INFLUENCE OF PRE-SLAUGHTER CAPTURE CHASE DURATION STRESS ON CARCASS AND MEAT QUALITY OF INDIGENOUS CHICKEN REARED UNDER TRADITIONAL SYSTEM IN BENIN

1. Laboratory of Animal Biotechnology and Meat Technology, Department of Animal Production and Health, Polytechnic School of Abomey-Calavi, University of Abomey-Calavi, 01 BP 2009 Cotonou, Republic of Benin. 2. Faculty of Agronomic Sciences, Department of Animal Production, University of Abomey-Calavi, 01 BP 526, Cotonou, Republic of Benin. 3. Department of Animal Production and Health, Polytechnic School of Abomey-Calavi, University of AbomeyCalavi, 01 BP 2009 Cotonou, Republic of Benin. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

The current study aims to evaluate the influence of the pre-slaughter capture chase duration stress on carcass and meat quality in local chicken of Benin.Sixty-four chickens of 6 to 7 months old divided into 4 flocks of 8 males and 8 females each reared under traditional system were used.Chickens of first group were not chased before slaughter.Whereas, chickens of the second, the third and the fourth groups were slaughtered respectively after 5 minutes, 10 minutes and 15 minutes of chase by 3 persons.Carcass and meat quality was evaluated.Carcass quality traits didn't vary according to the preslaughter capture chase stress.The two longer capture chase duration chickens had the lower breast pH at the first measure time.But it was higher in those chased during 15 minutes at 48 hours after slaughter.Control birds showed lower pH than the 5 minutes stressed one at 1 and at 12 hours.The thigh pH values were higher with the most chased chickens.However, drip loss at 24 hours after slaughter didn't vary.The breast lightness was higher in the most chased on the slaughter day.Meanwhile, the breast yellow index was higher with chickens of 15 minutes of chase.But no difference was found for the meat red index values of the four flocks.The meat flavor, juiciness, tenderness and global acceptance didn't vary according to the preslaughter capture chase stress.In sum, the sensory and technological meat qualities of local chickens decrease more with the capture chase duration stress.
For animals destined to slaughter, the environmental conditions, the capture, the manipulations, the transportation, the feed withdrawal are some stress factors that can have consequences on the production (Lara et al., 2013), animal welfare (Voslarova et al., 2007) and on carcass and meat quality (Radu et al., 2012).But genetics and biotope can affect the extent of these consequences.Genetics can explain 40% to 50% of the variability of breast ultimate pH observed within a population (Le Bihan-Duval et al., 2001 and2008;Chabault et al., 2012).
Researchers are already working on how to control carcass and meat quality changings due to pre-slaughter stress factors across America, Europe, Asia and North Africa (González et al., 2007;Zhang et al., 2014;Perai et al., 2014) where, the consequences of these factors on their genetic resources are already known.Meanwhile, the influence of local pre-slaughter stress conditions on indigenous chicken carcass and meat quality isn't fully investigated in West Africa in general and in Benin in particular.These chickens are often slaughtered after a capture chase of which stress has detrimental effects on the meat quality due to the divagation and the almost non-existence of habitat that characterize the traditional breeding system (Bonou, 2014).Ten minutes of pre-slaughter capture chase stress had negatively affected meat pH, lightness and its red index mostly those of the thigh.Meat was darker, redder with a lower acidity degree and then, could be favorable to microorganism proliferation (Bonou et al., 2017).Or, a prior survey revealed that in the Atlantic region of Benin, local chickens are chased to be capture during 8 to 19 minutes in an open area, in a fence, or in a building or henhouse (Bonou, 2014).But the reaction of the meat quality of this animal resource to stress factors duration is less investigated.Thus, from which minor capture chase duration, meat and carcass quality attributes of these chickens are affected and what are the consequences when the duration flows?This work is to answer these questions by the assessment of the influence of pre-slaughter capture chase duration stress on carcass and meat quality of indigenous chicken reared under traditional system in Benin.

Area of study:-
The study was carried out in the Laboratory of Animal Biotechnology and Meat Technology of the Department of Animal Production and Health of the Polytechnic School of Abomey-Calavi.The chickens used were produced under traditional breeding system in Abomey-Calavi.This area benefits from climatic conditions of subequatorial type characterized by two rainy seasons with an uneven spatial and temporal repartition of rainfall (the major, from April to July and the minor, from September to November).These seasons are separated by two dry seasons.Average rainfall is close to 1200 mm per year.The monthly average temperatures vary between 27°C and 31°C.The relative air humidity fluctuates between 65% from January to March and 97% from June to July.

Birds rearing and Sampling:-
Sixty-four (64) local chickens of six to seven months old produced from two (2) roosters and ten (10) hens all of South ecotype of Benin were used.These birds were reared under traditional breeding system where, they have a habitat for night housing or protection against bad weather and a course of 400 m 2 .They fed themselves around and also received grains, agricultural by-products and kitchen rests.Birds were vaccinated against fowl pox and Newcastle disease.On the eve of the slaughter day, chickens were divided into four homogeneous flocks of 8 males and 8 females each.They were registered and kept where they will be chased the following day.
Pre-slaughter conditions, slaughter process and carcass cutting:-Birds of the flock 1 were the control chickens and didn't undergo any stress before slaughter.Chickens of the flock 2 were chased during 5 minutes in a henhouse of 32 m 2 , those of the flock 3 during 10 minutes in a yard of 212 m 2 and the one of the flock 4 during 15 minutes in a closed area of 400 m 2 .Three persons were involved.After capture, birds were weighted and immediately slaughtered by section of the jugular vein.Then, chickens were scalded in a hot water (75°C) and plucked manually.Legs have been sectioned at the tibio-tarsusmetastasal joint level.The head were separated from the neck at the skull-atlas junction.The abdominal and thoracic cavities organs were taken off.Hot carcasses have been weighted and immediately cut.
189 Data Collecting:-Live weight before slaughter, hot carcass weight and carcass cuts weight (breast, wings and thigh-drumstick) were registered.Carcass yield was determined from the live weight and the percentage of each carcass cut from the hot carcass weight.
The pH was measured in the right slice of the breast muscle (Pectoralis major) and in the right thigh muscle (Iliotibialis superficialis) at 2 cm depth with a portable pH-meter (HANNA Instrument R, Italy) provided with a specialized probe and a temperature control system.Measures were taken at 1h, 12h, 24h and 48h after slaughter.For every measure, 5 repetitions were performed.On each measure day, the pH-meter has been calibrated previously with two buffers pH-meter: pH 4 and pH 7 following a procedure described by the manufacturer.
The drip loss was determined with the left slice of the breast muscle according to the procedure described by Honikel (1987).Each sample was suspended to a hook, put into a refrigeration bag without touching its bottom.After 24 hours at 4°C in hung position, the samples were taken out of the bag without touching the bottom that contains the draining juice.They were mopped, weighted and drip loss was calculated as the percentage of weight loss during the storage.
The meat color was determined using a Minolta Chromameter CR-400 (Japan) in the trichromatic system (CIE L*a*b *) after storage of the samples at 4°C during 1 h 30 min.This is based on three dimensional space with one dimension for luminance (L* is the lightness) and two for color a* (redness) and b * (yellowness) (Zhang and Barbut, 2005).The chroma (C) and the hue angle (h) were determined as followed: C= (a* 2 + b* 2 ) 1/2 and h = tan - 1 b*/a*.For each measure, 5 repetitions were performed.The measures were taken on the ventral face, at the third superior on the thickest part of the breast muscle left slice and on the middle of the ventral face of the left thigh muscle.The Minolta was calibrated using standard color tiles.The color was measured on the slaughter day and at 24 hours post mortem.
The right slice of the Pectoralis major of each chicken was used for the sensory analysis.The samples were put in cooking bags separately without seasoning and boiled in a bain-marie until the meat core temperature reached 75°C.A trained jury of 10 members was used for the test.After cooling to room temperature, each sample of meat cooked was cut into ten identical pieces at least.Every judge received in a plate divided by the manufacturer in four parts of different colors a piece of each category and each flock of chicken and filled in a recapitulative results form.In total, eight samples of which two by flock (one from a male and one from a female) were put by turn in the plate under numbers 1 to 8. The judges have appreciated the tenderness, the juiciness, the flavor and the global acceptance of the meat under marks going from 1 to 5.

Statistical Analysis:-
The data collected on carcass and meat quality were analyzed using the software SAS (Statistical Analysis System, 2006).The General Linear Model procedure was used for the variance analysis.The Fisher test was used to test the significance of the capture chase duration stress and the sex effects on carcass and meat quality traits.Means were compared pairwise by the Student test.

Results:-
Carcass traits of indigenous chicken according to the pre-slaughter capture chase duration stress:-Carcass traits are given by pre-slaughter capture chase duration stress in table 1.The live weight, the hot carcass weight, the breast weight, the thigh-drumstick weight and the wings weight were similar for the control and the different chased birds.The hot carcass yield didn't even statistically vary according to the pre-slaughter capture chase duration stress.The yields of the breast, of the thigh-drumstick and of the wings were also the same.
The carcass traits of males and of those of females by flock are presented in the table 2. The wings weights of males were higher with 5 and 10 minutes chased birds than those of their counterpart females.The tendency was the same with the thigh-drumstick yield of 5 and 15 minutes chased chickens and with the wings yield of the last one.

Variation of pH and of drip loss of indigenous Chicken:-
The variation of the pH is given in the table 3. The pH of the breast muscle at 12, 24 and 48 hours post mortem was higher in the most chased chickens.Meanwhile, the other flocks showed similar breast pH except at 12 hours after slaughter where, it was lower with control birds.However, at one hour, birds of 10 and 15 minutes had lower breast 190 pH than the one of 5 minutes chase of which pH was higher than the one of the control (p<0.001).In the thigh, the pH values were higher with stressed chickens.Those of 10 and 15 minutes had the higher pH.Besides, for the different flocks of chickens, the most important pH fall was observed in the two muscles during the first twelve hours post mortem (figure 1 and figure 2).
The variation of the pH of males and females of the four flocks is presented in the table 4. The breast meat pH of males was higher than the one of females at one hour in the stressed birds and at the other measures times in chickens chased during 5 and 15 minutes.The tendency was not statistically significant in the control.In the thigh, apart from 1 and 12 hours in the control, pH values of males were also higher than those of females of all the flocks.The drip loss was statistically similar between flocks (Table 1) and sexes (Table 2).However, females and the less chased chickens tend to show the important proportions.

Color of the Pectoralis major and of the Iliotibialis superficalis muscles
Color traits on the slaughter day and at 24 hours post mortem are presented in table 5.In the thigh, the yellow index b * was higher in the 10 and 15 minutes chased chickens than in the others on the slaughter days but similar at 24 hours after.No difference was found in the other color traits with this muscle at the two times.For the breast meat, the first days, the lightness was lower with the control and the 5 minutes stressed animals (p<0.05).The yellow index b * and the chroma were higher in the 15 minutes stressed chickens (p<0.05).The following day, the yellow index b * was higher in the 5 and 15 minutes chickens.The others parameters were the same.
The variation of color by sex for the four groups is presented in table 6.In the thigh muscle, on the slaughter day, the yellow index and the chroma in females chased for 10 and 15 minutes were higher than the one of their correspondent males (P <0.05).The hue angle showed the inverse.At 24 hours post mortem, the yellow index in females chased for 10 and 15 minutes was also higher.Meanwhile the red index a * and the hue were more important in males than in females chased during 5 and 15 minutes.
In the breast meat, on the first day, the lightness was higher in females of 5 and 10 minutes of chase than in their counterpart males.The tendency was the same for yellow index of these two groups and for the chroma of the last one.The red index and the hue were similar.At 24 hours, the red index was more important in the males with control and 10 minutes chased chickens.The hue of these birds and of the 15 minutes one presented the same tendency.On the contrary, the yellow index was lower in males of the different groups.

Sensory analysis of the Pectoralis major of indigenous chicken
The flavor, the juiciness, the tenderness and the global acceptance of the breast meat didn't vary between the four groups of chickens (Table 1).From one sex to the other, they didn't even vary (Table 2).

Carcass traits of indigenous chicken according to the pre-slaughter capture chase duration stress:-
The live weight, the hot carcass weight, the breast weight, the thigh-drumstick weight and the wings weight as well as the yields of the hot carcass, of the breast, of the thigh-drumstick and of the wings were similar for the control and the different stressed birds.Apart from the wings weight and the yields of the thigh-drumstick and of the wings, the parameters were also the same between sexes.The similarity observed between the carcass traits shows that the experimental flocks are homogenous.The weight and the yield results of the current study are close to those recorded by Youssao et al., (2009), Tougan (2010) and Bonou et al., (2017).The non-existence of significant difference between weight and yield parameters according to the stress in the present study was also reported by Bonou et al., (2017) with stress of one hour of transportation and of 10 minutes of capture chase.This situation could be explained by the short stress durations and the immediate slaughter of birds after the process.Otherwise, the immune reaction could result in reduction of feed intake, growth disturbance and weight loss.As example, Sohail et al., (2012) recorded in broiler exposed to chronic heat stress a reduction of 16.4% of feed intake, of 32.6% of body weight and an increasing of feed conversion ratio of 25.6%.

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The yields of the thigh-drumstick results of the current study according to the sex are opposite to those of Chabault et al., (2012).They reported in commercial lines that for a given age, the breast and the thigh yields are often higher with females due to their most precocity muscle development in comparison to males.This precocity observed in females is not true in the local chickens.

Variation of pH and of drip loss of indigenous chicken:-
The pH of the breast muscle at 12, 24 and 48 hours post mortem was higher in the most chased chickens.Meanwhile, the other flocks showed similar breast pH except at 12 hours after slaughter where, it was lower with control birds.The muscle acidification was then least with chickens of 15 minutes of chase.Their glycogen stock level could be lower.They could have certainly use part of their reserve to produce energy during the physical activities they endured in the stress process.According to Berri (2015), the ultimate pH depends on the glycogen concentration of the muscles at the slaughter time.Transportation for 3 hours decreases the plasma glycogen concentration in broilers (Zhang et al., 2014).Animal's disturbance lead to the depletion of muscle glycogen content and then to a higher meat pH (Cartier and Moëvi, 2007).The wings flapping duration on the slaughter line is negatively correlated to the muscle glycogen potential (Berri et al., 2005).
At one hour, birds chased for 10 and 15 minutes had lower breast pH than those of 5 minutes of which, pH was higher than the one of the control.Acidification was then abnormally higher in the two most chased chickens at that time.These birds had certainly produced more lactic acid not yet resorbed.Besides, the lower pH of the control chickens at 1 and 12 hours post-mortem compare to those of 5 minutes chase one, indicates that this short time of capture chase already affects meat quality.This observation is most obvious in the thigh for, control thigh pH values were lower all the times.
The results of the current study are similar to those of other authors with comparable stress factors.Gigaud et al., (2007) observed with the free-range chicken that as for the transportation duration, a long waiting time (superior to 4 hours) result in higher pHu.Longer is the transportation duration, higher is the pHu.Berri et al., (2005) studying the effect of the activity on the slaughter line recorded that the increasing of the wings flapping duration provokes a higher pHu in broilers.Debut et al., (2003) noticed that the thigh pHu is one of the main parameters influenced by pre-slaughter stress conditions.They observed that a two hours of transportation leads to a higher ultimate pH (6.21  Bonou et al., 2017).On the contrary, the thigh muscle pH was higher in the chased birds and was respectively 6.15, 6.29 and 6.34 from the less to the most chased one.Bonou et al., (2017) also registered similar result with local chickens chassed during 10 minutes.So, the thigh meat of these chased birds could be favorable to microbial proliferation and then, presents important sanitary risks for the consumers.
In the two muscles, and for the different flocks, the most important pH fall occurred in the first twelve hours post mortem.Bonou et al., (2017) found a similar result.During this period, the muscle glycogen was more available for anaerobic glycolysis reactions that take place in meat maturation process.
Besides, from one sex to the other, males showed higher pH values than their homologues females at several measures times.Bonou et al., (2017) also recorded similar situation.The glycogen potential was therefore least in males.They seem more sensitive to the stress than females.Schneider et al., (2012) reported an ultimate breast pH in the males higher than the one in the females (5.96 vs 5.87).
The drip loss was statistically similar for the different groups.Color of the Pectoralis major and of the Iliotibialis superficalis muscles:-In the breast meat, the lightness was higher in the 10 and 15 minutes chased chickens on the slaughter day but the same the day after.It was similar in the thigh at the two moments.The higher values in the most chased birds could be a color defect.High lightness was also reported with other close pre-slaughter stress factors.As example, the activity on the slaughter line was associated with higher meat lightness (Berri et al., 2005).On the contrary, lower meat lightness was found in certain studies.The yellow index b * registered in the breast was higher in the chickens chased for 15 minutes at the two times and in the one of 5 minutes of chase only the second day.In the thigh, it was higher with 10 and 15 minutes chased birds only the first day.As the breast lightness, the yellow index was influenced by the long durations chase notably on the slaughter day.It was more abundant in those with higher lightness.In addition, this study showed that the higher lightness tend to be associated with higher yellow index.Bonou et al., (2017) also remarked such relation with non-stressed chickens and with females in most of the cases.Harford et al., (2014) wrote a similar report.Indeed, the selection for the increasing of the lightness resulted in an increasing of the yellow index.However, the negative relationship reported between the red index and the yellow index is not observed while comparing the flocks in this study.
In general, the higher lightness and yellow indexes were found in females whereas the higher red indexes were observed in males.These reports are the consequence of pH that tends to be higher in males.The results correspond to the relationships described above between these parameters of color and the pH (Sheard et al., 2012 ; Harford et al., 2014 ;Bonou et al., 2017 ;Xing et al., 2015).The negative correlation between the yellow index and the red index that was not observed above is nevertheless remarked in the breast meat of 10 minutes chased chickens at 24 hours post-mortem.Besides, El Rammouz (2005) indicated that in poultry, the concentration of the myoglobin, pigment responsible for the red color, is more abundant in the breast and thigh muscles of the males than in those of the females.

Sensory analysis of the Pectoralis major of indigenous chicken:-
The flavor, the juiciness, the tenderness and the global acceptance of the breast meat didn't vary between the groups and sexes of local chickens.Bonou et al., (2017) also recorded similar result with control, 10 minutes chased and one hour of transportation chickens.These quality traits depend on muscle composition and structural property especially on its major components such as muscular fiber, connective tissue and intramuscular lipids (Lefèvre andBugeon., 2008, Listrat et al., 2015).Meat sensory quality determinatives pointed out by these authors didn't therefore vary in chickens in this study.Besides, the non-existence of difference between sensory quality attributes according to the stress could be explained by the non-conservation of the meat used for the test during a long time.
The analysis was done at 48 hours after slaughter.Otherwise, the difference could affect meat juiciness and tenderness which are directly in relationship with meat pH (Hocquette et al., 2000;Geay et al., 2002). 197 The marks given by the jury to the sensory meat attributes are around 3/5. Similar results were gotten by Youssao et al., (2009), Tougan (2010) and Bonou et al., (2017).

Conclusion:-
The study of the influence of the pre-slaughter capture chase duration stress on carcass and meat quality of indigenous chicken reared under traditional system in Benin reveal that these stress conditions doesn't influence the carcass quality but, from 5 minutes of chase, the meat quality is negatively affected.The two longer chase durations acidify precociously the breast meat that is less dark and more yellow.However, the acidification doesn't reach the one of PSE or acid meat.But two days after, the acidity level is lower with the most chased chickens.The longer chase durations reduce more seriously the acidification of local chicken thigh meat that is in such conditions favorable to microbial proliferation.

Figure 1 :Figure 2 :
Figure 1:-Breast meat pH fall according to the capture chase duration stress during the 48 hours post-mortem

Table 1 :
-Carcass traits, drip loss and sensory quality of the Pectoralis major of indigenous chicken Means of the same line followed by different letters differ significantly at the threshold of 5%; NC : Non-chased ; CA : Chased for 5 minutes; CB : Chased for 10 minutes ; CC : Chased for 15 minutes ; ANOVA : Variance Analysis

Table 2 :
-Carcass traits, drip loss and sensory quality of the Pectoralis major of males and females of the indigenous chicken according to the pre-slaughter capture chase duration stress.
NS : P > 0.05 ; * : P < 0.05 ; Means between the classes of the same line followed by different letters differ significantly at the threshold of 5%; NC : Non-chased ; CA : Chased for 5 minutes; CB : Chased for 10 minutes ; CC : Chased for 15 minutes ; ANOVA : Variance Analysis

Table 3 :
-Breast and thigh muscles pH of indigenous chicken according to the pre-slaughter capture chase duration stress Means of the same line followed by different letters differ significantly at the threshold of 5%; NC : Non-chased ; CA : Chased for 5 minutes; CB : Chased for 10 minutes ; CC : Chased for 15 minutes ; ANOVA : Variance Analysis.

Table 4 :
-Breast and thigh muscles pH of males and females of the indigenous chicken according to the preslaughter capture chase duration stress * : P < 0.05 ; ** : P < 0.01 ; *** : P < 0.001; Means between the classes of the same line followed by different letters differ significantly at the threshold of 5%; NC : Non-chased ; CA : Chased for 5 minutes; CB : Chased for 10 minutes ; CC : Chased for 15 minutes ; ANOVA : Variance Analysis

Table 5 :
-Color of the Pectoralis major and of the Iliotibialis superficalis muscles of indigenous chicken according to the pre-slaughter capture chase duration stress

Table 6 :
-Color of the Pectoralis major and of the Iliotibialis superficalis muscles of males and females of indigenous chicken according to the pre-slaughter capture chase duration stress.

Mome nt Musc le Variab le Chicken NC Chicken CA Chicken CB Chicken CC Standard Error
* : P < 0.05 ; L* : lightness ; a* : red index ; b* : yellow index ; Means between the classes of the same line followed by different letters differ significantly at the threshold of 5% ; NC : Non-chased ; CA : Chased for 5 minutes; CB : Chased for 10 minutes ; CC : Chased for 15 minutes ; ANOVA : Variance Analysis Discussion:- (Berri and Jehl, 2001;Quentin et al., 2003;Debut et al., 2003: Fanatico et al., 2005;Tougan (2010)es,Barbut et al., (2005), Oba et al., (2009), Langer et al., (2010) and Xing et al., (2015) have recorded Pale Soft and Exudative (PSE) chicken meat with short lengths of transportation at high temperature.The pHu usually observed in chicken meat is around 5.8(Gigaud et al., 2007).The pH48 of the breast meat was respectively 5.72, 5.76, 5.72 and 5.82 with control, 5, 10 et 15 minutes chased chickens.These values seem acceptable for, close to those reported in the literature(Berri and Jehl, 2001;Quentin et al., 2003;Debut et al., 2003: Fanatico et al., 2005;Tougan (2010); Schneider et al., (2012)meat pH48 in the current study with the normal ultimate pH value could justify this.Bonou et al., (2017)also reported the same thing in such situation.Debut et al., (2003)didn't found difference in the drip loss when pH values were normal.On the other hand,Berri et al., (2005), studying the effect of the stress of the activity on the slaughter line preceded or not by heat exposure, found that drip loss was more important in the stressed chickens of which pHu was relatively lower.Schneider et al., (2012) and Zhang et al., (2014) also reported lower drip loss when the pH was higher.196Driplossdidn't statistically vary by sex but females showed the important arithmetic proportions.This tends to confirm the negative correlation that exists between meat pH and meat drip loss.In the study ofSchneider et al., (2012), the difference was clear.The drip loss of females (2.34) was significantly higher than the one of the males (1.99%).
Debut et al., (2003))observed that as for the chase duration, a long waiting time, (superior to 4 hours) result in a lower lightness.Debut et al., (2003)observed a similar effect also after two hours of transportation but only in the thigh meat.Bonou et al., (2017) registered lower lightness with local chickens stressed by the transportation or by the capture chase.
Bonou et al., (2017)obtained similar results with non-stressed chickens and with females in most of the cases..In both breast and thigh, the red index a* was the same at the two times for all the flocks.The capture chase duration didn't affect the red index in the current study.On the contrary,Bonou et al., (2017)got redder breast meat in local chickens stressed by 10 minutes capture chase.
The local chicken meat pH and color of the current study results analysis reveals that breast meat of the most chased birds have lower pH at one hour post mortem associated to higher lightness and yellow index on the slaughter day.A similar relation was described in several studies.Thus,Berri etal., (2005), Gigaud et al., (2006), Gigaud and Berri (2007), Gigaud et al., (2007 and 2008), Sheard et al., (2012), Harford et al., (2014) and Xing et al.,(2015)reported that the color of meat in poultry especially the lightness and the ultimate pH are in significant negative correlation.