The objective was to evaluate the influence of prenatal exposure to endophyte-infected tall fescue (toxic fescue) on postweaning glucose metabolism in crossbred steers. Pregnant multiparous cows (n = 36) were maintained on replicated novel or toxic fescue pastures throughout gestation and bermudagrass pastures following calving. From the subsequent calf crop, weaned steers (257±28 d of age) of similar body weight (234±32 kg Toxic; 236±44 kg Novel) were randomly selected (n = 8 Toxic; n = 7 Novel) for a glucose tolerance test. Steers were fitted with jugular vein catheters and fasted for a minimum of 12 h before intravenous administration of a 50% dextrose solution (0.5 mL/kg of body weight). Blood was collected at -10, 0, 10, 20, 30, 45, 60, 90, 120, and 150 min (0 min=glucose administration). Plasma glucose and serum insulin were determined by hexokinase colorimetric assay and radioimmunoassay, respectively. Glucose, insulin, and the insulin to glucose (I:G) ratio were analyzed using MIXED procedures of SAS specific for repeated measures with treatment as a fixed effect and sire as random. All other variables were analyzed using MIXED procedures of SAS with treatment as a fixed effect and sire as random. As expected, glucose, insulin, and the I:G ratio increased in response to glucose administration (time P < 0.01). There was no effect of treatment (P > 0.39) or the treatment by time interaction (P > 0.19) for glucose, insulin, or the I:G ratio. However, Toxic steers exhibited numerically increased glucose, decreased insulin, and decreased I:G ratios relative to Novel steers following glucose administration. There was no difference (P > 0.13) in baseline, peak, time at peak, or time at return to baseline concentrations for insulin or glucose. While prenatal exposure to toxic fescue did not influence glucose or insulin homeostasis in response to exogenous glucose administration in this preliminary study, numerical differences warrant future evaluation with increased animal numbers.
The objective was to evaluate growth performance and estimates of body composition in offspring of dams that consumed diets containing tall fescue seed with (E+) or without (E-) the toxic endophyte and with or without melatonin during mid-late gestation. Pregnant heifers (n = 57) artificially inseminated with sex-sorted semen (X chromosome-bearing sperm) from a single Angus sire were administered dietary treatments in a 2 x 2 factorial treatment arrangement (E- without melatonin, E-/NM; E- with melatonin, E-/M; E+ without melatonin, E+/NM; or E+ with melatonin, E+/M; melatonin dose: 100 µg/kg of BW) for a 70-d period between May and July starting at 160 ± 13 days of gestation to mimic ergot alkaloid concentrations in a grazing scenario. All diets contained corn gluten and molasses and were fed using SmartFeed Pro (C-Lock Inc.) controlled feeding units between 0900 and 1400 h daily. Cattle were removed from dietary treatments 39 ± 19 days before calving. Two replicates were housed separately in an open-air barn, each with a 1.2-ha paddock. before and following the 70-d treatment period, all cattle were maintained as a single group free from toxic fescue. Calves were weaned at 226 ± 19 d of age. Gestation length, calf birth weight, 205-day adjusted weaning weight (205-d WW), carcass ultrasonography measures (ribeye area, REA; REA/CWT; percent intramuscular fat, IMF; rib fat thickness, UFAT; rump fat thickness, URUMP), post-weaning weights (recorded every 28 days between weaning and 84 days post-weaning), and post-weaning ADG (between weaning and 84 days post-weaning) were evaluated in offspring (n = 44). Post-weaning calf weights were analyzed using the MIXED procedure of SAS specific for repeated measures with treatment and time as fixed effects and replicate as random. All other variables were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and replicate as random with gestation length as a covariate for birth weight. Gestation length, birth weight, 205-d WW, and post-weaning calf weight were decreased (P < 0.04) in offspring of dams that consumed E+ relative to E- during gestation. Birth weight was increased (P = 0.02) in offspring of dams receiving melatonin relative to those without melatonin during gestation. The 205-d WW and REA were decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P < 0.03). Post-weaning weight tended to be decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P = 0.06). UFAT tended to be decreased (P = 0.06) in offspring of dams that consumed E+ relative to E- during gestation. There were no other effects of treatment, time or the interaction (P > 0.10). To our knowledge, these preliminary results are the first to evaluate the potential of melatonin as a therapeutic to recover performance losses in offspring born to pregnant cattle consuming toxic fescue.
The objective was to evaluate growth performance and estimates of body composition in offspring of dams that consumed diets containing tall fescue seed with (E+) or without (E-) the toxic endophyte and with or without melatonin during mid-late gestation. Pregnant heifers (n = 57) artificially inseminated with sex-sorted semen (X chromosome-bearing sperm) from a single Angus sire were administered dietary treatments in a 2 x 2 factorial treatment arrangement (E- without melatonin, E-/NM; E- with melatonin, E-/M; E+ without melatonin, E+/NM; or E+ with melatonin, E+/M; melatonin dose: 100 µg/kg of BW) for a 70-day period between May and July starting at 160±13 d of gestation to mimic ergot alkaloid concentrations in a grazing scenario. All diets contained corn gluten and molasses and were fed using SmartFeed Pro (C-Lock Inc.) controlled feeding units between 0900 and2 1200 h daily. Cattle were removed from dietary treatments 39 ± 19 d before calving. Two replicates were housed separately in an open-air barn, each with a 1.2-ha paddock. Prior to and following the 70-d treatment period, all cattle were maintained as a single group free from toxic fescue. Calves were weaned at 226 ± 19 d of age. Gestation length, calf birth weight, 205-day adjusted weaning weight (205-d WW), carcass ultrasonography measures (ribeye area, REA; REA/CWT; percent intramuscular fat, IMF; rib fat thickness, UFAT; rump fat thickness, URUMP), post-weaning weights (recorded every 28 d between weaning and 84 d post-weaning), and post-weaning ADG (between weaning and 84 d post-weaning) were evaluated in offspring (n = 44). Post-weaning calf weights were analyzed using the MIXED procedure of SAS specific for repeated measures with treatment and time as fixed effects and replicate as random. All other variables were analyzed using the MIXED procedure of SAS with treatment as a fixed effect and replicate as random with gestation length as a covariate for birth weight. Gestation length, birth weight, 205-d WW, and post-weaning calf weight were decreased (P < 0.04) in offspring of dams that consumed E+ relative to E- during gestation. Birth weight was increased (P = 0.02) in offspring of dams receiving melatonin relative to those without melatonin during gestation. The 205-d WW and REA were decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P < 0.03). Post-weaning weight tended to be decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M (P = 0.06). The UFAT tended to be decreased (P = 0.06) in offspring of dams that consumed E+ relative to E- during gestation. There were no other effects of treatment, time or the interaction (P > 0.10). To our knowledge, these preliminary results are the first to evaluate the potential of melatonin as a therapeutic to recover performance losses in offspring born to pregnant cattle consuming toxic fescue.
The objective was to examine the influence of prenatal (Experiment 1) or postnatal (Experiment 2) exposure to gossypol from cottonseed meal (CSM) on semen quality in commercial boars. In Experiment 1, pregnant sows (n = 5) were fed a diet containing 0% (n = 1), 0.04% (n = 2), or 0.08% (n = 2) gossypol between d 56 and 86 of gestation. Boars (n = 11) born to sows in each treatment group (0% gossypol n = 3; 0.04% gossypol n = 4; 0.08% gossypol n = 4) were fed a common diet without CSM, and semen was collected at 269±2 d of age using a live sow in estrus. In Experiment 2, boars (n = 21) were fed a diet containing 0%, 0.02%, or 0.04% gossypol between 63±1 and 105±1 d of age (Initial BW: 19.85±0.43 kg). After the treatment period, boars were fed a common diet without CSM, and semen was collected at 238±7 d of age using a breeding dummy. Sperm cell concentration, percentage of motile sperm cells, and percentage of progressively motile sperm cells were analyzed using the MIXED procedure of SAS with treatment as a fixed effect in Experiment 1 and 2 and dam as a random effect in Experiment 1. In Experiment 2, semen was not successfully collected from every boar; therefore, chi-square analysis was used to assess semen collection status between treatment groups using the FREQ procedure of SAS. In Experiment 1, there was no difference in sperm concentration (P = 0.45), percent motility (P = 0.71), or percent progressive motility (P = 0.27) between treatment groups. In Experiment 2, there was no difference in sperm concentration (P = 0.72), percent motility (P = 0.17), or percent progressive motility (P = 0.87) between treatment groups. No difference was observed in boar collection status between treatment groups (P = 0.77). In conclusion, prenatal or postnatal exposure to gossypol from CSM did not influence semen quality in commercial boars.
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