Effect of immunocastration and housing conditions on pig carcass and meat quality traits1

Abstract

<jats:title>Abstract</jats:title> <jats:p>The present study investigated the effects of immunocastration and housing conditions on carcass, meat, and fat quality traits. Immunocastrates (IC, n = 48), entire (EM, n = 48), and surgical castrates (SC, n = 48) male pigs were reared under three different housing conditions. The conditions were standard (n = 36), enriched (n = 36, twice as much space as standard and additional outdoor access), or standard with repeated social mixing (n = 72). Pigs of the IC group were vaccinated at the age of 12 and 22 wk. The animals were slaughtered in four batches, balanced for sex category and housing, at the age of 27 wk reaching 124.7 ± 1.0 kg. Immunocastration led to increased fat deposition (i.e., thicker subcutaneous fat at different anatomical locations, more leaf fat, fatter belly in IC than EM, P &amp;lt; 0.05) but did not affect muscularity traits. As a result, EM exhibited higher and SC lower (P &amp;lt; 0.05) carcass leanness than IC. Fatty acids composition of either subcutaneous or intramuscular fat (IMF) agreed with general adiposity, that is, IC were intermediate between EM and SC exhibiting the lowest and highest fat saturation (P &amp;lt; 0.05), respectively. Compared to SC, EM exhibited higher (P &amp;lt; 0.05) levels of muscle oxidation and collagen content than SC, with IC taking an intermediate position in the case of the level of peroxidation and collagen content, or closer to SC as regards to oxidation of muscle proteins (i.e., carbonyl groups). Meat quality (including marbling score, cooking loss, subjective color redness, and chroma) of IC was similar to EM, and both differed (P &amp;lt; 0.05) from SC. However, IC and SC had less (P &amp;lt; 0.05) tough meat than EM, consistent with protein oxidation. The effect of housing was less evident. Mixing of pigs resulted in lower (P &amp;lt; 0.05) carcass weight and fatness in all sex categories with lower (P &amp;lt; 0.05) oleic and higher (P &amp;lt; 0.05) arachidonic acid in IMF of EM.</jats:p>

The Use of Pork from Entire Male and Immunocastrated Pigs for Meat Products—An Overview with Recommendations

“…In EM, higher PUFA content is observed even at the same fat thickness as in SC, which may be due to the differences in the lipid metabolism during growth (i.e., synthesis [ 18 ] and probably also differential fatty acid utilization), governed by the presence of anabolic steroids, that negatively affect lipogenesis and promote lipid expenditure [ 19 ], which increase most notably after the puberty onset [ 5 ], when the most of the fattening pigs are usually slaughtered. The differences in PUFA content between EM and SC can range from 2% to over 3% points [ 20 , 21 ], with the differences reported in the intramuscular fat (IMF) as much as 7% points (i.e., 26.0 vs. 18.8 g PUFA/100 g lipids in EM and SC, respectively) [ 22 ]. Therefore, fat from EM is potentially more prone to oxidation [ 23 ], although there is still a lack of literature data or experimental evidence to directly link higher oxidation and fat of EM.…”

“…This concern (i.e., in terms of attachment between fat tissue layers and to underlying muscles [ 26 ]) is especially important when processing products from integral meat pieces such as hams and bellies [ 17 ]. Apart from the issue of unsaturated fat, EM also exhibit extensive carcass leanness and very low IMF content [ 6 , 23 , 27 ] with values below 2% [ 27 ] or close to 1% [ 22 ], which may be associated with traits like color, juiciness, tenderness, aroma and low processing yields, discussed in the further sections of the manuscript.…”

“…With IC, after the second immunization (usually performed 4–6 weeks prior to slaughter and at the age of 19–20 weeks), which is marked by the decline of testicular steroids, increase in voluntary feed intake, swift change in metabolism from boar-like to more castrate-like and lower basal metabolic rate, the metabolism rapidly changes towards increased fat synthesis [ 9 , 28 , 29 ]. While not markedly affecting muscle growth (remaining at the similar level), the changes are most notably observed on various carcass fat depots [ 22 ]. In this sense, meta-analytical data [ 30 ] show IC presented 0.56–2.07 mm thinner backfat than SC and 0.77–1.7 mm thicker than EM.…”

“…Similarly, higher pH and DFD were observed when EM were held overnight after transport before slaughter in comparison to SC [ 46 ]. Newer studies, however, demonstrated no differential response to stress (EM vs. IC or SC [ 47 , 48 ] and IC vs. SC [ 49 ]) or even lower stress response of EM in comparison to gilts [ 50 ] or SC [ 39 ], with little or no notable effect on meat quality [ 22 , 48 ]. It is, however, worth noting here, that the mentioned results refer to different levels and duration of stress (either chronic or acute), which may have very divergent effects on the animal physiology [ 51 ].…”

“…Similarly divergent (i.e., very study-dependent) are the results for meat color traits ( Table 1 ), which are (being also under the influence of pH) affected by similar slaughter and preslaughter factors [ 43 ]. Despite this, there are some indications for either darker (meta-analytical study results [ 14 ]), more intensive or more red muscle color in the EM compared to the SC or IC [ 22 ]. There may be several reasons for this, including the before-mentioned tendency towards faster glycogen utilization and low intramuscular fat, but also more oxidative muscle metabolic profile and associated higher pigment content (as also indicated by some recent research [ 52 ]).…”