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

Gustavo Julio Mello Monteiro de Lima,Letícia dos Santos Lopes,Roberto de Oliveira Roça,Naiana Einhardt Manzke,Osmar Antonio Dalla Costa,Natalia Bortoleto Athayde,Vivian Feddern

doi:10.1590/1678-992x-2016-0321

Gustavo Julio Mello Monteiro de Lima, Letícia dos Santos Lopes

Open Access

https://doi.org/10.1590/1678-992x-2016-0321

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Abstract

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 103rd and 136th day of life. A completely randomized design, with two treatments (PC and IC), was used from the 1st until the 60th 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.

Highlights

The meat market demands high nutritional value products with low fat content, suitable tenderness and attractiveness to the most selective consumers
immunocastrated pig (IC) pigs had higher body weight (BW) and final BW (p < 0.001) but there were no differences in average daily feed intake (ADFI), average daily gain (ADG) and feed conversion, compared to the physically castrated (PC) category
The growth rate of different body tissues depends on many factors such as animal age, genotype, sex, physiological maturity, body composition, initial and final body weight, level of feed intake, growth rate, thermal environment, immunological status and feed processing and delivery (Patience et al, 2015)

Summary

Introduction

The meat market demands high nutritional value products with low fat content, suitable tenderness and attractiveness to the most selective consumers. An immunocastrated pig (IC) is a boar immunized against gonadotrophin-releasing factor (GnRF). This practice, together with the addition of ractopamine, is one technological innovation available to achieve these goals. Ractopamine hydrochloride (RAC) is used as a repartitioning agent in pig diets 28 days before slaughter to increase muscle protein synthesis (Ulrey et al, 2013), improve animal performance (Puls et al, 2014) and reduce carcass fat (Moore et al, 2009) without altering meat quality (Elsbernd et al, 2015). Swine nutritionists elected RAC in a survey as the 13th most important technological innovation out of 20 that comes to mind when considering the top nutritional discoveries of the past century (Cromwell, 2009)

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