Ractopamine for finishing barrows fed restricted or ad libitum diets: performance and nitrogen balance

Abstract

Supplementation of 5 ppm of ractopamine, associated or not to feed restriction in diets with a high total lysine content (1.04%) was evaluated on performance and nitrogen balance. In experiment 1, 60 hybrid castrated male swine (76.2 ± 2.3 kg) were housed in pairs according to a randomized complete block design in a factorial treatment arrangement (2 ×2 + 1) with or without ractopamine supplementation, two forms of feeding, ad libitum and feed restriction with 1.04% lysine, and an additional treatment (control), with ad libitum feed without ractopamine with 0.8% lysine, amounting to five treatments and six replications. The final live weight, daily weight gain, daily feed intake and feed conversion for 28 days were evaluated. There were improvements in supplementation with ractopamine for final live weight, daily weight gain and feed conversion. The ad libitum feeding improved both final live weight and daily weight gain compared with ractopamine. Compared with the control, there was a decrease in feed conversion with ractopamine supplementation and improvement for final weight (FW) in the treatment with the ractopamine and ad libitum feed. In experiment 2, 30 hybrid castrated male swine (74.1 ± 2.5 kg) were housed in metabolism cages and fed the same experimental treatments to evaluate the percentages of absorbed nitrogen (Nabs), retained nitrogen (Nret), nitrogen retained from the absorbed nitrogen (Nret/Nabs) and the plasma urea concentration at 14 and 28 days. At 14 days, there was an increase in the Nret/Nabs and plasma urea concentration with ractopamine supplementation. Compared with the control, there was a decrease in the plasma urea concentration for feed restriction with ractopamine. At 28 days, there was an increase in the Nret/Nabs with ractopamine supplementation. Thus supplementation with 5 ppm ractopamine improved the performance and efficiency of swine nitrogen use. Feed restriction interfered negatively in weight gain, but it improved the efficiency of the nitrogen use of barrows.

Ractopamine and lysine levels on performance and carcass characteristics of finishing pigs

“…The backfat thickness was lower and the carcass meat yield was greater in females than in barrows. Similar results were obtained by Latorre et al (2004), Amaral et al (2009), Cantarelli et al (2009a and Cantarelli et al (2009b). By studying the effect of sex on carcass characteristics of pigs with high weights, Latorre et al (2004) considered that the influence of hormonal activity, the higher basal metabolism and the reduced consumption capacity of females may explain these results.…”

Effects of ractopamine and arginine dietary supplementation for sows on growth performance and carcass quality of their progenies1

“…Also, β-adrenergic can increase blood flow to the fetuses, via the receptors present in the smooth muscle cells of the blood vessels elevating cAMP causing vasodilation, as shown with human umbilical arteries in vitro (Karadas et al, 2007). As shown by Cantarelli et al (2009), Rac increases nitrogen retention, which can contribute to a greater amount of protein synthesis in the fetus, thereby increasing the formation of muscle tissue.…”

“…This could be associated with the fact that sows receiving Rac and Arg both separately and together had a numeri-cally greater number of total piglets born. The greater number of total piglets born could be associated with a higher embryonic survival due a better nutrient flow originated by Arg and Rac supplementation (Bird et al, 2003;Karadas et al, 2007) and the redirection of nutrients toward protein synthesis by the Rac (Cantarelli et al, 2009). According to van der Lende and van Rens (2003), at approximately 100 d of gestation, fetal mortality can increase due to limited uterine space.…”

Ractopamine as a metabolic modifier feed additive for finishing pigs: a review

“…The reduction in plasma urea occured within 30 hours of ractopamine feeding, and its withdrawal caused a marked increase (21%) circulating plasma urea nitrogen (Dunshea and King 1994). Pigs receiving 5 ppm ractopamine showed a decrease of 12% in plasma urea concentrations within 14 days of feeding, but not within 28 days; thus, the agonist may act more efficiently on protein metabolism during the first 14 days of supplementation (Cantarelli et al 2009a).…”