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Effect of surgical castration, immunocastration and chicory-diet on the meat quality and palatability of boars
Meat Science 94 (2013) 402–407
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Effect of surgical castration, immunocastration and chicory-diet on the meat quality and palatability of boars M. Aluwé a,⁎, K.C.M. Langendries a, K.M. Bekaert a, F.A.M. Tuyttens a, D.L. De Brabander a, S. De Smet b, S. Millet a a
Institute for Agricultural and Fisheries Research (ILVO), Animal Sciences Unit, Scheldeweg 68, 9090 Melle, Belgium Ghent University, Faculty of Bioscience Engineering, Department of Animal Production, Laboratory of Animal Nutrition and Animal Product Quality, Proefhoevestraat 10, 9090 Melle, Belgium
b
a r t i c l e
i n f o
Article history: Received 1 September 2011 Received in revised form 25 January 2013 Accepted 26 February 2013 Keywords: Entire male pigs Immunocastration Meat quality Boar taint Chicory
a b s t r a c t This study evaluates 1) carcass quality, meat quality and palatability for barrows, immunocastrates and boars and 2) the effect of chicory supplemented feed during 10 days before slaughter on boar meat quality. At comparable carcass weights, estimated carcass lean meat percentage was higher in immunocastrates and boars than in barrows. Muscle thickness was higher for immunocastrates and barrows compared to boars, while fat thickness was lowest for immunocastrates and boars. Barrows, immunocastrates and boars differed in water holding capacity and boar taint. Home consumer panels were conducted to evaluate palatability. The consumers did detect differences in tenderness and juiciness, but not for boar taint. The chicory feed supplemented in boar feed decreased skatole concentration in backfat, without largely influencing meat quality or palatability. Not only boar taint, but also carcass and meat quality should be considered when evaluating alternatives for surgical castration. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Vaccination of boars against GnRH (Improvac®) to avoid boar taint, an unpleasant odour released by heating the meat of intact boars, has been recently accepted for use in the European Union (European European Medicines Agency, 2013). While vaccination has been shown to be effective against boar taint, performances may differ between boars and boars vaccinated against GnRH. Boars and barrows have been shown to differ in carcass and meat quality (Lundstrom, Matthews, & Haugen, 2009). Immunocastrates physiologically turn into barrows at a later age (4–8 weeks before slaughter depending on the time of second vaccination); however, the effect of this hormonal modification on performance and carcass and meat quality remains unclear. Results vary greatly depending on genetics (D'Souza & Mullan, 2003), feeding (ad lib. vs. restricted), time of second vaccination (4 weeks or more before slaughter) or housing (group or individually housed) as described by Skrlep et al. (2010). Boar taint is caused by skatole and androstenone, and to a lesser extent by indole. Various management strategies are currently being investigated to reduce boar taint in entire male pigs (Zamaratskaia & Squires, 2009). Skatole reduction efforts focus mainly on feeding strategies. Several feed components, e.g., raw potato starch, sugar beet pulp and lupines, have been tested in varying concentrations from 1 to several ⁎ Corresponding author. Tel.: +32 92722587; fax: +32 92722601. Email Addresses: [email protected], [email protected] (M. Aluwé). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.02.015
weeks before slaughter (Wesoly & Weiler, 2012). Literature also indicates reduced incidence of boar taint when boars are fed either crude/dried chicory roots or pure inulin from chicory (Hansen et al., 2006; Nielsen, Hansen, & Byrne, 2007). Byrne, Thamsborg, and Hansen (2008) suggest that the sesquiterpene lactones (bitter compounds) present in chicory also reduce skatole but to a lesser extent than inulin. In a previous study we found that supplementing feed with 5% feed grade inulin (or 3.3% pure inulin) did not significantly reduce skatole concentrations (Aluwe et al., 2009). According to Kjos, Overland, Fauske, and Sorum (2010), optimal skatole reduction results from adding 6% chicory inulin (or 4.2% pure inulin) during the last 4 weeks before slaughter. Zammerini, Whittington, & Nute (2010) evaluated the effect of 0, 3, 6 and 9% inclusion of dried chicory roots during 1 or 2 weeks on skatole reduction. Only the addition of 9% (±5.4% inulin) during 2 weeks before slaughter was effective to reduce skatole below cut-off level. To curb costs, the use of the lowest effective supplementation levels and dried chicory roots to pure inulin is preferred. Rosenvold et al. (2002) fed gilts a diet supplemented with high inulin content for 4 weeks before slaughter. This diet resulted in lower drip loss and darker but less tender meat as compared with gilts on a control diet. Ultimate pH and cooking loss were not affected. The researchers proposed that the reduced tenderness was probably due to the reduced muscle glycogen stores arising from feed that contained a low level of digestible carbohydrate and high level of fermentable carbohydrate. In general, boars have darker, less tender and less juicy meat than barrows (Bonneau & Lebret, 2010). We therefore investigated whether chicory supplementation also affects boar meat in the same way.
M. Aluwé et al. / Meat Science 94 (2013) 402–407
This study was performed to compare carcass quality, meat quality and palatability characteristics of barrows, boars vaccinated against GnRH and control boars and to evaluate the effect of 5% chicory pulp + 5% dried chicory roots inclusion in boar feed during the 10 days before slaughter. 2. Materials and methods 2.1. Animals and management On a commercial farm, 97 male piglets (hybrid sow × Pietrain boar) were surgically castrated at 4 days of age (barrows, BA), 100 male piglets were kept entire (boars, BO) and 100 male piglets were vaccinated twice against GnRH with a 2 mL dose given subcutaneously in the neck, first at 136 days of age and again at 163 days of age or 4 weeks before slaughter (boars vaccinated against GnRH, IMP). The fattening stable was divided in 7 comparable compartments which consisted of 8 pens per compartment. Pigs were allocated to 3 of these compartments at 10 weeks of age. So barrows were kept together in one compartment and immunocastrates were kept together in a second compartment of the same stable. Boars were housed in a third compartment with 4 pens with boars fed the standard diet until slaughter and 4 pens with boars which received the chicory diet during 10 days before slaughter. Average stocking density was 12 to 13 pigs per pen. Pigs had free access to water at all times and feed was given ad libitum. All BA, IMP and BO began at the same diet. Starting at 10 days before slaughter, BA, IMP and 53 boars received a standard diet (BO) and 47 boars received a mixture of 90% standard diet and 5% dried chicory pulp (1 mm) + 5% ‘Fibrofos 60’ (CBO). Fibrofos 60 (SOCODE, Warcoing, BE) is a chicory root dried at a low temperature, reduced to a powder (±1 mm), and supplemented with an anticaking agent. Minimum inulin level is 60% of dry matter. The average inulin level of the dried chicory pulp is 7%. The standard diet, the chicory diet, ‘Fibrofos 60’ and the chicory pulp were subject to proximate analysis according to EC-methods (Table 1): dry matter (EEC 1971a and 1971b), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) (Van Soest, Robertson, & Lewis, 1991), crude fibre (EC 1992) and ash (EEC 1971a, 1971b). Sugars were determined with the Luff Schoorl reagens (ISO 71/250/EEC), crude protein level was calculated based on the nitrogen level (N × 6.25), determined following Kjeldahl (ISO 5983–2) and starch was determined by enzymatic hydrolysis (NEN 3574). Pigs were fasted for 24 h before slaughter. All pigs were slaughtered on the same day by exsanguination after electric stunning. Warm carcass weight was determined after evisceration. Longissimus dorsi muscle thickness and fat thickness were determined at the slaughter line with the (GIRALDA CHOIROMETER) PG 200. The apparatus is equipped with a probe (Siemens KOM 2110) 6 mm in width, a light diode (LED Siemens F 28) and a light sensor (Siemens F 232). Lean meat content in the carcass was estimated
Table 1 Nutrient levels (g/kg) of the standard fattening diet, the chicory diet, Fibrofos and chicory pulp. Nutrients (g/kg)
Standard diet
Chicory diet
FIBROFOS 60
Chicory pulp
Dry matter NDF ADF ADLignine Crude protein Crude fat Crude ash Crude fibre Sugars Starch
879.6 164.8 57.7 9.0 145.7 51.2 43.9 51.7 49.7 400.6
886.3 155.7 59.4 5.8 142.8 50.1 46.3 47.6 83.0 330.3
931.1 58.6 53.4 0.0 50.2 5.0 47.9 39.3 574.0 86.3
887.2 267.9 245.6 11.7 65.9 14.3 54.0 186.3 156.0 36.1
403
(Ŷ ) based on this PG 200 measurement with the equation approved for use in Belgian abattoirs (97/107/EC): ^ ¼ 70; 09860−0; 84616 X þ 0; 091860 X Y 1 2 with X1 as the thickness of backfat (including rind) in millimetres, measured perpendicularly to the back of the carcass (70 mm off the split line on the outside and ±40 mm off the split line on the inside) between the third and the fourth last ribs, and X2 the thickness of the dorsal muscle in millimetres, measured at the same time, in the same place and in the same way as X1. Feed consumption, weight at 10 weeks of age and weight at slaughter (26.5 weeks of age) were determined at compartment level. For the boars (BO and CBO together), feed consumption of the chicory feed was also recorded and taken into account to calculate daily feed intake of all the boars together. Daily feed intake, daily gain and feed conversion ratio were calculated based on this data for the group of immunocastrated male pigs, the barrows and both groups of boars together. 2.2. Sampling Dorsal neck fat samples with skin were collected on the slaughter line for all BO, CBO, the first 24 BA, and the first 48 IMP to evaluate boar taint with the hot iron method. All visible meat was trimmed from the fat samples. Neck fat samples of all BO and CBO were stored vacuum packed (without skin layer) and frozen (− 20 °C) for laboratory analysis of boar taint compounds (see 3.2). Longissimus thoracis et lumborum samples with backfat layer were taken at the slaughterhouse 24 h after slaughter, vacuum packed, and stored under refrigeration (5 °C) until analysis at day 4 or 5 after slaughter. Samples of the different groups were evenly distributed over these two days. The samples were trimmed of visible fat and cut into slices of 25 mm. For the home consumer panel, 20 samples were collected from the middle of the left and right loin. Four samples were vacuum packed per animal per package. Five packages were then prepared per animal: 4 packages for the home consumer panel and 1 package for backup. Samples used for the home consumer panel and measurement of shear force and cooking loss were stored frozen at −18 °C. 3. Measurements 3.1. Meat quality Ultimate pH (pHu) was measured on two freshly cut (intact) meat samples per animal at least 48 h after slaughter (Knick, Portamess, Type 911 pH with a Xerolyt puncture-type electrode (Mettler Toledo). Colour determinants (L*, a*, b*) were measured using a HunterLab miniscan (45/0 geometry) on 2 meat samples per animal after 15 min of blooming. Average values of pHu and colour determinants were used for further statistical analysis. Drip loss was determined on meat samples of about 150 g (Honikel, 1987). Drip loss was measured using a method based on that described by Honikel (1987). Samples (109 ± 26 g) were hung by a nylon cord and placed in a plastic bag for 24 h. The percentage drip loss is calculated as follows. After wiping the sample dry, the raw meat sample was weighed. The difference in weight of the meat sample before and after 24 h was divided by the sample weight at the beginning and multiplied by 100. Initial weight of the meat samples was on average 109 ± 26 g. To measure cooking loss and Warner–Bratzler shear force measurements (Boccard et al., 1981), meat cuts (25 mm) were placed in a closed plastic bag in a hot water bath of 75 °C for 50 min, then cooled by placing the bagged samples in a cold tap water bath for 40 min. Cooking loss (%) is defined as the difference in weight of the meat sample (after wiping dry) before and after cooking and cooling, divided by the sample weight at the beginning and multiplied by 100. Average
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raw weight of the meat samples was 297 ± 69 g at the beginning of this measurement. Shear force was determined for 10 round cores (∅ 12.5 mm) per meat sample and the average value was used for further analysis. 3.2. Boar taint The neck fat samples collected at the slaughter line were used to assess boar taint using the hot iron method (Aluwé et al., 2011). For this method, neck fat was heated with a hot iron and then evaluated by an expert on a 9-point scale from 0 (neutral), 0.5, 1, 1.5, 2, 2.5, 3, 3.5 to 4 (very strong boar taint). The hot iron method was performed at the day of slaughter. Skatole, indole and androstenone concentration were determined for all boar neckfat samples (BO + CBO) by Labo CCL, ter Veghel in the Netherlands. Analysis was performed in melted fat. Skatole and indole concentration were analysed by high-performance liquid chromatography (Mathur et al., 2012). Androstenone concentration was analysed by gass-chromatography-mass spectrometry (Kragten et al., 2011). Limit of detection was 0.01 ppm for indole and skatole, and 0.04 ppm for androstenone.
Table 2 Performance of barrows (BA), boars vaccinated against GnRH (IMP) and boars (BO) measured per compartment.
Daily feed intake (kg) Daily gain (g) Feed conversion ratio (kg/kg)
BA
IMP
BO
2.19 782 2.55
2.05 812 2.24
1.97 774 2.33
triangle test with 2 bottles containing water and 1 bottle containing 0.17 mg/ml androstenone dissolved in water. Participants were asked if they could detect a difference in 1 out of the 3 bottles and smelled each bottle only once. This methodology is based on the method of Lunde, Skuterud, Nilsen, and Egelandsdal (2009). We preferred to use a simplified 4-point scale from 1 (very light), 2 (light), 3 (moderate) to 4 (very strong), which represents the simplified scale of the hot iron method. A person was determined as sensitive when a score of 3 or 4 was given to the correct bottle. This classification was adapted from the study of Weiler et al. (2000) in which a 7-point scale was used (from extremely weak to extremely strong), with score 5 to 7 classified as highly sensitive.
4. Home consumer panel 5. Statistical analysis 4.1. Home test The consumer test was performed in 407 households. Consumers were non-randomly sampled (convenience sample). Hence, sample cannot be considered as representative for the Flemish population and results are only indicative and should not be generalised to the whole population. For the recruitment of these households, employees of eight companies located in Flanders and Brussels were contacted: The institute for agricultural and fisheries research (Melle – Merelbeke), the faculty of veterinary medicine of the university of Ghent (Merelbeke), JBT Food Tech NV (Sint-Niklaas), PCS – Research Centre for Ornamental Plants (Destelbergen), Inagro – Provincial Research and Information Centre for Agriculture and Horticulture (Roeselare), Alcon (Puurs), Berkenboom primary school (Sint-Niklaas) and the agriculture and fisheries agency (Brussels). Conditions for participation: 1) each household should evaluate all three packages, 2) minimum age of 16 years old for both cook and taster. Gender and age were questioned as demographic data for both cook and taster. Participation was performed on voluntary basis, without incentive, but received all three meat packages for free. Participants were stimulated to evaluate all packages as five of the households who filled in all three questionnaires made a chance to win a gift package with regional products (with a value of € 25 per package). For 3 consecutive weeks, each household received a package (vacuum packed and frozen) with 4 slices of pork loin (originating from one animal per package). Each animal was evaluated by 4 households (i.e., the cook and a taster). Each week, each household received a package from one out of the three treatment groups (no differentiation was made between BO and CBO when organizing the distribution of the packages over the households), so each household evaluated one animal of each treatment (sex) group. Order of treatment was randomized over the three consecutive weeks. The cook was free to choose the method of preparing the sample as long as the method used was similar each week and without addition of other meat. Evaluated variables were colour (cooked), odour, flavour, juiciness, tenderness and general appreciation. The cook also evaluated the cooking odour and uncooked colour. Variables were scored on a scale from 1 (very bad) to 9 (very good). 4.2. Androstenone sensitivity After the cooking tests were completed, 136 randomly chosen participants were tested for androstenone sensitivity. This was done using a
Statistical analysis was performed using STATISTICA 9 (Statsoft, Tulsa, USA). Treatment effects were tested with ANOVA (significance level P b 0.05). Effect of sex was evaluated between BA, IMP and BO. Tukey post hoc test was used to compare treatment means. Effect of feed was evaluated between BO and CBO. Effect of sex and feed was evaluated for the carcass quality traits (warm carcass weight, estimated lean meat %, muscle thickness, fat thickness), meat quality (pHultimate, L*, a*, b*, drip loss, cooking loss, shear force), boar taint (hot iron score) and the results of the home consumer panel as evaluated by the cook and the taster. Boar taint compounds (indole, skatole and androstenone) were log transformed before statistical analysis to obtain a normal distribution and effect of feed was evaluated between BO and CBO with ANOVA. To examine associations between boar taint detection, meat quality parameters and the variables evaluated by the home consumer panel Pearson correlation coefficients were calculated (significance level P b 0.05). Table 3 Mean values of carcass and meat quality parameters of barrows (BA), boars vaccinated against GnRH (IMP), control boars (BO) and boars fed chicory (CBO). BA
Carcass (n) Carcass weight (kg) Carcass lean meat (%) Muscle thickness (mm) Fat thickness (mm) Meat quality (n) pHultimate L* a* b* Drip loss (%) Cooking loss (%) Shear force (N) Boar taint (n) Hot iron score
90 93.6 57.7a 62.4b 17.7b 97 5.6b 57.3 8.5a 16.4ab 2.9a 28.3a 28.0 25 0.2a
IMP
98 92.9 60.6b 62.5b 14.2a 100 5.6b 56.3 8.9b 16.4a 3.8b 30.8c 28.4 46 0.5a
BO
52 90.1 60.3b 60.4a 13.6a 54 5.4a 57.2 8.8ab 16.8b 3.8b 29.8b 28.1 53 1.2b
CBO
47 93.0 60.9 60.9 13.1 47 5.6 56.7 8.8 16.6 4.8 30.0 27.5 46 1.4
s.e.
P Sex
Feed
0.56 0.17 0.30 0.19
0.074 b0.001 0.021 b0.001
0.098 0.195 0.689 0.303
0.01 0.20 0.06 0.05 0.09 0.14 0.28
b0.001 0.066 0.020 0.020 b0.001 b0.001 0.778
b0.001 0.499 0.744 0.230 b0.001 0.727 0.622
0.07
b0.001
0.384
s.e.: standard error of means. P sex: P-value for the comparison of BA, IMP and BO, P feed: P-value for the comparison of BO versus CBO. L*: Luminosity, a*: redness, b*: yellowness. a,b,c : Values within one row and within the three sex groups BA, IMP and BO with no common superscript are significantly different at P b 0.05 according to Tukey's post hoc test.
M. Aluwé et al. / Meat Science 94 (2013) 402–407 Table 4 Results of the home consumer study for barrows (BA), boars vaccinated against GnRH (IMP), control (BO) and chicory fed boars (CBO) according to the cook and the taster. BA
Cook Colour uncooked Colour cooked Cooking odour Odour Flavour Juiciness Tenderness General Taster Colour Odour Flavour Juiciness Tenderness General
6.3 6.7 6.3 6.4 6.6 6.1 6.1b 6.4
6.5 6.4 6.6 6.1 5.9 6.4
IMP
6.3 6.7 6.3 6.5 6.6 6.0 5.9ab 6.3
6.4 6.3 6.5 5.8 5.8 6.2
BO
6.3 6.8 6.4 6.5 6.6 5.9 5.7a 6.2
6.4 6.3 6.4 5.7 5.6 6.1
CBO
6.2 6.6 6.3 6.4 6.4 5.8 5.6 6.1
6.4 6.5 6.5 5.7 5.5 6.1
s.e.
0.04 0.04 0.04 0.04 0.04 0.05 0.05 0.04
0.04 0.04 0.04 0.05 0.05 0.04
Table 6 Influence of androstenone sensitivity and androstenone level in fat in boars on the results of the home consumer panel for cooking odour, odour and flavour.
P
Not sensitive
Sex
Feed
0.719 0.712 0.617 0.467 0.829 0.335 0.044 0.150
0.645 0.286 0.439 0.151 0.388 0.770 0.424 0.513
0.285 0.283 0.124 0.049 0.140 0.087
405
0.914 0.141 0.425 0.751 0.636 0.830
P sex: P-value for the comparison of BA, IMP and BO, P feed: P-value for the comparison of BO versus CBO. a,b : Values within one row and within the three sex groups BA, IMP and BO with no common superscript are significantly different at P b 0.05 according to Tukey's post hoc test.
In the boar results, a GLM was performed to evaluate the influence of androstenone sensitivity (categorical variable) and androstenone level in fat (continuous variable) on the results of the home consumer panel for cooking odour, odour and flavour. The interaction between androstenone sensitivity and androstenone level in fat was non-significant (P > 0.05) and was omitted from the analysis. 6. Results and discussion Boar taint as scored with the hot iron method was higher for BO compared to BA and IMP, in agreement with the well-known fact that surgical castration and vaccination against GnRH are effective in reducing boar taint. This agrees with other studies (Pauly, Spring, O'Doherty, Kragten, & Bee, 2009; Skrlep et al., 2010; Zamaratskaia et al., 2008). Of all boars, 8% had levels higher than 100 ppb indole and only 1% had skatole levels higher than 250 ppb. Twenty six percent and 13% had androstenone levels higher than 1000 and 2000 ppb, respectively. Overall, Pearson correlation coefficients for the hot iron method were 0.50 with indole (P b 0.001), 0.15 with skatole (P = 0.161) and 0.57 with androstenone (P b 0.001). The low correlation coefficient between skatole concentration in backfatand the score given by the hot iron method is probably due to the low skatole levels of the boars involved in this study. Also in previous experiments performed at our institute, more boars deviated for androstenone as compared to skatole (Aluwé et al., 2010).
Cooks: n (%) Tasters: n (%) Total : n (%) Cooking odour1 Odour Flavour 1
16 (28%) 17 (22%) 33 (24%) 6.6 ± 1.0 6.6 ± 1.0 6.9 ± 1.2
Sensitive
41 (72%) 62 (78%) 103 (76%) 6.4 ± 1.1 6.3 ± 1.2 6.4 ± 1.4
P Sensitive
Androstenone
0.140 0.065 0.051
0.771 0.821 0.868
Cooking odour was only evaluated by the cooks
Daily feed intake (DFI), daily gain (DG) and feed conversion ratio (FCR) were calculated on compartment level. Therefore, statistics were not possible due to lack of replicates, but values are given in Table 2.DFI was highest for BA and lowest for BO. Daily gain was highest for IMP. This resulted in a numerically lower feed conversion ratio for IMP compared to BA and intermediate for BO, which is in line with results in literature for ad libitum fed pigs (Millet, Gielkens, De Brabander, & Janssens, 2011). Warm carcass weight was not significantly affected by sex. Estimated carcass lean meat percentage was higher for BO and IMP compared to BA (Table 3). In other studies, lean meat percentage of IMP is often intermediate between BO and BA (Millet et al., 2011). In the present study, however, lean meat percentage of IMP was comparable to that of boars, possibly because only 4 weeks elapsed between the second vaccination and slaughter. Muscle thickness, measured at longissimus dorsi (LD), was higher for BA and IMP compared to BO. Fat thickness of IMP and BO was lower than for BA. The carcass characteristics were not influenced by the feed treatment. Fabrega et al. (2010) and Skrlep et al. (2010) found similar results for fat thickness, while other studies reported a higher backfat thickness in IMP compared to BO. Muscle thickness may depend on the protein deposition capacity of the animals, together with their feed intake. As long as the maximal protein deposition is not reached, an increased feed intake will lead to increased muscle deposition (Millet et al., 2011). Other studies revealed no differences for muscle thickness between BA, BO or IM (Skrlep et al., 2010), while we found a higher muscle thickness for BA and IMP compared to BO. Therefore, it is likely that the protein deposit of the boars used in the present experiment was limited more by the lower feed intake of the boars compared to barrows than by their genetic capacity for lean growth. All meat quality parameters were affected by sex except for shear force (Table 3). Ultimate pH was lower for BO than for BA or IMP. Drip loss as well as cooking loss were lowest for BA compared to BO and IMP. Cooking loss was also higher for IMP compared to BO. This contradicts several other studies (D'Souza & Mullan, 2003; Gispert et al., 2010; Pauly et al., 2009; Skrlep et al., 2010; Zamaratskaia et al., 2008). Colour determinants were affected as well. BA and BO tended to have lighter meat (L*) than IMP. The redness value (a*) was higher in IMP than in
Table 5 Pearson correlation coefficients between the home consumer panel (cook) and the meat quality characteristics.
Hot iron Indole Carcass Weight Meat % Fat thickness pH L Drip loss Shear force
Colour uncooked
Colour cooked
Cooking odour
Odour
Flavour
Juiciness
Tenderness
General
−0.01 0.05 0.08 −0.03 0.05 0.11T −0.17⁎ 0.01 0.08
−0.11 0.03 0.03 0.02 −0.02 −0.04 0.00 −0.02 0.20⁎
−0.02 0.03 0.10T 0.03 −0.01 −0.03 −0.02 −0.01 0.09
−0.05 −0.19T 0.06 0.02 −0.01 −0.04 −0.06 −0.03 0.06
−0.17⁎ −0.11 0.07 −0.08 0.04 0.03 −0.03 −0.09 0.04
−0.13 −0.02 0.04 −0.11T 0.05 0.10T −0.06 −0.13⁎ 0.01
−0.20⁎ −0.10 0.08 −0.11T 0.10T 0.10T −0.01 −0.13⁎ −0.03
−0.18⁎ −0.11 0.08 −0.11T 0.10T 0.11⁎ −0.03 −0.10T 0.05
T: trend (P b 0.1). ⁎ Significant correlation (P b 0.05).
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600 BO CBO
Skatole (ppb)
500 200
100
0 0
1000
2000
3000
4000
5000
Androstenone (ppb) Fig. 1. Skatole and androstenone levels (ppb) of the control boars (BO) and the boars fed chichory (CBO).
BA. The yellowness value (b*) was higher in IMP than in BO. Results for the meat colour determinants are inconsistent in literature. Pauly et al. (2009) found no differences; Skrlep et al. (2010) found only b* higher for BA compared to BO with IMP in between; and Gispert et al. (2010) found the same result for a* as our results, but the opposite for L* as boars had darker meat than BA, with IMP intermediate. Muscle fibre characteristics may depend on genotype as well as environmental factors, such as nutrition, preslaughter and slaughter conditions. A combination of these factors probably accounts for these differences (Klont, Brocks & Eikelenboom, 1998). Of the 407 households surveyed in the home consumer study, 374 completed all 3 evaluation papers. 68% of the cooks were female (average age 38 ± 10 years) and 32% were male (average age 42 ± 13 years). The tasters were mostly male (64%, average age of 34 ± 10 years) and 36% were female (average age 40 ± 14 years). In contrast to the results of the meat quality measurements, no differences between BA, IMP and BO were found in colour before and after cooking, cooking odour, odour, flavour or general appreciation according to the results of the home consumer study (Table 4). The cooks found tenderness to be lowest for BO, intermediate for IMP and best for BA. According to the tasters there were sex differences for juiciness with BA scoring highest, but no further differentiation could be made using Tukey's post hoc test. For the general evaluation of the meat samples, BA tended to receive higher scores as compared to IMP and BO. The differences in meat quality parameters observed in this study were not all confirmed by the home consumer panel as they found no difference in colour (uncooked/cooked), (cooking) odour or flavour. Only the lower juiciness and tenderness of BO and IMP compared to BA was in line with the higher drip and cooking losses. Only a few studies have explored the effect of vaccination against GnRH on meat quality as evaluated by experts or consumers. Furnols et al. (2009) investigated the experts' sensory evaluation of BA, BO, IMP and gilts (FE). The results indicated juicier pork from BA, FE and IMP compared to BO. Pork from BO was less tender than pork from BA or IMP. Consumers preferred the odour and flavour of BA, IMP and FE in comparison with BO (Furnols et al., 2009). D'Souza & Mullan, 2003 found no effect of castration method on pH, colour or drip loss, but the consumer evaluation (aroma, flavour, tenderness, juiciness, overall acceptability) revealed an interaction between 2 genotypes and castration method. For the lean genotype, BA were preferred over BO and IMP. For the other genotype, which has a propensity for increased subcutaneous fat deposition, consumers preferred IMP over BA and BO. BO also has lower tenderness compared to BA, despite similar shear force values (Aluwé et al., 2008). In the present study, consumers did not identify problems related to boar taint in cooking odour, odour or flavour in boar meat despite the
clear presence of boar taint as revealed by the hot iron method and the laboratory analysis. Furthermore, the correlation coefficients between the boar taint detection methods and the variables assessed by the home consumer panel (as scored by the cook) were low (Table 5). Only flavour was correlated with the hot iron method (r = −0.17, P b 0.05). For the laboratory analysis, only indole was correlated with the odour scored by the cook (r = -0.19, P b 0.1). Given the generally low level of skatole in the fat, the lack of correlations is not surprising. However, the correlation between the hot iron method and androstenone concentration in the fat was rather strong (r = 0.56). It could have been expected that the correlation with androstenone is lower for a consumer panel than for the hot iron method, as not all consumers are androstenone sensitive. In total, 136 subjects were tested in this study for androstenone sensitivity (male = 38%, female = 62%; age 22-64). 76% of the subjects identified the correct bottle and scored the odour as moderate to strong. Odour and flavour scores tended to be affected by androstenone sensitivity, with androstenone-sensitive consumers giving lower odour and flavour scores (Table 6), but meat was still judged as acceptable. In line with the low correlation coefficients between the results of the home consumer panel and the boar taint compounds, we found no effect or no interaction between sensitivity and the androstenone concentration of the animals. This is in line with the results of several other studies which indicate that high androstenone levels only had limited effect on odour and flavour scores during eating when skatole levels are low (Bonneau & Chevillon, 2012; Lunde, Skuterud, Hersleth, & Egelandsdal, 2010; Meiler-Dinkel et al., 2013). Our results indicate that cooking odour was not influenced for the lean loin meat samples with low skatole levels used in our experiment. The addition of 5% chicory pulp and 5% ‘Fibrofos 60’ decreased the level of skatole from 36 ± 78 ppb to 12 ± 11 ppb (P b 0.001) (Fig. 1). However, the indole level increased from 36 ± 61 ppb to 58 ± 69 ppb (P = 0.001). No effect of diet was found on the level of androstenone (P = 0.803), with a mean level of 856 ± 786 ppb for BO and 965 ± 988 ppb for CBO. No differences were observed between BO and CBO by the sensory boar taint assessments using the hot iron method (Table 3) and the home consumer panel (Table 4). So chicory feeding was effective in decreasing skatole, while it increased indole. Xu, Hu, and Wang (2002) also found that adding fructooligosaccharides to the diet stimulated the bacterial conversion of tryptophan to indole at the expense of skatole. Similar effects were found with fermented liquid feed. However, Hansen et al. (2006) found different results when feeding chicory: the plasma indole level was reduced within a few days after chicory was included in the diet. After a feeding period of 6 weeks this reduction was no longer observed. The increase in drip loss when feeding chicory does not agree with the findings of Rosenvold et al. (2002). The reason for this discrepancy is unclear. Nevertheless, this difference in water holding capacity did not affect juiciness or tenderness between BO and CBO as scored by the home consumer panel.
7. Conclusion Meat quality measurements indicated differences between BA, IMP and BO for boar taint, pH, colour, drip loss and cooking loss. However, the results of our home consumer panel suggest that boar taint is not the consumer’s first concern; rather, tenderness and juiciness are mainly affected by the castration method. In terms of raising boars whose meat appeals to consumers, influencing tenderness and juiciness by management measures may become more important than attempting to reduce boar taint. The timing of the second vaccination is important due to its effect on performances and carcass quality, but the influence on meat quality should also be included. Further research is needed to determine whether vaccinating against GnRH more than 4 weeks before slaughter would further improve the meat quality of immunocastrated boars.
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Acknowledgments This study was financially supported by the Institute for Agriculture and Fisheries Research (ILVO), the Agriculture and Fisheries Agency (Flemish Government), Boerenbond, Belporc and VLAM and SOCODE-COSUCRA. Thanks for all the practical support given by many of our colleagues at ILVO, particularly Stefan Meirlaen. We also thank Miriam Levenson for English language editing. References Aluwé, M., Bekaert, K., Tuyttens, F., De Smet, S., De Brabander, D. L., & Millet, S. (2010). (Missing) link between different boar taint detection methods. Book of abstract of the 61th Annual Meeting of the European Association for Animal Production, 23-8-2010 (140 pp.). Aluwé, M., Millet, S., Bekaert, K. M., Tuyttens, F. A. M., De Brabander, D. L., & Van Oeckel, M. J. (2008). Tenderness of meat from entire male pigs: Effects of breed, slaughter weight and measuring method. Role of Science in the growing demand for red meat. Proc.54th ICOMST, 10-8-2008 (131 pp.). Aluwe, M., Millet, S., Nijs, G., Tuyttens, F. A. M., Verheyden, K., De Brabander, H. F., De Brabander, D. L., & Van Oeckel, M. J. (2009). Absence of an effect of dietary fibre or clinoptilolite on boar taint in entire male pigs fed practical diets. Meat Science, 82, 346–352. Aluwé, M., Tuyttens, F. A. M., Bekaert, K. M., De Smet, S., De Brabander, D. L., & Millet, S. (2011). Evaluation of various boar taint detection methods. Animal, 6, 1868–1877. Boccard, R., Buchter, L., Casteels, M., Cosentino, E., Dransfield, E., Hood, D. E., Joseph, R. L., MacDougall, D. B., Rhodes, D. N., Schön, I., Tinbergen, B. J., & Touraille, C. (1981). Procedures for measuring meat quality characteristics in beef production experiments. Report of a Working Group in the Commission o fthe European Communuities (CEC) Beef Production research Programme. Livestock Production Science, 8, 385–397. Bonneau, M., & Chevillon, P. (2012). Acceptability of entire male pork with various levels of androstenone and skatole by consumers according to their sensitivity to androstenone. Meat Science, 90, 330–337. Bonneau, M., & Lebret, B. (2010). Production systems and influence on eating quality of pork. Meat Science, 84, 293–300. Byrne, D. V., Thamsborg, S. M., & Hansen, L. L. (2008). A sensory description of boar taint and the effects of crude and dried chicory roots (Cichorium intybus L.) and inulin feeding in male and female pork. Meat Science, 79, 252–269. D'Souza, D. N., & Mullan, B. P. (2003). The effect of genotype and castration method on the eating quality characteristics of pork from male pigs. Animal Science, 77, 67–72. Fabrega, E., Velarde, A., Cros, J., Gispert, M., Suarez, P., Tibau, J., & Soler, J. (2010). Effect of vaccination against gonadotrophin-releasing hormone, using Improvac (R), on growth performance, body composition, behaviour and acute phase proteins. Livestock Science, 132, 53–59. Furnols, M. F. I., Gonzalez, J., Gispert, M., Oliver, M. A., Hortos, M., Perez, J., Suarez, P., & Guerrero, L. (2009). Sensory characterization of meat from pigs vaccinated against gonadotropin releasing factor compared to meat from surgically castrated, entire male and female pigs. Meat Science, 83, 438–442. Gispert, M., Oliver, M. A., Velarde, A., Suarez, P., Perez, J., & Furnols, M. F. I. (2010). Carcass and meat quality characteristics of immunocastrated male, surgically castrated male, entire male and female pigs. Meat Science, 85, 664–670. Hansen, L. L., Mejer, H., Thamsborg, S. M., Byrne, D. V., Roepstorff, A., Karlsson, A. H., Hansen-Moller, J., Jensen, M. T., & Tuomola, M. (2006). Influence of chicory roots (Cichorium intybus L) on boar taint in entire male and female pigs. Animal Science, 82, 359–368. Honikel (1987). How to measure the water-holding capacity of meat? Recommendation of standardized methods. In P. V. Tarrant, G. Eikelenboom, & G. Monin (Eds.), Evaluation and control of meat quality in pigs (pp. 129–142). Dordrecht, The Netherlands: Martinus Nijhof. Kjos, N. P., Overland, M., Fauske, A. K., & Sorum, H. (2010). Feeding chicory inulin to entire male pigs during the last period before slaughter reduces skatole in digesta and backfat. Livestock Science, 134, 143–145.
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Meat Science journal homepage: www.elsevier.com/locate/meatsci
Effect of surgical castration, immunocastration and chicory-diet on the meat quality and palatability of boars M. Aluwé a,⁎, K.C.M. Langendries a, K.M. Bekaert a, F.A.M. Tuyttens a, D.L. De Brabander a, S. De Smet b, S. Millet a a
Institute for Agricultural and Fisheries Research (ILVO), Animal Sciences Unit, Scheldeweg 68, 9090 Melle, Belgium Ghent University, Faculty of Bioscience Engineering, Department of Animal Production, Laboratory of Animal Nutrition and Animal Product Quality, Proefhoevestraat 10, 9090 Melle, Belgium
b
a r t i c l e
i n f o
Article history: Received 1 September 2011 Received in revised form 25 January 2013 Accepted 26 February 2013 Keywords: Entire male pigs Immunocastration Meat quality Boar taint Chicory
a b s t r a c t This study evaluates 1) carcass quality, meat quality and palatability for barrows, immunocastrates and boars and 2) the effect of chicory supplemented feed during 10 days before slaughter on boar meat quality. At comparable carcass weights, estimated carcass lean meat percentage was higher in immunocastrates and boars than in barrows. Muscle thickness was higher for immunocastrates and barrows compared to boars, while fat thickness was lowest for immunocastrates and boars. Barrows, immunocastrates and boars differed in water holding capacity and boar taint. Home consumer panels were conducted to evaluate palatability. The consumers did detect differences in tenderness and juiciness, but not for boar taint. The chicory feed supplemented in boar feed decreased skatole concentration in backfat, without largely influencing meat quality or palatability. Not only boar taint, but also carcass and meat quality should be considered when evaluating alternatives for surgical castration. © 2013 Elsevier Ltd. All rights reserved.
1. Introduction Vaccination of boars against GnRH (Improvac®) to avoid boar taint, an unpleasant odour released by heating the meat of intact boars, has been recently accepted for use in the European Union (European European Medicines Agency, 2013). While vaccination has been shown to be effective against boar taint, performances may differ between boars and boars vaccinated against GnRH. Boars and barrows have been shown to differ in carcass and meat quality (Lundstrom, Matthews, & Haugen, 2009). Immunocastrates physiologically turn into barrows at a later age (4–8 weeks before slaughter depending on the time of second vaccination); however, the effect of this hormonal modification on performance and carcass and meat quality remains unclear. Results vary greatly depending on genetics (D'Souza & Mullan, 2003), feeding (ad lib. vs. restricted), time of second vaccination (4 weeks or more before slaughter) or housing (group or individually housed) as described by Skrlep et al. (2010). Boar taint is caused by skatole and androstenone, and to a lesser extent by indole. Various management strategies are currently being investigated to reduce boar taint in entire male pigs (Zamaratskaia & Squires, 2009). Skatole reduction efforts focus mainly on feeding strategies. Several feed components, e.g., raw potato starch, sugar beet pulp and lupines, have been tested in varying concentrations from 1 to several ⁎ Corresponding author. Tel.: +32 92722587; fax: +32 92722601. Email Addresses: [email protected], [email protected] (M. Aluwé). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.02.015
weeks before slaughter (Wesoly & Weiler, 2012). Literature also indicates reduced incidence of boar taint when boars are fed either crude/dried chicory roots or pure inulin from chicory (Hansen et al., 2006; Nielsen, Hansen, & Byrne, 2007). Byrne, Thamsborg, and Hansen (2008) suggest that the sesquiterpene lactones (bitter compounds) present in chicory also reduce skatole but to a lesser extent than inulin. In a previous study we found that supplementing feed with 5% feed grade inulin (or 3.3% pure inulin) did not significantly reduce skatole concentrations (Aluwe et al., 2009). According to Kjos, Overland, Fauske, and Sorum (2010), optimal skatole reduction results from adding 6% chicory inulin (or 4.2% pure inulin) during the last 4 weeks before slaughter. Zammerini, Whittington, & Nute (2010) evaluated the effect of 0, 3, 6 and 9% inclusion of dried chicory roots during 1 or 2 weeks on skatole reduction. Only the addition of 9% (±5.4% inulin) during 2 weeks before slaughter was effective to reduce skatole below cut-off level. To curb costs, the use of the lowest effective supplementation levels and dried chicory roots to pure inulin is preferred. Rosenvold et al. (2002) fed gilts a diet supplemented with high inulin content for 4 weeks before slaughter. This diet resulted in lower drip loss and darker but less tender meat as compared with gilts on a control diet. Ultimate pH and cooking loss were not affected. The researchers proposed that the reduced tenderness was probably due to the reduced muscle glycogen stores arising from feed that contained a low level of digestible carbohydrate and high level of fermentable carbohydrate. In general, boars have darker, less tender and less juicy meat than barrows (Bonneau & Lebret, 2010). We therefore investigated whether chicory supplementation also affects boar meat in the same way.
M. Aluwé et al. / Meat Science 94 (2013) 402–407
This study was performed to compare carcass quality, meat quality and palatability characteristics of barrows, boars vaccinated against GnRH and control boars and to evaluate the effect of 5% chicory pulp + 5% dried chicory roots inclusion in boar feed during the 10 days before slaughter. 2. Materials and methods 2.1. Animals and management On a commercial farm, 97 male piglets (hybrid sow × Pietrain boar) were surgically castrated at 4 days of age (barrows, BA), 100 male piglets were kept entire (boars, BO) and 100 male piglets were vaccinated twice against GnRH with a 2 mL dose given subcutaneously in the neck, first at 136 days of age and again at 163 days of age or 4 weeks before slaughter (boars vaccinated against GnRH, IMP). The fattening stable was divided in 7 comparable compartments which consisted of 8 pens per compartment. Pigs were allocated to 3 of these compartments at 10 weeks of age. So barrows were kept together in one compartment and immunocastrates were kept together in a second compartment of the same stable. Boars were housed in a third compartment with 4 pens with boars fed the standard diet until slaughter and 4 pens with boars which received the chicory diet during 10 days before slaughter. Average stocking density was 12 to 13 pigs per pen. Pigs had free access to water at all times and feed was given ad libitum. All BA, IMP and BO began at the same diet. Starting at 10 days before slaughter, BA, IMP and 53 boars received a standard diet (BO) and 47 boars received a mixture of 90% standard diet and 5% dried chicory pulp (1 mm) + 5% ‘Fibrofos 60’ (CBO). Fibrofos 60 (SOCODE, Warcoing, BE) is a chicory root dried at a low temperature, reduced to a powder (±1 mm), and supplemented with an anticaking agent. Minimum inulin level is 60% of dry matter. The average inulin level of the dried chicory pulp is 7%. The standard diet, the chicory diet, ‘Fibrofos 60’ and the chicory pulp were subject to proximate analysis according to EC-methods (Table 1): dry matter (EEC 1971a and 1971b), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) (Van Soest, Robertson, & Lewis, 1991), crude fibre (EC 1992) and ash (EEC 1971a, 1971b). Sugars were determined with the Luff Schoorl reagens (ISO 71/250/EEC), crude protein level was calculated based on the nitrogen level (N × 6.25), determined following Kjeldahl (ISO 5983–2) and starch was determined by enzymatic hydrolysis (NEN 3574). Pigs were fasted for 24 h before slaughter. All pigs were slaughtered on the same day by exsanguination after electric stunning. Warm carcass weight was determined after evisceration. Longissimus dorsi muscle thickness and fat thickness were determined at the slaughter line with the (GIRALDA CHOIROMETER) PG 200. The apparatus is equipped with a probe (Siemens KOM 2110) 6 mm in width, a light diode (LED Siemens F 28) and a light sensor (Siemens F 232). Lean meat content in the carcass was estimated
Table 1 Nutrient levels (g/kg) of the standard fattening diet, the chicory diet, Fibrofos and chicory pulp. Nutrients (g/kg)
Standard diet
Chicory diet
FIBROFOS 60
Chicory pulp
Dry matter NDF ADF ADLignine Crude protein Crude fat Crude ash Crude fibre Sugars Starch
879.6 164.8 57.7 9.0 145.7 51.2 43.9 51.7 49.7 400.6
886.3 155.7 59.4 5.8 142.8 50.1 46.3 47.6 83.0 330.3
931.1 58.6 53.4 0.0 50.2 5.0 47.9 39.3 574.0 86.3
887.2 267.9 245.6 11.7 65.9 14.3 54.0 186.3 156.0 36.1
403
(Ŷ ) based on this PG 200 measurement with the equation approved for use in Belgian abattoirs (97/107/EC): ^ ¼ 70; 09860−0; 84616 X þ 0; 091860 X Y 1 2 with X1 as the thickness of backfat (including rind) in millimetres, measured perpendicularly to the back of the carcass (70 mm off the split line on the outside and ±40 mm off the split line on the inside) between the third and the fourth last ribs, and X2 the thickness of the dorsal muscle in millimetres, measured at the same time, in the same place and in the same way as X1. Feed consumption, weight at 10 weeks of age and weight at slaughter (26.5 weeks of age) were determined at compartment level. For the boars (BO and CBO together), feed consumption of the chicory feed was also recorded and taken into account to calculate daily feed intake of all the boars together. Daily feed intake, daily gain and feed conversion ratio were calculated based on this data for the group of immunocastrated male pigs, the barrows and both groups of boars together. 2.2. Sampling Dorsal neck fat samples with skin were collected on the slaughter line for all BO, CBO, the first 24 BA, and the first 48 IMP to evaluate boar taint with the hot iron method. All visible meat was trimmed from the fat samples. Neck fat samples of all BO and CBO were stored vacuum packed (without skin layer) and frozen (− 20 °C) for laboratory analysis of boar taint compounds (see 3.2). Longissimus thoracis et lumborum samples with backfat layer were taken at the slaughterhouse 24 h after slaughter, vacuum packed, and stored under refrigeration (5 °C) until analysis at day 4 or 5 after slaughter. Samples of the different groups were evenly distributed over these two days. The samples were trimmed of visible fat and cut into slices of 25 mm. For the home consumer panel, 20 samples were collected from the middle of the left and right loin. Four samples were vacuum packed per animal per package. Five packages were then prepared per animal: 4 packages for the home consumer panel and 1 package for backup. Samples used for the home consumer panel and measurement of shear force and cooking loss were stored frozen at −18 °C. 3. Measurements 3.1. Meat quality Ultimate pH (pHu) was measured on two freshly cut (intact) meat samples per animal at least 48 h after slaughter (Knick, Portamess, Type 911 pH with a Xerolyt puncture-type electrode (Mettler Toledo). Colour determinants (L*, a*, b*) were measured using a HunterLab miniscan (45/0 geometry) on 2 meat samples per animal after 15 min of blooming. Average values of pHu and colour determinants were used for further statistical analysis. Drip loss was determined on meat samples of about 150 g (Honikel, 1987). Drip loss was measured using a method based on that described by Honikel (1987). Samples (109 ± 26 g) were hung by a nylon cord and placed in a plastic bag for 24 h. The percentage drip loss is calculated as follows. After wiping the sample dry, the raw meat sample was weighed. The difference in weight of the meat sample before and after 24 h was divided by the sample weight at the beginning and multiplied by 100. Initial weight of the meat samples was on average 109 ± 26 g. To measure cooking loss and Warner–Bratzler shear force measurements (Boccard et al., 1981), meat cuts (25 mm) were placed in a closed plastic bag in a hot water bath of 75 °C for 50 min, then cooled by placing the bagged samples in a cold tap water bath for 40 min. Cooking loss (%) is defined as the difference in weight of the meat sample (after wiping dry) before and after cooking and cooling, divided by the sample weight at the beginning and multiplied by 100. Average
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raw weight of the meat samples was 297 ± 69 g at the beginning of this measurement. Shear force was determined for 10 round cores (∅ 12.5 mm) per meat sample and the average value was used for further analysis. 3.2. Boar taint The neck fat samples collected at the slaughter line were used to assess boar taint using the hot iron method (Aluwé et al., 2011). For this method, neck fat was heated with a hot iron and then evaluated by an expert on a 9-point scale from 0 (neutral), 0.5, 1, 1.5, 2, 2.5, 3, 3.5 to 4 (very strong boar taint). The hot iron method was performed at the day of slaughter. Skatole, indole and androstenone concentration were determined for all boar neckfat samples (BO + CBO) by Labo CCL, ter Veghel in the Netherlands. Analysis was performed in melted fat. Skatole and indole concentration were analysed by high-performance liquid chromatography (Mathur et al., 2012). Androstenone concentration was analysed by gass-chromatography-mass spectrometry (Kragten et al., 2011). Limit of detection was 0.01 ppm for indole and skatole, and 0.04 ppm for androstenone.
Table 2 Performance of barrows (BA), boars vaccinated against GnRH (IMP) and boars (BO) measured per compartment.
Daily feed intake (kg) Daily gain (g) Feed conversion ratio (kg/kg)
BA
IMP
BO
2.19 782 2.55
2.05 812 2.24
1.97 774 2.33
triangle test with 2 bottles containing water and 1 bottle containing 0.17 mg/ml androstenone dissolved in water. Participants were asked if they could detect a difference in 1 out of the 3 bottles and smelled each bottle only once. This methodology is based on the method of Lunde, Skuterud, Nilsen, and Egelandsdal (2009). We preferred to use a simplified 4-point scale from 1 (very light), 2 (light), 3 (moderate) to 4 (very strong), which represents the simplified scale of the hot iron method. A person was determined as sensitive when a score of 3 or 4 was given to the correct bottle. This classification was adapted from the study of Weiler et al. (2000) in which a 7-point scale was used (from extremely weak to extremely strong), with score 5 to 7 classified as highly sensitive.
4. Home consumer panel 5. Statistical analysis 4.1. Home test The consumer test was performed in 407 households. Consumers were non-randomly sampled (convenience sample). Hence, sample cannot be considered as representative for the Flemish population and results are only indicative and should not be generalised to the whole population. For the recruitment of these households, employees of eight companies located in Flanders and Brussels were contacted: The institute for agricultural and fisheries research (Melle – Merelbeke), the faculty of veterinary medicine of the university of Ghent (Merelbeke), JBT Food Tech NV (Sint-Niklaas), PCS – Research Centre for Ornamental Plants (Destelbergen), Inagro – Provincial Research and Information Centre for Agriculture and Horticulture (Roeselare), Alcon (Puurs), Berkenboom primary school (Sint-Niklaas) and the agriculture and fisheries agency (Brussels). Conditions for participation: 1) each household should evaluate all three packages, 2) minimum age of 16 years old for both cook and taster. Gender and age were questioned as demographic data for both cook and taster. Participation was performed on voluntary basis, without incentive, but received all three meat packages for free. Participants were stimulated to evaluate all packages as five of the households who filled in all three questionnaires made a chance to win a gift package with regional products (with a value of € 25 per package). For 3 consecutive weeks, each household received a package (vacuum packed and frozen) with 4 slices of pork loin (originating from one animal per package). Each animal was evaluated by 4 households (i.e., the cook and a taster). Each week, each household received a package from one out of the three treatment groups (no differentiation was made between BO and CBO when organizing the distribution of the packages over the households), so each household evaluated one animal of each treatment (sex) group. Order of treatment was randomized over the three consecutive weeks. The cook was free to choose the method of preparing the sample as long as the method used was similar each week and without addition of other meat. Evaluated variables were colour (cooked), odour, flavour, juiciness, tenderness and general appreciation. The cook also evaluated the cooking odour and uncooked colour. Variables were scored on a scale from 1 (very bad) to 9 (very good). 4.2. Androstenone sensitivity After the cooking tests were completed, 136 randomly chosen participants were tested for androstenone sensitivity. This was done using a
Statistical analysis was performed using STATISTICA 9 (Statsoft, Tulsa, USA). Treatment effects were tested with ANOVA (significance level P b 0.05). Effect of sex was evaluated between BA, IMP and BO. Tukey post hoc test was used to compare treatment means. Effect of feed was evaluated between BO and CBO. Effect of sex and feed was evaluated for the carcass quality traits (warm carcass weight, estimated lean meat %, muscle thickness, fat thickness), meat quality (pHultimate, L*, a*, b*, drip loss, cooking loss, shear force), boar taint (hot iron score) and the results of the home consumer panel as evaluated by the cook and the taster. Boar taint compounds (indole, skatole and androstenone) were log transformed before statistical analysis to obtain a normal distribution and effect of feed was evaluated between BO and CBO with ANOVA. To examine associations between boar taint detection, meat quality parameters and the variables evaluated by the home consumer panel Pearson correlation coefficients were calculated (significance level P b 0.05). Table 3 Mean values of carcass and meat quality parameters of barrows (BA), boars vaccinated against GnRH (IMP), control boars (BO) and boars fed chicory (CBO). BA
Carcass (n) Carcass weight (kg) Carcass lean meat (%) Muscle thickness (mm) Fat thickness (mm) Meat quality (n) pHultimate L* a* b* Drip loss (%) Cooking loss (%) Shear force (N) Boar taint (n) Hot iron score
90 93.6 57.7a 62.4b 17.7b 97 5.6b 57.3 8.5a 16.4ab 2.9a 28.3a 28.0 25 0.2a
IMP
98 92.9 60.6b 62.5b 14.2a 100 5.6b 56.3 8.9b 16.4a 3.8b 30.8c 28.4 46 0.5a
BO
52 90.1 60.3b 60.4a 13.6a 54 5.4a 57.2 8.8ab 16.8b 3.8b 29.8b 28.1 53 1.2b
CBO
47 93.0 60.9 60.9 13.1 47 5.6 56.7 8.8 16.6 4.8 30.0 27.5 46 1.4
s.e.
P Sex
Feed
0.56 0.17 0.30 0.19
0.074 b0.001 0.021 b0.001
0.098 0.195 0.689 0.303
0.01 0.20 0.06 0.05 0.09 0.14 0.28
b0.001 0.066 0.020 0.020 b0.001 b0.001 0.778
b0.001 0.499 0.744 0.230 b0.001 0.727 0.622
0.07
b0.001
0.384
s.e.: standard error of means. P sex: P-value for the comparison of BA, IMP and BO, P feed: P-value for the comparison of BO versus CBO. L*: Luminosity, a*: redness, b*: yellowness. a,b,c : Values within one row and within the three sex groups BA, IMP and BO with no common superscript are significantly different at P b 0.05 according to Tukey's post hoc test.
M. Aluwé et al. / Meat Science 94 (2013) 402–407 Table 4 Results of the home consumer study for barrows (BA), boars vaccinated against GnRH (IMP), control (BO) and chicory fed boars (CBO) according to the cook and the taster. BA
Cook Colour uncooked Colour cooked Cooking odour Odour Flavour Juiciness Tenderness General Taster Colour Odour Flavour Juiciness Tenderness General
6.3 6.7 6.3 6.4 6.6 6.1 6.1b 6.4
6.5 6.4 6.6 6.1 5.9 6.4
IMP
6.3 6.7 6.3 6.5 6.6 6.0 5.9ab 6.3
6.4 6.3 6.5 5.8 5.8 6.2
BO
6.3 6.8 6.4 6.5 6.6 5.9 5.7a 6.2
6.4 6.3 6.4 5.7 5.6 6.1
CBO
6.2 6.6 6.3 6.4 6.4 5.8 5.6 6.1
6.4 6.5 6.5 5.7 5.5 6.1
s.e.
0.04 0.04 0.04 0.04 0.04 0.05 0.05 0.04
0.04 0.04 0.04 0.05 0.05 0.04
Table 6 Influence of androstenone sensitivity and androstenone level in fat in boars on the results of the home consumer panel for cooking odour, odour and flavour.
P
Not sensitive
Sex
Feed
0.719 0.712 0.617 0.467 0.829 0.335 0.044 0.150
0.645 0.286 0.439 0.151 0.388 0.770 0.424 0.513
0.285 0.283 0.124 0.049 0.140 0.087
405
0.914 0.141 0.425 0.751 0.636 0.830
P sex: P-value for the comparison of BA, IMP and BO, P feed: P-value for the comparison of BO versus CBO. a,b : Values within one row and within the three sex groups BA, IMP and BO with no common superscript are significantly different at P b 0.05 according to Tukey's post hoc test.
In the boar results, a GLM was performed to evaluate the influence of androstenone sensitivity (categorical variable) and androstenone level in fat (continuous variable) on the results of the home consumer panel for cooking odour, odour and flavour. The interaction between androstenone sensitivity and androstenone level in fat was non-significant (P > 0.05) and was omitted from the analysis. 6. Results and discussion Boar taint as scored with the hot iron method was higher for BO compared to BA and IMP, in agreement with the well-known fact that surgical castration and vaccination against GnRH are effective in reducing boar taint. This agrees with other studies (Pauly, Spring, O'Doherty, Kragten, & Bee, 2009; Skrlep et al., 2010; Zamaratskaia et al., 2008). Of all boars, 8% had levels higher than 100 ppb indole and only 1% had skatole levels higher than 250 ppb. Twenty six percent and 13% had androstenone levels higher than 1000 and 2000 ppb, respectively. Overall, Pearson correlation coefficients for the hot iron method were 0.50 with indole (P b 0.001), 0.15 with skatole (P = 0.161) and 0.57 with androstenone (P b 0.001). The low correlation coefficient between skatole concentration in backfatand the score given by the hot iron method is probably due to the low skatole levels of the boars involved in this study. Also in previous experiments performed at our institute, more boars deviated for androstenone as compared to skatole (Aluwé et al., 2010).
Cooks: n (%) Tasters: n (%) Total : n (%) Cooking odour1 Odour Flavour 1
16 (28%) 17 (22%) 33 (24%) 6.6 ± 1.0 6.6 ± 1.0 6.9 ± 1.2
Sensitive
41 (72%) 62 (78%) 103 (76%) 6.4 ± 1.1 6.3 ± 1.2 6.4 ± 1.4
P Sensitive
Androstenone
0.140 0.065 0.051
0.771 0.821 0.868
Cooking odour was only evaluated by the cooks
Daily feed intake (DFI), daily gain (DG) and feed conversion ratio (FCR) were calculated on compartment level. Therefore, statistics were not possible due to lack of replicates, but values are given in Table 2.DFI was highest for BA and lowest for BO. Daily gain was highest for IMP. This resulted in a numerically lower feed conversion ratio for IMP compared to BA and intermediate for BO, which is in line with results in literature for ad libitum fed pigs (Millet, Gielkens, De Brabander, & Janssens, 2011). Warm carcass weight was not significantly affected by sex. Estimated carcass lean meat percentage was higher for BO and IMP compared to BA (Table 3). In other studies, lean meat percentage of IMP is often intermediate between BO and BA (Millet et al., 2011). In the present study, however, lean meat percentage of IMP was comparable to that of boars, possibly because only 4 weeks elapsed between the second vaccination and slaughter. Muscle thickness, measured at longissimus dorsi (LD), was higher for BA and IMP compared to BO. Fat thickness of IMP and BO was lower than for BA. The carcass characteristics were not influenced by the feed treatment. Fabrega et al. (2010) and Skrlep et al. (2010) found similar results for fat thickness, while other studies reported a higher backfat thickness in IMP compared to BO. Muscle thickness may depend on the protein deposition capacity of the animals, together with their feed intake. As long as the maximal protein deposition is not reached, an increased feed intake will lead to increased muscle deposition (Millet et al., 2011). Other studies revealed no differences for muscle thickness between BA, BO or IM (Skrlep et al., 2010), while we found a higher muscle thickness for BA and IMP compared to BO. Therefore, it is likely that the protein deposit of the boars used in the present experiment was limited more by the lower feed intake of the boars compared to barrows than by their genetic capacity for lean growth. All meat quality parameters were affected by sex except for shear force (Table 3). Ultimate pH was lower for BO than for BA or IMP. Drip loss as well as cooking loss were lowest for BA compared to BO and IMP. Cooking loss was also higher for IMP compared to BO. This contradicts several other studies (D'Souza & Mullan, 2003; Gispert et al., 2010; Pauly et al., 2009; Skrlep et al., 2010; Zamaratskaia et al., 2008). Colour determinants were affected as well. BA and BO tended to have lighter meat (L*) than IMP. The redness value (a*) was higher in IMP than in
Table 5 Pearson correlation coefficients between the home consumer panel (cook) and the meat quality characteristics.
Hot iron Indole Carcass Weight Meat % Fat thickness pH L Drip loss Shear force
Colour uncooked
Colour cooked
Cooking odour
Odour
Flavour
Juiciness
Tenderness
General
−0.01 0.05 0.08 −0.03 0.05 0.11T −0.17⁎ 0.01 0.08
−0.11 0.03 0.03 0.02 −0.02 −0.04 0.00 −0.02 0.20⁎
−0.02 0.03 0.10T 0.03 −0.01 −0.03 −0.02 −0.01 0.09
−0.05 −0.19T 0.06 0.02 −0.01 −0.04 −0.06 −0.03 0.06
−0.17⁎ −0.11 0.07 −0.08 0.04 0.03 −0.03 −0.09 0.04
−0.13 −0.02 0.04 −0.11T 0.05 0.10T −0.06 −0.13⁎ 0.01
−0.20⁎ −0.10 0.08 −0.11T 0.10T 0.10T −0.01 −0.13⁎ −0.03
−0.18⁎ −0.11 0.08 −0.11T 0.10T 0.11⁎ −0.03 −0.10T 0.05
T: trend (P b 0.1). ⁎ Significant correlation (P b 0.05).
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600 BO CBO
Skatole (ppb)
500 200
100
0 0
1000
2000
3000
4000
5000
Androstenone (ppb) Fig. 1. Skatole and androstenone levels (ppb) of the control boars (BO) and the boars fed chichory (CBO).
BA. The yellowness value (b*) was higher in IMP than in BO. Results for the meat colour determinants are inconsistent in literature. Pauly et al. (2009) found no differences; Skrlep et al. (2010) found only b* higher for BA compared to BO with IMP in between; and Gispert et al. (2010) found the same result for a* as our results, but the opposite for L* as boars had darker meat than BA, with IMP intermediate. Muscle fibre characteristics may depend on genotype as well as environmental factors, such as nutrition, preslaughter and slaughter conditions. A combination of these factors probably accounts for these differences (Klont, Brocks & Eikelenboom, 1998). Of the 407 households surveyed in the home consumer study, 374 completed all 3 evaluation papers. 68% of the cooks were female (average age 38 ± 10 years) and 32% were male (average age 42 ± 13 years). The tasters were mostly male (64%, average age of 34 ± 10 years) and 36% were female (average age 40 ± 14 years). In contrast to the results of the meat quality measurements, no differences between BA, IMP and BO were found in colour before and after cooking, cooking odour, odour, flavour or general appreciation according to the results of the home consumer study (Table 4). The cooks found tenderness to be lowest for BO, intermediate for IMP and best for BA. According to the tasters there were sex differences for juiciness with BA scoring highest, but no further differentiation could be made using Tukey's post hoc test. For the general evaluation of the meat samples, BA tended to receive higher scores as compared to IMP and BO. The differences in meat quality parameters observed in this study were not all confirmed by the home consumer panel as they found no difference in colour (uncooked/cooked), (cooking) odour or flavour. Only the lower juiciness and tenderness of BO and IMP compared to BA was in line with the higher drip and cooking losses. Only a few studies have explored the effect of vaccination against GnRH on meat quality as evaluated by experts or consumers. Furnols et al. (2009) investigated the experts' sensory evaluation of BA, BO, IMP and gilts (FE). The results indicated juicier pork from BA, FE and IMP compared to BO. Pork from BO was less tender than pork from BA or IMP. Consumers preferred the odour and flavour of BA, IMP and FE in comparison with BO (Furnols et al., 2009). D'Souza & Mullan, 2003 found no effect of castration method on pH, colour or drip loss, but the consumer evaluation (aroma, flavour, tenderness, juiciness, overall acceptability) revealed an interaction between 2 genotypes and castration method. For the lean genotype, BA were preferred over BO and IMP. For the other genotype, which has a propensity for increased subcutaneous fat deposition, consumers preferred IMP over BA and BO. BO also has lower tenderness compared to BA, despite similar shear force values (Aluwé et al., 2008). In the present study, consumers did not identify problems related to boar taint in cooking odour, odour or flavour in boar meat despite the
clear presence of boar taint as revealed by the hot iron method and the laboratory analysis. Furthermore, the correlation coefficients between the boar taint detection methods and the variables assessed by the home consumer panel (as scored by the cook) were low (Table 5). Only flavour was correlated with the hot iron method (r = −0.17, P b 0.05). For the laboratory analysis, only indole was correlated with the odour scored by the cook (r = -0.19, P b 0.1). Given the generally low level of skatole in the fat, the lack of correlations is not surprising. However, the correlation between the hot iron method and androstenone concentration in the fat was rather strong (r = 0.56). It could have been expected that the correlation with androstenone is lower for a consumer panel than for the hot iron method, as not all consumers are androstenone sensitive. In total, 136 subjects were tested in this study for androstenone sensitivity (male = 38%, female = 62%; age 22-64). 76% of the subjects identified the correct bottle and scored the odour as moderate to strong. Odour and flavour scores tended to be affected by androstenone sensitivity, with androstenone-sensitive consumers giving lower odour and flavour scores (Table 6), but meat was still judged as acceptable. In line with the low correlation coefficients between the results of the home consumer panel and the boar taint compounds, we found no effect or no interaction between sensitivity and the androstenone concentration of the animals. This is in line with the results of several other studies which indicate that high androstenone levels only had limited effect on odour and flavour scores during eating when skatole levels are low (Bonneau & Chevillon, 2012; Lunde, Skuterud, Hersleth, & Egelandsdal, 2010; Meiler-Dinkel et al., 2013). Our results indicate that cooking odour was not influenced for the lean loin meat samples with low skatole levels used in our experiment. The addition of 5% chicory pulp and 5% ‘Fibrofos 60’ decreased the level of skatole from 36 ± 78 ppb to 12 ± 11 ppb (P b 0.001) (Fig. 1). However, the indole level increased from 36 ± 61 ppb to 58 ± 69 ppb (P = 0.001). No effect of diet was found on the level of androstenone (P = 0.803), with a mean level of 856 ± 786 ppb for BO and 965 ± 988 ppb for CBO. No differences were observed between BO and CBO by the sensory boar taint assessments using the hot iron method (Table 3) and the home consumer panel (Table 4). So chicory feeding was effective in decreasing skatole, while it increased indole. Xu, Hu, and Wang (2002) also found that adding fructooligosaccharides to the diet stimulated the bacterial conversion of tryptophan to indole at the expense of skatole. Similar effects were found with fermented liquid feed. However, Hansen et al. (2006) found different results when feeding chicory: the plasma indole level was reduced within a few days after chicory was included in the diet. After a feeding period of 6 weeks this reduction was no longer observed. The increase in drip loss when feeding chicory does not agree with the findings of Rosenvold et al. (2002). The reason for this discrepancy is unclear. Nevertheless, this difference in water holding capacity did not affect juiciness or tenderness between BO and CBO as scored by the home consumer panel.
7. Conclusion Meat quality measurements indicated differences between BA, IMP and BO for boar taint, pH, colour, drip loss and cooking loss. However, the results of our home consumer panel suggest that boar taint is not the consumer’s first concern; rather, tenderness and juiciness are mainly affected by the castration method. In terms of raising boars whose meat appeals to consumers, influencing tenderness and juiciness by management measures may become more important than attempting to reduce boar taint. The timing of the second vaccination is important due to its effect on performances and carcass quality, but the influence on meat quality should also be included. Further research is needed to determine whether vaccinating against GnRH more than 4 weeks before slaughter would further improve the meat quality of immunocastrated boars.
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