RESUMO: Realizou-se este estudo com o objetivo de avaliar níveis de energia líquida (EL), mantendo a relação caloria: nutriente, no desempenho e características de carcaça de suínos dos 30 aos 70 kg. Foram utilizados 60 suínos machos castrados, com pesos iniciais de 31,94 ± 3,54 kg e finais de 71,98 ± 5,99 kg. Os animais foram distribuídos em delineamento experimental de blocos casualizados, em cinco níveis de EL (2,40; 2,45; 2,50; 2,55; 2,60 Mcal de EL kg-1 de dieta), com seis repetições e dois animais por unidade experimental. O período experimental foi dividido em fase I: 30 aos 50 kg e fase II: 50 aos 70 kg. As variáveis analisadas foram os consumos de ração diária (CRD), energia líquida (CEL) e lisina digestível (CLdig), ganho de peso diário (GPD), conversão alimentar (CA), peso final (PF), conversão de lisina digestível: ganho (CLdig:G), custo: ganho (C:G), área de olho de lombo (AOL), profundidade de músculo (PM), espessura de toucinho da primeira camada (ET1), espessura de toucinho da segunda camada (ET2), espessura de toucinho total (ETt), percentual de carne magra (CM) e o índice de bonificação de carcaça (IB). Dos 30 aos 50 kg, verificou-se aumento linear (P < 0,05) do PF, GPD e dos CEL e CLdig com o aumento dos níveis de EL na dieta. Dos 50 aos 70 kg, o aumento dos níveis de EL na dieta promoveu melhora linear (P < 0,05) do PF, GPD, CEL, CLdig e da CA dos suínos. No período total, verificou-se aumento linear (P < 0,05) do GPD, CEL, CLdig e melhora linear (P < 0,05) da CA de acordo com o aumento do nível de EL na dieta. As demais variáveis de desempenho não foram afetadas (P > 0,05) pelos níveis de EL. Verificou-se aumento (P < 0,05) da ET2 de acordo com o aumento do nível de EL, porém sem alterar (P > 0,05) as demais características de carcaça. Recomenda-se o nível 2,60 Mcal de EL kg-1 de dieta para suínos machos castrados dos 30 aos 70 kg.

ABSTRACT: This study evaluated the effect of dietary net energy (NE) levels on growth performance and carcass characteristics of barrows from 30 to 70 kg of body weight (BW). Sixty barrows with initial body weight (IBW) of 31.94 ± 3.54 kg and final body weight (FBW) of 71.98 ± 5.99 kg were allotted to one of five dietary NE levels (2.40, 2.45, 2.50, 2.55, and 2.60 Mcal kg-1), using a completely randomized block design with six replicates and two barrows per replicate. The experimental period was divided into phase I: 30 to 50 kg and phase II: 50 to 70 kg. The variables analyzed were average daily feed intake (ADFI), net energy intake (NEI), digestible lysine intake (LysI), average daily gain (ADG), feed conversion (FC), FBW, digestible lysine conversion:gain (LysI:G), Cost:Gain (C:G), loin eye area (LEA), muscle depth (MD), first backfat layer (BF1), second backfat layer (BF2), total backfat (BFt), lean meat percentage, and carcass bonus index (BI). In phase I, there was a linear increase (P < 0.05) in FBW, ADG, NEI, and LysI with increasing NE levels in the diet. In phase II, increasing dietary NE levels also increased (P < 0.05) FBW, ADG, NEI, LysI, and FC linearly. Overall, there was a linear increase (P < 0.05) in ADG, NEI, LysI, and FC with increasing NE levels in the diet. The other performance variables were not affected (P > 0.05) by the NE levels. There was an increase (P < 0.05) in BF2 with increasing NE levels, but the other carcass characteristics were not altered (P > 0.05). We recommended 2.60 Mcal of NE kg-1 in the diet for growing barrows from 30 to 70 kg.

RESUMO: Realizou-se este estudo com o objetivo de avaliar as suplementações de cromo e a restrição energética em substituição a ractopamina para leitoas em terminação tardia. Foram utilizadas 60 leitoas, com pesos inicial de 98,87±0,25 kg e final de 122,69 ± 10,97 kg, distribuídas em delineamento de blocos ao acaso com cinco dietas: controle; cromo levedura (0,8 ppm); picolinato de cromo (0,48 ppm); ractopamina (20 ppm) e restrição energética (redução de 150 kcal de EMkg-1 de ração), com seis repetições e dois animais por unidade experimental. A dieta contendo ractopamina proporcionou melhor (P<0,05) conversão alimentar e maior peso de carcaça quente das leitoas. A dieta contendo ractopamina apresentou menor (P<0,05) custo de ração por quilograma de ganho e maior índice de eficiência econômica em relação as dietas contendo cromo e restrição energética que, por sua vez, foram superiores em comparação a dieta controle. Dietas suplementadas com cromo e ractopamina apresentaram maior (P<0,05) percentual e quantidade de carne magra e maior índice de bonificação de carcaça em relação a dieta controle e restrição energética. Concluiu-se que a redução energética não prejudica as respostas das leitoas em relação a dieta controle. A suplementação de ractopamina possibilita melhor conversão alimentar, menor custo de ração por quilograma de ganho e maior índice de eficiência econômica. As suplementações de cromo e ractopamina expressam aumento do percentual e quantidade de carne magra e do índice de bonificação das carcaças. O picolinato de cromo e o cromo levedura são potenciais substitutos a ractopamina para otimizar as características de carcaça das leitoas.

ABSTRACT: This study evaluated chromium supplements and energy restriction as substitutes for ractopamine in the diets of late finishing gilts. Sixty gilts were used, with initial weights of 98.87 ± 0.25 kg and final weights of 122.69 ± 10.97 kg, distributed in a randomized block design with five diets: control; yeast chromium (0.8 ppm); chromium picolinate (0.48 ppm); ractopamine (20 ppm) and energy restriction (reduction of 150 kcal of EM kg-1 of feed), with six replicates and two animals per experimental unit. Feeding diet containing ractopamine enabled better (P<0.05) feed conversion and greater weights of the hot carcass of the gilts. The diet containing ractopamine exhibited a lower (P<0.05) cost of feed per kilogram of gain and higher economic efficiency, when compared to diets containing chromium and energy restriction; these exhibited better outcomes, compared to the control diet. Diets supplemented with chromium and ractopamine resulted in a higher (P<0.05) percentage and quantity of lean meat and a higher rate of carcass bonus, when compared to the control diet and energy restriction. The energy reduction did not harm the gilts’ responses, compared to the control diet. Ractopamine supplementation allowed for a better feed conversion, lower feed cost per kilogram of gain, and a higher economic efficiency index. Supplements of chromium and ractopamine increased the percentage and quantity of lean meat and the bonus index of the carcasses. Therefore, chromium picolinate and chromium yeast are potential substitutes for ractopamine for optimizing the gilts carcass characteristics.

RESUMO: Realizou-se este estudo com o objetivo de avaliar os efeitos de níveis de cromo levedura e lisina digestível, desempenho e características de carcaça de suínos em terminação. Foram utilizados 64 machos castrados com peso inicial de 72,77 ± 7,20 kg e final de 119,44 ± 9,47 kg, distribuídos em esquema fatorial 2 x 2, sendo dois níveis (Cr0: 0 ppb e Cr800: 800 ppb) e dois níveis de lisina digestível (L0: nível recomendado e L+10%: 10%). A temperatura do ar registrada de 30,9 ± 3,7 ºC durante o período experimental foi considerada como de estresse por calor. As variáveis de desempenho não foram influenciadas (P>0,05), contudo L+10% aumentou (P<0,05) o consumo de lisina digestível diário. As características de carcaça dos animais não foram influenciadas (P>0,05) pelos níveis de cromo levedura e lisina digestível. A suplementação de 800 ppb de cromo levedura, e o aumento em 10% do nível de lisina digestível, isolados ou associados, não melhoram o desempenho e as características de carcaça de suínos em terminação submetidos a temperaturas ambientais elevadas.

ABSTRACT: This study evaluated the effects of chromium yeast and digestible lysine levels on the performance and carcass characteristics of finishing pigs. Sixty-four barrows with an initial weight of 72.77 ± 7.20 kg and final weight of 119.44 ± 9.47 kg were used, distributed in a 2 x 2 factorial scheme, with two levels of chromium yeast (Cr0: 0 ppb and Cr800: 800 ppb) and two levels of digestible lysine (L0: recommended level and L+10%: 10%). The recorded air temperature of 30.9 ± 3.7 ºC during the experimental period was considered as heat stress. Performance variables were not influenced (P>0.05); however, L+10% showed an increase (P<0.05) in daily digestible lysine intake. Carcass characteristics of the animals were not influenced (P>0.05) by the chromium or digestible lysine levels. Supplementation with 800 ppb of yeast chromium and a 10% increase in the level of digestible lysine, isolated or associated, did not improve the performance and carcass characteristics of finishing pigs, subjected to high ambient temperatures.

ABSTRACT This experiment was conducted to evaluate growth performance and carcass characteristics of barrows from 25 to 100 kg fed diets with different dietary net energy (NE) levels. Seventy-two barrows with initial body weight (BW) of 25.19±2.13 kg were allotted using a completely randomized block design to one of six dietary NE treatments (2300, 2380, 2460, 2540, 2620, and 2700 kcal kg−1), which had two pigs per replicate and six replicates per treatment. Diets were formulated to be fed in three phases (25 to 60, 60 to 70, and 70 to 100 kg BW). The six different dietary NE densities were met by adding soybean oil in place of the inert ingredient (kaolin) to a corn-soybean meal-based diet. Increasing dietary NE decreased average daily feed intake and average daily standardized ileal digestible (SID) lysine intake in all of the three phases evaluated and improved the feed:gain ratio and SID lysine:gain ratio in the first and third phases. In the first and second phases, average daily NE intake and NE:gain ratio were similar among treatments, but NE increased and NE:gain worsened during the last phase as dietary NE increased. Average daily gain was not affected by dietary NE in the first and second phases; however, it improved in the last phase. Backfat was thicker, and lean percentage was reduced by increasing the dietary NE in all three phases of this study. Thus, barrows consume less feed, but carcass fat increases if dietary NE is increased from 2300 to 2700 kcal kg−1.

ABSTRACT This study was conducted to evaluate nutritional plans of digestible phosphorus for barrows weighing between 30 and 100 kg. Eighty animals were distributed in a randomized block design with five nutritional plans containing 2.19-1.86-1.71, 2.57-2.23-2.09, 2.94-2.61-2.46, 3.32-2.99-2.84, and 3.70-3.36-3.32 g of digestible phosphorus kg−1 of diet, respectively, for the phases of 30 to 50 kg, 50 to 70 kg, and 70 to 100 kg, with eight replications and two barrows per experimental unit. The nutritional plans of digestible phosphorus had no effect on the final body weight, feed intake, daily weight gain, or feed conversion of barrows. The daily intake of digestible phosphorus increased with the dietary concentrations of digestible phosphorus. Of the carcass characteristics assessed, only muscle depth responded significantly to the highest concentration of digestible phosphorus, as assessed in barrows sequentially fed the 3.70-3.36-3.32 g kg−1 diet. The nutritional plans had no effect on backfat, rib eye area, or carcass lean tissue mass, percentage, and deposition. The nutritional plan containing 2.19-1.86-1.71 g kg−1 of digestible phosphorus meet the nutrient requirements for performance and carcass characteristics of barrows weighing from 30 to 100 kg.

Abstract In this study, the potential antileukemic activity of grandisin, a lignan extracted from Piper solmsianum, was evaluated against the leukemic line K562. The cytotoxicity of grandisin (0.018 to 2.365 µM) was evaluated in K562 and normal peripheral blood lymphocytes by Trypan Blue Exclusion and MTT methods after 48h exposure to the drug. In both methods, cellular viability was concentration-dependent and the IC50 values were lower than 0.85µM. Analysis of K562 cells after treatment with grandisin showed that the cell cycle was arrested in the G1 phase with a 12.31% increase, while both S and G2 phases decreased. Morphological studies conducted after the exposure of K562 to grandisin revealed changes consistent with the apoptosis process, which was confirmed by anexin V stain and caspase activation. Thus, lignan grandisin showed antileukemic activities against the K562 cell line and the cell death process occurred via apoptosis.

RESUMO: Este estudo foi conduzido com o objetivo de avaliar o efeito dos níveis de energia líquida no perfil lipídico da gordura e carne suína. Foram utilizados 90 animais, com peso inicial de 71,94±4,43kg, distribuídos em delineamento de blocos ao acaso em cinco níveis de energia líquida (2.300, 2.425, 2.550, 2.675 e 2.800Kcal kg-1 de ração), com nove repetições e dois animais por unidade experimental. Foram analisados os perfis lipídicos da gordura subcutânea e da carne por cromatografia gasosa. O aumento do nível de energia líquida usando óleo de soja melhorou o perfil lipídico da gordura subcutânea e da carne, aumentando linearmente (P<0,05) a concentração dos ácidos graxos poli-insaturados, especialmente ácido linoleico e α-linolênico, reduzindo linearmente (P<0,05) os ácidos graxos monoinsaturados e saturados e ômega 6: ômega 3. No tecido adiposo foi observado redução linear (P<0,05) dos índices aterogênico e trombogênico. Em conclusão, o aumento do nível de energia líquida da dieta, com a utilização do óleo de soja, melhora o perfil lipídico da gordura subcutânea e da carne suína.

ABSTRACT: This study was conducted to evaluate the effects of net energy levels on the lipid profile of adipose tissue and muscle of swines. A total of 90 animals, with initial weight of 71.94±4.43kg, were used, and distributed in a randomized block design in five net energy levels (2,300, 2,425, 2,550, 2,675, and 2,800Kcal kg-1 feed), with nine replicates and two animals per experimental unit. Lipid profiles of adipose tissue and muscle were analyzed using gas chromatography. Increasing the levels of net energy using soybean oil, improved the lipid profile of adipose tissue and muscle, increased linearly (P<0.05) the concentrations of polyunsaturated fatty acids, especially linoleic and α-linolenic acid, reduced linearly (P<0.05) the monounsaturated and saturated fatty acids and omega 6: omega 3. In adipose tissue was observed linear reduction (P<0.05) of atherogenic and thrombogenic indexes. In conclusion, increasing the level of net energy of the diet using soybean oil improved the lipid profile of adipose tissue and muscle.

ABSTRACT This study was carried out to evaluate the levels of digestible phosphorus in diets for barrows with a high potential for lean meat deposition from 50 to 80 kg. Eighty barrows, with an initial weight of 47.93±3.43 kg, were distributed in completely randomized blocks, with each group given five levels of digestible phosphorus (1.86, 2.23, 2.61, 2.99, and 3.36 g kg−1). There were eight replicates, and two animals per experimental unit. Phosphorus levels did not significantly influence feed intake, weight gain, or feed conversion ratio. Daily digestible phosphorus intake increased linearly as levels of phosphorus in the diet were increased. Phosphorus levels did not significantly influence muscle depth, loin eye area, backfat thickness, or the percentage and quantity of lean meat in the carcass. A linear increase was observed for feeding cost as the levels of digestible phosphorus in the diet were increased, and the level of 1.86 g kg−1 cost 29.4% less when compared with the level of 2.61 g kg−1. The dry matter, natural matter, the coefficient of the residue, and volatile solids of the waste were not significantly influenced by phosphorus levels. Conversely, it was possible to observe an increasing linear effect for total solids, total phosphorus, and total nitrogen in the waste of animals receiving diets with increased levels of digestible phosphorus. The level of 1.86 g kg−1, which corresponded to a daily intake of 4.77 g−1 of digestible phosphorus, meets the requirements of barrows weighing 50 to 80 kg.

Realizou-se este estudo com o objetivo de avaliar o desempenho técnico-econômico e determinar a lucratividade, por meio da análise de sensibilidade econômica, de suínos machos imuno (IM) e cirurgicamente castrados (MC). Foram realizados dois experimentos, em delineamento inteiramente casualizado, composto por dois tratamentos (IM e MC), com oito repetições de 10 animais cada, totalizando 160 suínos por experimento. Verificou-se que suínos IM apresentam menor consumo de ração e melhor conversão alimentar nas fases de crescimento em relação aos MC. Na fase de terminação, suínos IM apresentam melhor ganho de peso, conversão alimentar, rendimento de carcaça e porcentagem de carne em relação aos MC. A utilização de IM aumenta a lucratividade na produção de suínos. A análise de lucratividade entre suínos IM e MC deve considerar todas as fases de criação, uma vez que o desempenho diferencial dos suínos não castrados na fase de crescimento influencia economicamente os resultados da produção.

This study was conducted to evaluate the technical and economic performance and determine profitability through the economic sensitivity analysis of immune (IM) and male pigs surgically castrated (SC). Two experiments were conducted in a completely randomized design, consisting of two treatments (IM and SC) with eight replicates of 10 animals each, totaling 160 pigs per experiment. It was found that IM pigs have lower feed intake and feed conversion during the growth phases in relation to SC. In the finishing phases, IM have better weight gain, feed conversion, carcass yield and lean meat percentage in relation to SC. The use of IM increases the profitability in pig production. The analysis of profitability differential between IM and SC should consider all stages of creation, since the differential performance of not castrated pigs during growth influences economic results of production.

O objetivo do trabalho foi avaliar o desempenho e as características quantitativas de carcaça de suínos machos castrados e imunocastrados, sob alimentação à vontade ou restrição quantitativa. Foram utilizados 240 animais, com peso inicial de 91,49±3,26kg, distribuídos em delineamento experimental de blocos ao acaso, em esquema fatorial 2x2 (dois manejos alimentares e duas categorias), com quatro repetições e 15 suínos cada. Suínos sob restrição alimentar apresentaram consumo inferior (P<0,05) em relação aos alimentados à vontade. O consumo de ração não diferiu (P>0,05) entre castrados e imunocastrados. Suínos alimentados à vontade apresentaram maior (P<0,05) ganho de peso em relação àqueles sob restrição. Os imunocastrados apresentaram ganho de peso superior (P<0,05) aos castrados. Houve interação (P<0,05) entre manejo e categorias para conversão alimentar, em que a restrição melhorou a conversão alimentar dos castrados em relação aos imunocastrados. Além disso, os imunocastrados apresentaram melhor (P<0,05) conversão alimentar em relação aos castrados, independente do manejo alimentar. Não houve interação (P>0,05) entre os fatores sobre as características de carcaça. A restrição não afetou (P>0,05) as características de carcaça. Machos imunocastrados apresentaram menor (P<0,05) espessura de toucinho e maior percentual de carne magra na carcaça. A restrição alimentar melhora a conversão alimentar de machos castrados. A restrição alimentar piora o ganho de peso e não altera as características de carcaça dos machos castrados e imunocastrados. Suínos imunocastrados apresentam desempenho superior, menor espessura de toucinho e maior percentual de carne magra em relação aos castrados.

The objective of this study was to evaluate the performance and carcass quantitative characteristics of barrows and immunocastrated swine fed ad libitum or under quantitative feeding restriction. Two hundred and forty animals were used, with initial weight of 91.49±3.26kg, distributed in a randomized blocks design, in a factorial scheme 2x2 (two management and two food categories), with four replicates of 15 pigs each. Pigs submitted to dietary restriction had lower consumption (P<0.05) than those fed ad libitum. Feed intake did not differ (P>0.05) between castrated and immunocastrated. Pigs fed ad libitum had higher (P<0.05) weight gain over those submitted to restriction. The immunocastrated showed higher weight gain (P<0.05) than castrated. There was an interaction (P<0.05) between management and categories for feed, in which the restriction improved castrated pigs. Immunocastrated had better (P <0.05) feed conversion compared to castrated, regardless of feed management. There was no interaction (P>0.05) among the factors on carcass traits. The restriction did not affect (P>0.05) carcass traits. Immunocastrated pigs had lower (P<0.05) back fat thickness and higher percentage of lean meat. Dietary restriction improves feed conversion of castrated pigs. The dietary restriction affects weight gain and does not affect carcass characteristics of barrows and immunocastrated. Immunocastrated pigs have higher performance, lower back fat thickness and a higher percentage of lean meat compared to the castrated.

O objetivo do trabalho foi avaliar níveis de energia líquida (EL) e ractopamina na dieta de leitoas em terminação sob altas temperaturas ambientais (29,5±2,3°C). Foram utilizadas 40 leitoas (peso inicial de 69,3±2,8kg) distribuídas no delineamento de bloco ao acaso em esquema fatorial 2x4 (0 e 20ppm de ractopamina e 2.300; 2.424; 2.548 e 2.668kcal de EL kg-1 de ração), com cinco repetições de um animal cada. Houve interação (P<0,05) entre EL e ractopamina, sendo que a inclusão de 20ppm em dietas com 2.548 e 2.668kcal reduziu (P<0,05) a espessura de toucinho e aumentou (P<0,05) a percentagem de carne magra das carcaças. A ractopamina melhorou (P<0,05) a conversão alimentar e a quantidade de carne magra nas carcaças (P<0,05), independente dos níveis de EL. Concluiu-se que a ractopamina na dose de 20ppm propicia benefícios no desempenho e características de carcaça de leitoas sob estresse térmico e que esse efeito é mais positivo em dietas contendo níveis energéticos mais elevados (2.548 e 2.668kcal de EL).

The objective of this paper was to assess net energy (NE) levels and ractopamine in the diet of finishing gilts maintained under high temperature environment (29.5±2.3°C). Forty gilts were used, with initial weight of 69.3±2.8kg, distributed in a randomized block design, in a factorial scheme 2x4 (0 and 20ppm of ractopamine; and 2,300; 2,424; 2,548 and 2,668kcal/kg NE kg-1 of feed), and five replications and one animal each. There was interaction (P<0.05) between NE levels and ractopamine, and the inclusion of 20ppm of ractopamine in the diets containing 2,548 and 2,668kcal reduced (P<0.05) backfat thickness and increased (P<0.05) the percentage of lean meat of carcasses. The use of ractopamine improved (P<0.05) feed gain ratio and increased (P<0.05) the amount of lean meat in carcasses. It was concluded that ractopamine at a dose of 20ppm provides benefits in performance and carcass traits of gilts under heat stress and this effect is more positive in diets containing higher energy levels (2,548 and 2,668kcal of NE kg-1).

Este estudo foi realizado com o objetivo de avaliar a duração da suplementação de ractopamina na dieta de leitoas em terminação, mantidas sob alta temperatura ambiente. Foram utilizadas 48 leitoas com peso inicial de 70,4±2,6kg, distribuídas no delineamento de blocos ao acaso, com seis tratamentos (suplementação de ractopamina por 0, 7, 14, 21, 28 e 35 dias pré-abate) e quatro repetições, sendo a unidade experimental constituída por dois animais. O peso final e o consumo de ração diário não foram influenciados (P>0,05) pelos tratamentos. O ganho de peso aumentou e a conversão alimentar reduziu linearmente (P<0,05) com o aumento do tempo de suplementação de ractopamina na dieta. As características quantitativas de carcaça (peso e rendimento de carcaça quente, espessura de toucinho, percentual de carne magra, profundidade de músculo e área de olho-de-lombo) não foram influenciadas (P>0,05) pela duração da suplementação de ractopamina na dieta. O peso dos pulmões, coração, fígado, rins e baço também não foi modificado (P>0,05) pelos tratamentos. Concluiu-se que a inclusão de 20ppm de ractopamina na dieta de leitoas em terminação, mantidas sob alta temperatura ambiente, durante 28 dias, maximiza a resposta de ganho de peso diário e, durante 35 dias, maximiza a resposta para conversão alimentar. Contudo, a inclusão do aditivo não altera as características quantitativas de carcaça e não afeta o desenvolvimento das vísceras.

The study was conducted to evaluate the duration of the supplementation of ractopamine in the diet of finishing gilts maintained under high temperature environment. Forty eight females, with initial weight of 70.4±2.6kg were used. The pigs were distributed in randomized blocks design of six treatments (supplementation of ractopamine for 0, 7, 14, 21, 28 and 35 days pre-slaughter) and four replications, each experimental unit consisted of two animals. The final weight and daily feed intake were not affected (P>0.05) by treatments. The weight gain increased and the feed conversion decreased linearly (P<0.05) according to the increased length of supplementation of ractopamine in the diet. The quantitative characteristics of carcass (weight and hot carcass yield, backfat thickness, percentage of lean meat, depth of muscle and loin eye area) was not influenced (P>0.05) by duration of supplementation of ractopamine in the diet. The weights of the lungs, heart, liver, kidneys and spleen were not modified (P>0.05) by treatments. It was concluded that inclusion of 20ppm of ractopamine in the diet of finishing gilts maintained under high temperature environment during 28 days maximizes the response of daily gain and during 35 days maximizes the response to feed conversion. However, the inclusion of the additive does not alter the quantitative characteristics of carcass and does not affect the development of the viscera.

Avaliaram-se o desempenho, as características quantitativas de carcaça e as respostas viscerais de suínos machos castrados mantidos em ambiente de estresse por calor e alimentados com dietas suplementadas com ractopamina. Foram utilizados 48 animais com peso inicial de 67,3 ± 3,8 kg, distribuídos em delineamento em blocos casualizados, com quatro níveis de ractopamina (0, 5, 10 e 20 mg/kg), cada um com seis repetições de dois animais. O período experimental foi de 28 dias. A temperatura do ar foi de 31,8 ± 2,0ºC, a umidade relativa foi de 72,6 ± 10,2% e índice de temperatura de globo e umidade (ITGU) de 82,7 ± 2,8. Os níveis de ractopamina não influenciaram o consumo diário de ração, mas melhoraram a conversão alimentar e aumentaram o ganho diário de peso e o peso final dos animais. As características quantitativas de carcaça não foram influenciadas pelos níveis de ractopamina. Os pesos de fígado e dos rins aumentaram de forma linear de acordo com os níveis de ractopamina nas dietas, ao passo que o peso dos demais órgãos e o comprimento do intestino delgado não foram afetados pela suplementação com ractopamina. O nível ótimo de ractopamina para melhor desempenho de suínos machos castrados sob estresse por calor é de 20 mg/kg e não altera as características quantitativas da carcaça.

The objective of this study was to evaluate performance, quantitative characteristics of carcass, and visceral responses of barrows maintained on heat stress enviroment and fed diets supplemented with ractopamine. It was used 48 animals with initial weight of 67.3 ± 3.8 kg, distributed in a randomized block design with four levels of ractopamine (0, 5, 10 and 20 mg/kg), each one with six replicates with two animals each. The experimental period lasted 28 days. Air temperature was 31.8 ± 2.0ºC, air humidity was 72.6 ± 10.2% and BGHI was 82.7 ± 2.8. Daily feed intake was not affect by the levels of ractopamine but they improved feed conversion and increased daily weight gain and final weight of the animals. The carcass quantitative characteristics were not affected by levels of ractopamine. The weights of the liver and kidneys showed linear increases accordingly to increase of ractopamine levels in the diet whereas weight of other organs and length of small intestine were not affected by supplementation with ractopamine. The optimum level of ractopamine for the best performance of barrows under heat stress is 20 mg/kg and it does not affect the quantitative characteristics of carcass.