Niveles de lisina y metionina en dietas bajas en proteína para cerdos en crecimiento

Abstract

El objetivo del estudio fue determinar el mejor nivel de lisina (Lis) y metionina (Met) digestibles y su interacción, en dietas sorgo-pasta de soya con baja proteína, evaluando el comportamiento productivo, características de la canal y urea en plasma de cerdos en crecimiento. En el primer experimento se evaluó el efecto de 1.0% de Lisina con 0.29, 0.34, 0.39, 0.44 y 0.49% de Metionina digestible, en 50 cerdos (31.39±5.33 kg) por 28 días, en un diseño completamente al azar. En el experimento 2 se utilizaron 1.0 y 1.1% de Lisina con 0.29, 0.34, 0.39 y 0.44% de Metionina en 56 cerdos (27.42±2.97 kg) por 32 días, en un diseño factorial 2×4. Los resultados del experimento 1 presentaron a las hembras con diferencias significativas en el consumo diario de alimento (CDA), grasa dorsal final (GDF) y concentración de urea en plasma (CUP); el análisis de regresión mostró efecto cúbico para CDA, peso final (PF) y GDF. Los machos redujeron el CDA y PF con 0.49% de Met; el CDA, PF, GDF y área del músculo longissimus (AML) presentaron efecto cúbico con regresión. Los resultados del experimento 2 demostraron que el CDA, ganancia de carne magra (GCM), GDF, PF y porcentaje de carne magra (PCM) fueron afectadas positivamente con 1.0 % de lisina; el AML se mejoró al aumentar metionina y CUP por la interacción de lisina×metionina. Los niveles superiores a 0.44% de metionina reducen el comportamiento productivo de los machos y aumentan la GDF y CUP en las hembras; el comportamiento productivo y características de la canal son mejores con 1.0% de lisina digestible; la disminución de la CUP depende de la interacción de Lisina-Metionina. _______________ LYSINE AND METHIONINE LEVELS IN LOW-PROTEIN DIETS FOR GROWING PIGS. ABSTRACT: The objective of the present study was to determine the better level of digestible lysine and methionine and their interaction, in sorghum-soybean meal with low-protein diets, on the productive variables, carcass characteristics and plasma urea nitrogen concentration in growing pigs. In the first experiment was evaluated the effect of 1.0% lysine with five levels of digestible methionine (0.29, 0.34, 0.39, 0.44 and 0.49%) by twenty-eight days, in fifty crossbred pigs (25 barrows and 25 gilts) with 31.39±5.33 kg of initial live weight, in a completely randomized design. In the second experiment was evaluated the effect of two digestible lysine levels (1.0 and 1.1%) and four digestible methionine levels (0.29, 0.34, 0.39 and 0.44%), were evaluated during thirty-two days in fifty-six pigs (25 barrows and 31 gilts) with 27.42±2.97 kg of initial live weight, in a factorial design 2x4. The results of experiment 1, gilts showed differences for average daily feed intake (DFI), backfat thickness (BF) and plasma urea nitrogen concentration (PUN); regression analysis showed cubic effect for DFI, final body weight (BW) and BF. Barrows had a reduction of DFI and BW with 0.49% of methionine; the DFI, BW, BF and longissimus muscle area (LMA) also presented cubic effect with regression analysis. In the experiment 2, the 1.0% lysine improved the DFI, lean meat gain (LMG), BF, BW and lean meat percentage (LMP); increasing methionine level improved LMG; interaction of lysine and methionine improved PUN. These results indicated that methionine level higher than 0.44% reduces growth performance of barrows and increases the BF and PUN in gilts; growth performance and carcass characteristics were improved by 1.0% digestible lysine; PUN reduction depends on the interaction of lysine-methionine.