Effects of mid-gestation supplementation with dried distillers’ grains and soybean hull-based total mixed ration silages on maternal metabolism, uteroplacental hemodynamics, and offspring development in beef cows

Maternal nutrition during gestation is a key determinant of maternal physiological adaptations and offspring developmental outcomes. This study evaluated how two total mixed ration (TMR)-based silages offered during mid-gestation influenced nutrient utilization, systemic physiology, uterine hemodynamics, and performance of pregnant beef cows and their offspring. Thirty-three multiparous Tabapuã cows (Bos taurus indicus) received one of the following treatments from day 130 to 230 of gestation: (1) TMR silage composed of Marandu grass and dried distillers' grains plus soluble (DDGS; n = 17); or (2) TMR silage composed of Marandu grass, soybean hulls (SH), and urea (n = 16). At day 230, all cows were regrouped and managed on pasture until calving. Cow-calf pairs remained together until weaning (∼175 d), after which calves were individually housed and monitored for 100 d. Maternal digestibility, nitrogen balance, and microbial protein synthesis were assessed at d 180; uterine blood flow was evaluated by Doppler ultrasonography at day 230 and 270; and maternal blood metabolites were measured at d 230. Statistical significance was declared at P ≤ 0.05. Cows fed DDGS-based TMR silage had greater dry matter (DM), crude protein, and neutral detergent fiber intakes (P ≤ 0.01), improved DM digestibility (P = 0.04), and increased nitrogen retention (P < 0.001) compared with SH + urea-based TMR fed cows. At day 230, DDGS-fed cows exhibited greater body weight (BW) and body condition score (BCS; P ≤ 0.04) and maintained higher BCS at calving (P < 0.01). Non-esterified fatty acids and beta-hydroxybutyrate concentrations were greater in SH + urea-fed cows (P ≤ 0.02), as was preprandial urea concentration (P < 0.01). At day 230, cows fed SH + urea and carrying female fetuses had greater pulsatility index, resistance index, and systolic/diastolic ratio (P ≤ 0.03). Maternal diet did not affect calf BW at birth, preweaning growth, or backgrounding performance (P ≥ 0.20). Milk yield tended to be greater at 60 d in milk (DIM) in SH-fed cows (P = 0.07), whereas milk composition was unaffected at either 60 or 120 DIM (P ≥ 0.21). Overall, mid-gestation supplementation with DDGS-based TMR silage improved maternal nutrient status, body condition, and uteroplacental adaptations, but no consistent effects on offspring growth were detected.