Browsing by Author "Kuehn, Larry Alexander"

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    Cytokine mRNA Expression in the Small Intestine of Weanling Pigs Fed Diets Supplemented with Specialized Protein or Peptide Sources
    Zhao, J.; Harper, Allen F.; Webb, Kenneth E. Jr.; Kuehn, Larry Alexander; Gilbert, Elizabeth R.; Xiao, X.; Wong, Eric A. (2008-12)
    Cytokines play a central role in the mucosal immune response and are involved in regulation of nutrient absorption, metabolism and animal growth This study investigated the effect of diet manipulation with specialized protein or peptide sources on expression of cytokine (IL-1, IL-6, IL-10, and TNF-alpha) mRNA abundance in different intestinal regions and at different ages post-weaning in piglets. A total of 48 (17 days of age, 6.16 +/- 0.34 kg BW) weanling pigs were fed either a corn-soy/whey protein basal diet, the basal diet supplemented with spray-dried plasma protein (SDPP), or the basal diet supplemented with Peptiva (R), a hydrolyzed marine plant protein. A fourth treatment group was fed the SDPP diet, but the feed intake level was limited (SDPP-LF). Pigs were killed at 3 and 10 d, and intestinal cytokine mRNA was measured by real-time PCR using the relative quantification method. The SDPP-LF group exhibited an increased TNF-alpha mRNA abundance compared with the ad libitum SDPP group (p<0.05). The TNF-alpha and IL-10 mRNA abundance increased from the proximal to distal part of the intestine, and the mRNA abundance was greater (p<0.01) in the distal intestine as compared with the proximal and middle intestine. The cytokines IL-1-beta, IL-10 and TNF-alpha mRNA abundance also increased from d3 to d10 postweaning (p<0.01). In summary, restricted feeding increased the TNF-alpha mRNA abundance in the small intestine, however neither SDPP nor peptide supplementation affected cytokine mRNA expression. Abundance of mRNA for most cytokines examined in this study increased with age post-weaning, suggesting that during 10 d after weaning the mucosal immune system is still under development.
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    Implications of Connectedness in the Genetic Evaluation of Livestock
    Kuehn, Larry Alexander (Virginia Tech, 2005-11-15)
    The reliability of genetic evaluations across separate management units (e.g. flocks) depends on the extent of genetic links or connections among animals in these units. Where poor connectedness exists, comparisons of estimated breeding values (EBV) across units may be biased. The objectives of this study were to identify breeding strategies to increase connectedness among units, to evaluate statistics that may reflect the reduction in bias as connectedness increases in such strategies, and to assess levels of connectedness in Suffolk and Targhee flocks participating in the National Sheep Improvement Program. Expectations of bias when production units have different genetic means were derived for a simple sire model. These expectations were applied to data involving two flocks of animals with three different types of connections: sharing of a common reference sire or use of either a full- or half-sibling sire in each flock. Bias decreased as numbers of progeny in each flock increased for all methods. Linking through a reference sire was most effective and was the only method that eliminated bias as progeny numbers became infinite. Pedigree and performance data on a single trait with heritability 0.25 were then simulated for 15 flocks with 40 to 140 ewes per flock. Each flock was simulated with a different founder genetic mean to introduce bias into the genetic evaluation. Flocks participated in sire referencing schemes by artificial insemination, with varying levels of participation, or by natural service. With sire referencing genetic gain was higher and inbreeding was lower than without, and bias was rapidly reduced to near-zero levels. Discontinuing the schemes led to lower genetic gain, but bias was not reintroduced. The prediction error correlation of flock genetic means was proposed as a connectedness measure because it was strongly associated with bias. Benchmarks of 0.05 and 0.10 for "good" and "superior" connectedness were established. Targhee flocks have increased connectedness across the breed by actively exchanging rams over 15 yr. In the Suffolk breed, connectedness has only improved within segregated clusters of flocks. Suffolk breeders need to engage in active ram exchange to decrease risk of biased across-flock EBV comparisons.
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    Livestock Update. August 2010
    Greiner, Scott P.; McCann, Mark A.; Kuehn, Larry Alexander; Thallman, Mark (Virginia Cooperative Extension, 2010-08-01)
    Includes articles on August beef management, summer pasture shortage, 2010 across-breed EPD table, upcoming stocker conference, upcoming Virginia Simmetal field day, sheep update, lamb management, and coping with drought for the sheep flock.