Effect of chronic melatonin supplementation during mid to late gestation on maternal uterine artery blood flow and subsequent development of male offspring in beef cattle

Authors: MCCARTY, KEELEE - Mississippi State University; OWEN, MEGAN - Mississippi State University; HART, CAITLIN - Mississippi State University; THOMPSON, ROBYN - Mississippi State University; BURNETT, DERRIS - Mississippi State University; KING, E. HEATH - Mississippi State University; HOPPER, RICHARD - Mississippi State University; LEMLEY, CALEB - Mississippi State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2018
Publication Date: 12/6/2018
Citation: McCarty, K., Owen, M., Hart, C., Thompson, R., Burnett, D., King, E., Hopper, R., Lemley, C. 2018. Effect of chronic melatonin supplementation during mid to late gestation on maternal uterine artery blood flow and subsequent development of male offspring in beef cattle. Journal of Animal Science. 96:5100-5111.

Interpretive Summary: Uteroplacental blood flow is imperative for normal fetal development in livestock species. Oxidative stress during pregnancy may disrupt fetal development leading to intrauterine growth restriction and decreased birth weights. To combat these disorders, researchers are evaluating the mediators of uterine hemodynamics during pregnancy. However, a paucity of information exists on prenatal programming of testicular development, which may persist into the postnatal and mature stages of bull development. For this study, melatonin supplementation increased uterine artery blood flow in mid to late gestating cattle but this was not accompanied by an increase in fetal weight. However, postnatal growth was increased in offspring born to melatonin supplemented dams versus control supplemented.

Technical Abstract: The objective of the current study was to examine the effects of supplemental melatonin implants on uterine artery blood flow from mid to late gestation in beef cattle and subsequent development of their male offspring. Commercial beef heifers (n = 32) and cows (n = 25) were bred via artificial insemination and assigned to one of two groups supplemented with melatonin implants (MEL) or without (CON) at d 180, 210, and 240 of gestation. Uterine artery blood flow was determined using color Doppler ultrasonography. A subset of twelve crossbred heifers (n = 6 MEL; n = 6 CON) underwent Cesarean sections on d 243 ± 2 of gestation to allow for placentome collection. Maternal and fetal serum were collected to analyze melatonin concentrations. The remaining cattle were allowed to calve and at weaning (195 ± 2 d of age), bull calves (n = 15) were castrated and testicular tissue harvested for seminiferous tubule analysis. Heifer uterine artery blood flow was increased (P = 0.009) at d 240 of gestation in MEL compared with CON heifers. Cow uterine artery blood flow was increased (P = 0.003) in MEL compared with CON cows irrespective of gestational day. Maternal and fetal concentrations of melatonin were increased (P < 0.05) in MEL compared with CON heifers. The percent of placentome capillary area per mm2 was decreased (P = 0.019) in MEL compared with CON heifers, while cotyledonary ANGPT1 mRNA tended to increase (P = 0.095) in MEL compared with CON heifers. At weaning, body weight of male offspring and their scrotal circumference were increased (P < 0.05) in calves born to MEL compared with CON dams, while seminiferous tubule diameter and area were not different (P > 0.40) between treatments. In summary, melatonin supplementation increased uterine artery blood flow in mid to late gestating cattle, but this was not accompanied by an increase in fetal weight. Alterations in postnatal development of bulls, including increased body weight and scrotal circumference, warrants future investigations related to attainment of puberty and subsequent fertility of offspring born to melatonin supplemented dams.