Ractopamine supplementation improves leanness and carcass yield, minimally affecting pork quality in immunocastrated pigs

Osmar Antonio Dalla Costa, Vivian Feddern, Natalia Bortoleto Athayde, Naiana Einhardt Manzke, Roberto de Oliveira Roça, Letícia dos Santos Lopes, Gustavo Julio Mello Monteiro de Lima
2018 Scientia Agricola  
This study was carried out to determine the combining effects of feeding up to 15 mg kg -1 ractopamine (RAC) to physically castrated (PC) pigs or those injected with an anti-GnRF vaccine (IC), on growth performance during suckling, weaning, growing and finishing phases. Out of a total of 1,160 male piglets, 50 % were surgically castrated at age 7, while 50 % underwent immunization against GnRF on the 103 rd and 136 th day of life. A completely randomized design, with two treatments (PC and IC),
more » ... tments (PC and IC), was used from the 1 st until the 60 th day of life. Afterwards, 792 animals, PC and IC, selected according to overall average weight (23.3 ± 0.69 kg) were allotted based on a completely randomized block design with a 2 × 4 factorial arrangement of treatments (castration categories × RAC levels) with 9 replications (11 animals) per main combination effect. IC growing pigs improved feed conversion due to lower average daily feed intake and higher average daily gain (ADG). During the finishing phase, both RAC and immunocastration increased body weight, but the effects were independent. RAC, on its own improved ADG and feed conversion. However, pigs fed 10 mg kg -1 RAC had higher blood lactate compared to those fed lower levels, suggesting that these animals were more susceptible to stress. Muscle depth was influenced only by RAC, whereas fat thickness was lower for IC. Lean meat increased and fat decreased in the shoulder and belly of IC; RAC had a positive effect on belly lean meat only. Either immunocastration or RAC inclusion (at least 5 mg kg -1 ) promoted muscle gain and fat reduction in pig carcass, adding value to pork. Animals, housing, and handling The experiment was conducted in commercial facilities, from the same integrator, located in the Midwest Region of the state of Santa Catarina, Brazil (27º08'58" S; 52º18'38" W; 550 m height). A total of 1,160 male piglets (Camborough 25 × AGPIC 337) were produced in 17 farms and selected according to weight (23.3 ± 0.69 kg) and birth within the same week. These genetic lines were chosen because they are directed to meat production and low fat deposition. Surgical castration was performed on half of the littermates on the 7 th day of life whereas the remaining animals were immunocastrated through two vaccinations on the 103 rd and 136 th days of age using a safety vaccination gun at a dose of 2 mL of commercial vaccine (0.4 mg of 2-10 GnRF conjugated to Diphtheria Toxoid) behind and below the ear base. The chronology of the experiment is illustrated in Figure 1 . At weaning, on day 27, mortalities and runt piglets accounted for a total of 56 piglets (PC = 43 and IC = 13). All animals from the 17 farms were weighed at weaning, and the remaining 1,104 animals were transferred to a single nursery and allotted by castration category to 40 pens of 27 or 28 pigs. The end of the initial phase was at 60 d of age, when all pigs were weighed again. Based on castration category and blocking for similar weight, 792 pigs were transferred to a growing-finishing facility divided into 72 pens of 11 animals each, according to a randomized complete block design (RCBD), in a 2 × 4 factorial arrangement (two castration categories × four levels of RAC inclusion) with nine replications per combination of main factors. Mash diets had the same ingredient composition throughout the experiment, except for the RAC inclusion levels which were only fed for 28 days prior to slaughter (Table 1) . Performance evaluation, pre-slaughter, and slaughter handling Pig performance was evaluated during the initial phase (0 to 27 days), the nursery (28 to 60 days), the
doi:10.1590/1678-992x-2016-0321 fatcat:shvhjpmqcjaqbof334sbb6xryu