Effect of genotype, housing system and hay supplementation on carcass traits and meat quality of growing rabbits

Meat Science 110 (2015) 126–134

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Effect of genotype, housing system and hay supplementation on carcass traits and meat quality of growing rabbits A. Dalle Zotte a,⁎, K. Szendrő b, Zs Gerencsér c, Zs Szendrő c,d, M. Cullere a, M. Odermatt d, I. Radnai c, Zs Matics c a

Department of Animal Medicine, Production and Health, University of Padova, Agripolis, Viale dell'Università 16, 35020 Legnaro (PD), Italy Kaposvár University, Faculty of Economic Sciences, 40., Guba Sándor Str., H-7400 Kaposvár, Hungary Kaposvár University, Faculty of Agricultural and Environmental Sciences, 40., Guba Sándor Str., H-7400 Kaposvár, Hungary d Olivia Ltd, Mizse 94, 6050 Lajosmizse, Hungary b c

a r t i c l e

i n f o

Article history: Received 24 February 2015 Received in revised form 27 May 2015 Accepted 13 July 2015 Available online 17 July 2015 Keywords: Rabbit Breed Housing Feeding Carcass traits Meat quality

a b s t r a c t The aim of the study was to examine the effects of genotype (Pannon Large × Pannon Ka/Large/or Hungarian Giant × Pannon Ka/Hung), housing system (Cage or small Pen) and hay supplementation (Pellet without or with Hay/P + Hay/) on carcass and meat (Longissimus dorsi/LD/ and hind leg/HL/) quality of growing rabbits. Large rabbits showed higher carcass weights, as well as higher fatness and meatiness compared to Hung rabbits. Caged rabbits were heavier, with higher prevalence of the mid part of the carcass, and showed higher fatness and lower meat toughness than Penned rabbits. Caged rabbits meat was richer in MUFA, but poorer in PUFA and Σ n−6 FA. Hay supplementation impaired carcass weight, carcass fatness, L* and a* color, and lipids content. P + Hay increased the HL meat content of C18:3 n−6 and C20:5 n−3 FA. Overall results offer further information on how alternative breeds, housing systems and feeding strategies can affect carcass traits and meat quality. © 2015 Elsevier Ltd. All rights reserved.

1. Introduction In addition to rabbit meat products from intensive systems, there is a growing interest in meats originating from less intensive breeds kept in alternative housing and feeding conditions (Dalle Zotte & Paci, 2014). This has led to the development of various alternative production systems. Most countries have one or more local breeds that play significant roles in commercial production. One such breed is the Giant rabbit, which can be used either as pet rabbit or terminal breed. Whereas several papers have been published on the carcass traits of Flemish Giant (Lukefahr, Hohenboken, Cheeke, Patton, & Kenninck, 1982; Ozimba & Lukefahr, 1991; Prayaga & Eady, 2003;), Spanish Giant (López & Sierra, 2002), German Giant (Bianospino, Wechsler, Fernandes, Roça, & Moura, 2006), Moravian Blue (Tůmová et al., 2013), and Hungarian Giant (Holdas & Szendrő, 2002), only few have investigated their meat quality (Bolet, 2002; Maj, Bieniek, Sternstein, Węglarz, & Zapletal, 2012). The effect of housing condition on carcass traits and meat quality has been summarized by Szendrő and Dalle Zotte (2011). Most studies showed that increasing group size led to lower dressing out percentage, fore part to reference carcass, meat to bones and fat depot ratios but higher hind part weight, while the mid part ratio remained the

⁎ Corresponding author. E-mail address: [email protected] (A. Dalle Zotte).

http://dx.doi.org/10.1016/j.meatsci.2015.07.012 0309-1740/© 2015 Elsevier Ltd. All rights reserved.

same (Dal Bosco, Castellini, & Mugnai, 2002; Dalle Zotte et al., 2009; Combes, Postollec, Cauquil, & Gidenne, 2010). In nutrition, one alternative method consists in adding fresh or dried forage to pelleted diets (Carabaño & Fraga, 1991). Scientists have tested several forages: dehydrated alfalfa on carcass traits and meat quality (Bianchi, Petracci, & Cavani, 2006), fresh alfalfa on carcass traits and fatty acid (FA) profile (Capra et al., 2013), or on FA profile (Dal Bosco et al., 2014), and green barley on dressing out percentage (Morales, Fuente, Juárez, & Ávila, 2009). In most of the experiments, the effect of each factor was investigated separately. The aim of the current study was to examine both the separate and combined effects of genotype, housing system, and hay supplementation on carcass traits and meat quality of growing rabbits. 2. Material and methods The study was approved by the Ethical Committee for Animal Experimentation of Kaposvár University. The experiment was carried out at Kaposvár University. Pannon Ka (maternal line of the Pannon Breeding Program) females were inseminated with pooled and diluted semen of Pannon Large (terminal line of the Pannon Breeding Program, hereafter Large) or Hungarian Giant (Hung) males. The Large rabbits were selected for daily weight gain and hind leg muscle volume based on computer tomography (CT) data (Matics et al., 2014). Hung rabbit semen was obtained from a private breeder. Hungarian Giant is a traditional breed in Hungary that originated from a native colored

A. Dalle Zotte et al. / Meat Science 110 (2015) 126–134

population that was crossed with Flemish Giant and other giant breeds (Holdas & Szendrő, 2002). Some breeders also use some intensive breeds now to improve performance, however. The Large and Hung rabbits (n = 336) were weaned at 5 weeks of age; one half was kept in cages (61 × 32 cm, 3 rabbits/cage), the other half in small open top pens (190 × 50 cm, 14 rabbits/pen). In both cases, the floors were wire-mesh, without elevated platform, and the stocking density was 16 rabbits/m2. Two subgroups were formed: rabbits receiving only commercial pellet and rabbits fed commercial pellet plus grass hay, ad libitum. The design of the experiment is shown in Fig. 1. Water was available ad libitum from nipple drinkers. The room temperature was 15–17 °C, and the daily lighting period was 16 h. Live performances of rabbits have been reported elsewhere (Szendrő et al., 2015). At 12 weeks of age, rabbits (n = 287) were transported to a slaughterhouse located 200 km from the experimental farm. Fasting time was 6 h, including the 4 h for transportation. Slaughter and carcass dissection procedures were performed using recommendations of the World Rabbit Science Association (WRSA) described by Blasco and Ouhayoun (1996). Rabbits were slaughtered by cutting the carotid arteries and jugular veins after electro-stunning. The slaughtered rabbits were bled, and then the skin, genitals, urinary bladder, gastrointestinal tract, and the distal part of legs were removed. Hot carcasses (with head, set of organs /consisting of thymus, trachea, esophagus, lung and heart/, liver, kidneys, and perirenal and scapular fat) were weighed, then chilled at +4 °C for 24 h. The chilled carcasses (CC) were then weighed. The head, set of organs, liver, and kidneys were removed from each carcass to obtain the reference carcass (RC), which included the meat, bones, and fat deposits. The carcasses were then cut between the 7th and 8th thoracic vertebra and between the 6th and 7th lumbar vertebra to obtain the fore, mid, and hind parts, which were weighed separately. The dressing out percentage (DoP: CC weight divided by slaughter weight /SW/ and multiplied by 100) and the ratio of the organs and carcass parts to either SW or RC weight were calculated as required. Subsequently, the Longissimus dorsi (LD) muscle and hind legs (HL) were dissected from all animals and then weighed. Chemical compositions of diets were shown by Szendrő et al. (2015), and FA compositions of pellet and hay are presented in Table 1. Lipid extraction and fatty acid methyl esters (FAME) determination of the experimental diets was performed according to Dalle Zotte et al. (2014). 2.1. Rabbit meat rheological and chemical analyses, lipid extraction and FA determination A total of n = 120 LD and HL were used for pH and color measurements. The pH was measured 24 h post mortem (ultimate pH or pHu)

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Table 1 Fatty acid composition of pelleted diets and hay. Fatty acid profile

Pelleted diet

Grass hay

C10:0 C12:0 C14:0 C14:1 C15:0 C15:1 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 n−9 (oleic) C18:1 n−11 (trans vaccenic) C18:2 ct n−6 (linoleic) C18:3 n−6 (γ-linolenic) C18:3 n−3 (α-linolenic) C18:2 c9-t11 C20:0 C20:1 n−9 C20:2 C20:3 n−6 C20:4 n−6 (arachidonic) C20:3 n−3 C20:5 n−3 (EPA) C23:0 C22:6 n−3 (DHA) SFA MUFA PUFA UFA/SFA Ʃ n−6 Ʃ n−3 n−6/n−3

0.10 0.07 0.27 0.04 0.07 0.07 12.9 0.23 0.14 0.06 3.10 27.6 0.80 46.5 0.00 4.08 0.14 0.22 0.00 0.00 0.22 0.00 0.00 0.09 0.10 0.03 17.0 28.8 51.1 4.72 46.8 4.20 11.13

0.13 0.27 0.68 0.20 0.52 0.22 18.8 0.39 0.38 0.07 9.21 8.32 0.86 30.4 0.07 14.7 0.12 0.70 0.00 0.20 0.31 0.07 0.21 0.25 0.34 0.08 31.0 10.1 46.4 1.82 30.9 15.26 2.02

at the 5th lumbar vertebra level of the LD, whereas HL pHu was measured at the Biceps femoris level. L*a*b* color values were recorded on a cross-section of the fresh surface of mid-LD between the 6th and 7th lumbar vertebrae. Both LD and HL cuts were then individually packed and frozen at −80 °C until further analysis. LD and HL cuts were allowed to thaw overnight at + 4 °C and weighed again for thawing loss measurement. Afterwards, n = 80 LD were individually vacuum-sealed in cooking PVC bags and cooked in a water bath at 80 °C for 1 h. Each sample was chilled with cold tap water, removed from its PVC bag, dried, and weighed for cooking loss determination. Cooked LD were used for Warner–Bratzler Shear Force (WBSF) measurements on cores (diameter 1.25 cm) sheared perpendicularly to muscle fiber direction with a Warner–Bratzler cell fitted

Fig. 1. Experimental design.

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on a dynamometer Texture TA-HD (SMS— Stable Micro System). WBSF was calculated by averaging 4 measurements per sample. Thawed HL were deboned in order to determine the meat to bones ratio (Blasco & Ouhayoun, 1996). Femur and tibia were also separately weighed and measured for length (femur bone), diameter, and fracture toughness (FT) with a dial caliper (±0.02 mm; JUWEL Digital-Schieblehre Rostfrei H4215/5X A12) at the level of minor thickness at the mid-diaphysis corresponding to the breaking point. Femur fracture toughness (FT) was calculated at the average bone length point by using a dynamometer Texture TA-HD (SMS— Stable Micro System) with a 6 cm wide cell and a load rate of 0.5 mm/s. Proximate composition was analyzed on n = 80 HL meat samples using AOAC methods (AOAC, 1995), with protein content calculated by difference. Heme iron content was analyzed on HL meat using the procedure described by Hornsey (1956). Lipid extraction of HL meat samples (n = 47) and FAME determination were performed according to the method described by Dalle Zotte et al. (2014).

Fig. 2. Combined effects of housing condition and hay supplementation (within genotype) on the ratios of fore, mid and hind parts to reference carcass. LCP: Pannon large, Cage, Pellet, LCH: Pannon large, Cage, Pellet plus hay, LPP: Pannon large, Pen, Pellet, LPH: Pannon large, Pen, Pellet plus hay, HCP: Hungarian giant, Cage, Pellet, HCH: Hungarian giant, Cage, Pellet plus hay, HPP: Hungarian giant, Pen, Pellet, LPH: Hungarian giant, Pen, Pellet plus hay. Hystograms of Large rabbit genotype have thin lines, whereas those of Hung rabbit genotype have thick lines abc Different superscripts of the same trait within genotype significantly differ (P b 0.05).

2.2. Statistical analysis Data concerning carcass traits and meat quality were computed by means of General Linear Model (SAS, 2011) with PROC MIXED procedure using the following equation:

treatments within genotypes were calculated by one-way ANOVA. LSD post-hoc test was used to denote the differences (Figs. 2–5).

Yi jk ¼ μ þ Gi þ H j þ Dk þ ðG x HÞi j þ ðG x DÞik þ ðH x DÞ jk þ ðG x H x DÞi jk þ ei jk

3. Results

μ general mean effect of Genotype (i = 1–2) Gi effect of Housing system (j = 1–2) Hj effect of Feeding (k = 1–2) Dk (G × H)ij effect of interaction of level i of factor G with level j of factor H (G × D)ik effect of interaction of level i of factor G with level k of factor D (H × D)jk effect of interaction of level j of factor H with level k of factor D (G × H × D)ijk effect of interaction of level i of factor G with level j of factor H with level k of factor D random errors. eijk

With the exception of the mid part of the carcass, expressed as ratio to RC, the other slaughter traits were significantly higher in Large than in Hung rabbits (Table 2). Regarding housing condition, caged rabbits were heavier, fatter, and had a higher mid part ratio to RC. On the other hand, the ratios of fore and hind parts to RC were higher in penned rabbits (P b 0.01). Carcass weights, measured as SW, CC or RC, and carcass fatness were higher in Pellet group than P + Hay group, leading to a higher (+0.4–0.7%) DoP in Pellet rabbits (P b 0.05). However, P + Hay rabbits exhibited significantly higher hind part ratio than Pellet rabbits (37.4 vs 36.8%, respectively; P b 001). The ratio of hind part to RC showed an increasing order in Large rabbits: Cage–Pellet (36.2%) b Cage–P + Hay (36.8%) b Pen–Pellet (37.1%) b Pen–P + Hay (37.5%) (P b 0.05; Fig. 2). The tendency was similar (P b 0.05) in Hung rabbits, but no difference was found between

Genotype, housing system and diet were considered as fixed effects. Cage and pen effects were included in the statistical model as random effects. P values were considered significant when b0.05. The effects of Table 2 Effect of genotype, housing system and hay supplementation on slaughter traits. Traits

n Slaughter weight (SW), g Chilled carcass (CC), g Reference carcass (RC)a, g

Genotype (G)

Housing (H)

Feeding (D)

SE

Large

Hung

Cage

Pen

Pellet

P + Hay

150 3109 1906 1618

137 2881 1736 1463

149 3055 1861 1577

138 2940 1785 1507

139 3046 1859 1578

148 2956 1791 1511

15.7 10.1 8.94

Prob.

Interactions

G

H

D

G×H

G×D

H×D

G×H×D

b0.001 b0.001 b0.001

b0.001 b0.001 b0.001

0.006 0.001 b0.001

0.109 0.046 0.022

0.574 0.523 0.576

0.518 0.387 0.321

0.432 0.503 0.520

Ratio to SW in % Dressing out % (DoP) Head LHb Liver Kidneys

61.3 5.05 0.76 2.81 0.59

60.2 5.35 0.79 2.64 0.64

60.9 5.12 0.77 2.71 0.61

60.7 5.28 0.77 2.75 0.61

61.0 5.10 0.75 2.75 0.61

60.6 5.29 0.79 2.71 0.62

0.1 0.02 0.01 0.03 0.004

b0.001 b0.001 0.018 0.002 b0.001

0.466 0.001 0.672 0.501 0.733

0.011 b0.001 0.001 0.361 0.220

0.071 0.054 0.026 0.534 0.445

0.614 0.295 0.393 0.023 0.195

0.346 0.293 0.280 0.355 0.917

0.942 0.169 0.350 0.876 0.271

Ratio to RC in % Fore part Mid part Hind part Perirenal fat Scapular fat

27.5 33.4 36.9 1.64 0.63

27.1 33.6 37.3 1.45 0.50

27.1 33.7 36.8 1.76 0.63

27.5 33.3 37.5 1.33 0.49

27.3 33.6 36.8 1.72 0.63

27.3 33.4 37.4 1.39 0.50

0.1 0.1 0.1 0.04 0.01

0.010 0.178 0.001 0.011 b0.001

0.008 0.002 b0.001 b0.001 b0.001

0.816 0.312 b0.001 b0.001 b0.001

0.721 0.186 0.164 0.734 0.009

0.915 0.662 0.575 0.756 0.996

0.106 0.365 0.196 0.382 0.077

0.446 0.905 0.454 0.027 0.689

Large: Pannon large × Pannon Ka, Hung: Hungarian giant × Pannon Ka, P + Hay: pellet plus hay. a RC: weight of the chilled carcass minus the head, liver and kidneys, organs of chest and neck. b LH: set of organs consisting of thymus, trachea, esophagus, lung and heart.

A. Dalle Zotte et al. / Meat Science 110 (2015) 126–134

Fig. 3. Combined effects of housing condition and hay supplementation (within genotype) on ratios of perirenal and scapular fat to reference carcass. LCP: Pannon large, Cage, Pellet, LCH: Pannon large, Cage, Pellet plus hay, LPP: Pannon large, Pen, Pellet, LPH: Pannon large, Pen, Pellet plus hay, HCP: Hungarian giant, Cage, Pellet, HCH: Hungarian giant, Cage, Pellet plus hay, HPP: Hungarian giant, Pen, Pellet, LPH: Hungarian giant, Pen, Pellet plus hay. Hystograms of Large rabbit genotype have thin lines, whereas those of Hung rabbit genotype have thick lines abc Different superscripts of the same trait within genotype significantly differ (P b 0.05).

Cage–P + Hay and Pen–Pellet groups. An inverse tendency was observed in the ratio of mid part to RC in Large genotype: Cage–Pellet (33.7%) = Cage–P + Hay (33.8%) N Pen–Pellet (33.2%) N Pen–P + Hay (33.0%). Cage and Pen Large rabbits fed P + Hay had different fore part to RC ratios (P b 0.05). Significant differences were found in G × H interaction for CC and RC weights and in scapular fat incidence (Table 2); in the scapular fat to RC ratio, the difference between Cage and Pen groups was larger in Large rabbits than in Hung rabbits (Large: Cage 0.74%, Pen 0.53%, Hung: Cage 0.53%, Pen 0.43%). The ratio of perirenal fat to RC was nearly identical in Large and Hung rabbits: Cage–Pellet (1.92 and 1.93%) N Cage–P + Hay (1.81 and 1.42%) N Pen–Pellet (1.60 and 1.30%) N Pen–P + Hay (1.21 and 1.17%) in Large and Hung, respectively (P b 0.05; Fig. 3). The highest values of Large and Hung rabbits in Cage–Pellet groups and the lowest values of the two genotypes in Pen–P + Hay groups were similar. Similar changes were observed in the ratio of scapular fat to RC (P b 0.05). The weights of HL bones, femur and tibia were heavier in Large than in Hung rabbits (P b 0.001) even if bone incidence was higher in Hung rabbits (Table 3) due to the latter's lower meat to bone ratio (5.81 vs 6.10, for Hung and Large rabbits, respectively; P b 0.01). Large rabbits were characterized by longer femur and by wider femur and tibia (P b 0.01). HL bone incidence (% HL) was higher in Pen than in Cage group, thus determining a lower meat to bone ratio (5.82 vs 6.10, respectively). However, femurs were longer in Cage than in Pen group (P b 0.01).

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Significant differences were found in the G × H interaction for meat to bone ratio, where Large rabbits reared in Cage exhibited higher meatiness than those reared in Pen (6.33 vs 5.88, respectively; P b 0.05). Referring to the H × D interaction, differences were observed within caged animals, where Pellet rabbits had higher femur FT values than P + Hay rabbits (40.9 vs 37.6 kg, respectively; P b 0.05). Genotype affected only L* and a* color values of the LD meat (Table 4). Specifically, L* value was higher in Hung than in Large rabbits (P b 0.05), whereas a* value was higher in Large than Hung rabbits (4.99 vs 4.18, respectively; P b 0.05). The pHu of HL and LD meat was lower in Pellet than in P + Hay groups (6.09 and 5.88 vs 6.16 and 5.97, for HL and LD, respectively). Regarding Feeding, Pellet group exhibited higher L* and a* values than P + Hay group (51.9 vs 50.6 and 5.03 vs 4.13, respectively; P b 0.05). The HL and LD weights were higher in Large than in Hung rabbits, in Cage than in Pen group, and in Pellet than in P + Hay group (Table 5). HL thawing losses were higher in Hung than in Large rabbits and in Cage than in Pen group (P b 0.05). Like HL, LD thawing losses were higher in Cage than in Pen group (P b 0.001). Cooking losses were significantly higher in Hung than Large rabbits (29.6 vs 28.5%, respectively; P b 0.01) and, inversely from thawing losses, higher in Pen than in Cage rabbits (P = 0.05). WBSF values were significantly (P b 0.001) higher in Pen than in Cage group (3.77 vs 2.58 kg/cm2) and in Pellet than in P + Hay group (3.57 vs 2.76 kg/cm2). Significant G × H interaction was found for thawing losses as well as for WBSF values (P b 0.001) of LD meat, with Large Pen-housed rabbits having tougher meat than Cage-housed ones (4.24 vs 2.13 kg/cm2, respectively). However, this was not observed in Hung rabbits. G × D affected only thawing losses of LD (P b 0.05), whereas H × D influenced LD thawing losses (P b 0.001), total losses (P b 0.05) and WBSF (P b 0.001). Specifically, Pen rabbits fed with Pellet had tougher meat than that of Pen rabbits fed with P + Hay (4.71 vs 2.83 kg/cm2, respectively). Considering that total losses were higher in Pen rabbits fed P + Hay than Pellet (33.8 vs 32.0%), this did not justify the observed WBSF trend. Proximate composition and heme iron content of HL meat are shown in Table 6. Housing system influenced only ash content, and was significantly higher in Pen than in Cage group (P b 0.05). Moisture (P b 0.01) and ash (P b 0.05) contents were higher in P + Hay than in Pellet group, whereas lipid content was higher in Pellet than in P + Hay group (2.63 vs 2.23%, respectively). Finally, H × D interaction affected protein content of HL meat (P b 0.05) with rabbits housed in Pen and fed only Pellet showing a higher protein content than animals fed P + Hay (21.9 vs 21.8%, respectively). Referring to main FA groups and their ratios (Table 7), MUFA content was higher in Cage than in Pen group, whereas PUFA and Σ n−6 were higher in Pen than in Cage group (P b 0.001). Hay supplementation affected MUFA content, and was higher in Pellet than in P + Hay group (P b 0.05).

Table 3 Effect of genotype, housing system and hay supplementation on rabbit hind leg (HL) bones traits. Traits

n HL bones, g HL bones, % HL Meat to bones ratio Femur, g Femur, % HL Femur minor Ø, mm Femur length, mm Tibia, g Tibia, % HL Tibia minor Ø, mm Femur fracture toughness, kg

Genotype (G)

Housing (H)

Feeding (D)

Large

Hung

Cage

Pen

Pellet

P + Hay

60 39.2 14.1 6.10 16.0 5.77 6.85 88.0 9.93 3.58 5.39 39.4

60 37.2 14.7 5.81 15.3 6.04 6.62 87.2 9.45 3.74 5.21 40.5

60 38.1 14.1 6.10 15.6 5.80 6.70 88.1 9.63 3.58 5.27 39.3

60 38.4 14.7 5.82 15.6 6.01 6.78 87.1 9.75 3.75 5.34 40.6

61 38.2 14.3 6.04 15.5 5.79 6.76 87.6 9.68 3.62 5.28 40.5

59 38.2 14.6 5.87 15.8 6.03 6.71 87.6 9.71 3.71 5.32 39.4

SE

0.24 0.09 0.04 0.10 0.04 0.02 0.16 0.07 0.03 0.02 0.51

Prob.

Interactions

G

H

D

G×H

G×D

H×D

G×H×D

b0.001 0.001 0.001 0.001 0.001 b0.001 0.009 0.001 0.002 b0.001 0.275

0.501 0.001 0.001 0.876 0.010 0.116 0.002 0.395 0.001 0.176 0.180

0.888 0.067 0.054 0.164 0.004 0.405 0.950 0.797 0.085 0.419 0.234

0.658 0.067 0.043 0.939 0.169 0.177 0.854 0.986 0.258 0.330 0.960

0.939 0.556 0.512 0.647 0.408 0.472 0.451 0.978 0.607 0.857 0.092

0.055 0.746 0.800 0.013 0.307 0.583 0.393 0.317 0.727 0.584 0.041

0.409 0.864 0.885 0.384 0.985 0.785 0.930 0.788 0.226 0.731 0.653

Large: Pannon large × Pannon Ka, Hung: Hungarian giant × Pannon Ka, P + Hay: pellet plus hay, Ø: diameter.

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Table 4 Effect of genotype, housing system and hay supplementation on Biceps femoris (BF) and Longissimus dorsi (LD) meat pH and color. Traits

n BF pHua LD pHu LD color values: L* a* b*

Genotype (G)

Housing (H)

Feeding (D)

Large

Cage

Pen

Pellet

P + Hay

Hung

SE

Prob.

Interactions

G

H

D

G×H

G×D

H×D

G×H×D

60 6.09 5.90

60 6.15 5.94

60 6.13 5.91

60 6.12 5.93

61 6.09 5.88

59 6.16 5.97

0.02 0.01

0.083 0.166

0.736 0.478

0.019 0.001

0.279 0.877

0.262 0.172

0.168 0.063

0.711 0.851

50.5 4.99 −0.07

52.0 4.18 0.24

51.5 4.36 −0.01

51.0 4.81 0.17

51.9 5.03 0.18

50.6 4.13 −0.02

0.34 0.19 0.10

0.023 0.036 0.117

0.538 0.229 0.372

0.044 0.019 0.283

0.651 0.095 0.833

0.927 0.600 0.804

0.467 0.644 0.848

0.146 0.195 0.417

Large: Pannon large × Pannon Ka, Hung: Hungarian giant × Pannon Ka, P + Hay: pellet plus hay. a pH measured 24 h post mortem.

The combined Genotype and Housing system effect impacted total MUFA, PUFA and Ʃ n−6 (P b 0.05). Interestingly, the interactive effect regarded only Hung rabbits. Specifically, Hung rabbits housed in Cage had higher MUFA content than Hung rabbits housed in Pen (34.5 vs 30.3% total FAME, for Hung–Cage and Hung–Pen rabbits, respectively). Inversely, hind leg PUFA content was higher in Hung–Pen than in Hung–Cage rabbits (30.7 vs 26.4% total FAME, respectively). The latter was attributable to the difference observed in the Ʃ n−6 fraction (P b 0.001). Genotype affected only a few FA: C12:0, C17:1 and C20:1 n−9 were significantly higher in Large than in Hung rabbits (Table 7). The C14:0, C16:0, C14:1, C16:1, C17:1, C18:1 n−9 were all significantly higher in Cage than in Pen group, whereas C15:0, C17:0, C18:0, C22:0, C15:1, C18:2 n− 6ct, C18:3 n− 6, C20:3 n− 6, C20:4 n− 6 and C20:5 n− 3 were higher in Pen than in Cage group. The C16:1, and C18:1 n− 9 were higher in Pellet than in P + Hay group, and C18:0, C18:3 n− 6 and C20:5 n−3 were higher in P + Hay than in Pellet group. Significant G × H interaction was found for C16:0, C17:0, C18:0, C18:1 n−9, C18:2 ct n−6, C18:3 n−6 and C22:6 n−3. This result was due to large differences between Cage and Pen groups in Hung rabbits, whereas in Large rabbits the differences were non-significant. H × D interaction was significant only in C15:1; the order among the groups was inverted (Cage: Pellet /0.225%/, P + Hay /0.27%/, Pen: Pellet /0.29%/, P + Hay /0.275%/). The G × H × D interaction was significant in C22:6 n−3 (P b 0.05). A fluctuation in main FA could be seen when combined effects were examined (Fig. 4). Main FA groups were affected by treatments only in Hung rabbits, where a continuously significant decrease was observed in MUFA contents (P b 0.05): Cage–Pellet (35.1%) N Cage–P + Hay (33.9%) N Pen–Pellet (31.1%) N Pen–P + Hay (29.5%). An inverse trend was observed in PUFA contents of Hung rabbits: Cage–Pellet (25.7%) b Cage–P + Hay (27.1%) b Pen–Pellet (30.2%) b Pen–P + Hay (31.2%) (P b 0.05). Examining the combined effect of Housing and Feeding (within Genotype) on meat Σ n− 3 and Σ n− 6 contents, and n− 6/n− 3 ratio (Fig. 5), significant differences were observed only for Σ n−6 in Hung rabbits between Cage and Pen (24.5 vs 27.4%, on average).

4. Discussion 4.1. Effect of genotype The weight of carcass is in accordance with the body weight of rabbits at slaughter (Lukefahr et al., 1982). Gómez, Baselga, Rafel, and Ramon (1998), and Larzul and Rochambeau (2004) also found larger carcasses, carcass parts and organs in heavier rabbits. The reason for the better DoP of Large than Hung rabbits could lie in their different genetic origin or selection. Dalle Zotte (2002) stated that when selected for growth rate, younger rabbits exhibit lower DoP at slaughter. Pla, Hernández, and Blasco (1996), and Pla, Guerrero, Guardia, Oliver, and Blasco (1998) demonstrated differences in DoP between maternal and terminal lines (selected for litter size and growth rate, respectively), with better results in lines with smaller adult body weight and higher degree of maturity. In the current study, Large and Hung rabbits have different genetic origins, but Large rabbits were selected for growth rate and carcass traits based on CT data. According to results published by Piles, Blasco, and Pla (2000) and Hernández, Aliaga, Pla, and Blasco (2004), even if selection for growth rate had no influence on carcass traits, selection for carcass traits based on CT data was shown to be effective in improving DoP (Szendrő, Matics, et al., 2009). Examining the ratio of fore, mid, and hind parts, similar results were found when lines with different adult weight were compared (Pla et al., 1998, 1996; Hernández, Ariño, Grimal, & Blasco, 2006) and when the effect of selection for improving growth rate was investigated (Piles et al., 2000). The differences between the Large and Hung rabbits could be attributed to the crossing of Hungarian giant rabbits with a medium sized breed. In most experiments, fat depots were lower in lines selected for growth rate than in maternal lines (Pla et al., 1998, 1996; Hernández et al., 2006); conversely, the ratios of perirenal and scapular fat to RC were higher in Large than in Hung rabbits. It is difficult to explain these results because literature shows that dissectible fat percentage decreases when rabbits are selected either for growth rate (Hernández et al., 2004) or improving hind leg meat (Szendrő et al., 2012), and the

Table 5 Effect of genotype, housing system and hay supplementation on rheological traits of hindleg (HL) and Longissimus dorsi (LD) meat. Traits

HL, n Weight, g Thawing losses, % LD, n Weight, g Thawing losses, % Cooking losses, % Total losses, % WBSF (kg/cm2)

Genotype (G)

Housing (H)

Feeding (D)

Large

Hung

Cage

Pen

Pellet

P + Hay

60 278 3.48 40 95.3 4.34 28.5 32.8 3.19

60 253 3.73 40 85.7 4.15 29.6 33.7 3.16

60 270 3.71 40 93.9 5.01 28.7 33.7 2.58

60 261 3.50 40 87.2 3.49 29.4 32.9 3.77

61 268 3.61 40 92.7 4.32 28.8 33.1 3.57

59 262 3.60 40 88.2 4.17 29.3 33.5 2.76

SE

Prob. G

Interactions H

D

G×H

G×D

H×D

G×H×D

1.28 0.04

b0.001 0.006

0.001 0.019

0.024 0.929

0.059 0.884

0.459 0.344

0.030 0.689

0.250 0.507

0.75 0.19 0.18 0.31 0.11

b0.001 0.702 0.004 0.141 0.865

b0.001 b0.001 0.050 0.218 b0.001

0.006 0.802 0.139 0.473 b0.001

0.056 b0.001 0.039 0.198 b0.001

0.508 0.038 0.737 0.130 0.566

0.875 b0.001 0.613 0.031 b0.001

0.156 0.748 0.001 0.086 0.001

Large: Pannon large × Pannon Ka, Hung: Hungarian giant × Pannon Ka, P + Hay: pellet plus hay.

A. Dalle Zotte et al. / Meat Science 110 (2015) 126–134

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Table 6 Effect of genotype, housing system and hay supplementation on proximate composition (%) and Heme iron (mg/kg meat) of hind leg meat. Chemical composition

n Moisture Protein Lipids Ash Heme iron

Genotype (G)

Housing (H)

Feeding (D)

Large

Hung

Cage

Pen

Pellet

P + Hay

SE

40 73.7 21.9 2.45 1.96 3.65

40 73.8 21.8 2.41 1.99 3.51

40 73.7 21.9 2.48 1.92 3.54

40 73.7 21.9 2.38 2.03 3.63

40 73.6 21.9 2.63 1.93 3.61

40 73.9 21.8 2.23 2.03 3.56

0.06 0.03 0.08 0.02 0.07

Prob.

Interactions

G

H

D

G×H

G×D

H×D

G×H×D

0.771 0.468 0.917 0.667 0.341

0.876 0.953 0.590 0.017 0.578

0.007 0.571 0.010 0.030 0.706

0.544 0.850 0.780 0.634 0.303

0.880 0.638 0.972 0.794 0.676

0.588 0.012 0.128 0.389 0.735

0.279 0.893 0.284 0.536 0.463

Large: Pannon large × Pannon Ka, Hung: Hungarian giant × Pannon Ka, P + Hay: pellet plus hay.

Pannon Large rabbits were selected for growth rate and muscle volume on hind legs by CT data (Matics et al., 2014). Higher weight, length and width of bones could be associated with the higher slaughter weight of Large rabbits. At the same time, their ratio to hind leg was lower in Large rabbits, which led to a higher meat to bones ratio. Only few studies have investigated the effect of genotype on bones characteristics. When rabbits were divergently selected for 63 d body weight, they exhibited shorter femur and lower tibia percentage and meat to bones ratios. Apart from these results, Szendrő et al. (2010) found no differences in bones, femur and tibia percentages or in meat to bones ratio among different genotypes (Szendrő et al., 2010; Pla et al., 1998; Piles et al., 2000). However, others have observed higher meat to bones ratios in cases of selection for growth rate or in large bodied lines (Hernández et al., 2004, 2006), thus supporting our findings. There is currently no evidence that thinner bones cause disadvantage, e.g., fracture occurrence. Similar to the present results, literature does not present any significant difference in pHu value among three genotypes (Pannon Ka,

Pannon White, and Pannon Large; Dalle Zotte et al., 2009), between lines selected for growth rate or for litter size (Pla et al., 1996) divergently selected for high and low growth rate (Gondret, Larzul, Combes, & de Rochambeau, 2005), or between generation 7 and 23 of a line selected for growth rate (Pascual & Pla, 2007). In a few experiments however, higher pHu values were obtained in the fast-growing line (Pla et al., 1998; Hernández et al., 2006). These results would indicate that pHu value is scarcely affected by genotype or selection. Dalle Zotte and Ouhayoun (1998) and Maj et al. (2012) observed differences in meat color among different genotypes. In contrast with our results, most researchers (Hernández, Pla, & Blasco, 1997; Ramírez et al., 2004) did not find significant differences in L* value. Although we found higher a* value in Large rabbits, our results did not show clear connection between meat color and genotype. Our study showed differences in HL thawing losses and LD cooking losses. Water holding capacity was similar in rabbits selected for growth rate or litter size; at the same time, cooking losses as well as meat water content were lower in rabbits selected for fast-growth (Pla et al., 1998).

Table 7 Effect of genotype, housing system and hay supplementation on single FAs (% of total FAME) of hind leg meat. Fatty acid

n C10:0 C12:0 C14:0 C15:0 C16:0 C17:0 C18:0 C20:0 C22:0 C23:0 C14:1 C15:1 C16:1 C17:1 C18:1 n−9 (oleic) C18:1 n−11 (trans vaccenic) C20:1 n−9 C18:2 ct n−6 (linoleic) C18:2 c9-t11 C20:2 C18:3 n−6 (γ-linolenic) C18:3 n−3 (α-linolenic) C20:3 n−6 C20:4 n−6 (arachidonic) C20:3 n−3 C20:5 n−3 (EPA) C22:6 n−3 (DHA) SFA MUFA PUFA UFA/SFA Ʃ n−6 Ʃ n−3 n−6/n−3

Genotype (G)

Housing (H)

Feeding (D)

Large

Hung

Cage

Pen

Pellet

P + Hay

23 0.21 0.23 2.39 0.61 23.9 0.65 7.47 0.15 0.12 0.05 0.23 0.26 3.15 0.33 27.8 1.47 0.32 22.3 0.05 0.49 0.11 2.36 0.35 2.16 0.11 0.10 0.05 35.8 33.6 28.1 1.73 24.9 2.63 9.54

24 0.18 0.18 2.20 0.63 24.0 0.68 7.68 0.15 0.13 0.05 0.20 0.26 2.67 0.31 27.1 1.55 0.27 22.6 0.06 0.49 0.11 2.29 0.36 2.38 0.12 0.11 0.05 35.9 32.4 28.5 1.70 25.4 2.58 10.1

23 0.21 0.22 2.42 0.59 24.4 0.62 7.28 0.14 0.12 0.06 0.26 0.25 3.53 0.34 28.2 1.51 0.32 21.4 0.05 0.46 0.09 2.27 0.32 2.01 0.10 0.10 0.05 36.1 34.4 26.9 1.70 23.9 2.51 9.56

24 0.19 0.20 2.18 0.65 23.5 0.71 7.87 0.16 0.14 0.05 0.17 0.28 2.31 0.30 26.8 1.51 0.27 23.4 0.06 0.52 0.12 2.38 0.38 2.53 0.13 0.12 0.05 35.6 31.7 29.7 1.73 26.4 2.69 10.1

24 0.20 0.21 2.31 0.61 23.9 0.64 7.31 0.14 0.13 0.05 0.24 0.25 3.27 0.33 28.0 1.55 0.31 22.1 0.05 0.48 0.09 2.26 0.34 2.18 0.10 0.10 0.05 35.5 33.9 27.8 1.74 24.7 2.51 9.90

23 0.19 0.21 2.28 0.63 24.0 0.69 7.85 0.16 0.13 0.05 0.19 0.27 2.52 0.31 26.9 1.47 0.28 22.8 0.06 0.50 0.13 2.39 0.36 2.38 0.13 0.11 0.06 36.2 32.0 28.9 1.69 25.7 2.70 9.73

Large: Pannon large × Pannon Ka, Hung: Hungarian giant × Pannon Ka, P + Hay: pellet plus hay.

SE

0.01 0.01 0.05 0.01 0.21 0.01 0.10 0.01 0.003 0.004 0.02 0.01 0.15 0.005 0.21 0.03 0.01 0.26 0.002 0.01 0.01 0.05 0.01 0.08 0.02 0.003 0.004 0.19 0.35 0.35 0.01 0.33 0.06 0.19

Prob.

Interactions

G

H

D

G×H

G×D

H×D

G×H×D

0.062 0.030 0.062 0.263 0.723 0.136 0.333 0.546 0.120 0.811 0.446 0.983 0.131 0.016 0.121 0.255 0.043 0.662 0.337 0.965 0.773 0.516 0.674 0.186 0.665 0.374 0.992 0.710 0.106 0.558 0.315 0.492 0.717 0.184

0.200 0.381 0.017 0.001 0.042 b0.001 0.006 0.108 0.026 0.603 0.013 0.038 b0.001 0.001 0.003 0.870 0.081 0.001 0.193 0.074 0.020 0.289 0.008 0.003 0.275 0.013 0.992 0.260 0.001 b0.001 0.365 0.001 0.202 0.215

0.590 0.975 0.756 0.247 0.883 0.063 0.009 0.295 0.660 0.845 0.113 0.226 0.021 0.250 0.018 0.199 0.153 0.201 0.337 0.688 0.006 0.213 0.335 0.225 0.311 0.032 0.575 0.094 0.009 0.115 0.064 0.168 0.155 0.677

0.084 0.136 0.051 0.090 0.031 0.028 0.008 0.703 0.086 0.462 0.635 0.318 0.115 0.882 0.008 0.084 0.163 0.049 0.661 0.553 0.017 0.717 0.113 0.094 0.230 0.361 0.022 0.151 0.030 0.037 0.389 0.041 0.410 0.448

0.895 0.963 0.556 0.882 0.643 0.792 0.899 0.607 0.035 0.649 0.283 0.372 0.407 0.703 0.808 0.053 0.630 0.997 0.258 0.856 0.773 0.342 0.316 0.808 0.365 0.298 0.500 0.600 0.465 0.924 0.356 0.923 0.315 0.330

0.400 0.763 0.506 0.882 0.341 0.538 0.395 0.817 0.785 0.603 0.400 0.048 0.701 0.692 0.937 0.909 0.829 0.175 0.141 0.333 0.354 0.927 0.934 0.932 0.275 0.698 0.399 0.445 0.916 0.357 0.300 0.289 0.883 0.638

0.253 0.248 0.563 0.205 0.518 0.505 0.801 0.875 0.972 0.436 0.319 0.575 0.971 0.592 0.499 0.588 0.380 0.687 0.193 0.292 0.872 0.934 0.436 0.263 0.436 0.786 0.041 0.334 0.655 0.511 0.430 0.540 0.881 0.429

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Fig. 4. Combined effects of housing condition and hay supplementation (within genotype) on main fatty acid groups. LCP: Pannon large, Cage, Pellet, LCH: Pannon large, Cage, Pellet plus hay, LPP: Pannon large, Pen, Pellet, LPH: Pannon large, Pen, Pellet plus hay, HCP: Hungarian giant, Cage, Pellet, HCH: Hungarian giant, Cage, Pellet plus hay, HPP: Hungarian giant, Pen, Pellet, LPH: Hungarian giant, Pen, Pellet plus hay. Hystograms of Large rabbit genotype have thin lines, whereas those of Hung rabbit genotype have thick lines abc Different superscripts of the same trait within genotype significantly differ (P b 0.05).

Examining the effect of divergent selection for growth rate, Gondret et al. (2005) did not find differences in water holding capacity or cooking losses. Similarly, no differences were found when comparing generations 7 and 23 of lines selected for rapid growth (Pascual & Pla, 2007). In contrast, Piles et al. (2000) obtained lower water holding capacity in a line selected for growth rate. Theoretically, this trait may decrease as a result of selection (Piles et al., 2000), especially when the water and fat content of meat are also modified. Similar to the results of Pla et al. (1998) and Hernández et al. (2004) comparing various lines, large rabbits were selected for improving hind leg meat volume, and as a side effect of selection, fat depot decreased (Szendrő et al., 2012). Although this could modify the water and the fat content of meat, only slight, non-significant differences were found in our experiment. The proximate composition of meat was independent of breed, in agreement with the results of Dalle Zotte et al. (2009). However, when comparing various lines, Pla et al. (1998) observed differences, with lower fat content of meat in the line selected for growth rate. Hernández et al. (2004) also found lower fat % in meat as a result of selection for growth rate. The fact that the selected animals were less mature at slaughter could be the reason for their leaner meat.

Fig. 5. Combined effects of housing condition and hay supplementation (within genotype) on Ʃ n−6, Ʃ n−3 and n−6/n−3 ratio. LCP: Pannon large, Cage, Pellet, LCH: Pannon large, Cage, Pellet plus hay, LPP: Pannon large, Pen, Pellet, LPH: Pannon large, Pen, Pellet plus hay, HCP: Hungarian giant, Cage, Pellet, HCH: Hungarian giant, Cage, Pellet plus hay, HPP: Hungarian giant, Pen, Pellet, LPH: Hungarian giant, Pen, Pellet plus hay. Hystograms of Large rabbit genotype have thin lines, whereas those of Hung rabbit genotype have thick lines abc Different superscripts of the same trait within genotype significantly differ (P b 0.05).

A less pronounced effect of genotype on FA profile was observed in this study than in the experiment of Dalle Zotte et al. (2009) in which significantly lower MUFA (C18:1 n− 7, C18:1 n− 9) and higher PUFA (C20:3 n− 6, C20:4 n− 6, C22:5 n− 3) were found in rabbits selected for meat volume by CT data since 1992, with no difference between maternal and Pannon Large lines. The n− 6/n− 3 ratio was similar in all three lines. Identical FA profiles were found comparing both two (SIKA vs hybrid; Gašperlin, Polak, Rajar, Skvaréa, & Žlender, 2006) and three genotypes (SIKA lines; Polak, Gašperlin, Rajar, & Žlender, 2006). Comparing lines selected for growth rate or litter size, SFA were higher and PUFA were lower in the terminal line than in the maternal line (Hernández, Cesari, & Blasco, 2008). After 16 generations of selection for growth rate, rabbits had higher SFA (C14:0, C16:0) and lower MUFA + PUFA (C18:2 n− 6, C20:4 n− 6) than in the control, nonselected line (Ramírez et al., 2005). With these results, although selection for growth rate or meat volume may affect the FA composition of rabbit meat, the role of genotype on FA profile is much less incisive. 4.2. Effect of housing system (group size) Housed in pens, the rabbits were able to move more freely (Dal Bosco et al., 2002), thus their weight gain and body weight were lower (Szendrő et al., 2015). One consequence of lower weight was that the weights of carcasses, carcass parts, organs and tissues were also lower, as observed by several other authors (Dal Bosco et al., 2002; Dalle Zotte et al., 2009; Matics et al., 2014). In most experiments, the DoP of penned rabbits was lower than that of caged rabbits (Xiccato et al., 2013); similar to the present experiment, however, in most cases differences were not significant (Dal Bosco et al., 2002; Dalle Zotte et al., 2009; Szendrő et al., 2009; Combes et al., 2010; Matics et al., 2014). Due to the higher locomotive activity in pens, the ratio of hind part to RC increased and that of perirenal fat and scapular fat decreased, which reflects the results in literature (Dalle Zotte et al., 2009; Szendrő, Princz, et al., 2009; Combes et al., 2010). The higher fore part to RC ratio might also be linked to higher activity, even if some contrary results were observed (Dal Bosco et al., 2002; Dalle Zotte et al., 2009). Since the ratios of two parts (fore and hind) to RC increased, the ratio of the third part (mid) was necessarily lower in Pen rabbits, similar to as observed by Matics et al. (2014). In most studies, however, the mid part to RC ratio was essentially the same for rabbits housed in cages or pens (Dal Bosco et al., 2002; Dalle Zotte et al., 2009; Szendrő, Princz, et al., 2009). The lower fat deposition of Pen rabbits compared to Cage ones could be ascribable to a combined effect of higher locomotive activity and lower energy intake due to social interaction with other rabbits. Similar to our results, lower fat deposition was observed in the larger groups (Dalle Zotte et al., 2009; Szendrő, Princz, et al., 2009; Combes et al., 2010); such differences were not significant in all cases, however. Linked to this increased opportunity for movement, bones of rabbits in Pen group were more developed, similar to the results published by Dalle Zotte et al. (2009) and Matics et al. (2014). Due to the higher percentage of bone in hind legs, the meat to bone ratio was lower in Pen rabbits. Dal Bosco et al. (2002), Szendrő, Princz, et al. (2009), Matics et al. (2014) and Xiccato et al. (2013) observed a similar tendency, but not all differences were significant. In this experiment, housing conditions did not affect meat pHu or color. In contrast to this statement, Dal Bosco et al. (2002), Dalle Zotte et al. (2009), and Combes et al. (2010) observed lower pHu and lighter meat color in larger groups, while the opposite results were published by Paci, Preziuso, D'Agata, Russo, and Dalle Zotte (2013). Total losses of LD meat were unaffected by the Housing system, confirming previous results (Dalle Zotte et al., 2009; Matics et al., 2014), even though Xiccato et al. (2013) found higher values for rabbits housed in small pens than those in large pens. Regarding WBSF values, results similar to those of our study were observed byPinheiro, Outor-Monteiro, Silva, Silva, and Mourao (2011),

A. Dalle Zotte et al. / Meat Science 110 (2015) 126–134

whose open air rabbits exibited higher WBSF than caged rabbits. This difference was a direct consequence of the higher cooking loss of meat taken from open air rabbits than caged rabbits. The same situation was observed in our trial in which Pen rabbits had higher cooking losses than Cage rabbits. Szendrő and Dalle Zotte (2011) found a close correlation between the amount of fat deposited and meat fat and water content. In our experiment, HL meat water and fat content were similar in Cage and Pen groups. These results were consistent with the data of Matics et al. (2014), whereas Dal Bosco et al. (2002), Szendrő, Princz, et al. (2009), and Combes et al. (2010) observed leaner meat with higher water content in larger groups. In agreement with our results, these authors noted no difference in protein content of meat derived from group size. The FA profile of HL meat was affected by the housing system, supporting what was observed by Dal Bosco et al. (2002). However, the differences could not be entirely ascribed to the activity of rabbits, because Szabó, Romvári, Fébel, Bogner, & Szendrő (2002) and Dalle Zotte et al. (2009) observed differences between the control and trained groups in other FA than those we observed in our experiment. Even if there was no difference in Cage and Pen rabbit HL meat lipid content, it was previously shown that carcasses of Cage rabbits were fatter than Pen rabbits (Table 2). This fact probably had a direct consequence on the FA profile of their meat. Specifically, with increasing fatness, SFA and MUFA increase more rapidly than PUFA, in this way explaining the results of our study (De Smet, Raes, & Demeyer, 2004). In addition, leaner animals are known to have a greater proportion of PUFA than fatter ones (Wood et al., 2008). 4.3. Effect of hay supplementation The addition of hay to pellets had a negative effect on body weight and weight gain (Szendrő et al., 2015) that influenced the weight of carcass, carcass parts and tissues. Feed intake is regulated by the energy level of the diet (Lebas, Coudert, de Rochambeau, & Thébault, 1997) and rabbits eat more if the energy content is low or the fiber level is high. Rabbits in P + Hay group consumed a diet with lower energy and protein and higher fiber content than rabbits in Pellet group, which presumably lowered DoP and fat depots. Results showed that hay supplementation seemed to reduce or simply slow down muscle tissue development, which was expressed by higher femur weight and consequent increase in the relative bone weight. A further corroboration to the latter hypothesis came from our work on the performance and ear lesions of growing rabbits from 5 to 12 weeks of age (Szendrő et al., 2015), and also from the work by Morales et al. (2009). Capra et al. (2013) did not observe any difference in meat pHu between groups fed diets with or without fresh alfalfa. Dalle Zotte, Ouhayoun, Parigi Bini, and Xiccato (1996) found a slight decrease in muscle pHu with no change in L* color value in rabbits that consumed less energetic diets. The pHu increased, however, in this experiment, whereas the L* and a* values decreased in P + Hay group. It seems that feeding method did not affect thawing or cooking losses, thus suggesting that the increase in the meat pHu was insufficient to determine a higher WHC in Pellet + Hay group. Unlike as in other meat species such as beef, a high pHu in rabbit meat is known to positively affect tenderness (Dalle Zotte, 2002) and this is exactly what we observed. In our study, as a consequence of the different energy and fiber contents of pellet and hay, fat depots and fat content of meat were higher in Pellet group at the expense of moisture content. Similar to our study, feeding rabbits increasing levels of fiber was reported to reduce the fat content of their meat and enhance its moisture (Parigi Bini, Xiccato, Dalle Zotte, & Carazzolo, 1994). Indeed, a high dietary fiber level has generally been reported to reduce carcass fat deposits in favor of water and protein. Moreover, also a low diet energy level reduced both carcass adiposity and intramuscular fat content

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(Hernández & Dalle Zotte, 2010). In our study, however, no differences in terms of protein contents were ascribable to the effect of hay supplementation. Feeding has the highest impact on FA composition of meat (Dalle Zotte & Szendrő, 2011). Some authors (Forrester-Anderson, McNitt, Way, & Way, 2006; Mugnai et al., 2008) examined the effect of pasture availability, and noted that FA profile changed considerably with grass intake; in these experiments, however, housing conditions also differed. Fiber content can also modify FA profile: Papadomichelakis, Karagiannidou, Anastasopoulos, and Fegeros (2010) compared low and high fiber content diets and observed lower MUFA, C18:1 n− 9, and C20:1, and higher PUFA and C18:2 n− 6 in the high fiber group. Capra et al. (2013) and Dal Bosco et al. (2014) gave plus fresh alfalfa to the experimental group and observed differences in several FAs; MUFA and Σ n−3 increased, thus n−6/n−3 decreased in meat of rabbits fed fresh alfalfa. In the present experiment, significant differences were found only in MUFA and four FAs. The difference in pellet intake between Pellet and P + Hay groups was 7.6%, which was lower than 11% in the experiment of Capra et al. (2013). It seems that the small amount of hay hardly modified the FA profile. 4.4. Combined effect of housing system and hay supplementation, within genotype Differences between Cage and Pen groups in ratios of fore and mid parts were greater in Large rabbits than in Hung rabbits. The reason could be that Hung rabbits have been housed in large cage/pen (larger group) for several generations, and therefore group size did not affect some carcass traits as strongly as in Large rabbits. Although volume and ratio of fat depots were higher in Large than in Hung rabbits, a very similar decline from the most intensive (Large–Cage–Pellet) to the least intensive group (Hung–Pen–P + Hay) was observed in both genotypes since both housing and feeding had similar effect on the volume and ratio of perirenal and scapulat fat to RC. These influences were confirmed by several authors (Dal Bosco et al., 2002; Dalle Zotte et al., 2009; Szendrő, Princz, et al., 2009; Combes et al., 2010). Irrespective of the studied effects, the n− 6/n− 3 ratio remained high (between 9.11 and 10.68) in each group, which was far from the recommended level for human health (Dalle Zotte & Szendrő, 2011). 5. Conclusions Results of the present experiment provide further information on understanding how the choice of alternative methods can impact rabbit carcass characteristics, carcass traits, and meat quality, ultimately allowing cost calculations. In general, all three effects (genotype, housing system, and hay supplementation) had great impact on rabbit carcass weight and carcass traits. Bone traits were mainly influenced by genotype and housing condition. Meat pHu and color were affected solely by hay supplementation, whereas FA profile was modified by both housing system and hay supplementation. Acknowledgments This research was supported by the European Union and the State of Hungary in the framework of AGR_PIAC_13-1-2013-0031 project, co-funded by the European Social Fund in the framework of TÁMOP 4.2.4. A/2-11-1-2012-0001 ‘National Excellence Program’, and co-funded by Padova University Ex60% 60A08-8521/06. We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us.

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