Níveis de lisina digestível e relações treonina:lisina digestíveis em rações para suínos mantidos em diferentes ambientes térmicos

• Autor(a) principal: Lima, Anderson Lazarini
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1815
• topic: Suínos; Desempenho; Estresse por calor; Termoneutralidade; Exigência; Nutrição; Pigs; Performance; Heat stress; thermoneutrality; Requirement; Nutrition; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PRODUCAO ANIMAL

This study was conducted to evaluate levels of digestible lysine and digestible threonine:lysine relations in diets for growing pigs from 15 to 30 kg, kept in different thermal environments (22, 31 and 35 oC). Were used 420 animals, 70 in each experiment. In six experiments the animals were distributed in randomized complete blocks design, with five levels of digestible lysine (0.945, 1.045, 1.145, 1.245 and 1.345%) or five relations of digestible threonine:lysine (0.53; 0.58; 0.63; 0.68; 0.73%), seven replicates and two animals per experimental unit. Diets and water were provided ad libitum. Were registered the temperatures and relative humidity inside the rooms in the six experiments, in order to characterize the thermal environment (22, 31 and 35 °C). The level of lysine influenced linearly, increasing the average daily gain (ADG) of animals in all thermal environments studied. However, in animals kept at 35 and 31 °C ADG was 27.26 and 7.09% lower, respectively, when compared with those created at 22 oC. The daily feed intake (DFI), regardless of the temperature at which the animals were kept, was not influenced by lysine levels of the diets, the values obtained with the animals kept at 35 and 31 °C were on average 19.07 and 5.46% lower than that observed at 22 oC. The daily intake of lysine (DIL) of the animals kept at 22, 31 and 35 °C increased linearly with the levels of lysine in diet. The daily intake of lysine of animals maintained under 22 °C was on average 18.51% higher than those kept 35 °C and 4.44% of the 31 oC. Also, the feed conversion (FC) linearly decreased in the three experiments. Featuring animals kept at 35 °C 12.16% FC to 31 °C and 8.99% worse than those kept in thermoneutrality. In all experiments, lysine levels influenced the efficiency of lysine utilization (ELU) for weight gain, which decreased linearly with worsening of 10.80% in the environment with higher temperature (35 oC). The fat deposition (FD) was influenced by the level of lysine in a different way according to the thermal environment studied. At 22 oC FD decreased linearly, while the 31 °C decreased quadratically up to the level of 1.077% and 35 °C also increased quadratically to the estimated level of 1.173%. The animals kept at 31 °C had the highest FD, 23.64% higher compared to smaller, observed in this study. The level of dietary lysine influenced the protein deposition (PD) in the carcass of animals kept at 22 °C, which increased quadratically to the estimated level of 1.329%. However, at 31 and 35 °C, the PD increased linearly with the levels of lysine. The PD was 26.50 and 24.08% higher, respectively, the 22 and 31 °C than that of animals reared at 35 oC. The animals kept at 35 °C showed an average increase of 148% and 44% to 31 oC in respiratory rate compared to the environment kept at 22 oC. The heat stress also decreased the weight of the carcass and viscera of animals kept at 31 and 35 oC. In an environment of 22 °C, the level of 1.329% of digestible lysine, corresponding to a daily intake of 15.8 g, provides greater protein deposition in the carcass of growing pigs, and in environments of 31 and 35 ºC, the level of 1.345% of digestible lysine, corresponding to a daily intake of 8.9 and 7.0 g, respectively, attended the daily weight gain and protein deposition in the carcass of growing pigs. Considering the experiments done to evaluated the effect of digestible threonine:lysine relations was observed a quadratic effect on a feed conversion of animals maintained under 23 °C improving until the calculated ratio of 0.66%. No other performance variable or the deposition of fat and protein were influenced by digestible threonine:lysine relation in the diet. At 31 °C the feed intake of animals linearly increased according to digestible threonine:lysine relation, and similarly at 21 °C was the only variable affected by treatments. The digestible threonine:lysine relation had no effect on performance neither protein and fat deposition in animals kept at 35 °C environment. Evaluating the effect of thermal environment in the performance variables, fat and protein deposition was found that in most of them the animals kept at thermoneutrality showed better results compared to those challenged by heat. Likewise, it was found that the pigs were maintained in high-temperature larger rectal temperatures and respiratory rate and consequent reduction in weight of viscera. In pigs from 15 to 30 kg maintained at a temperature of 22 °C, the calculated ratio of 0.66% threonine:lysine relation provides better feed conversion, while at ambient temperature of 31 oC and 35 oC, the relation 0.53% of threonine:lysine relation permit the best performance results and deposition of protein and fat.