Recipient Organization
UNIVERSITY OF ARKANSAS
(N/A)
FAYETTEVILLE,AR 72703
Performing Department
(N/A)
Non Technical Summary
The predominant cool-season forage in the southeastern U.S., endophyte-infected tall fescue (toxic fescue), negatively impacts health and performance of livestock, contributing to over $1 billion in annual agricultural loses. The endophyte in toxic fescue produces ergot alkaloids that lead to peripheral vasoconstriction and fescue toxicosis. While negative effects of toxic fescue on livestock have been long-established, an effective and cost-efficient therapeutic has not yet been identified and introduced into practice. Furthermore, limited research has evaluated the effects of ergot alkaloids consumed by pregnant dams on offspring health and performance. In agreement with our preliminary results, calves born to dams exposed to toxic fescue during mid to late gestation had decreased birth and weaning weights. Additionally, toxic fescue consumption reduced uterine artery and vein cross-section areas in pregnant heifers, consistent with our recent findings demonstrating decreased uterine artery blood flow in pregnant heifers consuming toxic relative to endophyte-free fescue seed. Melatonin implants have been associated with increased uterine artery blood flow and subsequent weaning weight of calves born to melatonin-treated dams. Our preliminary results showed that supplementing pregnant heifers consuming toxic fescue seed with melatonin during late gestation resulted in increased birth, weaning, and postweaning body weights of offspring. Our overarching goal is to identify novel methods to improve postnatal health and performance phenotypes of offspring born to dams grazing toxic fescue during gestation. Specific objectives are to 1) Determine the effects of melatonin supplementation on uterine and coccygeal artery hemodynamics in pregnant cattle grazing toxic fescue, and 2)Assess growth performance-related phenotypes of calves born to dams grazing toxic fescue and supplemented with or without melatonin during gestation.Supplementing dams grazing toxic fescue with melatonin is expected to improve uterine and coccygeal artery hemodynamics, and thereby decrease toxic fescue-associated reductions in growth performance of offspring. Accomplishing our specific objectives is expected to not only provide an essential start to filling a profound gap in the current literature, but it also has the potential to provide a cost-effective therapeutic that could be quickly incorporated into practice. For example, powdered melatonin, 50 mg, can be purchased and packed into implant shells for approximately$1.20/implant. Therefore, melatonin supplementation in pregnant cattle grazing toxic fescue has the potential to not only improve offspring growth performance but increase producer return on investment.
Animal Health Component
40%
Research Effort Categories
Basic
60%
Applied
40%
Developmental
(N/A)
Goals / Objectives
Specific Objective #1: Determine the effects of melatonin supplementation on uterine and coccygeal artery hemodynamics in pregnant cattle grazing toxic fescue.Specific Objective #2: Assess growth performance-related phenotypes of calves born to dams grazing toxic fescue and supplemented with or without melatonin during gestation.
Project Methods
Specific Objective #1: A total of 150 multiparous fall-calving commercial beef cows at the Livestock and Forestry Research Station (Batesville, AR) will be bred by artificial insemination using male sex-sorted semen from a single sire to target 75 bred cows. Cattle will be fed a mineral and vitamin supplement and supplemented with mixed grass hay (primarily bermudagrass) as needed. Pregnant cows (n = 75) will be stratified randomly into 1 of 3 treatment groups based on maternal body weight at 150 days of gestation. Treatments will include pregnant cattle grazing toxic fescue and supplemented with melatonin (n = 25), pregnant cattle grazing toxic fescue without melatonin (n = 25), and pregnant cattle grazing non-toxic, novel endophyte-infected fescue without melatonin (n = 25) for a 70-day period (day 158-228 of gestation) between May and July. Prior to and following the 70-day period, cows will be maintained in replicated non-toxic fescue pastures, each with equal representation of treatment groups. During the 70-day period, cattle will be maintained in replicated toxic or non-toxic fescue pastures at equal stocking rates. Melatonin will be preparedby mixing powdered melatonin (Cayman Chemical Company; Ann Arbor, MI) in 100% ethanol and the solution mixed with feed at a target dose modeled after preliminary studies of 100 μg/kg of body weight. Cattle will be fed according to body weight using C-Lock SmartFeed Pro (Rapid City, SD) controlled feeding units, with daily access to allotted feed limited to between 9 a.m. and 12 p.m. Cattle will be weighed every 2 weeks and diets adjusted for change in body weight. Each replicated toxic fescue pasture will contain cattle supplemented feed with and without melatonin, while each replicated non-toxic pasture will only contain cattle supplemented feed without melatonin (equal stocking rates will be maintained among all pastures). At days 156 ± 3 and 226 ± 3 (beginning and end of 70-day period), Doppler ultrasonography will be conducted on the uterine and coccygeal arteries. Blood samples will be collected for quantification of prolactin, melatonin, and total antioxidant capacity. Forage samples will be collected from pastures for ergovaline and ergovalinine quantification every 2 months during the period prior to and following the 70-day period. Forage samples will be collected from pastures for a full ergopeptine alkaloid and ergovaline quantification at the beginning and end of the 70-day period. Approximately 5 samples/hectare will be hand-clipped to a 5-cm stubble height, placed immediately on ice, and stored at -80°C prior to and following lyophilization.Specific Objective #2: Calves (n = 75) born to dams in Specific Objective #1 will be evaluated in Specific Objective #2. Based on preliminary results indicating melatonin's potential to recover toxic fescue-associated losses in calf growth performance, we propose the evaluation of growth performance-related phenotypes in calves born to dams grazing toxic fescue with or without melatonin. To evaluate the influence of gestational treatment on dam milk yield and its association with calf growth performance, a weigh-suckle-weigh method will be used to evaluate milk production (n = 75) at days 60 and 90 post-calving. To monitor calf growth, calves (n = 75) will be weighed every 28 days between weaning and day 112 postweaning. Calves (n = 75) will undergo body composition ultrasounds at weaning and at 112 days postweaning to estimate REA, REA/cwt (REA/45.5 kg of body weight), rib fat, and rump fat. Because both melatonin and toxic fescue have independently been associated with changes to the microbiome, fecal samples will be collected from pregnant dams prior to and following the 70-day period and again at calving for microbiome analysis. These samples will be compared to corresponding calf fecal microbiome samples taken at birth, weaning, 56 days postweaning, and 112 days postweaning (n = 36 dam and 36 offspring samples for microbiome analysis). A glucose tolerance test will beconducted a minimum of 28 days after weaning on a subset of steer calves (n = 36). Specifically, glucose, insulin, NEFA and blood urea nitrogen (BUN) will be evaluated in response to the intravenous administration of a 50% dextrose solution (0.5 mL/kg of body weight). Calves (n = 75) will undergo a 56-day feed intake and efficiency trial a minimum of 2 weeks after the glucose tolerance test. Calves will be housed on concrete and offered a total mixed ration for ad libitum intake using C-Lock SmartFeed Pro controlled feeding units. Cattle will be weighed on day 0, 1, 28, 56, and 57. Beginning on day 30, digestibility will be evaluated in a subset of calves (n = 36) by incorporating titanium dioxide (TiO2) into the diet at 1.5 g TiO2/kg and fecal samples collected twice daily (composited by calf) between day 35 and 42 (Glindemann et al., 2009). Fecal TiO2 concentrations will be used to estimate fecal output. Digestibility will be calculated as intake minus fecal output divided by intake. Cattle (n = 75) will be shipped to the Tri-County Steer Carcass Futurity (Lewis, IA) to obtain feedlot performance data, hot carcass weight, dressing percent, fat cover, REA, REA/cwt, %KPH (percent kidney, pelvic, and heart fat), yield grade, percent retail product, marbling score, and quality grade.