Castration is a handling practice for control the boar taint but is stressful for the animal and mandatory in Brazil. In this context, immunocastration has more space because represents a new alternative that aims to control the substances involved in this odor, and is a noninvasive method to the animal. In commercial pig production, where the maximization of performance is the focus, ractopamine represents another alternative of interest. Ractopamine is an agonist beta-adrenergic that has been used as a divider energy in swine diets during the finishing phase and characteristics benefit variables performance of pigs. A total of 640 animals, weighing initial average of 23 kg (± 1 kg) will be housed in phases growing and finishing within 120 days and weighing slaughter average of 115 Kg (± 5 kg). These animals will be divided into 64 pens (10 pigs / pen), according to the following treatments: two types of castration (Surgical castration and imunucastration) x 4 levels of ractopamine administered for 28 days before slaughter, divided into two periods of 14 days, (the first 14 days will be administered the following doses: 0, 5, 5 and 7.5 ppm and in the last 14 days the doses 0, 5, 10:10 ppm), representing eight treatments. The blocks are defined according to the weight of pigs at weaning (with 21 days) and out the nursery (63 days). Will be analyzed the performance (weight gain, feed intake and feed conversion), welfare (carcass and skin damages and parameters physiological of stress) and meat quality (pH, color, drip loss, cooking loss, texture, fat intramuscular and carcass traits). Animals will undergo a fast of 12 hours before slaughter will be chosen on this occasion two pigs per pen for evaluation of meat quality parameters and physiological stress. The experimental design will be blocks with 8 treatments and 4 repetitions. The data will be submitted for analysis univariate and multivariate analysis of variance involving an full factorial design with two factors (2 categories of castration and 4 levels of ractopamine). Analyses will be implemented through the SAS statistical software (2008). The aim of this study was avaliate the effect of interaction between categories of castration and levels of ractopamine on susceptibility to stress, performance and pork meat quality.
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