Abstract
Synthetic amino acid supplementation has provided facilities in the adjustment of feed formula, making it possible to obtain the required levels of essential amino acids. Lysine is pronounced the second greatest restrictive amino acid in broiler nutrition. The synthetic amino acid lysine is used as the orientation amino acid in poultry for the reason that it is mainly consumed for protein synthesis. In order to characterize the requirements of lysine, 240 male broilers of the lineage Avian Farms were kept in an environment with average temperature of 25.6°C. The 22 to 42 days old broilers presented initial average weight of 541 ± 3.6 g. The basal ration contained 19.57% of crude protein (CP), 3100 kcal of metabolizable energy (ME)/kg and 0.88% of total lysine, which was supplemented with 0.000, 0.076, 0.153, 0.230 and 0.306% de L-lysine hydrochloric acid (HCL), resulting in rations with 0.88, 0.94, 1.00, 1.06 and 1.12% of total lysine. The experimental design was completely randomized with five treatments of total lysine, six repetitions and eight broilers per repetition. During experiments, the temperature was kept at 25.6 ± 0.24°C, relative moisture ate 68.4 ± 6.30%, black globe temperature at 25.7 ± 0.25°C and the wet-bulb globe temperature (WBGT) at 74 ± 0.6°C. Treatments influenced the absolute weight of carcass, breast with bone, leg, thigh, abdominal fat and relative weight of breast with bone. Lysine levels had a quadratic effect over the food conversion (FC), which increased up to the level 1.03% of total lysine. Lysine levels had a quadratic influence over the weight gain (WG), which increased up to the level 1.05% of total lysine. Key words: Chickens for meat production, growth phase, lysine, thermal environment.
Highlights
Birds, as well as mammals, are homeothermic animals, which indicated that means that even there are fluctuations at the environmental temperature, they can keep the body temperature constant (Borges et al, 2002)
Lysine levels had a quadratic effect over the food conversion (FC), which increased up to the level 1.03% of total lysine
Lysine levels had a quadratic influence over the weight gain (WG), which increased up to the level 1.05% of total lysine
Summary
As well as mammals, are homeothermic animals, which indicated that means that even there are fluctuations at the environmental temperature, they can keep the body temperature constant (Borges et al, 2002). Oba et al (2007) reported that the range of thermal neutrality for broilers is between 24 and 28°C. Any environmental change out of the thermal comfort of these animals requires behavioral, physical or physiological adjustments as attempts to adapt to the new condition. Considering these adjustments, the ration intake stands out, which are reduced as temperature increases, causing the decrease of growth rate and worsening of food conversion (Baziz et al, 1996).
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