Gestational Vitamin and Mineral Supplementation in F0 Beef Heifers: Impacts on F1 Heifer Nutrient Digestibility, Metabolic Balance, and F1 Dam and F2 Fetus Development

Angus-based heifers (F0; n = 72; 14 to 15 mo; initial body weight [BW] = 380.4 ± 50.56 kg) were ranked by BW, bred via artificial insemination (AI) with female-sexed semen, and assigned to receive a basal diet (CON; n = 36) or the basal diet plus a vitamin and mineral supplement (VTM; n = 36) with the total mixed ration. Treatments were applied from breeding through calving, after which cow-calf pairs (n = 14 CON; n = 17 VTM) received a common diet. A subset of F1 heifers (n = 7 CON; n = 9 VTM) were bred via AI with female-sexed semen and evaluated from breeding through d 250 of gestation when pregnant heifers were slaughtered. Nutrient balance and energy metabolism were measured each trimester via apparent total tract digestibility and indirect calorimetry. Blood samples were collected each trimester and at harvest for hormone/metabolite analysis. Data were analyzed using the MIXED procedure of SAS with repeated measures where appropriate, with treatment, time, and interaction included as fixed effects and animal as the experimental unit. In F1 heifers, digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, and N was not influenced by treatment (P ≥ 0.21) but decreased (P ≤ 0.03) as gestation advanced. Fecal energy (FE) losses, heat production (HP) as a percentage of gross energy intake, and retained energy (RE) were not affected by treatment (P ≥ 0.52); however, FE and HP increased (P ≤ 0.03) while RE decreased (P = 0.01) with advancing gestation. Circulating insulin concentration was greater (P < 0.01) in VTM heifers, whereas glucose decreased (P < 0.01) and non-esterified fatty acids and blood urea nitrogen increased (P ≤ 0.01) as gestation progressed. Body weight was greater (P < 0.01) in VTM heifers and at slaughter, VTM heifers tended (P ≤ 0.10) to have heavier carcasses and greater ribeye area than CON. The F1 CON heifers had heavier spleens relative to BW (P = 0.04) whereas other organs did not differ (P ≥ 0.17). In F2 fetuses, CON tended to have heavier reproductive tracts and spleens (P ≤ 0.10) with no other differences in organ weights (P ≥ 0.13), whereas VTM fetuses had greater (P = 0.01) blood glucose concentration. These results indicate that prenatal micronutrient supplementation programs growth and metabolic function across generations, with minimal effects on organ mass. Advancing gestation reduced efficiency of energy and nitrogen use, reflecting nutrient partitioning shifts supporting fetal growth.