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Thesis (Ph. D.)--University of Kentucky, 2007. / Title from document title page (viewed on March 25, 2008). Document formatted into pages; contains: xii, 216 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 171-210).

Made available in DSpace on 2015-03-26T13:55:25Z (GMT). No. of bitstreams: 1 texto completo.pdf: 778375 bytes, checksum: 97156e3e6f5b7ceee5985d54b84d365c (MD5) Previous issue date: 2014-07-23 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / To evaluate the effect of chromium yeast (CY) and ractopamine (RAC) on performance, carcass characteristics, meat quality, and blood, an experiment was conducted with 96 commercial castrated crossbred pigs with an average initial body weight of 75.07 ± 3.9 kg. Animals were distributed in a randomized-block experimental design with six treatments, eight blocks and two animals per stall. The treatments consisted of feeding plans (FP) in two phases: from 0 to 14 days; and from 14 to 42 days of age, respectively, composed of diets: Control/Control (CD/CD); Chromium yeast/Amino acids (CY/AA); Chromium yeast/Amino acids + Ractopamine (CY/AA+RAC); Control /Chromium yeast (CD/CY); Control/Amino acids + Chromium Yeast (CD/AA+CY); and Chromium Yeast/Amino Acids + Ractopamine + Chromium Yeast (CY/AA+RAC/CY). The greatest final weight and daily weight gain (P<0.0001) were observed in the animals subjected to CY/AA+RAC+CY. Feeding plan CY/AA+RAC provided an intermediate final weight and daily weight gain, similar to those obtained with the use of CY/AA+RAC+CY, CD/CD, CY/AA and CD/CY, but greater than CD/AA+CY. The pigs fed CY/AA+RAC+CY showed a greater fasted body weight (FW) (P<0.0001) as compared with CD/CD, CY/AA, CD/CY and CD/AA+CY. Feeding plan CY/AA+RAC provided an intermediate FW, similar to that obtained with the use of CY/AA+RAC+CY, CD/CD, CY/AA, but greater than CD/AA+CY. The evaluated FP did not influence (P>0.05) daily feed intake. The best feed-conversion results (P<0.0001) were obtained with CY/AA+RAC+CY and CY/AA+RAC. A larger loin-eye area was found in pigs subjected to CY/AA+RAC as compared with the use of CD/CY. The greatest muscle fiber diameter (P<0.011) was found in the pigs subjected to CY/AA+RAC+CY and CD/CY, which were higher than the group fed CD/CD. The liquid loss due to thawing determined in the meat of the pigs subjected to CD/CD was lower (P<0.009) than that observed with the use of CY/AA+RAC. A higher value of Cie a* was determined in the meat of the animals subjected to CY/AA+RAC as compared with CY/AA+ RAC+ CY. The pigs fed CY/AA+ RAC+ CY had a brighter meat than the other animals. The lowest TBARS concentration (P<.001) was observed in the meat of pigs subjected to CY/AA+RAC in relation to the group that consumed CY/AA. A greater concentration of myristic fatty acid (FA) (14:0) was found in the groups that received CY/AA+RAC as compared with the group fed CY/AA+RAC+CY. The pigs that received the FP with CY/AA+RAC+CY and CD/CY displayed greater levels of linoleic FA (18:2n6) in the longissimus dorsi muscle, as compared with the pigs fed CY/AA. The feeding plans did not affect the evaluated blood parameters (P>0.05). The use of chromium yeast and ractopamine or alone promoted positive alterations in the development of muscle cells in the pigs and in the meat quality, which should be considered when this mineral is used. The association of chromium yeast with ractopamine revealed improvements in the animal performance. / Para avaliar o efeito do cromo levedura (CrL) e ractopamina (RAC) em rações sobre o desempenho, características da carcaça, qualidade de carne e variáveis sanguíneas, foi realizado um experimento com 96 suínos machos castrados híbridos comerciais com peso corporal médio inicial de 75,07 ± 3,9 kg, distribuídos em delineamento experimental em blocos casualizados, com seis tratamentos, oito blocos e dois animais por baia. Os tratamentos foram constituídos de planos nutricionais (PN) em dois períodos consecutivos: período 1 de 0 a 14 dias e o período 2 de 14 a 42 dias, respectivamente, compostos pelas rações: Controle/Ração Controle (RC/RC); Cromo levedura/Aminoácidos (CrL/AA); Cromo Levedura/Aminoácidos + Ractopamina (CrL/AA+RAC); Controle/Cromo Levedura (RC/CrL); Ração Controle/Aminoácidos + Cromo Levedura (RC/AA+CrL) e Cromo Levedura/Aminoácidos+Ractopamina+Cromo Levedura (CrL/AA+RAC+CrL). Maior peso final (PF) e ganho de peso diário (GPD) (P<0,001) foi observado para os suínos submetidos ao PN CrL/AA+RAC+CrL. O PN CrL/AA+RAC proporcionou PF e GPD intermediário, semelhante aos obtidos com o uso de CrL/AA+RAC+CrL, RC/RC, CrL/AA e RC/CrL e superior ao PN RC/AA+CrL. Os suínos alimentados com o PN CrL/AA+RAC+CrL apresentaram maior peso de jejum (PJ) (P<0,0001) quando comparados aos PN RC/RC, CrL/AA, RC/CrL e RC/AA+CrL. O PN CrL/AA+RAC promoveu PJ intermediário, semelhante ao obtido com o uso de CrL/AA+RAC+CrL, RC/RC, CrL/AA e superior ao RC/AA+CrL. Os PN avaliados não influenciaram (P > 0,05) o consumo diário de ração. Os melhores resultados de conversão alimentar (P<0,001) foram obtidos com os PN CrL/AA+RAC+CrL e CrL/AA+RAC. Maior área de olho de lombo foi determinada nos suínos submetidos ao PN CrL/AA+RAC quando comparado a utilização de RC/CrL. Maior diâmetro da fibra muscular (P<0,011) foi verificado nos suínos submetidos aos PN CrL/AA+RAC+CrL e RC/CrL sendo estes superiores ao grupo consumindo RC/RC. A perda líquida por descongelamento determinada na carne dos suínos submetidos ao PN RC/RC foi inferior (P<0,009) a obtida com o uso do PN CrL/AA+RAC. Maior valor Cie a* foi determinado na carne dos animais submetidos ao PN CrL/AA+RAC quando comparado ao PN CrL/AA+ RAC+ CrL. Os suínos submetidos ao PN CrL/AA+ RAC+ CrL apresentaram maior tonalidade na carne frente aos demais animais. Menor concentração de TBARS (P<0,001) foi verificada na carne dos suínos submetidos ao PN CrL/AA+RAC frente ao grupo consumindo ração CrL/AA. Maior teor de ácido graxo (AG) mirístico (14:0) foi verificado para os suínos submetidos ao PN CrL/AA+RAC quando comparado ao grupo CrL/AA+RAC+CrL. Os suínos que receberam os PN com CrL/AA+RAC+CrL e RC/CrL apresentaram maior concentração de AG linolêico (18:2n6) no músculo Longissimus dorsi, frente aos suínos do PN CrL/AA. Os PN não influenciaram as variáveis sanguíneas avaliadas (P>0,05). O uso de cromo levedura e ractopamina promoveram alterações positivas sobre o desenvolvimento de células musculares nos suínos e na qualidade da carne que devem ser consideradas quando da utilização do mineral e o uso em associação a ractopamina revelou melhorias sobre o desempenho dos animais.