Levels of circulating thyroid hormones, performance and carcass and meat quality of growing-finishing swine/Niveis de hormonios tireoideanos circulantes, desempenho e qualidade de carcaca e carne de suinos em crescimento e terminacao

The objective of this study was to compare serum concentrations of the hormones triiodothyronine ([T.sub.3]) and thyroxine ([T.sub.4]) in pigs on commercial line beginning and end of growing-finishing phase, correlating them with productive performance and quality characteristics of carcass and meat. Blood samples were collected from 48 animals at the beginning and end of growing-finishing phase by puncturing the jugular vein, around the same time (08:00 to 10:00a.m.). Measurements of serum thyroid hormones were made by enzyme-immunoassay. It was evaluated the performance and quality of carcass and meat. At the beginning and end of the housing, serum [T.sub.3] concentrations were 1.85 and 1.32nmol [L.sup.-1], respectively, and [T.sub.4] of 100.33 and 86.53nmol [L.sup.-1], respectively. There was negative correlation between [T.sub.3] and low-end and average daily weight gain, final weight and backfat thickness. Inicial [T.sub.4] was moderately and moderately negatively correlated with initial weight. The values of [T.sub.3] and [T.sub.4] in pigs early in the growing-finishing phase are larger than in termination. The thyroid hormones are associated with the initial and final weight, backfat thickness at the last lumbar, [pH.sub.45min] and [pH.sub.24h] of growing-finishing pigs. Key words: swine production, weight gain, triiodothyronine, thyroxine. Objetivou-se neste estudo comparar as concentracoes sericas de triiodotironina ([T.sub.3]) e tiroxina ([T.sub.4]) em suinos de linhagem comercial no inicio e termino da fase de crescimento-terminacao, correlacionando-os com o desempenho produtivo, caracteristicas de qualidade de carcaca e da carne. As amostras sanguineas de 48 animais foram coletadas no inicio e no final da fase de crescimento-terminacao por puncao da veia jugular externa, sempre no mesmo horario (8-10h). As determinacoes sericas dos hormonios tireoideanos foram feitas por enzimaimunoensaio. Foram feitas avaliacoes de desempenho e de qualidade de carcaca e de carne. No inicio e final do alojamento, as concentracoes sericas de [T.sub.3] foram de 1,85 e 1,32nmol L1, respectivamente, e para [T.sub.4] de 100,33 e 86,53nmol L1, respectivamente. Houve correlacao negativa e baixa entre [T.sub.3] final e ganho de peso medio diario, peso final e espessura de toucinho. [T.sub.4] inicial correlacionou-se negativamente e moderadamente com peso inicial. Os valores de [T.sub.3] e de [T.sub.4] em suinos no inicio da fase de crescimento-terminacao sao maiores qu