Impact of dietary supplementation of beef cows with rumen-protected methionine during the periconceptional period on prenatal growth and performance to weaning.

Changes in maternal nutrition during the periconceptional period can influence postnatal growth in cattle. This study aimed to identify the impact of supplementing beef cows with rumen-protected methionine (RP-Met) during the periconceptional period on their female progeny. In experiment 1, plasma methionine (Met) levels were analyzed in samples from 10 Angus crossbred, non-lactating beef cows. Cows were randomly assigned to receive 454 g of cottonseed meal with 15 g/d of RP-Met (RPM; Smartamine M, Adisseo) or not (CON) for 5 d and data were analyzed as a completely randomized design with repeated measures. A treatment-by-day interaction was observed (P < 0.001), where plasma Met concentrations increased in the RPM treatment yet remained basal in CON. In experiment 2, 114 cows were fed a roughage-based diet and randomized to receive 454 g/d of corn gluten supplemented with 15 g/d of RP-Met (RPM n = 56) or not (CON n = 58) from days -7 to 7 relative to timed-artificial insemination using sexed semen to obtain females. Amino acids were measured in plasma samples from days -8, 0, and 7 in cows. In the female progeny, body weight, withers height, body length, and heart girth were measured every 60 d from birth through weaning at an average age of 242 ± 5.8 d. Liver, adipose tissue, and longissimus dorsi muscle biopsies were collected at 187.88 ± 5.5 d of age and a subset of 20 random samples (CON = 10; RPM = 10) were selected for RNA-seq on each tissue. Data were analyzed using a generalized randomized block design with repeated measures. Methionine was increased (P < 0.01) in plasma from cows in the RPM treatment on days 0 and 7. After calving, 34 female calves (CON = 16; RPM = 18) remained in the study and no difference was observed in birth weights between treatments. Calves were taller at the withers for RPM than CON (P = 0.03; CON = 92 ± 1.0 cm; RPM = 95 ± 1 cm) but there were no effects of treatment on other measures of body size. A total of 30, 24, and 2 differentially expressed genes (DEGs; P < 0.01) were observed in liver, longissimus dorsi muscle, and adipose tissue respectively. In summary, feeding RP-Met to cows in the periconceptional period resulted in female calves that were taller than CON before weaning. There were DEGs in the tissue samples but no other changes in measurements associated with body size. In conclusion, supplementation of RP-Met to beef cows during the periconceptional period caused minor changes in the female offspring before weaning.