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The aim of this study was to compare production variables, carcass and meat quality parameters, boar taint compounds and fatty acid composition of green and dry-cured hams, between Duroc immunocastrated males, surgically castrated males and female pigs.
Seventy-five purebred Duroc piglets were distributed by sexes thought three groups, namely females (FE, n=22), males immunocastrated (IM, n=29) and surgically castrated males (CM, n=24). Entire males were vaccinated against gonadotrophin-releasing factor (GnRF) in two doses, at an average age of 88 days (V1)and 172 days (V2) of age, respectively. Pigs were slaughtered in one day (S), at age of 215 days (average liveweight of 138.7±8.27 kg) i.e. six weeks after V2. Surgical castration was performed when piglets were under 7 days of age. Animals were reared in commercial conditions and kept in groups of 9 pigs per pen (one pen per treatment) of same sex and similar weight.
There was no significant difference in liveweight between sexes at the time of V1 and V2 vaccination. However, at the end of the treatment, IM pigs were 5.8 kg heavier than CM and 6.1 kg heavier than FE. This can be explained by the fact that ADG of IM pigs from V1 to S-1 and especially from V2 to S-1 was higher than those of FE and CM. ADG from V2 to S-1 was 139.3 g/day higher in IM than in CM and 145.9 g/day higher than in FE.
There was no significant difference in back fat depth at V1 between sexes. However, at V2, back fat thickness was 2.3 mm thicker in CM compared with FE and 3.9 mm thicker in CM compared with IM. Also at this moment, loin depth was not significantly different between sexes. Thus, the first vaccination appeared not to affect body composition of vaccinated males compared with CM. At S-1, back fat thickness in CM was 3.2 mm thicker than in IM and FE were in between. Fat thickness measured in vivo the day before slaughter had a high correlation with those measured in the carcass in the loin area with FOM or with a ruler and in the ham with a ruler. There were no significant differences in loin depth between sexes. Furthermore, no significant differences in back fat and loin depth evolution after V2 was found.
Liveweight at slaughter and carcass weight was not significantly different among sexes. The highest dressing percentage was for CM animals and the lowest for IM animals. The dressing percentage in IM is lower than FE and CM, and this could be explained by testes and associated fat and skin removal. No differences in carcass length were found between sexes. Minimum fat coverage over the GM muscle in the ham was not significantly different among sexes. This result shows that hams from IM are similar than those from FE and CM, regarding this fat thickness and it is an important result for dry cured ham production. Fat thickness variation at the last rib in the midline was 6.3 mm higher in CM compared to IM. However, between the 3rd and 4th last rib level, fat thickness measured with FOM was 4.4 mm thicker in CM than in FE and not significantly different than in IM. Despite these differences, the correlation between these three fat depths is high (r=0.89, Pb0.0001, n=72 between fat over GM and at the last rib; r=0.82, Pb0.0001, n=72 between fat over GM and between 3rd and 4th last ribs, and r=0.82, Pb0.0001, n=72 between fat at the last rib and between the 3rd and 4th last ribs). Carcass lean meat percentage was 5 percentage points higher in FE compared with CM, IM being in between. Percentage of the carcass represented by hams in IM was similar to FE, but it was 0.8 percentage points higher than in CM and this would be beneficial if the objective is dry cured ham production. Overall, pork evaluated in this study was of good quality. With the exception of pH in the SM muscle, there were no significant differences in meat quality between sexes. The pH value in the SM muscle was higher in IM compared with FE, but in all sexes the pH was very good and this difference is not relevant. There was no apparently detrimental effect of vaccination on intramuscular fat content, which was not significantly different from that of CM and FE in this study, and this is good since in dry cured ham production, the level of intramuscular fat is important to ensure a product of quality.
64% of the samples tested presented less than 0.01 μg/g of skatole (quantification limit), 32% of the samples presented 0.01 μg/g of skatole and the rest (4%), 0.02 μg/g of this compound. Regarding indole, the 57% of the samples tested less than 0.01 μg/g (quantification limit), 25% presented 0.01 μg/g, 7% presented 0.02 μg/g or 0.03 μg/g and the rest (4%) 0.04 μg/g. In this study fat had concentrations of indole and skatole well below the thresholds of 0.10 μg/g and 0.20 μg/g, above which pork would have been defined as tainted. In this trial, the 93% of the samples presented less than 0.2 μg/g (quantification limit) androstenone levels and 3.5% of the samples presented 0.2 μg/g of androstenone. Presence of higher than normal levels of androstenone in IM pigs has been reported in previous studies.
The sex effect on the subcutaneous fat composition in green hams: regarding saturated fatty acids (SFA) there were no significant differences among sexes in any of them. The percentage of total monounsaturated fatty acid (MUFA) in FE was 1.2% higher than in IM with CM being in between. This result was influenced by the percentage of oleic acid (C18:1(n−9)), which is the major monounsaturated fatty acid in subcutaneous fat and whose content was 1.3% higher in FE than in IM. No differences in total polyunsaturated fatty acids (PUFA) were found between sexes in the present study. The fatty acid composition of dry cured hams: there were significant differences among sexes only in the percentage of stearic acid, which was 0.9% higher in IM compared with CM and in the total MUFA, which were 0.9% lower in IM compared with CM. In both cases FE were in between. No important differences in fatty acid profiles have been seen in green and dry cured ham.
This result indicates that there are no differences during the curingdrying process due to the sex of the animal in the fatty acid composition and that ham from IM is suitable to produce dry-cured ham. The
high importance of the diet on the fatty acid composition iswell known. This makes it difficult to compare studies and to find out common results between them when sex effect is considered. Nevertheless, the present study shows that neither in green nor in dry-cured ham, changes in fatty acid composition of subcutaneous fat between sexes were not relevant, even though back fat thickness varied among sexes. The n−6/n−3 ratio was not modified by the sex and this implies that metabolic pathway of the long chain n−6 and n−3 fatty acid is not affected.
Conclusions
Immunocastration is a good alternative to surgical castration for the control of boar taint, moreover it produces known changes in production parameters and carcass characteristics of pigs but it hardly
modifies meat quality and fatty acid composition on fresh meat and dry-cured ham. Consequently, under the conditions of this study Duroc pigs immunocastrated are suitable for the production
of high quality dry-cured ham.
M. Font-i-Furnols, M. Gispert , J. Soler, M. Diaz J.A. Garcia-Regueiro, I. Diaz, M.C. Pearce. Effect of vaccination against gonadotrophin-releasing factor on growth performance, carcass, meat and fat quality of male Duroc pigs for dry-cured ham production. Meat Science. Vol. 91 (2):148?154.