(265) Sexual Dimorphism of Supplementation with Rumen-Protected Methionine in Early Gestation in Beef Cattle Systems

Jose L. Infante-Cangrejo¹, Daniella C. Heredia¹, Maria C. Lopez-Duarte¹,Federico Tarnonsky^1, Vitoria Toffolo-Ruiz ¹, Mauro Venturini¹,Daniel Luchini², Peter J. Hansen¹, Nicolas DiLorenzo¹ Angela M. Gonella-Diaza¹.

¹ Department of Animal Sciences, University of Florida, Gainesville, USA.

² Adisseo USA Inc.

Abstract Text:

Maternal supplementation with rumen-protected methionine (RPM) has the potential to improve embryo development and subsequent calf performance, particularly when fed during early gestation. Previous data from our group indicated that male calves from dams supplemented with RPM during the periconceptional period were heavier at birth compared to control calves, while there were no differences in birth weight when comparing females, suggesting a possible sexually dimorphic response to RPM supplementation.We hypothesize that supplementing beef cows with RPM during the periconceptional period will influence embryo development, resulting in larger and heavier male calves with no differences in the females.In this study, lactating beef cows, from 58 ± 18 days postpartum were randomized to receive 454 g/d of corn gluten supplemented with 15 g/d of RPM (RPM; n =124) or not (CON; n = 126) from days −7 to 7 relative to timed-artificial insemination (TAI = day 0) using conventional semen from 2 bulls. Treatment supplementation was conducted using an automated feeder that allowed us to track supplement consumption and only animals with adequate and consistent supplement consumption remained in the study (CON; n = 69; RPM; n = 75). Cows were handled in 3 groups for easier management.On days 30 and 52, transrectal ultrasonography was conducted for pregnancy diagnosis and only pregnant cows (CON; n =27; RPM; n = 29) remain in the study. After calving, calves were weighed and identified with ear tags (CON; n =23; RPM; n = 25).Preliminary data was analyzed using the MIXED procedure of SAS (SAS Institute), using treatment, sex and their interaction as fixed effects, and group as random effect.Gestation length (CON: 273.95 ± 1 days; RPM: 274.50 ± 1 days; P = 0.73) and birthweight (CON: 33.15 ± 0.67 kg; RPM: 33.56 ± 0.62 kg; P = 0.64) were not affected by treatment or by treatment by sex interaction (P = 0.40). However, sex tended to affect birthweight where males were heavier than females (males: 34.11 ± 0.66 kg; females: 32.6 ± 0.63 kg; P = 0.09). Placenta length (CON: 60.64 ± 0.94 cm; RPM: 61.98 ± 0.88 cm) and weight (CON: 3059 ± 242.93 g; RPM: 3559 ± 243.87 g) were not different between treatments (P ≥ 0.05). At one month of age, there were no differences between treatment for body weight (CON: 33.15 ± 0.67 kg; RPM: 33.56 ± 0.62 kg; P = 0.64), hearth girth (CON: 74.53 ± 2.25 cm; RPM 73.83 ± 2.19 cm; P = 0.83), or hip height (CON: 65.99 ± 1.98 cm; RPM 66.76 ± 1.92 cm; P = 0.78). Sex affected body weight (males 56.55 ± 1.82 kg; females 51.17 ± 1.68 kg; P = 0.04), and there was a tendency for males to be longer than females (males: 60.59 ± 1.73; females: 56.23 ± 1.62; P = 0.07). These preliminary results suggest that RPM supplementation does not affect birth weight, gestation length, or placental traits. Further analyses are necessary to determine the long-term effects of RPM on postnatal performance.