Períodos de suplementação de ractopamina em dietas para fêmeas suínas abatidas acima de 130 kg

Abstract

This study aimed to evaluate the effects of different supplementation periods of ractopamine (RAC) to finished pigs above 130 kg on performance, blood parameters, economic viability, carcass characteristics, meat quality, bonus index and profitability. During the experimental period (101 to 170 days of age), 32 gilts were distributed in a randomized block design, with four treatments and eight replicates each, considering the pen with one animal as the experimental unit. The treatments consisted of: SRAC – Control group, diet without RAC supplementation; RAC14 – Diet with 10 ppm RAC supplementation from 143 to 170 days of age; RAC14/14 – Diet with 10 ppm RAC supplementation from 129 to 142 and 157 to 170 days of age; RAC28/28 – Diet supplemented with 10 ppm of RAC from 101 to 128 and 143 to 170 days of age. In period I (101 to 128 days of age), gilts in the RAC28/28 had better feed conversion than the other treatments (P< 0.05). In period II (101 to 142 days of age), gilts in the RAC28/28 group had significantly lower feed conversion than those in the SRAC and RAC14 groups (P< 0.05), but did not differ from gilts in the RAC14/14 group. In period III (101 to 156 days of age), the RAC28/28 and RAC14/14 groups showed better feed conversion than SRAC (P< 0.05). Considering the total period (101 to 170 days of age), gilts from the RAC28/28, RAC14/14 and RAC14 groups presented higher ADG in relation to SRAC (P< 0.05). Furthermore, in this period, the RAC28/28 group maintained the lowest feed conversion, followed by gilts from the RAC14/14 and RAC14 groups (P< 0.05). Gilts in the RAC28/28 group had lower backfat thickness (P< 0.05) at 156 and 170 days of age, compared to the control group, followed by gilts in the RAC14/14 and RAC14 groups in the last period analyzed. Gilts in the RAC28/28 group had higher serum concentrations of total cholesterol and LDL, as well as lower plasma urea levels, followed by gilts in the RAC14 and RAC14/14 groups at 170 days of age (P< 0.05). Gilts in RAC28/28 had a lower average cost per kilogram of live weight and cost index, as well as a higher economic efficiency index, gross and net income without bonus index in relation to SRAC (P< 0.05), not differing from RAC14 and RAC14/14. Dietary supply of RAC, regardless of the period tested, provided greater slaughter weight, hot carcass weight, loin depth and bonus index, as well as higher gross and net income with bonus index in relation to the SRAC group (P< 0.05). Gilts from RAC14/14 and RAC28/28 showed lower fat thickness and greater loin eye area, quantity and percentage of lean meat in relation to the SRAC group (P< 0.05), not differing from RAC14. There was no significant effect (P> 0.05) of the experimental treatments on the meat quality parameters. Ractopamine supplementation for finishing gilts promotes higher serum concentrations of total and LDL cholesterol, reduces plasma urea levels, improves performance, slaughter weight and carcass conformation, as well as contributing to greater economic viability, gross and net income, especially when provided during two periods of 28 days, with 14-day intervals between them.