Behavioural and Physiological Fear Responses in Ducks: Genetic Cross Effects

Animal (2008), 2:10, pp 1518–1525 & The Animal Consortium 2008 animal doi:10.1017/S1751731108002784

Behavioural and physiological fear responses in ducks: genetic cross effects

- I. Arnaud1,2, S. Mignon-Grasteau1, C. Larzul3,G.Guy4, J.-M. Faure1 and D. Gue´mene´ 1

1INRA, UR83, 37380 Nouzilly, France; 2SYSAAF, UR83, 37380 Nouzilly, France; 3INRA, UR337, 78352 Jouy-en-Josas, France; 4INRA, UE89, 40280 Benquet, France

(Received 16 January 2008; Accepted 3 June 2008; First published online 15 July 2008)

Mule duck, a cross between a Muscovy drake and a Pekin female, is reported by the farmers to frequently express fear behaviours, such as man avoidance. The genetic basis of fear responses in mule ducks was therefore investigated in this study. According to a previous experiment, the dominant effect of Pekin genotype was hypothesised; however, due to the absence of birds from the reciprocal cross, a superiority of the Pekin in additive effect could not be distinguished from a direct maternal additive effect. In order to clarify this, ducks from the mule genotype, the two parental genotypes (Pekin and Muscovy) and the reciprocal intercross (hinny) underwent a set of physiological and individual behavioural tests of fear. Both parental genotypes were highly fearful but exhibited responses of different patterns: Pekin ducks manifested a higher locomotor activity, whereas the Muscovy ducks showed a higher avoidance to man. Hybrids expressed higher panic responses and specific fear of man than the two parent breeds. Both hybrids expressed similar patterns and the maternal effects were not significant. Significant heterosis effects were found for most of the behavioural responses, in agreement with the fact that higher fear responses were expressed by the hybrids compared to the parental genotypes. A significant heterosis effect was also found for basal adrenal activity; hybrids having higher basal level than parental genotypes. Maximum capacity of adrenal response appeared to be determined by direct additive effects with a superiority of the Pekin genotype.

Keywords: behaviour, corticosterone, duck, fear, genetic cross effects

Introduction for tonic immobility (TI) duration or sociability (Mills and Faure, 1991). Results have shown that the different beha- Intensive animal production conditions are thought to be a vioural and physiological stress indicators measured were source of chronic stress (Dantzer and Morme`de, 1979). only partially linked (Mignon-Grasteau et al., 2003; Hazard Although a minimum level of stress would be beneficial to et al., 2008). Consequently, a variety of experimental tests generate good adaptation capacity (Zulkifli and Siegel, 1995; must be used in order to take into account the multifactorial Jensen and Toates, 1997), acute or chronic stress can result in nature of stress response. Physiological response to acute poor welfare (Dobson et al., 2001). For this reason, many stress includes activation of the hypothalamo–pituitary– studies have been conducted in various husbandry systems adrenocortical axis (HPA) and the subsequent release of to assess causes and subsequent effects of stress (Zulkifli corticosterone (CORT) from the adrenal gland. This corti- and Siegel, 1995; Jensen and Toates, 1997; Dobson et al., costeroid plays a key role in maintaining homoeostasis and 2001). Moreover, aversive handling of farm animals can contributes to behavioural adaptation (Morme`de et al., result in man avoidance, a behavioural response of fear that 2007). For example, restraint in a net has been shown to be is considered as a response to a stress (Rushen et al., 1999). one among the physical stresses, promoting the highest Stress remains difficult to evaluate. Several behavioural corticosterone responses in ducks (Faure et al., 2003). and physiological parameters have to be used to char- Injection of a high dose of 1-24 ACTH allows to assess acterise stress responses under different experimental maximal secretion capacity from the adrenal glands (Harvey conditions (Siegel, 1971). Previous studies on responses to et al., 1980). Conversely, initial CORT level is very sensitive fear were realised in Japanese quails divergently selected to environmental condition (Noirault et al., 1999) and may partly result from a sensibility to capture. Behavioural tests - E-mail: [email protected] involved different features including coping with new

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environment, social isolation, specific response towards Material and methods human and antipredator strategy. Openfield (OF) test lead Animals and rearing conditions the animal first to cope with an unknown environment, Male Muscovy ducks (Md 5 Cairina moschata, n 5 30), then to face social isolation (Faure et al., 1983). A long Pekin ducks (Pd 5 Anas platyrhynchos, n 5 31), mule hybrid latency to first immobilisation, a high level of mobility, ducks (Mh 5 intercross between a Muscovy drake and a exploratory behaviour and vocalisation activities could Pekin female, n 5 31) and hinny hybrid ducks (Hh 5 reflect a low level of fearfulness of the novel environment intercross between a Pekin drake and a Muscovy female, and an important social motivation (Suarez and Gallup, n 5 28) were reared in four independent pens, each pen 1980). However, an intensive locomotor activity right at the measuring 12 m2. Pekin and Muscovy ducks used to pro- beginning of the test can also be interpreted as a result of a duce their respective offspring and their hybrid ducks were panic behaviour. Panic is characterised by hyper excitability, from the same genetic origin (Grimaud Fre`res Se´lection, violent escape reactions and ‘pile ups’ under the feeders or La Corbie`re, 49450 Roussay, France). They were given against the walls (Mills and Faure, 1990). In test involving the ad libitum access to a standard diet. The animals were presence of human (RH), the same dilemma between fear of maintained under natural photoperiod (December 2003 to the novel environment and social isolation stress occurs. But February 2004, 448N France) in a windowed barn, except moreover, the distance from human and the direction of the during the first 3 days of life during which ducks received first displacement (to the opposite or towards human) cor- continuous artificial lighting. Animals were kept indoors respond to a specific response to human presence (Gue´mene´ during the whole experiment. et al., 2002). The antipredator strategy is assessed through the TI test. This innate behavioural response induces physical immobility similar to a catatonic-like state, resulting in Experimental measures decreased predator’s attention. The number of attempts Ducks were submitted to the following physiological and to induce TI and the duration of TI are both indicators of behavioural tests during the 8th week of age in the fol- the level of human fear (Jones and Faure, 1981). The higher lowing order: initial CORT level, CORT level after placement the number of attempts and the longer the TI duration, the in a net, CORT level after challenge with 1-24 ACTH, OF, stronger the fear (Gallup, 1977). CORT after OF, response to man (RM) presence, TI and The hypothesis of a genetic determinism of fear CORT after TI. For each test, ducks were alternatively taken responses has been evidenced in birds through divergent from each pen in order to limit any possible effect of the selection experiments: Japanese quails selected on beha- testing order. Tests were performed in a separate room lit vioural responses as TI duration or sociability (Mills and and maintained at the same ambient temperature as the Faure, 1991) or selected on physiological traits as the CORT rearing room. level after social stress for the three first generations then the CORT level after 10 min restraint for the next genera- Behavioural measures tions (Satterlee and Johnson, 1988). However, genetic Videos from openfield and RM tests were analysed by focal approach using specific crosses has brought novel infor- sampling using The Observer 3.0 program (Noldus Infor- mation on the transmission of such traits in other species mation Technology, 1989–1990, Business & Technology (Leroy, 1964; Manning and Dawkins, 1998; Boujard et al., Center, Costerweg 5, 6702 AA Wageningenn, NL). 2007; Gironi Carnevale et al., 2007; Roy et al., 2007). Mule Openfield (OF) test. Birds were tested individually in an OF duck, an interspecific hybrid between a Muscovy drake and 2 a Pekin duck, is reported to express man avoidance in measuring 2.0 3 1.5 m , sub-divided into four equal zones rearing systems. Fear reactions were characterised in by two perpendicular fictive lines (Figure 1a). Ducks were Muscovy and Pekin ducks, as well as in mule ducks (Faure first placed in Zone 1 and behaviour was video recorded et al., 2003). Mule ducks showed responses similar to one during 5 min. Behaviour patterns were scored in focal parent or intermediate between the two parents, for most sampling as follows: latency to the first immobilisation, of the behavioural traits studied and CORT measurements number of zones visited, duration of mobility, number of performed. When the two parental genotypes differed sig- pecks directed to the floor or the walls, vocalisations and nificantly, Pekin ducks exhibited higher fearfulness than body shaking. Muscovy ducks. Interestingly, a heterosis effect appeared on (a) (b) the distance from human. Due to the absence of the reci- 2 m procal intercross in this experiment, it was not possible to 4 3 distinguish between the superiority of the Pekin in additive 12 m

effects and speciﬁc maternal effects. For this, Pekin and 3 m 1 2 1 23 4567 Muscovy drakes as well as males from the two intercrosses, 1 m mule and hinny ducks, were submitted to several fear assessment tests. Both behavioural and physiological parameters were measured to assess and characterise fear Figure 1 Experimental set-up of the openﬁeld test lasting 5 min (a) and responses of each genotype. the response to the man test lasting 1 min (b).

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Response to the presence of man (RM) test. The experi- glands level. Also, the ratio of CORT Net to CORT ACTH was mental set-up for this test consisted of a plain wall corridor, calculated to assess the relative amplitude of this response in measuring 12 3 1m2, longitudinally sub-divided in seven comparison with the maximum capacity of adrenal glands. equal zones numbered 1 to 7 (Figure 1b). A man was placed in Zone 1 and ducks were introduced individually through a Genetic effect estimation trap located between Zones 4 and 5. The test, lasting one Genetic effects were estimated by linear combinations of minute, was video recorded and several parameters were genotype means as described by Dickerson (1969). They later monitored: direction of the first displacement (towards were standardised as follows: or away from the man), latency to the first immobilisation, number of zones visited, duration of mobility, time spent in Direct Additive a ¼ðþMd þ Mh Hh PdÞ=2d; each zone. An avoidance index (AI) was calculated using the following formula: Heterosis h ¼ðþMh þ Hh Md PdÞ=2d; X7 AI ¼ tizi; i¼1 Maternal Additive m ¼ðþHh MhÞ=2d; where Md, Pd, Mh and Hh are the mean for each genotype where ti is the time in seconds spent in the i th zone and zi the zone identification number (i 5 1 to 7) (Faure et al., and d the standard deviation of the character. A positive 2003). Therefore, AI could theoretically range to just above (negative) value reflects respectively a genetic superiority 60 (all time spent in Zone 1) to just below 480 (all time (inferiority) of Muscovy for direct additive effects, a positive spent in Zone 7). The number of vocalisations, body shaking (negative) heterosis and superiority (inferiority) of Muscovy and pecks directed to the floor or the walls were measured. for maternal additive effects.

Tonic immobility (TI) test. Each bird was placed on its back Statistical analysis Data were first analysed using non-parametric statistical in a cradle (Jones and Faure, 1981) and held in this position 2 for 10 s before being released. Time elapsing before birds tests by overall comparison of the four genotypes (x test or stood on their own was measured. If the bird did not stay at Kruskal–Wallis test). When significant (P , 0.05), data were least 10 s after release, the TI attempt was considered as further analysed by multiple pair comparisons tests (Mann– unsuccessful and another attempt was performed. The Whitney associated with a sequential Bonferroni correction number of TI attempts was noted. If five attempts were procedure (Holm, 1979)). CORT values after the different unsuccessful, TI was scored 0 and the number of inductions treatments for each genotype were compared with a non- was considered equal to 5. If the duck was still in TI after parametric test for not independent data (Wilcoxon test). 8 min, the test was interrupted. Analyses were performed using the StatView program (SAS 5.0, Institute Inc., 1992–1998; Cary, NC, USA). In order to Physiological measures test for a preferential orientation of the ducks, the first Blood was collected at the occipital sinus (Vuillaume and direction in the corridor (towards or away from the man) Tournut, 1975) from all ducks under five experimental was tested using a simple binomial test in each genotype. conditions: (i) before any assessment (CORT Initial), (ii) after Because the TI test generated censored data, a survival 10 min of restraint in a net (CORT Net), (iii) 10 min after an analysis was done according to the Weibull model of the intramuscular injection of 5 mg/kg BW of 1-24 ACTH (CORT Survival Kit program (Ducrocq and So¨ lkner, 1998). Statistical ACTH) (Synacthe`ne imme´diat, Novartis Pharma, Rueil- significance of the estimated genetic effect was tested by Malmaison, France), (iv) 10 min after initiation of the OF using the CBE program (Wolf et al., 2005). test (CORT OF) and (v) after the TI test (CORT TI). The 10 min delay after ACTH treatment was chosen because it Results has been previously shown that it allowed maximal CORT level to be reached in ducks (Noirault et al., 1999). Plasma Behavioural recordings was separated by centrifugation and kept at 2208C prior to In the OF test, the two hybrids did not differ significantly analysis. CORT levels were measured using the previously from each other for any of the measurements performed. described specific RIA (Etches, 1976). Ratio of CORT TI and Mule and hinny ducks did not differ significantly from CORT OF relative to CORT Net was calculated. These spe- Muscovy ducks for pecking and body shaking behaviour. For cific ratios were chosen in order to assess the physiological vocalisation, mule ducks and hinny ducks did not differ response to these behavioural tests in comparison with significantly from their maternal genotype. Duration of CORT Net, which induces among the highest corticosterone locomotor activity and latency to first immobilisation of the levels measured in ducks in response to physical stress mule ducks were significantly longer than those of the (Gue´mene´ et al., 1998), which involved the whole HPA as parental species (Table 1). well as the sensorial and cognitive mechanisms, contrary to In the RM test, the two hybrids did not differ significantly the 1-24 ACTH challenge that only involved the adrenal from each other for the different measures, except for first

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Table 1 Behavioural and physiological results (means 6 s.e.) for muscovy ducks (Md), pekin ducks (Pd), mule hybrid duck (Mh) and hinny hybrid duck (Hh) submitted to the openﬁeld test (OF), response to man test (RM), tonic immobility test (TI) and various corticosterone measures (CORT, ng/ml plasma): before restraint in a net (CORT Initial), after 10 min restraint in a net (CORT Net), after OF (CORT OF), after TI (CORT TI) and 10 min after injection of 1-24 ACTH (CORT ACTH) Parameters Muscovy (Md) Mule (Mh) Hinny (Hh) Pekin (Pd) P

OF Mobility duration (s) 172.9 6 11.1a 269.7 6 10.2b 259.6 6 9.2b 144.0 6 14.3a *** Immobility latency (s) 4.2 6 0.4a 117.52 6 13.4c 107.0 6 15.8bc 23.4 6 9.1ab *** Vocalisation 72.4 6 8.5a 110.07 6 11.7bc 87.75 6 10.5ab 115.8 6 9.2c ** Pecking 4.8 6 1.3b 4.3 6 1.2b 3.2 6 0.9ab 0.7 6 0.3a *** Body shaking 0.7 6 0.1a 0.9 6 0.3a 0.9 6 0.2a 2.7 6 0.2b *** RM Avoidance index 333.1 6 18.1b 350.8 6 7.3bc 390.7 6 14.5c 292.0 6 17.2a *** Mobility duration (s) 23.3 6 2.2a 48.7 6 2.8c 48.3 6 2.4c 32.7 6 2.4b *** Immobility latency (s) 9.5 6 0.7a 22.1 6 4.5b 20.0 6 4.0b 11.4 6 2.2a * Vocalisation 23.4 6 3.6a 43.3 6 4.0b 46.9 6 4.5b 31.8 6 3.3a *** Pecking 0.4 6 0.2a 2.83 6 1.1b 3.18 6 0.7b 0.03 6 0.1a *** Body shaking 0.37 6 0.1 0.14 6 0.1 0.07 6 0.1 0.48 6 0.1 ns TI Number of attempts 1.1 6 0.1a 1.5 6 0.1b 1.6 6 0.2b 1.5 6 0.1b * Duration (s) 322.6 6 32.1 336.1 6 28.2 373.6 6 28.6 385.4 6 28.2 ns % disrupted at 480 s 40.0b 41.9b 46.4b 71.0a ** CORT CORT Initial 2.43 6 0.5a 16.83 6 2.1c 13.05 6 1.2bc 10.26 6 1.4b *** CORT Net 18.90 6 2.0a 47.26 6 4.4b 49.50 6 5.9b 51.68 6 4.9b *** CORT OF 11.18 6 1.2a 14.38 6 1.4a 15.85 6 2.3a 38.19 6 3.5b *** CORT TI 13.87 6 1.3a 16.27 6 2.4a 15.28 6 2.6a 33.98 6 3.3b *** CORT 1-24 ACTH 24.38 6 3.1a 61.43 6 6.1b 81.41 6 6.6bc 109.63 6 10.0c *** CORT OF/CORT Net 0.79 6 0.1b 0.38 6 0.1a 0.44 6 0.1a 1.08 6 0.2b *** CORT TI/CORT Net 0.99 6 0.2b 0.41 6 0.1a 0.33 6 0.1a 0.97 6 0.2b *** CORT Net/CORT ACTH 0.82 6 0.1 0.91 6 0.1 0.71 6 0.1 0.62 6 0.1 ns

Within a line, means with different superscript letters differed signiﬁcantly (P , 0.05).

direction. Muscovy and hinny ducks oriented preferentially 1.0 away from the man (66.7% and 71.4%, respectively, binomial test P . 0.05), whereas Pekin and mule ducks 0.8 Pekin oriented randomly at ﬁrst (54.8% and 62.1%, respectively, 0.6 binomial test P , 0.05). Except for this ﬁrst direction and

S(t) Hinny body shaking, the two hybrids showed significantly higher 0.4 Mule values than Pekin ducks. The situation was similar between Muscovy hybrids and Muscovy ducks, even if the difference between 0.2 mule and Muscovy ducks was not significant for the 0.0 avoidance index. Overall, all genotypes showed higher 0 50 100 150 200 250 300 350 400 450 480 avoidance index than the theoretical average index of TI Duration (s) avoidance (IE corresponding to all the time spent in the middle of the corridor: 3.5 3 60 5 210) (Table 1). Figure 2 The estimated probability S(t) of being in tonic immobility (TI) In the TI test, the number of attempts required to induce TI as affected by time since induction for the four genotypes. differed significantly according to the genotype. Significantly fewer attempts were needed to induce TI in Muscovy ducks ducks, whereas they did not differ significantly for Muscovy as compared to the other genotypes. Duration of TI did not and mule ducks (Figure 3). The two hybrids did not differ differ significantly between genotypes, but around 50% of the significantly for any of the CORT measures (Table 1). Their duckswerestillinTIbytheendofthe8mintest(Table1). CORT OF and CORT TI were not significantly different from The survival analysis showed that Pekin ducks had a prob- CORT Initial (Figure 3). For CORT Initial and CORT ACTH, ability of still being in TI at a specific time S(t), significantly hybrids showed significantly higher concentration than higher than ducks from the three other genotypes (Figure 2) Muscovy ducks, but only mule duck levels differed sig- (x2 test, 4 d.f., x2 test 5 6.80, P , 0.01). nificantly from those of the Pekin ducks (Table 1). For levels measured following the behavioural tests, the two hybrids Physiological measures differed significantly from the Muscovy ducks for CORT Net CORT ACTH and CORT Net were significantly higher than and from the Pekin ducks for CORT OF and CORT TI (Table 1). the initial levels for all genotypes (Figure 3). CORT Net was Ratios of CORT OF or CORT TI relative to CORT Net were significantly lower than CORT ACTH for Pekin and hinny significantly lower for hybrids than for the parental lines,

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140 CORT Initial and the two hybrids did not differ significantly from each other (Table 1). No significant difference was found CORT OF d 120 between the four genotypes for the ratio of CORT Net CORT TI relative to CORT ACTH (Table 1). 100 CORT Net c CORT ACTH Genetic effect estimation 80 b Two maternal effects for CORT ACTH and avoidance index c in the RM test were slightly significant. Numerous direct 60 b additive and heterosis effects were found significant. b Negative direct additive and positive heterosis effects were 40 c significant for CORT Initial and CORT Net (Figure 4). a a b Negative direct additive and heterosis effects were sig- Corticosterone level (ng/ml plasma) Corticosterone level 20 a nificant for both CORT OF and CORT TI (Figure 4). Negative a direct additive effect was significant for CORT ACTH (Figure 4). 0 Muscovy Mule Hinny Pekin Negative heterosis effects were significant for both the Treatment ratio CORT OF/CORT Net and CORT TI/CORT Net (Figure 4). Positive direct additive effect was significant for the ratio Figure 3 Corticosterone levels (ng/ml plasma) in non-treated ducks CORT Net/CORT ACTH (Figure 4). (CORT Initial), following restraint in a net (CORT Net), openfield (CORT No significant genetic effect was found for the number of OF) and tonic immobility (CORT TI) tests and 10 min after an injection of induction or duration of TI. 1-24 ACTH (5 mg/kg BW, CORT ACTH) for each genotype. Within a genotype, means without a common superscript letter differ significantly For the OF test, positive direct additive effect was sig- (P , 0.05). nificant for pecking. Negative direct additive and heterosis

Additive Effect Heterosis Effect Maternal Effect

Net / ACTH * TI / Net **

OF / Net ** ACTH * **

CORT TI ** ** OF ** ** Net ** ** Initial ** ** Duration TI Attempt number Pecking ** Body Shaking ** ** Vocalisation OF

Immobility Latency ** Mobility Duration **

Pecking ** Body Shaking ** Vocalisations **

RM Immobility Latency **

Mobility Duration ** Avoidance Index ** **

–1 –0.5 0 0.5 1

Figure 4 Genetic effects estimated for the basal level of corticosterone (CORT Initial), after placement in a net (CORT Net), openfield (CORT OF) and tonic immobility (CORT TI) and 10 min after 1-24 ACTH injection (CORT ACTH); for the ratio of corticosterone levels after openfield to level after placement ina net (CORT OF/CORT Net), ratio of corticosterone levels after tonic immobility to level after placement in a net (CORT TI/CORT Net) and ratio of corticosterone levels after placement in a net to levels after ACTH injection (CORT Net/CORT ACTH), and for parameters measured during tonic immobility (TI), openfield (OF) and in response to man (RM) tests.

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effects were significant for body shaking. Positive heterosis the fact that both genotypes are very sensitive to stress and effects were significant for immobility latency and mobility are fearful, especially to human presence or handling, but duration. express different response strategies. The non-significant For the RM test, positive heterosis effects were significant correlations (data not shown) between behavioural and for pecking, vocalisations, immobility latency, mobility duration physiological parameters are in agreement with previously and avoidance index. Negative heterosis effect was significant published results in duck (Faure et al., 2003) or in quail for body shaking (Figure 4). (Mignon-Grasteau et al., 2003). These important differences in the physiological and behavioural response patterns between Pekin and Muscovy Discussion ducks resulted in interesting effects in hybrids, allowing the The present study supports and expands the knowledge investigation of further genetic transmission mechanisms. found in earlier experiments describing the differences The initial CORT level was higher for mule genotype com- between the parental genotypes in responses to the pared to the parental lines. This over-dominance was con- behavioural and physiological tests. The maximal response firmed by the fact that a positive significant estimated of the adrenal glands, as illustrated by the result to the 1-24 heterosis effect was found for this measure and is further ACTH challenge, and the level of corticosterone after supported by the fact that mule ducks have previously restraint in a net, were lower in Muscovy ducks compared been shown to be very sensitive to capture and handling to Pekin ducks, which is in agreement with what was (Gue´mene´ et al., 2006). On the other hand, hinny’s initial level observed in a previous study (Faure et al., 2003). Muscovy did not differ significantly either from the mule’s or from the ducks also showed a lower physiological sensibility to stress Pekin ones, and consequently estimated that maternal induced by the OF and TI tests than Pekin ducks. No dif- effect was not significant for this parameter. Following the ferences were found, however, in responses relative to 1-24 ACTH challenge, maximal response reactivity for mule maximal reactivity as shown by the calculation of the ratio ducks was intermediate between the parental responses between HPA activation from an acute stress (restraint in a and a significant negative additive effect was estimated for net) and adrenal maximal reactivity assessed by the 1-24 this parameter, which was associated with the absence of ACTH challenge. Likewise, no difference was observed for heterosis effect. This negative additive effect revealed a the ratio of levels measured after the OF and TI behavioural superiority of the Pekin genetic level in this cross for tests relative to the level after restraint in a net. Interest- maximal adrenal reactivity. Moreover, hinny’s response to ingly, the two parental genotypes showed different overall the 1-24 ACTH challenge did not differ significantly either responses in terms of HPA, as indicated by the absolute from mule or from Pekin ones, and consequently estimated levels measured, but their relative adrenal reactions were that maternal effect for this parameter was slightly sig- similar. Regarding behavioural responses, Pekin and Muscovy nificant. After restraint in a net, hybrids showed higher genotypes showed the same locomotor activity during the responses than the Muscovy’s but they did not differ from OF test; however, it probably resulted from different the Pekin one. Interestingly, the specific stress response underlying mechanisms. Pekin ducks probably look for a associated with the restraint in a net seems to result from social reinstatement as shown by a high level of vocalisa- a Pekin genetic dominance in both hybrids as indicated by tion (Faure et al., 1983) and the expression of a higher rate the findings of significant estimated heterosis effect for of body shaking that can be interpreted as a moderate level this trait. The OF and TI tests did not induce significant of fear in a novel environment. On the other hand, Muscovy increases in CORT levels in the hybrids. It can be interpreted ducks’ locomotion activity during the OF test is likely to because there was no physiological response to these correspond to an exploration of the novel environment as specific experimental situations or because initial levels illustrated by a higher rate of pecking activity (Suarez and were already elevated due to an extreme sensibility of Gallup, 1980). In the RM test, behaviours expressed were these genotypes to the experimental and sampling proce- different from those observed in the OF test, thus specific dure. Nevertheless, hybrids CORT levels following OF or TI responses to human presence were assessed in this test. were comparable with those of the Muscovy genotype. Although body shaking, pecking or vocalisations were These results argued for a dominance of the Muscovy similar for both parental genotypes, Pekin ducks moved genotype in its genetic transmission. Indeed, significant more than Muscovy ducks, which in turn showed a higher heterosis effects were estimated for both parameters. avoidance index. Therefore, both genotypes expressed sig- Interestingly, when ratios of corticosterone levels measured nificant fear of man but the response patterns differed: following the OF or TI test relative to the measured level Pekin ducks appeared to exhibit panic behaviour, whereas following a placement in a net were calculated, hybrid Muscovy exhibited avoidance. The results for the TI test ratios were significantly lower than those of both parental suggested the hypothesis that Pekin and Muscovy ducks species. This result suggested an over-dominance, which is react differentially to predation. Muscovy ducks required a supported by the fact that significant negative heterosis lower number of attempts to induce TI but the survival effects were estimated for these ratios. Alternatively, analysis revealed that Pekin ducks had a longer TI duration whereas maximal capacities of the HPA differ significantly than the other genotypes. Altogether, these data indicate between genotypes, the ratios of levels after net relative to

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the subsequent 1-24 ACTH challenge did not. This result is (i.e. body shaking in the OF test, pecking and body shaking in interesting from a physiological point of view because it the RM test) and heterosis effects were significant for nine might reveal a strong regulation mechanism upon acute traits (i.e. body shaking, latency of first immobilisation and stress physiological responses. A hypothesis that is in mobility duration in the OF test; all RM test measures). agreement with the absence of heterosis or maternal Heterosis effects were limited in hybrid ducks for growth or effects for this ratio. A slightly significant positive direct muscle traits (Tai and Rouvier, 1998; Chartrin et al., 2006; additive effect was revealed, suggesting a small superiority Larzul et al., 2006), but the present work provided further of the Muscovy genetic level for this ratio. evidence that over-dominance effects were involved in the In this study, behavioural results from the OF test sug- genetic expression of most of the behavioural responses to gested that, for hybrids, social isolation stress was more stress in this interspecific cross. Indeed, hybrids showed important than fear of the novel environment compared to stronger panic behaviour and avoidance of man than the two parental genotypes (Suarez and Gallup, 1980). Hybrids parental genotypes. Likewise, they also appeared to be more latency to first immobilisation appeared to be longer and sensitive to social stress than the parental species. As men- hybrids moved, pecked and body shaked more than Pekin or tioned by Faure et al. (2003), heterosis effects are expected Muscovy ducks. This result is not in contradiction with the on traits related to fitness, but genetic distance between observation that hybrids had low CORT response following Pekin and Muscovy ducks, species from two different tribes in OF, since it has been previously shown that bird’s HPA the Anatinae classification (Johnsgard, 1965), could explain reactivity to social stress is low in relation to other stressors the finding of significant heterosis effects even for traits with like manual restraint or others, as found in quail (Hazard moderate or high heritability values, such as fear reactions. et al., 2008). Other results have been reported for beha- On the contrary, most of the CORT responses were submitted vioural responses during OF in a previous study in which to negative direct additive effects, suggesting the superiority Pekin ducks expressed responses similar to those of mule of the Pekin genetic level in the transmission of the HPA ducks (Faure et al., 2003). This previous study was carried functionality in relation to stress response. To further inves- out with different genotypes than those used in this study, tigate HPA functionality and the link of physiological which may explain the difference observed. The over- responses to stress on behavioural responses of fear in this dominance found in the present study was further con- intercross, it would be fruitful to investigate the physiological firmed by the estimation of significant heterosis effects, and behavioural consequences of a divergent selection pro- especially with regard to mobility duration and latency to gram on corticosterone response to stress in Pekin ducks in first immobilisation. In the RM test, panic and social stress both parental genotype and mule ducks. Indeed, it was behavioural responses of the hybrids were clearly confirmed shown in a previous study that quails, divergently selected for by long mobility duration and latency to first immobilisa- high or low level of corticosterone after immobilisation, tion, high rate of vocalisation and pecking. Furthermore, expressed divergent responses to fear in various behavioural presence of man revealed a specific oriented fear response, tests (Jones et al., 1992a, 1992b and 1994). illustrated by the high values measured for the avoidance index. Hybrids, as well as Muscovy ducks, showed higher Acknowledgements avoidance to human than Pekin ducks, which is in agree- We greatly acknowledge Michel Couty for his technical con- ment with previous findings (Gue´mene´ et al., 2004). From tribution, the technicians of the experimental station Unite´ a genetic point of view, differences between genotypes Expe´rimentale des Palmipe`des a` Foie-Gras, especially Isabelle were due to heterosis effects only. Direct additive effect Meyer, for their expert animal care and help during tests, levels were found to be similar for Pekin and Muscovy Grimaud Fre`res Se´lection for providing ducks from the differ- genotypes for all RM parameters. Half of the ducks of ent genotypes, as well as Clara Bureau for improving the each genotype were still in TI by the end of the 8 min test quality of the manuscript. This study was financially supported period, which emphasised the fact that our hybrids, like our by the Institut National de la Recherche Agronomique (INRA) parental genotypes, showed a very important level of fear and the Comite´ Interprofessionel des palmipe`des a` FOie Gras to predation restraint. (CIFOG). IA is employed by the SYndicat des Se´lectionneurs To conclude, Mule and hinny’s responses were compar- Avicoles et Aquacoles Français (SYSAAF) and financially able in most of the behavioural and physiological tests. The supported by a PhD CIFRE grant attributed by the Agence present results also allowed the conclusion that hybrid Nationale de la Recherche Technique (ANRT) and by the Office responses were only genetically determined by direct des Viandes. additive and heterosis effects. Thus from the genetic analyses, out of the eight physiological traits measured, direct additive effects were significant for six traits (i.e. CORT Initial, CORT References Net, CORT OF, CORT TI and CORT Net/CORT ACTH) and Boujard T, Ramezi J, Vandeputte M, Labbe´ L and Mambrini M 2007. Group heterosis effects were significant for six traits (i.e. CORT feeding behaviour of brown trout is a correlated response to selection for growth shaped by the environment. Behavior Genetics 37, 525–534. Initial, CORT Net, CORT OF, CORT TI, CORT OF/CORT Net and Chartrin P, Me´teau K, Juin H, Bernardet MD, Guy G, Larzul C, Re´mignon H, CORT TI/CORT Net). Out of the 14 behavioural traits mea- Mourot J, Duclos MJ and Bae´za E 2006. Effect of intramuscular fat levels on sured, direct additive effects were significant for three traits sensory characteristics of duck breast meat. Poultry Science 85, 914–922.

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Dantzer R and Morme`de P 1979. Le stress en e´levage intensif. Masson, Paris. Jones RB, Satterlee DG and Ryder FH 1992b. Fear and distress in Japanese Dickerson G 1969. Experimental approaches in utilising breed resources. quail chicks of two lines genetically selected for low or high adrenocortical Animal Breeding Abstracts 37, 191–202. response to immobilization stress. Hormones and Behavior 26, 385–393. Dobson H, Tebble JE, Smith RF and Ward WR 2001. Is stress really all that Jones RB, Satterlee DG and Ryder FH 1994. Fear of humans in Japanese quail important? Theriogenology 55, 65–73. selected for low or high adrenocortical response. Physiology and Behavior 56, 379–380. Ducrocq V and So¨ lkner J 1998. The Survival Kit – a Fortran package for the analysis of survival data. In 6th World Congress on Genetics Applied to Larzul C, Imbert B, Bernardet MD, Guy G and Re´mignon H 2006. Meat quality Livestock Production, Armidale (AU), pp. 447–448. in an intergeneric factorial crossbreeding between Muscovy (Cairina moschata) and Pekin (Anas platyrhyncos) ducks. Animal Research 55, 219–229. Etches RJ 1976. A radio immunoassay for corticosterone and its application to the measurement of stress in poultry. Steroı¨ds 28, 763–773. Leroy Y 1964. Analyse de la transmission de divers parame`tres des signaux acoustiques chez les hybrides interspecifiques de grillons. In Proceedings of the Faure JM, Jones RB and Bessei W 1983. Fear and social motivation as factors XXI International Congress of Ethymology, London, p. 339. in open-field behaviour of the domestic chick. A theoretical consideration. Biology of Behaviour 8, 103–116. Manning A and Dawkins MS 1998. An introduction to animal behaviour. Cambridge University Press, Halftones. Faure JM, Val-Laillet D, Guy G, Bernardet MD and Gue´mene´ D 2003. Fear and stress reactions in two species of duck and their hybrid. Hormones and Mignon-Grasteau S, Roussot O, Delaby C, Faure JM, Mills AD, Leterrier C, Behavior 43, 568–572. Gue´mene´ D, Constantin P, Mills M, Lepape G and Beaumont C 2003. Factorial correspondence analysis of fear-related behaviour traits in Japanese quail. Gallup GG Jr 1977. Tonic immobility: the role of fear and predation. The Behavioural Processes 61, 69–75. Psychological Record 1, 41–61. Mills AD and Faure JM 1990. Panic and hysteria in domestic fowl. In Social Gironi Carnevale UA, Vitullo E, Varriale B, Ruocco LA and Sadile AG 2007. stress in domestic animals (ed. R Zayan and R Dantzer), pp. 248–272, Kluwer A classical Mendelian cross-breeding study of the Naples high and low Academic Publishers, Dordrecht-Boston-London. excitability rat lines. Behavioural Brain Research 183, 130–140. Mills AD and Faure JM 1991. Divergent selection for duration of tonic Gue´mene´ D, Guy G, Destombes N, Garreau-Mills M and Faure JM 1998. immobility and social reinstatement behavior in Japanese quail (Coturnix Aptitude physiologique du canard mulard male a` re´pondre a` un stress aigu coturnix japonica) chicks. Journal of Comparative Psychology 105, 25–38. pendant la pe´riode de gavage. In 3e Journeés de la Recherche sur les Palmipe`des a` Foie Gras, Bordeaux, pp. 63–68. Morme`de P, Andanson S, Aupe´rin B, Beerda B, Gue´mene´ D, Malmkvist J, Manteca X, Manteuffel G, Prunet P, Van Reenen CG, Richard S and Vessier I Gue´mene´ D, Gobin-Fournel E, Faure JM and Guy G 2002. Effets geńotype, 2007. Exploration of the hypothalamic-pituitary-adrenal function as a tool to pheńotype, aˆge et mode d’e´levage sur les re´ponses comportementales et evaluate animal welfare. Physiology and Behavior 92, 317–339. endocriniennes de canards mulard maˆles. In L’Ethologie Appliqueé, pp. 65–72, Claude Baudoin, Levallois-Perret. Noirault J, Gue´mene´ D, Guy G and Faure JM 1999. Corticosterone plasma concentration in male mule ducks: effects of samplings site and ACTH Gue´mene´ D, Larzul C, Bouy S, Bernardet MD, Guy G and Faure JM 2004. injections. British Poultry Science 40, 304–308. Couleur du plumage et de´terminisme geńe´tique des comportements de peur chez le canard mulard. In 6e Journeés de la Recherche sur les Palmipe`des a` Roy V, Merali Z, Poulter MO and Anisman H 2007. Anxiety responses, plasma Foie Gras, Arcachon, pp. 99–103. corticosterone and central monoamine variations elicited by stressors in reactive and nonreactive mice and their reciprocal F hybrids. Behavioural Gue´mene´ D, Guy G, Noirault J, Destombes N and Faure JM 2006. Rearing 1 conditions during the force-feeding period in male mule ducks and their impact Brain Research 185, 49–58. upon stress and welfare. Animal Research 55, 443–458. Rushen J, Taylor AA and de Passille´ A 1999. Domestic animals’ fear of humans and Harvey S, Merry BJ and Phillips JG 1980. Influence of stress on the secretion of its effects on their welfare. Applied Animal Behaviour Science 65, 285–303. corticosterone in the duck. Journal of Endocrinology 87, 161–171. Satterlee DG and Johnson WA 1988. Selection of Japanese quail for contrasting Hazard D, Couty M, Richard S and Gue´mene´ D 2008. Intensity and duration of blood corticosterone response to immobilization. Poultry Science 67, 25–32. corticosterone response to stressful situations in Japanese quail divergently Siegel HS 1971. Adrenals, stress and the environment. World’s Poultry Science selected for tonic immobility. General and Comparative Endocrinology 155, Journal 27, 327–349. 288–297. Suarez SD and Gallup GG Jr 1980. An ethological analysis of open-field Holm S 1979. A simple sequentially rejective multiple test procedure. behaviour in ducks Anas Platyrhyncos. Bird Behavior 2, 93–105. Scandinavian Journal of Statistics 6, 65–70. Tai C and Rouvier R 1998. Crossbreeding effect on sexual dimorphism of body Jensen P and Toates FM 1997. Stress as a state of motivational systems. weight in intergeneric hybrids obtained between Muscovy and Pekin duck. Applied Animal Behaviour Science 53, 145–156. Genetics, Selection, Evolution 30, 163–170. Johnsgard PA 1965. Handbook of waterfowl behaviour. Cornell University Vuillaume A and Tournut J 1975. Une nouvelle technique de pre´le`vement de Press, Ithaca, NY. sang chez les palmipe`des et les autres volailles. In Groupements Techniques Jones RB and Faure JM 1981. Sex and strain comparisons of tonic immobility Ve´te´rinaires, pp. 83–89. (‘‘righting time’’) in the domestic fowl and the effects of various methods of Wolf J, Zavadilova´ L and Nemcova´ E 2005. Non-additive effects on milk induction. Behavioural Processes 6, 47–55. production in Czech dairy cows. Journal of Animal Breeding and Genetics 122, Jones RB, Satterlee DG and Ryder FH 1992a. Openfield behavior of Japanese 332–339. quail chicks genetically selected for low or high plasma corticosterone Zulkifli I and Siegel HS 1995. Is there a positive side to stress? World’s Poultry response to immobilization stress. Poultry Science 71, 1403–1407. Science Journal 51, 63–76.

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