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 1 of 2 groups supplemented with melatonin implants (MEL) or without (CON) at day 180, 210, and 240 of gestation. Uterine artery blood flow was determined using color Doppler ultrasonography. A subset of 12 crossbred heifers (n = 6 MEL; n = 6 CON) underwent Cesarean sections on day 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 day 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.

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The aim of this study was to evaluate the effect of bovine somatotropin (bST) on fetal and placental development during the first third of gestation in beef heifers. Angus heifers (n = 97) were randomly assigned to either receive a 500 mg injection of bST (BST) biweekly on d 0, 15, 29, 43, and 57 of gestation, or not receive bST (CTL) throughout the experiment. Body weight (BW) was assessed on d -9, -3, 0, 15, 22, 29, 43, 50, 57, 64, and 77, while blood samples were collected on d 0, 22, 50, and 64. Pregnancy status was determined via transrectal ultrasonography on d 29 and 64. A subset of pregnant heifers (BST, n = 7; CTL, n = 5) were harvested on d 84 and complete gravid reproductive tracts and liver tissue were collected for analysis. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A), and uridine 5’-diphospho-glucuronosyltransferase (UGT) activities were determined. Mean change in BW and average daily gain of heifers between fixed-time artificial insemination (d 0) and d 77 did not differ between treatments (P ≥ 0.05). Mean concentrations of insulin-like growth factor 1 (IGF-1) were greater (P &lt; 0.001) in BST (347 ± 27.7 ng/mL) compared to CTL (135 ± 32.8 ng/mL) heifers. Mean placental weight, fetal membrane weight, uterine weight, ovarian and corpus luteum (CL) weights, as well as fetal morphometric data did not differ (P ≥ 0.05) between treatments. However, BST heifers had greater (P = 0.03) quantities of combined fetal fluid compared to CTL (521.6 ± 22.9 g vs. 429.6 ± 27.14 g, respectively). Tendencies were observed for BST heifers to have reproductive tracts with fewer placentomes (P = 0.08) and fetuses with greater umbilical diameters (P = 0.09) compared to CTL. Activity of CYP1A did not differ (P ≥ 0.05) within maternal and fetal liver, caruncle, cotyledon, or CL tissue samples between treatments. Furthermore, CYP3A activity was only observed in maternal liver samples and was not different between treatments (P ≥ 0.05). Interestingly, CYP2C activity was greater (P = 0.01) in the liver of BST vs. CTL heifers, and UGT activity was greater (P = 0.02) in the CL from BST heifers compared to CTL. In conclusion, administration of bST during the first third of gestation increased plasma concentrations of IGF-1, which resulted in an increase in fetal fluid, decrease in placentome number, and greater umbilical diameter, but failed to alter fetal development.

One way to extend the grazing season in the southeast United States is to plant cool-season forages into native pastures to provide additional forages for the winter and spring grazing. The objective of this study was to evaluate the effects of two different medicated (Monensin) supplementation types, with or without protein, on stocker calves grazing native pasture overseeded with wheat through the months of February to May. Cross-bred steers (n = 36; BW = 291.76 kg ± 29.92) and heifers (n = 29; BW = 288.17 kg ± 25.22), sired primarily by Hereford bulls, were assigned to two treatment groups at two locations blocked by sex and weight. All mineral supplementation was provided ad libitum. The first supplementation consisted of a commercial loose mineral (Advanced Mineral Performance Technology (AMPT); ADM; Quincy, Illinois), and the second was a commercial protein block (MoorMan’s, Mintrate Blonde Block RU; ADM; Quincy, IL) containing 42.0% Crude Protein. Average Daily Gain was compared using PROC MIX with the main effects: treatment, pasture, gender, and their interactions. The starting weights of the treatment groups were not different (P = 0.996). No significant interactions (P &lt; 0.05) were detected and only the main effects will be reported. Steers gained more (P &lt; 0.0001) than heifers (1.25 kg ± 0.025 kg vs. 0.96 kg ± 0.029 kg, respectively). ADG for the mineral was 1.14 kg ± 0.027 kg, compared to 1.06 kg ± 0.028 kg for the protein block (P &lt; 0.05). Differences in ADG was observed between pastures (P &lt; 0.07). At 124 days the final body weight of heifers averaged 119.56 kg and the steers averaged 154.70 kg. These results indicate that the mineral improved ADG over the block supplementation.