PS11-9. Impacts of Maternal Prepartum Rumen Protected Choline Supplementation on Beef Calf Performance.

Abstract Prepartum supplementation of rumen protected choline (RPC) has increased milk production and colostrum yield in dairy cows and had positive impacts on feed efficiency and marbling in beef×dairy calves raised until processing. The objective of this study was to determine if maternal supplementation of RPC in pregnant beef cows would alter calf growth, blood metabolites, or total DNA methylation. Pregnant Angus cattle (n = 300 total) were supplemented RPC (60g/d/cow, ReaShure®, Balchem® or not (CTL), in a TMR fed on a pen basis for a target of 45d prepartum. Upon calving, calves were able to suckle their dams for 90d. At weaning, jugular blood samples (n = 79, randomly selected) were collected. Given the potential stress of weaning and exposure to pathogens, blood samples were also collected 3 wks after weaning. Blood was analyzed from all calves for cholesterol, BHB, BUN, glucose, FA, TG, and L-lactate. A subset of calves (n = 65) were selected for analysis of insulin, IGF-1, LBP, and total DNA methylation. Body weight and ultrasound measurements (n = 224) were taken at 1 year of age. Data were analyzed using mixed models (SAS 9.4). Variables were transformed for normality, and back-transformed means are presented. Due to the field nature of the study, statistical significance was declared at P ≤ 0.1, with tendencies defined as 0.10.15) of treatment (TRT) effect on birth or wean weight was observed. At weaning, RPC calves had decreased cholesterol (P = 0.06; 118.59, 106.11mg/dL) and glucose (P = 0.01; 71.48, 67.77mg/dL), but greater LBP concentrations (P = 0.03; 6.71, 8.05mg/L). Total DNA methylation did not differ (P = 0.80) by TRT. Males had decreased (P = 0.10) BUN (10.5, 11.3mg/dL) and insulin (P ≤ 0.01) concentrations compared to females (0.08, 0.14µg/L). There was a TRT×sex interaction where female RPC calves tended to have decreased (P = 0.11) TG concentrations (19.6, 17.5mg/dL). No differences (P > 0.15) were observed in FA, IGF-1, or L-lactate. These differences were maintained at 3 wks post-weaning, without additional differences. Body weights were similar between TRT groups at time of ultrasound (P = 0.70; 951, 947kg). Ultrasound ribeye area was smaller (P = 0.02) in RPC males compared to CTL (94.18, 91.56cm²). Backfat (0.66, 0.58cm) and adjusted rib fat (0.69, 0.61cm) was decreased (P < 0.004) in RPC animals. In males, adjusted ribeye area (P = 0.02) was smaller in RPC animals (94.17, 91.59cm²). Marbling and adjusted intramuscular fat (P ≥ 0.39) were not affected by TRT. Differences in cholesterol and glucose suggest that maternal supplementation of RPC may alter glucose and lipid metabolism. Decreases in ultrasound-measured rib fat are aligned with changes in glucose metabolism and, without associated differences in body weight, may suggest improved feed efficiency. Additional research is needed to measure feed efficiency and carcass characteristics.