Effects of dietary lysine and energy density on performance and carcass characteristics of finishing pigs fed ractopamine1

Abstract

Two hundred sixteen crossbred barrows and gilts (84.3 kg BW) were used to test the effects of dietary energy density and lysine:energy ratio (Lys:ME) on the performance, carcass characteristics, and pork quality of finishing pigs fed 10 ppm ractopamine. Pigs were blocked by BW and gender, allotted to 36 pens (six pigs per pen), and pens were assigned randomly within blocks to dietary treatments (as-fed basis) arranged in a 2 x 3 factorial design, with two levels of energy (3.30 or 3.48 Mcal/kg) and three Lys:ME (1.7, 2.4, or 3.1 g lysine/Mcal) levels. Pigs were fed experimental diets for 28 d, and weights and feed disappearance were recorded weekly to calculate ADG, ADFI, and G:F. Upon completion of the feeding trial, pigs were slaughtered and carcass data were collected before fabrication. During carcass fabrication, hams were analyzed for lean composition using a ham electrical conductivity (TOBEC) unit, and loins were collected, vacuum-packaged, and boxed for pork quality data collection. Energy density had no (P> 0.22) effect on ADG or ADFI across the entire 28-d feeding trial; however, pigs fed 3.48 Mcal of ME were more (P < 0.02) efficient than pigs fed 3.30 Mcal of ME. In addition, ADG and G:F increased linearly (P < 0.01) as Lys:ME increased from 1.7 to 3.1 g/Mcal. Carcasses of pigs fed 3.48 Mcal of ME were fatter at the last lumbar vertebrae (P < 0.08) and 10th rib (P < 0.04), resulting in a lower (P < 0.03) predicted fat-free lean yield (FFLY). Conversely, 10th-rib fat thickness decreased linearly (P = 0.02), and LM depth (P < 0.01) and area (P < 0.01) increased linearly, with increasing Lys:ME. Moreover, FFLY (P < 0.01) and actual ham lean yield (P < 0.01) increased as Lys:ME increased in the diet. Dietary energy density had no (P > 0.19) effect on pork quality, and Lys:ME did not (P > 0.20) affect muscle pH, drip loss, color, and firmness scores. Marbling scores, as well as LM lipid content, decreased linearly (P < 0.01) as Lys:ME increased from 1.7 to 3.1 g/Mcal. There was a linear (P < 0.01) increase in shear force of cooked LM chops as Lys:ME increased in the finishing diet. Results indicate that 3.30 Mcal of ME/kg (as-fed basis) is sufficient for optimal performance and carcass leanness in pigs fed ractopamine. The Lys:ME for optimal performance and carcass composition seems higher than that currently used in the swine industry; however, feeding very high Lys:ME (> 3.0 g/Mcal, as-fed basis) to ractopamine-fed pigs may result in decreased marbling and cooked pork tenderness.

Energia líquida e ractopamina para leitoas em terminação sob altas temperaturas ambientais

“…Porém, APPLE et al (2004) concluíram que o aumento da CM em suínos alimentados com dietas contendo ractopamina exige aumento da concentração energética da dieta, fato que contraria os resultados do presente estudo.…”

Relação da ractopamina com componentes nutricionais e desempenho em suínos: um estudo meta-analítico

“…O conteúdo de lisina nas dietas afeta a magnitude com que os suínos respondem a ractopamina (APPLE et al, 2004). Nos animais suplementados, o aumento na densidade de lisina nas dietas pode ser associado com a redução no consumo voluntário de alimento e com o incremento no ganho de peso e na eficiência alimentar (DUNSHEA et al, 1993;WEBSTER et al, 2007).…”

“…Alguns estudos sugerem que o nível de proteína altera a eficiência da ractopamina em promover a retenção de nitrogênio, sendo esta mais efetiva quando o consumo proteico é maior (REEDS & (APPLE et al, 2004). Por outro lado, a relação lisina:energia nas dietas parece afetar linearmente o ganho de peso e a eficiência alimentar dos animais (CASTELL et al, 1994;APPLE et al, 2004).…”

“…Por outro lado, a relação lisina:energia nas dietas parece afetar linearmente o ganho de peso e a eficiência alimentar dos animais (CASTELL et al, 1994;APPLE et al, 2004). É provável que o uso de aditivos adrenérgicos esteja relacionado com um aumento nas exigências de energia de mantença (REEDS & MERSMANN, 1991), mas que se relacione mais estritamente com as exigências de proteína e aminoácidos dos animais.…”

“…Assim, um aumento substancial no ganho de peso, por exemplo, estaria relacionado com a necessidade de um maior aporte de lisina nas dietas, visto a relação direta entre esse nutriente e a deposição proteica (APPLE et al, 2004). Apesar disso, o aditivo muitas vezes é utilizado a campo sem que a base nutricional das dietas seja alterada.…”