Melatonin alters bovine uterine artery hemodynamics, vaginal temperatures, and fetal morphometrics during late gestational nutrient restriction in a season-dependent manner

Abstract

The objectives were to examine melatonin mediated changes in temporal uterine blood flow (UBF), vaginal temperatures (VT), and fetal morphometrics in 54 commercial Brangus heifers (Fall, n = 29; Summer, n = 25) during compromised pregnancy. At d160 of gestation, heifers were assigned to 1 of 4 treatments consisting of adequately fed (ADQ-CON; 100% NRC; n = 13), global nutrient restricted (RES-CON; 60% NRC; n =13), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL, n = 13; RES-MEL, n = 15). In the morning (0500 h; AM) and afternoon (1300 h; PM) of d220 of gestation, UBF was determined via Doppler ultrasonography while temperature data loggers attached to progesterone-free CIDRs were used to record VT. At d240 of gestation, heifers underwent Cesarean sections for fetal removal and morphometrics determination. The UBF and VT data were analyzed using repeated measures of ANOVA; while the morphometrics were analyzed by the MIXED procedure of SAS. Seasons were analyzed separately. In Fall, a nutrition by treatment interaction was observed, where the RES-CON heifers exhibited reduced total UBF compared to ADQ-CON (5.67±0.68 vs. 7.97±0.54 L/min; P = 0.039). In Summer, MEL heifers exhibited increased total UBF compared to the CON counterparts (8.16±0.73 vs. 6.00±0.70 L/min; P = 0.048). Moreover, there was a nutrition by treatment by time interaction in VT for Fall and Summer heifers (P ≤ 0.005). In Fall, all groups had decreased VT in the morning compared to the afternoon (P < 0.05). Whereas, in Summer, VT increased for ADQ-CON and RES-CON (P < 0.0001) from morning to afternoon, while the ADQ-MEL and RES-MEL remained constant throughout the day (P = 0.648). Furthermore, the RES-MEL-PM exhibited decreased VT compared to ADQ-CON-PM (38.91±0.09 vs. 39.26±0.09°C; P = 0.018). Lastly, in Fall, a main effect of nutrition was observed on fetal weights, where the RES dams had fetuses with decreased body weight when compared to ADQ (24.08±0.62 vs. 26.57±0.64 kg; P = 0.0087). In Summer, a nutrition by treatment interaction was observed on fetal weights where the RES-CON dams had fetuses with reduced weight when compared to ADQ-CON and RES-MEL (P < 0.05). In summary, nutrient restriction decreased UBF and melatonin supplementation increased UBF depending on the season. Additionally, melatonin appeared to decrease VT and rescue fetal weights when supplemented in the Summer.

Effects of Maternal Nutrient Restriction and Melatonin Supplementation on Cardiomyocyte Cell Development Parameters Using Machine Learning Techniques

“…Maternal body weight results are further explained in Contreras-Correa et al [20]. Briefly, maternal body weight, fetal body weight, and fetal thoracic girth were decreased (p < 0.05) in RES-versus ADQ-fed heifers at day 240 of gestation (Table 1).…”

“…Eighty Brangus heifers were artificially inseminated using a single sire at the H. H. Leveck Animal Research Center (Starkville, MS, USA). Animal management and developmental programming results are further presented in [ 20 ]. Pregnancy was confirmed by day 35 post-insemination and only singleton bearing heifers were enrolled in the study.…”

“…Maternal body weight and fetal growth parameters from day 240 of gestation. Data adapted from Contreras-Correa et al[20].…”

Melatonin in Health and Disease: A Perspective for Livestock Production

“…Melatonin supplementation was shown to reduce core body temperature during daytime in humans; a drop of 0.30 °C was observed when supplemented with 5 mg of melatonin [ 54 ]. More recently, Contreras-Correa et al [ 42 ] reported that 20 mg/d of dietary melatonin decreased vaginal temperature in pregnant heifers during the summertime. Nevertheless, Samuel et al [ 55 ] reported no differences in rectal temperature in late gestational cows after supplementing with melatonin implants during summer.…”

Going Up Inflame: Reviewing the Underexplored Role of Inflammatory Programming in Stress-Induced Intrauterine Growth Restricted Livestock

“…Indeed, fetal hypoxemia and hypoglycemia in heat stress-induced sheep models of placental insufficiency can exceed 50% reductions near term ( Macko et al, 2016 ; Wai et al, 2018 ; Stremming et al, 2020 ), creating a clear need for changes in metabolic processes and growth trajectories ( Lackman et al, 2001 ; Gagnon, 2003 ). The phenomenon of fetal hypoglycemia can be partially mimicked by sustained maternal undernutrition, which can decrease fetal growth despite little or no impact on the size or vascularity of the placenta ( Lemley et al, 2012 ; Eifert et al, 2015 ; Edwards et al, 2020 ; Contreras-Correa et al, 2021 ). Interestingly, diminished placental transfer of amino acids due to downsizing of system A and L transporters does not necessarily manifest in reduced fetal blood concentrations ( Pantham et al, 2016 ; Wai et al, 2018 ), as the IUGR fetus compensates by slowing its protein utilization and accretion rates ( Rozance et al, 2018 ; Wai et al, 2018 ; Stremming et al, 2020 ).…”