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Browsing by Author "Guay, Jennifer Fincham"

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    Compatibility, Yield, and Quality of Matua Prairie Grass, Bromus willdenowii (Kunth), with Legumes
    Guay, Jennifer Fincham (Virginia Tech, 2003-12-08)
    Matua prairie grass has a potential to extend the grazing season in Virginia due to its higher early spring and fall production. However, little is known about the compatibility of Matua prairie grass with legumes or the effects of legumes on the yield and quality of Matua prairie grass/legume mixtures. An experiment was conducted in 1998 and 1999 to investigate the botanical composition, yield, and chemical composition of Matua prairie grass grown with legumes. Legume treatments consisting of ladino clover (Trifolium repens), red clover (Trifolium pratense), alfalfa (Medicago sativa), and annual lespedeza (Lespedeza stipulacea) were drilled into a Matua prairie grass stand. Nitrogen was applied once each fall at two treatment levels of 0 or 84 kg/ha. The experiment was arranged in a randomized split block design with four replications. Legume treatments had no effect on percentage Matua prairie grass or total dry matter yield in 1998. However, in 1999 the ladino clover and red clover treatments increased (P<0.05) total dry matter yield, but also resulted in a substantial decrease (P<0.05) in percentage Matua prairie grass. Nitrogen application in the fall of 1998 had a residual effect (P<0.05) on the percentage Matua prairie grass and yield in 1999. The highest response to nitrogen fertilization occurred in the harvest immediately after fertilization, in October of 1999, which resulted in the largest increase (P<0.05) in percentage Matua prairie grass and yield, and the greatest decrease (P<0.05) in percentage legumes. The legume and nitrogen treatments similarly influenced the chemical composition of the Matua prairie grass/legume mixed forage. Ladino clover, red clover, and alfalfa treatments generally improved forage quality as indicated by a decrease (P<0.05) in NDF, ADF, hemicellulose, and cellulose, and an increase (P<0.05) in CP and IVDMD. Nitrogen fertilization did not influence the chemical composition of the forages to the same extent as the legume treatments, as a decrease in fiber components and an increase in CP and IVDMD were observed due to nitrogen. Overall, alfalfa appeared to be most compatible with Matua prairie grass, and the incorporation of alfalfa into a Matua prairie grass stand resulted in some improvements in total dry matter yield and nutritive value of the forage, without the detrimental suppression of Matua prairie grass.
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    Fatty Acid Composition of Diets, Metabolism, and Deposition in Subcutaneous Adipose Tissue of Pasture and Feedlot Finished Cattle
    Guay, Jennifer Fincham (Virginia Tech, 2005-04-06)
    An experiment was conducted to evaluate the effects of pasture finishing versus high-concentrate finishing, over time, on fatty acid metabolism in Angus crossbred (n = 24) beef steers. Ruminal fluid, serum, and adipose tissue biposies were obtained on d 0, 28, 84, and 140. Pasture forages and diet ingredient samples were obtained at 14 d intervals to determine nutritive value and fatty acid composition. The high-concentrate diet consisted of corn silage, cracked corn, soybean meal, and a vitamin and mineral supplement. The pasture-finished steers grazed sequentially on triticale (Triticale hexaploide)/annual ryegrass (Lolium multiflorum), alfalfa (Medicago sativa)/orchardgrass (Dactylis glomerata), and a cool-season grass/legume mixture. The high-concentrate diet consisted of 57 % linoleic acid and 7 % linolenic acid (of total fatty acids). The pasture forages contained an average 9 % linoleic acid and 66 % linolenic acid (of total fatty acids). Adipose tissue concentrations of 18:2 cis-9, trans-11 CLA were higher (P < 0.05) in the pasture-finished steers than high-concentrate finished steers. Concentrations of 18:2 cis-9, trans-11 CLA declined in the high-concentrate finished steers (P < 0.05) from d 0 to 28 and d 28 to 84. In the pasture-finished steers concentrations peaked (P < 0.10) on d 28, and remained high throughout the duration of the study. Concentrations of linolenic acid were higher (P < 0.05) in adipose tissue, ruminal fluid, and serum of the pasture-finished steers, compared to the high-concentrate finished steers. In the pasture-finished steers linolenic acid concentrations peaked (P < 0.05) on d 28, and remained high throughout the study. Concentrations of linolenic acid gradually decreased (P < 0.05) over time within the high-concentrate finished steers. Thus, it appears that only a short time is needed to alter the omega-3 and CLA composition of adipose tissue in cattle finished on pasture.