303 Identification of candidate genes related to temperament in Brahman cattle

Abstract

Abstract The objective of this study was to identify genomic regions and genes associated with beef cattle temperament. Temperament, measured as exit velocity (EV; m/s), was recorded in 1,370 Brahman cattle from Texas A&M AgriLife Research at Overton, TX. We identified two groups of temperament-contrasting animals. Cows were calm if their EV of 0.16–3.41 m/s and bulls if their EV was 0.4–3.12 m/s (n-119). Cows were temperamental if their EV was 3.55–7.66 m/s and bulls if their EV was 3.13–10.83 m/s (n = 79). The 198 animals were genotyped using the GGP-HD-150K chip. 139,376 SNPs were evaluated for association with temperament. 13 SNP′s were associated with EV (P < 4.0E-05). The SNPs GABRG2-26484, NRXN3-26436 and TBX20-191081 are located in introns of the GABRG2, NRXN3 and TBX20 genes, respectively. The GABRG2 gene encodes a GABA receptor, the major inhibitory neurotransmitter in the mammalian brain. The NRXN3 gene encodes receptor proteins related to chemical transmission at synapses. TBX20 is a member of the T-box transcription factor family expressed in the developing stages of heart, limbs, eye and ventral neural tube. To test the effect of these 3 SNP′s on EV, Pen-Score and Temperament-Score, a general linear model was fitted including the fixed effects of sex of calf and year of birth, and the individual effect of the 3 SNPs. The marker TBX20-191081 was associated with the three traits evaluated (P < 0.01), where the GG genotype was associated with the calmest temperament. The GG genotype had a significant effect on EV (P < 0.0001) that was 1.35 and 1.95 m/s slower than AG and AA, respectively. For TS, the GG genotype had a TS that was 1.41 and 1.24 DS less than those of the AA and GA genotypes. Our study indicates that genetic control of cattle temperament has a wide network of genes with divergent functions and genetic background specificity.