The impact of ractopamine, energy intake, and dietary fat on finisher pig growth performance and carcass merit3

Abstract

An experiment was conducted to determine the effect of ractopamine, energy intake, dietary fat level, and sex on performance and carcass composition in finishing pigs. Three hundred six barrows and gilts were used in a factorial arrangement of treatments replicated over three seasons. Treatments consisted of two ractopamine levels (0 vs 44.7 mg/d), two sexes (barrows and gilts), two levels of fat addition (0 vs 5% added fat), and four energy intake levels (8.3, 8.9, 9.5, and 10.1 Mcal of ME/d for barrows and 7.7, 8.3, 8.9, and 9.5 Mcal of ME/d for gilts). Diets were formulated to maintain an equal lysine (28.5 g/d) intake at each feeding level through cornstarch dilution of the basal (7.7 Mcal of ME/d) diets. Pigs were fed daily based on a standard feed intake curve and prior weekly body weights. At slaughter (104 kg), carcass measurements and TOBEC HA-1 scanner measurements were recorded. Dietary fat addition improved live weight and lean efficiency (grams of carcass lean gain/kilogram of feed, P < .05). Dietary fat addition did not affect growth rate or carcass composition. Increasing energy intake resulted in a linear increase in average daily gain for both barrows and gilts (P < .01). Dietary ractopamine influenced the response of lean tissue accretion, lean tissue accretion efficiency, and fat tissue accretion to energy intake. Pigs with no added ractopamine demonstrated increased lean tissue accretion and improved efficiency and decreased fat tissue accretion with increasing energy intake (up to 9.5 Mcal of ME intake for barrows and 8.9 Mcal of ME intake for gilts). In contrast, pigs with added ractopamine did not respond to increasing energy intake and demonstrated increased fat tissue accretion with increasing energy intake. The response to ractopamine for growth was greatest from d 6 to 22 on test or during the test gain period of 7 to 18 kg. After d 22, the response of ractopamine declined linearly. These results indicate that ractopamine increases growth rapidly at the onset of feeding until a plateau is reached, after which there is a linear decline in growth response.

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

“…Por outro lado, a inclusão deste aditivo nas dietas contendo os demais níveis energéticos não influenciou (P>0,05) a ET dos animais. O mesmo foi constatado por WILLIAMS et al (1994), que verificaram menor ET em suínos alimentados com dietas contendo ractopamina quando apresentaram baixos consumos de energia metabolizável. A partir dos resultados observados no presente estudo, pode-se inferir que a eficiência da ractopamina em reduzir a lipogênese no tecido adiposo do suíno é mais pronunciada nas situações em que as dietas apresentam maior conteúdo energético, principalmente sob a forma de lipídios.…”

“…De acordo com WILLIAMS et al (1994), leitoas alimentadas com dieta sem ractopamina apresentaram melhora na percentagem de carne magra até o consumo de 8,9Mcal de energia metabolizável dia -1 , todavia o aumento da ingestão energética não resultou em melhora da deposição de carne magra. 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.…”

Desempenho, características de carcaça e composição óssea de suínos alimentados com diferentes níveis de ractopamina e fitase

“…O experimento teve duração de 21 dias, como forma de observar a máxima resposta em desempenho, como sugerido por Williams et al (1994) e Armstrong et al (2004), que observaram queda nas respostas após esse período devido ao fenômeno chamado down-regulation ou dessensibilização dos receptores β-adrenérgicos (Moody et al, 2000).…”

Características químicas y sensoriales de la carne de cerdo, en función del consumo de dietas con ractopamina y diferentes concentraciones de lisina

“…Both, the manufacturer and different authors (16,17) , recommend RAC to be applied in diets containing a minimum of 16% crude protein (CP) to ensure a sufficient amount of amino acids concentration to support muscular development. However, other authors believe that the effect of RAC is more efficient by dietary energy restriction than protein levels (18,19) .…”

“…Sin embargo, otros autores (18,19) sugieren que los efectos de la RAC pueden ser afectados más por la restricción de energía, que por la de proteína.…”