Effect of CLA supplementation to low-protein diets on the growth performance, carcass characteristics, plasma urea nitrogen concentration, and fatty acid profile in the meat of pigs

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.

Respuesta productiva y concentración de urea en plasma de cerdos en crecimiento alimentados con dietas sorgo-pasta de soya con baja proteína / Growth performance and plasma urea concentration of growing pigs fed sorghum-soybean meal, low-protein diets

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.