Investigation of DRD2
Adams, S., C. J. Kojima, J. Andrae, and S. Duckett.  2018.  Journal of Animal Science, Volume 96, Issue suppl_3, 7 December 2018, Page 208.

Abstract:
The objective of this study was to investigate effects of dopamine 2 receptor (DRD2) single nucleotide polymorphism (SNP; rs41749780) in cows grazing toxic or non-toxic tall fescue during the last trimester on cow and calf performance. Campbell et al. (2014) suggested the DRD2 SNP may play a role in Angus-based cattle grazing toxic tall fescue (E+). Pregnant cows (n = 250) were genotyped for the DRD2 SNP (AA, AG, GG). Cows with an AA or GG genotype (n = 77) were assigned within genotype to fescue treatment (E+: Kentucky 31; N: Jesup Max Q). Cows were allotted to fescue treatments by genotype in two pasture replicates for the last trimester of gestation. Cows grazed pastures and E+ or N hay was provided when grazing was limited. Data was collected at 30 d increments throughout late gestation including: hair coat score (HCS), body condition score (BCS), dam weights (BW). Calf birth weight, calf 30d weight, and weigh-suckle-weigh at 30 d of age were conducted. Data were analyzed in a 2X2 factorial model with dietary treatment (E+ or N), genotype (AA or GG), and the interaction in the model. Cows grazing E+ treatment had lower BW gain during the last trimester and had higher HCS than cows on N treatment (P< 0.05), but these variables were not altered by genotype. AA cows gained less rump fat during the last trimester than GG cows (P< 0.05). Calf birth weight tended to differ by dam genotype (P< 0.10) with AA calves weighing more at birth. Day 30 calf weights did not differ by dam genotype or fescue treatment. Milk production estimated by weigh-suckle-weigh at d30 of age did not differ by dam genotype or treatment. Grazing toxic fescue negatively impacted dam weight gain; whereas, dam genotype influenced calf birth weight and cow body condition.