Abstract

LOPEZ, M. et al. Digestible lysine and threonine levels in sorghum-soybean meal diets for growing pigs. Arch. zootec. [online]. 2010, vol.59, n.226, pp.205-216. ISSN 1885-4494.

Was evaluated the effect of digestible lysine and threonine supplemented to sorghum-soybean meal diets for growing pigs on growth performance, carcass characteristics, and plasma urea nitrogen concentration (NUP). In experiment 1, five dietary digestible lysine levels (0.67, 0.75, 0.83, 0.91 and 0.99%) were evaluated during four weeks. Fifty barrows with 22.34 ± 3.45 kg of initial weight were used. In experiment 2 five dietary digestible threonine levels (0.42, 0.47, 0.52, 0.57 and 0.62%) were evaluated during six weeks. Fifty pigs (25 barrows and 25 gilts) with 24.02 ± 3.73 kg of initial weight were used. Pigs were alloted in a completely randomized design with five replicates of two pigs per experimental unit. The analyzed variables were as follows: average daily feed intake (CDA), average daily gain (GDP), feed:gain ratio (CA), fat free lean gain (GCM), final body weight (PF), backfat thickness (GD), lean meat percentage (%CM), longissimus muscle area (AML), and plasma urea nitrogen concentration (NUP). The CDA, GDP and CA were recorded weekly and analyzed with the PROC MIXED procedure of SAS; the variables obtained at the end of the experiment were analyzed with GLM procedure. The means comparison was performed with Tukey test; and orthogonal contrasts were applied to detect linear, quadratic or cubic effects. The best digestible lysine level for CDA and GDP was 0.75%; for CA was 0.91%; and for PF was 0.99%. The orthogonal contrasts analysis showed a cubic effect of digestible lysine on CDA; a lineal effect on CA; and a quadratic effect on AML, %CM, and NUP. The digestible threonine levels did not affect growth performance, nor carcass characteristics; they just linearly reduced NUP as digestible threonine levels increased. The barrows also reduced NUP as the level of dietary digestible threonine increased. These results indicate that the level of digestible lysine affects differently growth performance, carcass characteristics and plasma urea nitrogen concentration; and that digestible threonine levels did not affect the analyzed variables.

Keywords : Essential amino acids; Growth performance; Carcass characteristics.

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