Growth performance, carcass characteristics, and meat quality of group-penned surgically castrated, immunocastrated, and entire male pigs
Pauly C2, Spring P2, Bee G1.
Affiliation: 1 Agroscope Liebefeld-Posieux Research Station ALP, Posieux, Switzerland; 2 Swiss College of Agriculture, Zollikofen, Switzerland.
Introduction
In Switzerland, castration of young male piglets without anaesthesia will be banned in 2009. Two alternatives, which allow avoiding surgical castration under anaesthesia, are immunocastration or fattening entire males (EM). Recently, Pauly et al. (2007) reported that EM grew slower than barrows (B) because of increased physical activity and/or limited appetite. However, the carcasses were markedly leaner whereas meat quality traits did not differ between EM and B. Until the second vaccination, immunocastrated pigs (IC) can be regarded as EM. Therefore, one can expect slower growth rate in the grower and part of the finisher period, which will then affect their overall performance. However, positive effects on carcass characteristics might be also anticipated. The study's objective was to compare the growth performance as well as the carcass characteristics and meat quality traits of B, EM and IC. Furthermore, the incidence of boar taint in the longissimus muscle (LM) was assessed by a trained sensory panel.
Materials and Methods
After weaning, 39 Swiss Large White pigs were blocked by BW into 12 blocks (11 blocks with 3 littermates per block; 1 block with 6 littermates) and assigned to B, IC, and EM. All pigs were group- penned from weaning to 107 kg BW and had ad libitum access to standard diets. In order to account for a higher protein deposition rate of EM, the amount of digestible amino acids in the diets was 10%
higher than the Swiss nutrient recommendations for grower-finisher pigs (ALP, 2005). The two IMPROVAC® injections were applied to the IC at an average BW of 22.2 and 74.3 kg, respectively.
Individual feed intake was recorded daily and BW once a week. Indole (I), skatole (S) and androstenone (A) concentrations (expressed per g lipid of the backfat) were analysed by HPLC, as described by Hansen-Møller (1994). The sensory evaluation of boar odour, boar flavour, tenderness, and juiciness of cooked loin chops was done by 10 panellists. They were specifically selected and trained based on their sensitivity to detect boar taint (S and A). Growth performance, carcass characteristics, meat quality and sensory data were analysed with the MIXED procedure (SAS Inst.
Inc., Cary, NC) with experimental treatment as fixed and litter as random effect. Least squares means were separated using the PDIFF option (P < 0.05). Non-parametric Friedman test and Bonferroni Procedure (P < 0.05) were used to evaluate I, S, and A concentrations.
Results
The ADG did not (P > 0.05) differ among the experimental groups (Table 1). However, EM consumed less feed and were more efficient than B (P < 0.001 for each). For IC, intermediate values were found, which differed (P < 0.001) from EM and B. Lean meat percentage in EM carcasses was greater (P <
0.001) than in IC, and carcasses of IC were leaner (P < 0.001) than carcasses of B. These differences resulted from higher (P < 0.001) ham percentages in the carcasses of EM and IC compared to B and higher (P < 0.001) loin percentage in the carcasses of EM compared to IC and Con. In accordance, carcasses of EM and IC had less (P < 0.001) backfat than those of B as suggested by the differences in Table 1: Growth performances and carcass characteristics of barrows (B), immunocastrates (IC) and entire male pigs (EM)
B IC EM P-values
ADG, g/d 931 920 883 0.09
ADFI, kg/d 2.36a 2.22b 2.06c < 0.001
G:F, kg/kg 0.39a 0.42b 0.43c < 0.001
Lean meat, % 53.2a 55.3b 56.7c < 0.001
10th rib fat thickness, mm 24.9a 19.3b 17.8b < 0.001
a,b,c
: Within a row, least squares means for experimental treatments without a common superscript differ (P < 0.05); P-values: probability values for the experimental groups; ADG: average daily gain; ADFI: average daily feed intake; G:F: gain to feed ratio; Lean meat: sum of denuded shoulder, back, and ham weights as a percentage of cold carcass weight
backfat thickness at the 10th rib level. Initial and ultimate pH, colour, percentage drip, thaw, and cooking loss did not (P > 0.05) differ among the experimental groups. Shear force values were higher (P < 0.01) in the LM of B and EM compared to IC (3.7, 3.8, and 3.5 kg, respectively).
EM had heavier (P < 0.001) testis (584 vs. 299 g), Bulbourethral (139 vs. 46 g), and salivary glands (68 vs. 46 g) than IC. As expected, the concentrations of A were higher (P < 0.01) in the backfat of EM than IC and B whereas the S concentrations were higher (P < 0.01) in the backfat of EM and IC than B (Table 2). It is worthwhile mentioning that the A and S concentrations in the backfat of EM was highly variable. The concentrations in the backfat of 2 and 4 EM were above the sensory threshold for A (≤ 1.7 µg) and S (≤ 0.25 µg), respectively, whereas A and S levels in the backfat of IC and B were below the aforementioned thresholds. On a scale from 1 (weak) to 9 (strong), sensory scores for boar odour and flavour were lower (P < 0.01) in the LM of B and IC than EM, whereas juiciness and tenderness scores did not (P > 0.05) differ.
Discussion
The present growth performance data confirmed those obtained in a recent Swiss field study (Jaros et al., 2005). Despite the lower ADG of IC during the grower period, the overall growth rate of IC did not differ from B due to higher ADFI and ADG after the second vaccination. Because IC can be regarded as EM until the second vaccination, the known anabolic potential of boars positively affected feed efficiency and lean tissue deposition. These benefits were not lost after the second vaccination as, overall, IC were still more efficient and had leaner carcasses than B. Compared to EM as well as B, one can observe that after the second vaccination ADFI of IC was markedly higher resulting in fatter carcasses for IC than EM. After the second vaccination, anti-GnRH response inhibits testis growth and A production. Furthermore, through changes in liver metabolism S concentrations in the backfat are also reduced. In this study, the A and S concentrations in the backfat of all IC were under the sensory thresholds, while parts of EM-littermates had higher concentrations. The low boar odour and flavour sensory scores from the LM of IC confirmed the good sensory quality of pork from animals castrated by immunization. One can conclude that compared to IC, EM were more efficient and their carcasses were leaner but the sensory scores were not satisfying. Thus, at the moment immunocastration seems to be the best alternative to avoid castration under anaesthesia.
References
ALP. Apports alimentaires et tables de la valeur nutritive pour porcs. 2005. LmZ, Zollikofen, 256 p.
Jaros P, Bürgi E, Stärk KDC, Claus R, Hennessy D and Thun R. Effect of active immunization against GnRH on androstenone concentration, growth performance and carcass quality in intact male pigs. Livestock Production Science 2005, 92, 31-38.
Hansen-Moller J. Rapid high-performance liquid chromatographic method for simultaneous determination of androstenone, skatole and indole in back fat from pigs. Journal of Chromatography B. Biomedical Applications 1994, 661, 219-230.
Pauly C, Spring P, O'Doherty JV and Bee G. Performance and carcass quality of castrates and boars fed a standard or a potato starch enriched diet. In 58th Annual Meeting of the European Association for Animal Production 2007, Dublin
Table 2: Androstenone, skatole, and indole concentrations (expressed in
µ
g per g lipid) in the backfat of barrows (B), immunocastrates (IC) and entire male pigs (EM)B IC EM P-values
Androstenone mean) (min - max)
≤ 0.2a 0.2a
≤ 0.2 – 0.5 1.2b
≤ 0.2 – 3.3 < 0.001
Skatole (mean)
(min - max)
0.05a
≤ 0.03 – 0.09
0.08b
≤ 0.03 – 0.14
0.31b
≤ 0.03 – 1.97
< 0.001
Indole (mean)
(min - max)
≤ 0.03 ≤0.03 0.04
≤ 0.03 – 0.11
0.06
a,b Within a row, least squares means for experimental treatments without a common superscript differ (P < 0.05). P-values: probability values for the experimental groups.
