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The objective was to determine if genetic markers related to mitochondrial function are associated with growth and feed intake of Bos taurus heifers fed forage-based diets. Weight data collected at birth, weaning, and as yearlings were available on 373 heifers. As yearlings, feed intake was measured using an Insentec system. Primary ancestral breeds of heifers included 204 British, 66 Continental European, 68 American Aberdeen, 29 British mix, and 6 American Aberdeen mix. Traits included DMI, ADG, G:F, adjusted birth weight (BWT), adjusted 205 weaning weight (WW), and average of start and end feed trial weight (FWT) and body volume (VOL). Heifers were genotyped using Neogen GGP150HD for beef cattle. Markers (n=56) were extracted if located within or flanking AMPK, PPARGC1A, FGF2, and SIRT1 or on mitochondrial DNA using ARS-UCD1.2 coordinates. After quality checks (minor allele frequency and call rate), 44 markers remained. No mitochondrial markers passed quality checks. For each trait, each marker was fit independently as a fixed effect in a model including year and group based on frame score (n=4), ancestry (n=5), and dam age (n=4; non-adjusted traits only). Pairwise comparisons were done using Tukey-Kramer method. No markers within FGF2 or SIRT1 had significant associations. Two markers were found significant for PPARGC1A, where Hapmap24121-BTC-039009 (P=0.0344) showed the C allele increased DMI. For weight traits, significant markers surrounding AMPK and within PPARGC1A (n=5; 0.0009≤P≤ 0.0468) identified dominance gene actions that indicate certain variants of the AMPK and PPARGC1A increased weight across time-points. For VOL, 16 of 22 markers within PPARGC1A were significant (0.0068≤P≤0.0467). Of the 16 markers, 14 identified a recessive variant that increased volume, but did not translate to increased weight. Further research is needed to better understand the roles that genetic markers for AMPK and PPARGC1A have on tissue level mitochondrial function and energy metabolism. |
