Browsing by Author "Smith, S. Raymond"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Effect Of A Cidr Insert And Flunixin Meglumine Administered At The Time Of Embryo Transfer On Pregnancy Rate And Resynchronization Of Estrus In Beef CattlePurcell, Scott Hudson (Virginia Tech, 2004-06-23)The objectives of this study were to evaluate the effects of flunixin meglumine (FM), an inhibitor of PGF2a synthesis, administered at the time of embryo transfer (ET) and insertion of an intravaginal progesterone-releasing device (CIDR) at the time of ET on pregnancy rates (PR) and the resynchronization of estrus. Beef cows (n = 796) and heifers (n = 108) at three locations were assigned randomly within age to one of four groups in a 2 x 2 factorial arrangement of treatments with injection of FM (500 mg i.m.; Phoenix Scientific, St. Joseph, MO) 2 to 12 min prior to ET and insertion of a CIDR (1.38 g progesterone; Pfizer, New York, NY) for 13 d immediately following ET as main effects. Fresh or frozen embryos (Stage = 4 or 5; Grade = 1 or 2) were randomly assigned to be transferred to recipients on d 6 to 9 of the estrous cycle. At Location 2 a subset of fresh embryos were split and transferred as fresh half embryos (n = 192). Recipients at Location 2 only (n = 493) were observed for signs of return to estrus beginning 9 d after ET. Recipients that returned to estrus at Location 2 were either bred by AI 12 h after estrus or received an embryo 7 d after estrus. Pregnancy was diagnosed by ultrasonography. Pregnancy rates were analyzed using the LOGISTIC procedure of SAS. Pregnancy rates of split embryo recipients were analyzed separately using the same statistical procedure. Variation in the timing of the return to estrus was determined by an F-test for heterogeneity of variances. Following the initial ET, pregnancy rates of recipients receiving whole embryos were not affected by CIDR administration (P > 0.05; 65% with CIDR, 70% without CIDR), however, there was a significant FM x location interaction on PR (Location 1, 89 vs. 57%; Location 2, 69 vs. 64%; Location 3, 64 vs. 67% for FM vs. no FM, respectively). There was a significant CIDR x FM interaction on PR of recipients receiving split embryos. Pregnancy rates of split embryo recipients receiving CIDR treatment (54%) or FM treatment alone (41%) were less than controls (64%). However, recipients receiving both CIDR and FM had PR similar to controls (60%). The timing of the return to estrus was more synchronous (P < 0.01) for recipients fitted with a CIDR, but PR of recipients bred following a return to estrus did not differ in cows receiving or not receiving a CIDR (P > 0.13; 68 and 62%, respectively). Effects of FM on PR were location dependent and CIDR insertion at ET improved synchrony of the return to estrus.
- Management and Livestock Performance of Alfalfa-Tall Fescue Mixed StandsRaines, Pepper Monique (Virginia Tech, 1998-03-15)Tall fescue (Festuca arundinacea Schreb.) and alfalfa (Medicago sativa L.) have many desirable forage attributes, are grown extensively throughout the USA, and combined form a productive pasture mixture. The objective of this research was to develop recommended management practices for alfalfa-tall fescue mixtures and compare livestock performance, forage quality, and productivity of this mixture to N-fertilized endophyte-free tall fescue. Forty-eight Angus or Angus crossbred steers were rotationally stocked on a four-replicate alfalfa-tall fescue and N-fertilized tall fescue pasture system during 2002 and 2003. Livestock gain, forage quality, and forage production were monitored throughout the seasons. Management treatments conducted within wire exclosures included defoliation height, rest period, exclosure movement, and month and were evaluated using detailed botanical composition and persistence measurements. Defoliation height, rest period, and month all affected alfalfa-tall fescue competition. Alfalfa was generally more competitive with longer rest periods and shorter heights, although results were not consistent. Alfalfa composition and persistence declined dramatically over the 2003 season due to climate, grazing management, and cultivar. Cool, high moisture conditions stimulated tall fescue growth and reduced alfalfa vigor and survival. Livestock gains were higher for pure tall fescue at one date in 2002, but higher overall for alfalfa-tall fescue during 2003. Forage quality (CP, NDF and ADF) was consistently higher for alfalfa-tall fescue during both seasons. In conclusion, both alfalfa-tall fescue and N-fertilized endophyte-free tall fescue produce productive pastures and high ADG in beef steers in Virginia, but continued management research is required to maintain the alfalfa component of this mixture.
- Phosphorus Losses from Simulated Dairy Mangement Intensive Grazing Forage SystemTeany, Laura Ellen (Virginia Tech, 2004-09-22)Dairy producers across the country are evaluating the effectiveness of management intensive grazing (MIG) systems as a means of reducing the economic pressures of confinement feeding and manure handling. Systems using MIG have been promoted as an environmentally safer way of managing nutrient balance on Center. However, little research has been conducted to evaluate how these systems affect phosphorus (P) loss from the Center through runoff and forage removal. The goal of this study was to investigate the effects of forage type and manure density on P levels in runoff from release plots that simulated a MIG dairy system. Two forage treatments were planted on runoff release plots and applied with three manure density treatments and four replications of each combination for a total of 24 plots. Orchardgrass (Dactylis glomerata) and a broad-leafed forage treatment consisting of buckhorn plantain (Plantago lanceolata), red clover (Trifolium pratense), and alfalfa (Medicago sativa) were planted on the runoff release plots in early spring. Manure densities with no manure (control), a density simulating a low stocking density (low), and a density simulating high stocking density (high) were applied to plots during grazing simulations. Six rainfall simulations were conducted over the season simulating grazing conditions when forage was removed and re-growth conditions when forage had reached its target re-growth height before re-grazing occurred. Thirty minutes of runoff was collected from the runoff release plots to determine first flush phosphorus losses from the various treatments. Mass losses of total phosphorus (TP) for manure treatments in series 1 were significant due to plot installation disturbance. No significant effect for ortho-phosphorus (ortho-P), particulate phosphorus (PP) or TP concentration or mass losses were observed for other simulation series. Significantly higher mass losses were observed in series 1 for both forage treatments, again due to installation disturbance. Seasonal mass losses for TP were significantly lower for the orchardgrass treatment. Forage mass removal over the season increased as the stands established. Orchardgrass treatments appeared to control P losses earlier in the season, while broadleaf treatments observed a steady increase in ortho-P losses up to series 5. Both mass and concentration losses of TP were controlled earlier in the season by orchardgrass, while PP showed no significant mass or concentration loss effects.
- Yield, Quality, and Botanical Composition of Autumn-Accumulated Grass-Legume Mixtures and Digestibility of Ensiled Autumn-Accumulated Orchardgrass and AlfalfaBarlow, Rebecca Louise (Virginia Tech, 2003-09-11)Beef cattle producers in the southeastern US often stockpile forage in late summer to extend the grazing season and reduce feeding costs. Three stockpiled grass-legume mixtures were evaluated for winter grazing. In addition, stockpiled forages were ensiled and evaluated as livestock feed. Four accumulation dates and seven harvest dates were randomized to small plots of tall fescue (Festuca arundinacea Schreb.) -red clover (Trifolium pratense L.), orchardgrass (Dactylis glomerata L.) -red clover, and orchardgrass-alfalfa (Medicago sativa L.). The amount of grass and legume in the fescue-red clover mixture shifted from less than 30% grass and more than 60% legume in October to over 60% grass and less than 10% legume in April. All forage mixtures contained at least 15% CP from November to March. Fescue-red clover was higher in TNC and lower in NDF, ADF and cellulose in January and March than the orchardgrass-legume mixtures. Fescue-red clover was higher in yield than the orchardgrass-legume mixtures from November to February. Delaying stockpiling until September 1 or 15 increased (P <.05) legume content and decreased dead grass content in orchardgrass-clover and orchardgrass-alfalfa. Accumulating growth from September 15 increased percent CP in fescue-red clover and orchardgrass-clover, compared to August 15, and decreased percent NDF in all forage mixtures. Percent IVDMD increased in orchardgrass-clover when stockpiling was delayed until September 15. May yields decreased only in orchardgrass-alfalfa when stockpiling was delayed until September. Orchardgrass stockpiled on August 3 and September 3, and alfalfa stockpiled on September 3 were ensiled alone. Chemical composition of silages was determined after 90 d of fermentation. Silages averaged 16.0% CP and 44.7% NDF. Digestibility of the ensiled stockpiled forages was estimated using acid insoluble ash as a marker with 18 wether lambs. No differences were observed in DM or CP digestibility, but NDF digestibility was lower for alfalfa silage than for orchardgrass silages. All stockpiled grass-legume mixtures provided high quality winter grazing, and all silages were of good quality and digestibility. Fescue-red clover maintained both good quality and higher yield than the other mixtures. Ensiling stockpiled alfalfa and orchard grass provided a method of maintaining CP and digestibility for subsequent feeding.