decrease the contents of healthy fatty acids 11-18:1 and SumCLA. Therefore, it is recommended that a multiple-trait selection index be used when genetic improvements of fatty acid composition, feed efficiency, feed intake, and growth are important in the breeding objective.

Breed dependent regulatory mechanisms of beneficial and non-beneficial fatty acid profiles in subcutaneous adipose tissue in cattle with divergent feed efficiency

“…When analyzing the FA profiles among the entire dataset, the predominant FAs identified from subcutaneous adipose tissue were C16:0 and C18:0 as SFA, c 9-18:1 as MUFA and 18:2n-6 as PUFA, which was comparable with the previous studies 36 – 38 . Breed effects on subcutaneous adipose tissue FA profiles have been widely reported for cattle.…”

“…The KC steers which were produced from crosses between Angus, Charolais or Alberta Composite bulls and University of Alberta Composite dam line 44 , showed uniquely high values in beneficial FAs ( c 9-18:1, CLA, t 11, t 13-18:2) and healthy FA index compared to ANG and CHAR steers, suggesting that beef products from KC may have more favorable FA profiles compared to ANG and CHAR breeds. Recently Zhang et al 38 have examined the heritability of individual FAs in subcutaneous adipose tissue of a large beef cattle population (N = 1,366) belonging to six different genetic backgrounds using two different matrices, and only identified weak to moderate heritability of 25 major FAs. Regardless the differences in the examined animal breeds between our study and Zhang et al 38 , significant variation among cattle breeds were also identified for most of these 25 FAs, suggesting that host genetics plays an essential role in regulating its subcutaneous adipose tissue FA profiles.…”

“…Recently Zhang et al 38 have examined the heritability of individual FAs in subcutaneous adipose tissue of a large beef cattle population (N = 1,366) belonging to six different genetic backgrounds using two different matrices, and only identified weak to moderate heritability of 25 major FAs. Regardless the differences in the examined animal breeds between our study and Zhang et al 38 , significant variation among cattle breeds were also identified for most of these 25 FAs, suggesting that host genetics plays an essential role in regulating its subcutaneous adipose tissue FA profiles. Similar to individual FAs, beneficial FA indicators n-6:n-3 ratio which indicates the percentage of beneficial FAs was found to be different across different breeds 45 .…”

Transcriptome analyses reveal reduced hepatic lipid synthesis and accumulation in more feed efficient beef cattle

“…The synthesized fatty acids are then used as substrates for biosynthesis of other lipids such as phospholipids, triglycerides and cholesterol esters. Therefore, differential expression of this gene between feed efficient and inefficient animals may contribute to the genetic linkage/correlations between feed efficiency and carcass fatty acid composition that have been reported in beef cattle 41 , 42 . Differential expression of the SCD gene between RFI divergent beef animals has been reported in pituitary, muscle, adipose and duodenum tissues where it was also downregulated in low-RFI Angus steers 28 .…”

Differences in liver microRNA profiling in pigs with low and high feed efficiency

“…In addition, ELOVL7 , a predicted target gene of miR-135a-5p, is down-regulated in liver of high-FE pigs. ELOVL7 is a key enzyme gene responsible for polyunsaturated fatty acid (PUFA) synthesis, and this gene has been reported to be associated with FE [ 62 – 65 ].…”