Effects of ractopamine administration and castration method on the response to preslaughter stress and carcass and meat quality in pigs of two Piétrain genotypes.

L. M. Rocha, A. M. Bridi, A. Foury, P. Mormède, A. V. Weschenfelder, N. Devillers, W. Bertoloni, L. Faucitano
Journal of Animal Science. 2013-08-01; 91(8): 3965-3977
DOI: 10.2527/jas.2012-6058

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1. J Anim Sci. 2013 Aug;91(8):3965-77. doi: 10.2527/jas.2012-6058. Epub 2013 May 8.

Effects of ractopamine administration and castration method on the response to
preslaughter stress and carcass and meat quality in pigs of two Piétrain
genotypes.

Rocha LM(1), Bridi AM, Foury A, Mormède P, Weschenfelder AV, Devillers N,
Bertoloni W, Faucitano L.

Author information:
(1)Department of Animal Science, Universidade Estadual de Londrina, Londrina
86051-990, Brazil.

The objective of this study was to evaluate the effects of ractopamine
supplementation, castration method, and their interaction on the behavioral and
physiological response to preslaughter stress and carcass and meat quality of 2
Piétrain genotypes. A total of 1,488 male pigs (115 ± 5 kg BW) were distributed
according to a 2 × 2 × 2 factorial arrangement of treatments. The first factor
was ractopamine supplementation with 2 groups of pigs (376 and 380 pigs each)
receiving 7.5 mg/kg of ractopamine (RAC) or not (NRAC) in their diet during the
last 28 d of the finishing period. The second factor was castration method, with
744 surgical castrates (SC) and 744 immunized males (IM), and the third factor
was the genotype with 2 crossbreeds containing 50% (genotype A, GA; n = 744) or
25% (genotype B, GB; n = 744) Piétrain genetics. Surgical castration took place
at 2 d of age, whereas immunization against gonadotropin-releasing factor (GnRF)
was performed through 2 subcutaneous injections of GnRF analog (Improvest, 2 mL)
at 10 and 4 wk before slaughter. At loading more vocal stimulation was needed by
the handler to drive GB pigs forward through the farm alley (P = 0.01) and
RAC-fed GB pigs through the ramp (P = 0.02). Feeding RAC to IM increased the
number of fights in lairage compared with SC (P = 0.03). Feeding RAC shortened
fighting bouts compared with NRAC pigs (P = 0.05). The SC-GA pigs showed a
greater gastrointestinal tract temperature during unloading (P = 0.05) and
lairage time (P = 0.03). Blood creatine kinase (CK) concentrations were greater
(P = 0.04) in SC compared with IM, and no difference was found in the
concentrations of stress hormones in urine collected postmortem. Dressing yield
was greater (P = 0.01) in RAC and SC-GB pigs. Carcasses from RAC pigs and IM were
leaner than those from NRAC and SC pigs (P < 0.001 and P = 0.002, respectively).
Feeding RAC to IM increased drip loss in the LM (P = 0.05). Warner-Bratzler shear
force values were slightly greater in the LM from RAC-GB pigs and from IM
compared with SC (P = 0.01 and P < 0.001, respectively) and in the
semimembranosus muscle of RAC pigs (P = 0.006). In conclusion, immunization
against GnRF more than the use of Piétrain genotypes appears to be a viable
alternative to the use of ractopamine, as it seems to promote production of lean
carcasses without compromising animal welfare and pork quality.

DOI: 10.2527/jas.2012-6058
PMID: 23658339 [Indexed for MEDLINE]

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