Abstract The objective was to evaluate the addition of xylanase in nursery pig diets with a high amount of wheat bran (WB) and two energy levels. Growth performance, carcass characteristics and plasma urea concentration were assessed. Forty-eight hybrid barrows were used (7.98 kg initial body weight and 28 d of age), allotted in a completely randomized design. Treatments (T) were: T1, control diet: 3350 Kcal; T2: 3275 Kcal + xylanase; T3: 3350 Kcal + xylanase; T4: 3350 Kcal + WB + xylanase; T5: 3275 Kcal + WB + xylanase; T6: 3350 + WB + xylanase. The variables were analyzed with ANOVA and treatment means were compared with Tukey's test (p ≤ 0.1). For average daily gain (ADG), average daily feed intake, final body weight and fat free lean gain (FFLG), better response was observed in pigs fed diets without WB (p ≤ 0.1) where xylanase compensated energy reduction. The inclusion of xylanase in WB diets reduced the ADG and final body weight (p ≤ 0.1). Supplementation with WB did not change backfat thickness, longissimus muscle area (LMA) and lean meat percentage (p > 0.1). The backfat thickness and LMA were not affected (p > 0.1) by reducing energy in diets without WB (p > 0.1). In conclusion, diets high in wheat bran content affect growth performance variables, but it is offset by the addition of xylanase, as long as the energy matrix is observed.

Resumen El objetivo fue evaluar la adición de xilanasas en dietas con alta cantidad de salvado de trigo (ST) y dos niveles de energía para cerdos en iniciación sobre la respuesta productiva, características de la canal y concentración de urea en plasma. Se utilizaron 48 cerdos híbridos castrados de 7.98 kg de peso inicial y 28 d de edad, distribuidos en un diseño completamente al azar. Los tratamientos (T) fueron: T1, dieta testigo: 3350 Kcal de EM kg-1; T2: 3275 Kcal de EM kg-1 + xilanasas; T3: 3350 Kcal de EM kg-1+ xilanasas; T4: 3350 Kcal de EM kg-1+ ST + xilanasas; T5: 3275 Kcal de EM kg-1+ ST + xilanasas; T6: 3350 de EM kg-1+ ST + xilanasas. Los datos se analizaron con ANOVA, las medias de los tratamientos se compararon con la prueba de Tukey (p ≤ 0.1). Para la ganancia de peso (GDP), consumo de alimento, peso final (PVF) y ganancia de carne magra (GCM) se observó mejor respuesta en cerdos alimentados sin ST (p ≤ 0.1); compensando las xilanasas la reducción de energía. La inclusión de xilanasas en dietas con ST redujo la GDP y el pVF (p ≤ 0.1). La inclusión de ST no modificó la grasa dorsal (GD), área del músculo longissimus (AML) y GCM (p > 0.1). La GD y AML no fueron afectadas al reducir la energía en las dietas sin ST (p > 0.1). Las dietas con alto contenido de salvado de trigo afectan las variables productivas; aunque se compensa con la adición de xilanasas mientras se respete la matriz energética.

To analyze the effect of conjugated linoleic acid (CLA) on the meat of pigs (0,1%) and three crude protein (CP) levels (nursery: 20.5, 16.0, 14.5%; growing: 16, 14.5, 11.5%; and finishing: 14.0, 12.5, 11% CP), studies were conducted with 36 hybrid (Yorkshire×Landrace×Duroc) barrows (17.3-83.5 kg), which were individually penned and allotted in a completely randomized design in a factorial (2×3) arrangement for 84 d. The analysis by phases indicated that CP level affected some variables. Average daily gain, average daily feed intake, fat free lean gain, backfat thickness, longissimus muscle area and final body weight were reduced (P≤0.05) feeding the lowest CP diet in nursery and growing pigs. Plasma urea nitrogen concentration was also lower (P≤0.05) in the growing and finishing phases when fed the lowest CP level. The global analysis showed that all the analyzed variables (except feed gain ratio, lean meat percentage and plasma urea nitrogen concentration) were reduced (P≤0.05) in the pigs fed low-protein diets; plasma urea nitrogen concentration tended to be lower (P=0.07) when CP was reduced. The fatty acid profile of the meat (semimembranosus and longissimus muscles) indicated that CLA addition increased CLA isomers and total saturated fatty acids, and reduced the total monounsaturated fatty acids (P≤0.05). α-Linolenic acid was lowered in longissimus muscle of pigs fed LPD (P=0.08). These results indicated that reducing the crude protein concentration in the diet of fattening pigs from 20.5 to 16.0% in nursery phase; from 16.0 to 14.5% in growing stage; and from 14.0 to 12.5% in finishing pigs, did not negatively affect the growth performance, nor carcass characteristics. The results also showed that the addition of CLA did not improve pig response and the concentration of unsaturated fatty acids and total lipids altered the feeding LPD.

The dietary crude protein (CP) can be reduced by four percentage units when corn-soybean meal (SBM) and crystalline amino acids (AA) are used to formulate diets for growing pigs. With sorghum the results have not been conclusive. Therefore, two experiments were conducted to determine the lowest CP value in sorghum-SBM, AA supplemented diets, using plasma urea nitrogen (PUN), growth performance, and carcass characteristics as the response criteria. In Experiment 1, the percentage of CP in the treatments was as follows: T1) 16.0, control diet; T2) 14.5; T3) 13.0; and T4) 11.5. Eight gilts were used in a cross-over design with four periods of 7 days each. Blood samples were collected the last day of the period to determine PUN. Several regression models were used to obtain the best prediction of PUN. The lowest PUN indicated that CP can be reduced from 16 to 11.5%. The best regression model was the nonlineal exponential, which can predict that the minimum plasma urea concentration is obtained with 10.48% of CP. In Experiment 2, the percentage of CP and metabolizable energy Mcal kg-1) were as follows: T1) 16, 3.265, control; T2) 16, 3.165; T3) 14.5, 3.265; T4) 14.5, 3.165; T5) 11.5, 3.265; and T6) 11.5, 3.165. Thirty barrows were assigned in a completely randomized design with a 3 × 2 factorial arrangement, six treatments and five replicates of one barrow (individually penned) for each treatment. The lowest CP reduced the average daily gain, feed gain ratio, and PUN. The lowest ME reduced the feed gain ratio. These results indicate that reducing CP diminishes PUN, although some productive variables are affected.

La proteína cruda (PC) puede reducirse cuatro unidades porcentuales cuando se utiliza maíz-pasta de soya y aminoácidos (AA) para cerdos en crecimiento. Con sorgo no se han obtenido resultados concluyentes. Por ello se realizaron dos experimentos para determinar el porcentaje mínimo de PC en dietas sorgo-pasta de soya adicionadas con AA, con base en la concentración de urea en plasma de cerdos en crecimiento, y su respuesta productiva. En el Experimento 1, el porcentaje de PC en los tratamientos fue: T1) testigo, 16.0; T2) 14.5; T3) 13.0; y T4) 11.5. Se utilizaron ocho cerdas en un diseño cruzado (cross-over), con cuatro periodos de siete días. El último día de cada periodo se obtuvo sangre para determinar la concentración de urea. Se utilizaron varios modelos de regresión para obtener el que mejor predijera la concentración de urea. El menor nivel de urea indicó que la proteína puede reducirse de 16% hasta 11.5%. El mejor modelo de regresión fue el no lineal exponencial, con el que se puede predecir que la mínima concentración de urea se obtiene con 10.48% de PC. En el Experimento 2, los porcentajes de PC y las Mcal EM kg-1 fueron: T1) testigo, 16, 3.265; T2) 16, 3.165; T3) 14.5, 3.265; T4) 14.5, 3.165; T5) 11.5, 3.265; y T6) 11.5, 3.165, que se proporcionaron a 30 cerdos machos castrados (cinco repeticiones por tratamiento), alojados individualmente, en un diseño completamente al azar con arreglo factorial 3 × 2, con seis tratamientos y cinco repeticiones por tratamiento. La menor PC redujo la GDP, la conversión alimenticia y la urea en plasma. La menor EM redujo la conversión alimenticia. Lo anterior indica que disminuir la proteína reduce la urea en plasma, aunque se afectan algunas variables productivas.

Abstract: There is little information on the use of low crude protein (CP) diets for nursery pigs. Therefore, two experiments were conducted to determine the minimum percentage of CP in sorghum-soybean meal diets that would not affect growth performance, using plasma urea as a marker. In experiment 1, the treatments (%CP) were: T1) control 20.5; T2) 19.0; T3) 17.5; T4) 16.0; T5 14.5, applied to 10 nursery female pigs using a cross over design with periods of 7 d. The last day of each period, a blood sample was obtained from the cava vein to determine urea. The lowest concentration of this metabolite indicated that the CP in the diet can be reduced by as much as 16%. Using exponential non-linear regression, it was determined that the CP in the diet can be reduced by as much as 14.86% and increased by as much as 20.12% to obtain the minimum and maximum plasma urea concentration. In experiment 2, the treatments (%CP and Mcal EM kg-1) were as follows: T1) standard diet, 20.5 and 3.265; T2) 20.5 and 3.165; T3) 16 and 3.265; T4) 16 and 3.165; T5) 14.5 and 3.265; T6) 14.5 and 3.165, for 24 barrows using a randomized complete blocks design. The lowest protein level reduced plasma urea, while backfat was reduced with a reduction in energy and food conversion increased. The above indicates that the urea is reduced when CP is reduced in the diet; that backfat is lower when energy is decreased; and that other factors such as initial weight also influence the performance of nursery pigs.

Resumen: Existe poca información acerca del uso de dietas con baja proteína cruda (PC) para cerdos en iniciación. Por tanto, se realizaron dos experimentos para determinar el porcentaje mínimo de PC en dietas sorgo-pasta de soya que no afecte el comportamiento productivo, utilizando urea en plasma como indicador. En el experimento 1, los tratamientos (% PC) fueron: T1) testigo 20.5; T2) 19.0; T3) 17.5; T4) 16.0; T5) 14.5, y se aplicaron a 10 cerditas en iniciación usando un diseño cruzado con periodos de 7 d. El último día de cada periodo se obtuvo una muestra de sangre de la vena cava para determinar urea. La menor concentración de este metabolito indicó que la PC en la dieta puede reducirse hasta 16%. Mediante regresión no lineal exponencial se determinó que la PC en la dieta se puede reducir hasta 14.86% y aumentar hasta 20.12% para obtener la mínima y máxima concentración de urea en plasma. En el experimento 2, los tratamientos (%PC y Mcal EM kg-1) fueron: T1) dieta estándar, 20.5 y 3.265; T2) 20.5 y 3.165; T3) 16 y 3.265; T4) 16 y 3.165; T5) 14.5 y 3.265; T6) 14.5 y 3.165, para 24 machos castrados usando un diseño en bloques completos al azar. El menor nivel de proteína redujo la urea en plasma, mientras que al reducir la energía disminuyó la grasa dorsal y aumentó la conversión alimenticia. Lo anterior indica que la urea se reduce al disminuir la PC en la dieta; que la grasa dorsal es menor al bajar la energía; y que otros factores como el peso inicial también influyen en la respuesta de los cerdos en iniciación.