Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1962 V47

Call number: LD2668 .T4 1984 A43 / Master of Science

Made available in DSpace on 2014-06-11T19:30:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-06-07Bitstream added on 2014-06-13T19:40:32Z : No. of bitstreams: 1 silva_ncc_dr_botib.pdf: 675325 bytes, checksum: 770804101b6bf91187e2941b56d767bb (MD5) / Staphylococcus sp é agente comum da mastite bovina, causando grandes perdas econômicas na pecuária brasileira. Esse micro-organismo possui fatores de virulência bastante conhecidos como a produção de hemolisinas, leucotoxinas e superantígenos como a toxina do síndrome do choque tóxico e enterotoxinas. Além disso, várias espécies de Staphylococcus podem adquirir genes de resistência aos antibióticos β lactâmicos. O objetivo do estudo foi caracterizar molecularmente isolados de Staphylococcus sp provenientes de leite de vacas com mastite clinica e subclínica de várias regiões do estado de São Paulo. Foram realizadas coletas de leite de vacas com mastite clinica e subclínica de diferentes fazendas no estado de São Paulo e realizados testes fenótipicos de resistência a antimicrobianos e de virulência (Toxina de Panton Valentine, sindrome do choque tóxico e toxinas esfoliativas), além de testes moleculares como Pulse Field Gel Eletrophoresis (PFGE), Multiloccus Sequence Typing (MLST) e Spa typing para comparação entre as cepas epidemiologicamente importantes e da tipagem do cromossomo cassette estafilocócico em cepas meticilina reistentes. As cepas resistentes a meticilina apresentaram amplo perfil de resistência e genes de resistência importantes e pouco relatados, sendo observados genes como fexA, lsaE, lnuB. Foram detectados dois novos spatyping (t10852 e t10856), bem como um novo alelo yqiL e um novo ST (2493). Os ECNs apresentaram resistências à maioria dos antibióticos estudados e foi observado a uma deleção no gene ermC, que codifica a resistência à eritromicina. / Staphylococcus sp. is the common agent of bovine mastitis, causing big economic losses in Brazilian cattle. This micro-organism have virulence factors have been well known as the production of hemolysin, and leucotoxinas toxin superantigens such as toxic shock syndrome and enterotoxins. In addition, several Staphylococcus species can acquire antibiotic resistance genes β lactamics. The objective of the study is to characterize molecularly Staphylococcus sp. from milk of cows with subclinical mastitis in various regions of the state of São Paulo. Samples were coleted from milk of cows with subclinical and clinical mastitis from different farms in the state of São Paulo. Tests were performed phenotypic antimicrobial resistance and virulence (toxin Panton Valentine, toxic shock syndrome and exfoliative toxins), molecular tests as Eletrophoresis Pulse Field Gel Electrophoresis (PFGE), Multiloccus Sequence Typing (MLST) and spa typing for comparison between epidemiologically important strains, as well as the typing of strains in staphylococcal cassette chromosome methicillin reistentes. Methicillin-resistant strains showed broad resistance profile and resistance genes important and underreported were detected as fexA, lsaE, lnuB. Two new spatyping (t10852 and t10856) were detected as well as a new allele yqiL and a new ST (2493). The ECN showed resistance to most antibiotics and was observed the deletion in ermC gene encoding resistance to erythromycin.

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Until recently, occurrence of milk fever (MF) has been attributed to prepartum calcium intake. However, researchers in Iowa have concluded that high prepartum dietary potassium (K) is the major cause of MF. Potassium concentrations have been increasing on manure fertilized soils over the last 20 years. Grasses grown on these fields mirror the increase in available soil K. When high K forages are fed to dry cows, it has been associated with increased MF in some, but not all cases. Our objective was to identify factors that differed between low and high occurrence of disorders when high K forages were fed. For 1 yr, monthly interviews were conducted on 10 dairies in Western Oregon. Close-up rations, dystocia rating, crowding, and cow comfort data were collected. Cows were diagnosed healthy or having one or more of the following metabolic diseases: MF, retained fetal membranes (RFM), and left displacement of the abomasum (LDA). Feedstuffs were collected each month and analyzed for dry matter, crude protein (CP), acid detergent fiber (ADF), and macrominerals. Of the multiparous cows (n=3,587) included, incidences of MF, RFM and LDA were 3.6, 11.3, and 1.5%, respectively. Increasing MF occurrence was associated with uncomfortable conditions, dystocia, increasing prepartum dietary Na and ADF, and increasing Ca to P ratios; there was also a dietary K by Mg concentration interaction. Increased dietary concentrations of Mg can prevent MF if dietary K is <2.6%. In addition, dietary conditions of K >2.6% and Mg >0.4% increase the occurrence of MF. Inversely, high concentrations of K can prevent MF in a Mg deficient diet. Dietary factors associated with an increase in the occurrence of RFM are increased dietary concentrations of Ca, S, CP, use of anionic salts, and the K forage source. Factors associated with an increase in hypocalcemia in the postpartum cow are crowding, uncomfortable housing, and a dietary K by Mg concentration interaction. In conclusion, improved cow comfort, and the addition of Mg to high K forage diets could decrease the risk of the cow exhibiting MF, RFM, and hypocalcemia. / Graduation date: 1999

Although the occurrence of ketosis is a postpartum phenomenon, recent studies have focused on the prepartum period as key in the development of the disorder. Indicators of prepartum energy status, such as depressed dry matter intake (DMI) and elevated plasma non-esterified fatty acid (NEFA) concentrations have been associated with the occurrence of ketosis. The objective of this study was to investigate the role of phosphoenolpyruvate carboxykinase (PEPCK) in the periparturient and ketotic cow. The enzyme PEPCK catalyzes the rate limiting step in gluconeogenesis in hepatocytes. Whereas, in adipocytes, it has been suggested that PEPCK functions in the synthesis of glycerol for the formation of triacylglycerol (TAG) when plasma glucose concentrations are low. Thirty-four pregnant multiparous Holstein dairy cows were fed a single prepartum ration that consisted of 50% oat hay, 18% corn silage and 32% grain mix (DM basis). The ration was formulated to meet or exceed NRC requirements of 14% CP and 1.6 Mcal/kg NE[subscript L]. At calving, cows were transitioned onto one of two postpartum diets: control (n=14) or 3.5% supplemental fat (n=20). The postpartum diets, fed from wk 1 to 3, were formulated to isonitrogenous and to meet NRC requirements. Both diets consisted of 25% alfalfa, 25% corn silage and 50% grain mix. The control and fat diets contained 17.2 and 17.6% CP and 1.67 and 1.74 Mcal/kg NE[subscript L] respectively. Liver biopsies from 28 cows and adipose tissue biopsies from 6 cows were collected at -14, 2 or 3 and 14 d relative to calving. Tissue samples were analyzed for PEPCK mRNA and activity. All results were analyzed by period: prepartum (-21 to -2 d), freshening (2 to 7 d) and postpartum (8 to 21 d). In a previous study in our lab, 25 and 75% cows on the control and fat diets, respectively, experienced ketosis. In the current study there a 40% occurrence of ketosis for both control and fat diet groups. The high occurrence in both diets may be attributed to the rapid transition from the dry cow ration (70:30 forage to concentrate ratio, DM basis) to the lactating cow ration (50:50 forage to concentrate ratio, DM basis). The cows on the fat diet had lower serum glucose at freshening. Cows with ketosis had higher prepartum body weights (788 kg) than non-ketotic cows (743 kg; P<.1). No prepartum differences were seen in body condition score, DMI, NE[subscript L] balance, NEFA, glucose or ��-hydroxybutyrate concentrations were detected between ketotic and non-ketotic cows. Expression of adipose PEPCK mRNA was not different between ketotic and non-ketotic cows. However, hepatic PEPCK mRNA expression was higher in non-ketotic cows at freshening when compared to ketotic cows. Cows that experienced ketosis had lower hepatic PEPCK activity prepartum (6.6 vs. 9.3 units /min/g protein) and postpartum (7.6 vs. 10.2 units/min/g protein; P<0.5) when compared to non-ketotic cows. Our data indicated that hepatic PEPCK is a useful prepartum predictor of a cows susceptibility to ketosis. / Graduation date: 1998

The objective of the first part of this study was to observe and describe the profile of test-day somatic cell counts throughout a lactation in individual cows, and to examine the correspondence between such profiles and various lactation measures of cell count presently available. The objective of the second part of the study was to obtain estimates of the genetic and phenotypic parameters of lactation measures of cell count in different lactations, possibly for use in a breeding program. / In the first part of the study, the lactation cell count profiles of eighteen Holstein heifers of the Macdonald College Herd were individually examined. Weekly cell counts were expressed as deviations from the herd test-day average and plotted against week of test. A labile cell activity was found for most of the plotted lactations. The cellular responsiveness of cows facing external challenges seemed a trait peculiar to each individual. Lactation measures of cell count were unable to give good descriptions of cell count profiles of individual cows. However, they were better expressions of the lactation cell count performance than single test-day observations. / In the second part of the study, monthly cell count observations were obtained between February, 1977, and February, 1982, for the Holstein cows in herds enrolled on the official option of the Quebec Dairy Herd Analysis Service. Maximum likelihood, I-MINQUE (iterative Minimum Norm Quadratic Unbiased Estimation), and multivariate REML (Restricted Maximum Likelihood) procedures were used for the estimation of genetic and phenotypic parameters. / Repeatabilities of log test-day cell counts and log of test-day cell counts corrected for milk yield varied between 0.36 and 0.42 in first, second, third, fourth, and fifth and later lactations. Repeatabilities of test-day cell counts (cells/ml) in the five lactation groups varied between 0.17 and 0.25. Repeatabilities of lactation expressions for cell count between lactations ranged from 0.13 to 0.44. / Heritabilities of lactation expressions of cell count were low and varied from 0.06 to 0.14 in the five lactation groups examined; however, the genetic correlations between lactations were very close to unity, 0.90 to 0.97.

No description available.