Ractopamina em raÃÃes para suÃnos em terminaÃÃo com alimentaÃÃo à vontade ou restrita / Ractopamine in rations for finishing pigs with feed ad libitum or restrict

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Two experiments were conducted to evaluate the supplementation of 5 ppm of ractopamine (RAC) associated or not with feed restriction in rations with a high content of total lysine (1.04%) on performance, carcass characteristics, carcass quality, economic viability, weight and commercial swine carcass cuts, nitrogen balance and determination of plasma urea. In experiment I, 60 hybrid, castrated swine (76.2  2.3 kg) were housed in two in a randomized block design in a factorial scheme 2x2+1 with or without the RAC supplementation, two ways of rationing, ad libitum (AV) and restricted feeding (RA) with 1.04% of lysine and an additional (control), with AV ration without RAC with 0.8% of lysine, amounting to five treatments and six replicates to evaluate the animals performance. At the end of the experimental period (28 days), the animals were slaughtered and the left carcass chilled for evaluation of it and of the primal cuts of the carcass. The variables investigated were: final weight (PF), daily weight gain (GPD), daily ration consumption (CDR), feed conversion (CA),carcass yield (RC), prepared left carcass weight (PCEP), loin eye area (AOL), backfat thickness (ET), amount of meat (Qcarne), percentage of meat (Pcarne), amount of fat (Qgord), percentage of fat (Pgord), meat: fat ratio (C:Gcarc) of the carcass, allowance index (IB), crude earnings (RB), the total cost (CT) and net earnings (RL) of each treatment, weight of ham (Ppern), shoulder (Ppal), boneless shoulder (Psobpal), bone-in loin (PcarrÃ) and tenderloin (Pfil), percentage of carne do ham (%Carpern), shoulder (%Carpal), boneless shoulder (%Carsobpal), bone in loin (%CarcarrÃ), belly weight, (Pbarr), average thickness of the belly (EMbarr), belly flexibility (FLbarr), in addition to the amount of meat, (Carbarr), fat (Gordbarr) and meat: fat ratio (C:Gbarr) of the belly. There were significant improvements for the groups of RAC-treated swine for PF (P<0.05), GPD (P<0.01) and CA (P<0.05), compared with the animals fed without supplementation with RAC. Compared with the control, there were significant improvements (P<0.05) in CA for the two treatments with RAC, but for the variable PF, there were significant improvements (P<0.05) only for the RAC-treatment and associated with the AV ration. There were significant improvements for the group of RAC-treated swine for AOL (P<0.05), ET (P<0.05), Qcarne (P<0.01), Pcarne (P<0.01), Qgord (P<0.05), Pgord (P<0.05), IB (P<0.01), RB (P<0.01), and RL (P<0.05), compared with the group of animals without RAC. The C:Gcarc was higher only for the treatment with RAC associated with RA. When RAC was compared with the control treatment, there were significant improvements (P<0.05) for RC, ET, Qcarne, Pcarne, and RB for the RAC-treated animals. Nevertheless, there were significant improvements in the variables Qgord, Pgord, C:Gcarc and IB only for the treatment with RAC associated with RA, when compared with the control. There was increase of the tenderloin weight (P<0.01) for the RAC-treated animals, when compared with the animals without RAC. There was an increase (P<0.05) in the percentage of meat of all the evaluated commercial cuts for the RAC-treated animals. Relative to the percentage of meat in the cuts, there was differences only in the %Carcarrà (P<0.05), with values higher for the RAC-treated animals, compared with the control and %Carpern (P<0.05), which was greater for the RAC-treated animals associated with RA, when compared with the control. There was difference in the FLbarr with higher values (P<0.05) for the animals were given AV ration. RAC-treated animals presented greater Carbarr (P<0.05) and greater C:Gbarr (P<0.01), when compared with the animals without RAC. As compared with the control, the animals which were given RAC showed higher Carbarr (P<0.05), lower Gorbarr (P<0.05) and higher C:Gbarr (P<0.05). In Experiment II, 30 hybrid, castrated male swine (74.1  2.5 kg) were housed in metabolism cages being given the same experimental treatments to evaluate the percentage of absorbed nitrogen (%Nabs), percentage of retained nitrogen (%Nret), percentage of nitrogen retained from the absorbed (%Nret/abs) and concentration of plasma urea (CUP) at 14 and 28 days. At 14 days, there was an increase (P<0.05) in the %Nret/abs and CUP with the supplementation of RAC. Compared with the control, there was a decrease (P<0.05) of the CUP for RAC with RA. At 28 days, there was an increase (P<0.05) in the %Nret/abs (P<0.05) with RAC supplementation. It follows that the supplementation with 5 ppm of ractopamine improves performance, the carcass characteristics and composition, the percentage of meat in the swine carcass cuts, the efficiency of utilizing nitrogen, making its use in diets fro finishing swine economically viable. The association of ractopamine with feed restriction reduces the fat in the carcasses. Feed restriction decrease the belly flexibility.

ASSUNTO(S)

ractopamina feed restriction suÃnos zootecnia restriÃÃo alimentar ractopamine pigs

ACESSO AO ARTIGO

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