Meat Quality and Cooking Characteristics in Broilers Influenced by Winter Transportation Distance and Crate Density

Abstract

A study was conducted to determine the effect of transportation distance and crating density on meat quality traits during winter. ROSS-308 broilers aged 35 days were divided into 10 treatment groups based on three transportation distances (80, 160, and 240 km) with three crating densities (10, 12, and 15 birds per crate) along with birds slaughtered on farm without crating as a control group. Each treatment was replicated 10 times and placed at various locations in the truck. The birds were transported in plastic crates of 0.91 m×0.55 m×0.30 m at ambient temperature and relative humidity of 3.6–9.5°C and 63.3–78.8%, respectively. The breast meat quality parameters including pH, color, drip loss, shear force, marinade uptake and retention, cooking losses, and yield were determined. The results showed significantly higher pH 15 min post-slaughter (PS), drip loss, lightness, marinade uptake, raw meat cooking yield, and shear force in birds slaughtered on farm without any transportation. The birds transported for 240 km had significantly higher pH at 2 hours (h) PS, marinade retention, and cooking yield. Whereas, pH at 24 h PS, meat redness, yellowness, chroma, and marinated meat cooking yield were significantly higher in all transported treatments compared to the control group. Among different crating densities, the birds transported with 10 birds per crate showed significantly higher meat redness, marinade retention, and cooking yield. The crating density of 15 birds per crate had significantly higher lightness, hue, cooking loss, and shear force. However, no effect of crating density was observed on meat pH, drip loss, and marinade uptake. It can be concluded that an increase in transportation distance and low crating density during winter can negatively affect physical quality of meat with significant improvement in marination and cooking characteristics.

Introduction

Broiler welfare and meat quality traits are serious concerns for the global poultry industry. After spending the growing phase in an environment-controlled poultry house, the sudden exposure of broilers to physiological stress, during their transportation to processing plants negatively affects their well-being (Savenije et al., 2002). The major factors associated with stress during transportation include feed and water deprivation, catching, crating density, thermal variations, and duration and distance of transportation (Delezie et al., 2007; Orlic et al., 2007). The interaction of these factors not only cause economic losses due to mortality and live weight shrinkage but can also deteriorate meat quality traits (Kannan et al., 1997; Nijdam et al., 2004).

The ambient temperature during transportation affects muscle metabolism by inducing physiological changes and fatigue in birds (Petracci et al., 2001). Higher temperatures are associated with higher carcass temperature and faster postmortem pH decline (Mitchell and Kettlewell, 2004; Guarnieri et al., 2004). Conversely, low environmental temperature coupled with air drafts due to movement of the truck can cause cold stress (Minka and Ayo, 2015). The cold stress can deteriorate meat quality traits because of depletion in body glycogen due to increased energy metabolism to maintain body temperature (Dadgar et al., 2010). The subsequent effect of these variables varies according to the length of journey due to depression in liver and muscle glycogen contents (Warriss et al., 1993; Kannan et al., 1997). Lower glycogen contents before slaughtering can cause low lactic acid production in birds (Gregory, 1994; Lawrie, 1998). Meat with low lactic acid content is expected to have higher ultimate pH (pH_u) than normal (Dadgar et al., 2010).

Investigating the effect of transportation distance, different studies have reported that an increase in transportation distance has been associated with higher pH_u, lower lightness, shear force, drip, and cooking losses (Yalçin and Güler, 2012; dos Santos et al., 2017). On the other hand, Zhang et al. (2009) reported no effect of transportation (up to 3 h) on meat quality traits in broilers. Similarly, Sowinska et al. (2013) also reported no effect of winter transportation (0–300 km) on meat pH and color parameters except water holding capacity (WHC), which increased with higher transportation distance. These studies suggest that variations in climatic conditions in different geographical regions of the world are associated with contradictory effects of transportation distance on meat quality. The ambient environment or climate during transportation changes the microclimate of the vehicle. The season of transportation, length of journey, and crating density are the major determinants of the microclimate of the vehicle (Barbosa filho et al., 2008).

The optimal loading density varies according to ambient temperature and bird size (Elrom, 2000; Whiting et al., 2007). Provision of more space will affect the transporter economically as well as produce chilling during winter, while less space can cause welfare issues (Watts et al., 2011). The space and traveling distance can also cause physical consequences such as bruising, injury, and death due to fighting, trampling, or suffocation (Moran and Bilgili, 1995; Elrom, 2000). The effect of elevated temperature transportation is comprehensively reviewed by many studies. However, data regarding meat quality under the influence of crating densities in the winter season and its interaction with journey length are scarce. Therefore, this study aimed to investigate the effects of winter transportation under various crating densities.

Materials and Methods

Experimental Birds

The study was conducted at the Department of Poultry Production, University of Veterinary and Animal Sciences, Lahore-Pakistan. ROSS-308 broilers (body weight 1900–2050 g; age: 35 days) were selected from a commercial farm after four hours of feed withdrawal before catching. During the growing phase, the broilers were fed with standard broiler rations and raised on a litter floor in an environmental controlled broiler house under optimum management conditions. The sampling was based on transportation distance and crating density (3×3=9 treatments+1 control group). Transportation distance was categorized as short (80 km), medium (160 km), and long (240 km) under three crating densities: 10 birds (0.050 m²/ bird), 12 birds (0.042 m²/bird), and 15 birds (0.033 m²/ bird) per crate. The control group comprises birds slaughtered on farm (n=30) without crating and transportation while applying four hours of feed withdrawal. The birds were transported in commercial trucks (capacity 144 crates) in loose plastic crates (Engi Plastic Industries Pvt. Ltd., Sundar, Lahore-Pakistan) having a dimension of 0.91 m (length) × 0.55 m (width) × 0.30 m (height). To reduce the effect of the microenvironment, each treatment was replicated 10 times and placed at various locations in the trucks and the meat sample (s) were collected randomly from all locations. All the protocols and birds handling were performed in accordance with the laws and regulations of Pakistan and approved by the Ethical Review Committee of the University of Veterinary and Animal Sciences, Lahore-Pakistan (No: DR/916-2017).

Climatic Indices

The experiment was conducted during the winter season (January) and the birds were transported in the vicinity of Kasur and Lahore district, in Punjab, Pakistan. The birds subjected to transportation distances of 160 and 240 km were first transported in laps of 40 km from the farm and then transported to a slaughtering facility located almost 80 km from the farm. The birds transported 80 km were directly sent for slaughtering. The temperature and relative humidity were recorded with the help of a digital weather tracker (Kestrel 4500 NV, Nielsen-Kellerman, USA). The temperature range and relative humidity measured at various times and distances remained between 3.6–9.5°C and 63.3–78.8%, respectively. There were patches of mild to severe fog at several locations along the journey.

Meat Quality Measurements

Upon reaching the slaughtering facility, three tagged birds from each replicate were randomly picked and slaughtered manually with a knife following halal slaughtering. Birds were then defeathered and eviscerated. After recording some initial parameters, carcasses were placed in chilled water to reduce the temperature and the following meat quality parameters were recorded.

pH Measurement

The pH of individual breasts was measured from three different places at 15 min (initial pH), 2 h and 24 h {ultimate pH (pH_u)} post-slaughtering using an electronic pH meter (ProfiLine pH 3110 SET 2, WTW, Germany). The probe was rinsed with deionized water after every reading and between the samples. The pH was measured from warm carcass at 15 min, while pH was recorded from deboned breast samples stored at 4°C in display chiller at 2 h and 24 h (S80100VVC, Tecnodom S.P.A., Italy).

Meat Color

The breast meat (pectoralis major) was separated from the carcass and placed in polystyrene food grade trays covered with cling film (250 mm thickness) and kept in a display chiller (S80100VVC, Tecnodom S.P.A., Italy) at 4°C. The meat color (L*=lightness, a*=redness, b*=yellowness, chroma=saturation, and hue=angle that the metric chroma line makes with the+a* axis) was measured at 24 h postmortem employing the Commission International de l'Eclairage (CIE, 1976) L*a*b* system using a chroma meter (Minolta^® CR-410, Konica Minolta, Inc. Japan). The color was measured by placing the Minolta head at cranial, middle, and caudal region (skin side) of the breast free of any obvious color defects such as bruises, discolorations, hemorrhages or any other condition that may have affected the uniform color reading.

Drip Loss (%)

Following Honikel (1998), the drip loss (%) was measured by hanging the breast muscle (weight 165–174 g) by a thread in a polythene bag under atmospheric pressure for 24 h at 4°C.

Marination

One day after slaughtering, the marination of six breast fillets per treatment (kept at 4°C) with 4% brine solution (chilled overnight) was performed. Marination was carried out by immersing a batch of 10 fillets (pre-weighed w1) in marinade solution and manually tumbling by hand for 15 minutes for maximum absorption of brine. After performing marination, the individual fillets were reweighed (w2) to determine the brine uptake. The fillets of each treatment were placed in polystyrene trays and held overnight at 4C before individual fillets were reweighed (w3) to calculate marinade retention using the formulas.

  

Cooking

The breast meat samples, with and without marination (having uniform weight in each type of meat), were individually packed in labeled polythene zipper bags (food grade). The bags were placed in a water bath (WNB45 Memmert GmbH, Schwabach, Germany) operating at 80°C. The samples were cooked until the core temperature reached 72°C. The temperature was monitored at the thickest part of the breast using a hand-held digital thermometer (TP-101, China). The cooked fillets were cooled on ice, drained, blotted dry, and reweighed (w4) to calculate the cooking loss and yield of raw and marinated breast fillets using the formula:   

Shear Force

The Warner Bratzler Shear Force value (N/cm²) of raw and marinated meat was analyzed using a texture analyzer (TA.XT plus^® texture analyzer, Stable Micro System, UK). Three rectangular blocks, each with a cross section of 1×1 cm and fiber direction parallel to a long dimension of 2 to 3 cm, were cut from each cooked fillet (Dadgar et al., 2010). The fibers were cut with a V slot blade perpendicular to their direction.

Statistical Analysis

The data collected were analyzed using the two-way analysis of variance (ANOVA) technique under completely randomized design. The means were considered significant at a p value of 0.05. For the separation of means, Tukey's HSD test was used with the help of SAS 9.4 (SAS Institute, 2013).

Results

In the present experiment, the pH of the meat measured at 15 min, 2 h and 24 h PS remained significantly different (P<0.05) among different transportation distances (Table 1). At 15 min PS, the birds in the control group showed the highest pH compared to all the transported treatments. On the other hand, at 2 h PS, the same control group had the lowest pH compared to the rest of the treatments. At 24 h PS (ultimate pH) the birds transported up to 240 km had the highest pH followed by those transported for 160 and 80 km and the least in the control group (Table 1). The findings revealed non-significant differences (P>0.05) among various crating densities for PS pH but the differences were significant in transportation distance × crating density interaction (Table 1).

Table 1. Meat pH and drip loss % under transportation distance and crating densities

Treatments	pH 15 min	pH 2h	pH 24h	Drip Loss %
Distance
0 Km	6.68±0.04a	6.14±0.03b	5.81±0.02c	1.87±0.07a
80 Km	6.55±0.03b	6.27±0.02a	6.01±0.02b	1.62±0.03b
160 Km	6.49±0.02b	6.26±0.02a	6.04±0.02b	1.17±0.03c
240 Km	6.48±0.02b	6.30±0.03a	6.12±0.02a	0.99±0.03d
Density
10 birds/crate	6.49±0.02	6.31±0.02	6.10±0.02	1.21±0.07
12 birds/crate	6.50±0.02	6.25±0.03	6.03±0.02	1.27±0.08
15 birds/crate	6.53±0.03	6.27±0.02	6.03±0.02	1.31±0.09
P-value
Distance	0.0001	0.0134	<0.0001	<0.0001
Density	0.4898	0.2566	0.066	0.6311
Interactions	0.0094	0.0373	<0.0001	<0.0001

Note: Different alphabets (^a, ^b, ^c) on means showing significant differences (P<0.05) among treatment groups (Mean±S.E.M.)

Similarly, the drip loss % was also found to be significantly different (P<0.05) among different transportation distances and interactions of transportation distance X crating density while the differences remained non-significant (P>0.05) among different crating densities (Table 1). Among different transportation distances, the birds slaughtered on farm had the highest drip loss % and a gradual decrease was observed with increase in transportation distance (Table 1).

Among different meat color parameters, the lightness (L*) of the meat was found to be significantly higher in the control group while the redness (a*), yellowness (b*), and chroma was significantly lowest in the control group compared to all transported treatments (Table 2). Similarly, among different crating densities, the birds transported with 15 birds per crate had the highest (P<0.05) lightness and lower redness compared to birds transported at 12 and 10 bird/crate density. The meat hue was found to be higher in the birds transported at 12 and 15 birds per crate density compared to those having 10 birds per crate density (Table 2). There was no significant difference in meat yellowness and chroma among different crating densities.

Table 2. Meat color under various transportation distance and crating density

Treatments	Lightness (L*)	Redness (a*)	Yellowness (b*)	Chroma (c)	Hue (h)
Distance
0 km	56.73±0.26a	13.20±0.53b	14.68±1.23b	19.79±1.15b	47.69±1.95
80 km	50.90±0.55b	16.86±0.41a	16.55±0.30a	23.67±0.31a	44.54±0.98
160 km	51.54±0.56b	16.09±0.31a	16.92±0.26a	23.36±0.32a	46.46±0.59
240 km	50.02±0.40b	17.32±0.34a	17.22±0.38a	24.47±0.34a	44.82±0.89
Crating Densities
10 birds/crate	49.96±0.43b	17.53±0.32a	16.58±0.24	24.15±0.30	43.433±0.65b
12 birds/crate	50.50±0.55ab	16.53±0.38ab	17.25±0.38	23.94±0.39	46.23±0.91a
15 birds/crate	52.01±0.44a	16.20±0.33b	16.86±0.31	23.41±0.32	46.16±0.80a
p-value
Distance	<0.0001	<0.0001	0.0106	<0.0001	0.1705
Crating Density	0.0121	0.0255	0.3287	0.2890	0.0245
Interaction	<0.0001	0.0001	0.0058	0.0001	0.0272

Note: Different alphabets (^a, ^b, ^c) on means showing significant differences (P<0.05) among treatment groups (Mean±S.E.M.)

The meat marination showed a significantly higher (P<0.05) marinade uptake (%) in the bird slaughtered on farm without any transportation. Whereas, a gradual decrease in marinate uptake % was observed with the increase in transportation distance (Table 3). On the other hand, the marinade retention was significantly higher (P<0.05) in birds transported for 240 km and decreased gradually with decrease in transportation distance. The cooking losses % in raw meat was found to be significantly higher in birds transported up to 80 km, followed by those in the control group and slaughtered after 160 km transportation, and lowest in those transported up to 240 km. In the marinated breast meat, the birds in the control group had the highest cooking losses while those in 240 km had the lowest (Table 3). Among different crating densities, marinade uptake % was non-significantly different (P>0.05), but marinade retention % and cooking yield %, both in raw and marinated breast meat, were found to be the highest in birds transported at 10 birds per crate density and lowest in those transported at 15 birds per crate density. The interactions showed significant differences among all treatments.

Table 3. Meat marination, cooking, and shear force as affected by transportation distance and crating density

Treatments	MU1 %	MR2 %	Cooking loss (%)		Cooking yield (%)		Shear Force (N/cm2)
			Raw	Marinated	Raw	Marinated	Raw	Marinated
Distance
0 Km	20.02±1.69a	95.34±0.25c	12.23±0.47b	23.07±0.36a	87.77±0.47a	88.01±0.91b	11.71±0.36a	8.88±0.07a
80 Km	15.68±0.72b	96.66±0.39b	13.66±0.48a	15.86±0.52b	86.34±0.48b	94.04±0.58a	10.27±0.48b	7.41±0.18bc
160 Km	13.34±0.57c	97.42±0.22ab	12.04±0.38b	16.05±0.45b	87.96±0.38a	92.68±0.56a	10.66±0.37ab	7.97±0.21b
240 Km	11.21±0.24d	97.74±0.19a	10.82±0.35b	14.28±0.34c	89.18±0.35a	93.17±0.45a	9.03±0.15c	7.33±0.15c
Crating density
10 birds/crate	13.12±0.63	97.84±0.19a	11.02±0.42b	14.83±0.37	88.98±0.42a	94.22±0.31a	9.44±0.26	7.16±0.20b
12 birds/crate	13.55±0.85	96.78±0.43b	12.91±0.55a	16.02±0.38	87.09±0.55b	92.22±0.21b	10.37±0.32	7.62±0.21ab
15 birds/crate	13.57±0.60	97.20±0.15ab	12.59±0.37a	15.34±0.61	87.41±0.37b	93.44±0.80ab	10.16±0.54	7.93±0.11a
p-value
Distance	<0.0001	0.0002	0.0001	<0.0001	0.0001	<0.0001	0.0010	0.0001
Density	0.8783	0.0367	0.0108	0.2061	0.0108	0.0274	0.2155	0.0135
Interaction	<0.0001	0.0003	<0.0001	<0.0001	<0.0001	<0.0001	0.006	<0.0001

Note: Different alphabets (^a, ^b, ^c) on means showing significant differences (P<0.05) among treatment groups (Mean±S.E.M.)

Marinated: Breast marinated with 4% brine solution for 15 minutes

¹  MU: Marinade uptake (% of water absorbed by breast meat during marination)

²  MR: Marinade retention (% of water retained by breast during 24 h storage at chilling temperature)

Shear force (N/cm²) in raw and marinated breast meat was found to be significantly higher in the control group and lowest in those transported up to 240 km (Table 3). Among different crating densities, non-significant differences were observed among different treatments for raw meat shear force. Birds transported at 15 birds per crate density had the highest shear force for marinated meat and those having 10 birds per crate had the lowest (Table 3).

Discussion

Results revealed that the initial pH of the meat was significantly higher (P<0.05) in birds that were slaughtered on farm compared to the rest of the treatments. The pre-slaughter cold stress and struggle in birds may have resulted in the production of more lactic acid before slaughtering and a relatively lower initial pH of the meat (Lee et al., 1976; Debut et al., 2005). Similarly, Yalçin and Güler (2012) also reported lower initial pH in birds transported for longer journeys, that is, 6.53 compared to those transported for relatively shorter periods with a pH of 6.58, but the differences were non-significant (P>0.05) among treatments. The pH at 2 h postmortem was significantly higher in all transported groups compared to those in the control group. The findings revealed a lower rate of pH fall in birds subjected to transportation compared to the control group. Furthermore, the ultimate pH was higher in birds transported up to 240 km (Table 1). It has been reported that during rigor mortis development, substrates such as glycogen and glucose are converted into lactate, which accumulates to acidify the meat (Price and Schweigert, 1987). The amount of glycogen in muscle will determine the ultimate pH of the meat (Lawrie, 1998). Therefore, due to a significant decrease in the muscle glycogen reserves with the stress associated to the length of journey (Lin et al., 2004) and increase in feed withdrawal period (Nijdam et al., 2004), the ultimate pH of transported birds was higher than the control group. Similarly, a significant increase in the pH of the meat with the increase in the length of transportation journey was also reported in many studies (Zhang et al., 2009; Yalçin and Güler, 2012). However, crating densities had no effect on the PS pH of the meat. Similarly, Delezie et al. (2007) also reported no effect of different crating densities on ultimate pH. However, significant differences were observed in the interaction of transportation distance and crating density (Table 1). The lower number of birds in each crate during the winter season resulted in cold stress in birds due to relatively less metabolic heat accumulation (Watts et al., 2011). Therefore, the struggle to maintain body temperature combined with the long transportation journey resulted in relatively higher pH_u of these treatments. Similarly, Dadgar et al. (2012) also reported significantly higher pH_u in treatments kept at low ambient temperature before slaughter.

Color is one of the most important sensorial characteristics influencing the acceptability or rejection of the meat (Fletcher, 2002). In the meat color characteristic observed at 24 h postmortem, the birds transported for various distances had significantly lower lightness and higher redness, yellowness, and chroma compared to birds slaughtered on farm without transportation (Table 2). Previous studies classified the meat with the aforementioned conditions as dark meat (Barbut et al., 2005; Bianchi et al., 2007). The color development in meat is dependent on denaturation of muscle proteins due to pH_u and rate of pH fall (Lawrie, 1998). The low pH_u (<6) of meat will result in greater lightness (L*) due to an increase in scattering of light while higher pH_u (≥6) will lead to darker meat (low L*) due to less light scattering (Swatland, 1994; Barbut, 1997; Barbut et al., 2005). Similarly, in the present trial, the longer transportation has probably resulted in depletion of glycogen reserves and higher pH_u of the meat causing darker meat color (Owens and Sams, 2000; Lin et al., 2004). Our findings are supported by several previous studies (Yaçgin and Güler, 2012; dos Santos et al., 2017) that also reported lower lightness and higher redness in birds transported for long distances. Among different crating densities, the birds transported with crating density of 10 birds per crate had the lowest lightness and higher redness compared to the other treatments (Table 2). Although there is lack of published data regarding effect of winter crating densities on meat quality, it is likely that the birds transported at lower crating densities during winter experienced relatively higher chilling effects compared to those transported with relatively higher crating densities. In agreement with the findings of the present study, Petracci et al. (2004) reported darker (low L*) breast meat in birds transported during the winter season compared to summer. Similarly, Dadgar et al. (2012) also reported higher redness in meat of birds exposed to lower crating temperatures. Similarly, Bianchi et al. (2006) also reported higher redness and saturation of meat kept for longer periods in crates at relatively lower temperatures. Moreover, Adzitey and Nurul (2011) reported that chronic stress can cause to dark-firm-dry (DFD)-like conditions in poultry.

The ability of meat to hold water is one of the most important parameters related to processor's economics and consumer perception of meat. The results of the present experiment revealed that the drip loss (%) and cooking loss (%) of raw and marinated breast meat were significantly higher in the control group and lowest in birds transported 240 km (Table 1, 3). Cooking yield was found to be higher in birds transported compared to the control group. Different crating densities had non-significant differences for drip loss % and marinated breast cooking loss %. However, the raw meat cooking loss was higher in the birds transported with 12 and 15 birds per crate compared to the control group (Table 3). The cooking yield was higher in the birds transported at 10 birds per crate. The water binding capacity of proteins and release of water from muscles are dependent on the isoelectric point of the meat, that is, the pH at which there is no net charge on muscle proteins (Offer and Knight, 1988; Le Bihan-Duval et al., 2010), which has been reported to be approximately 5.5 (Swatland, 1994). The farther the muscle pH from the isoelectric point, the higher the net charge on the proteins will be and more intracellular spaces will be available for water (Van Laack et al., 2000; Huff-Lonergan and Lonergan, 2005). Similarly, the birds in the control group had lower pH_u and higher losses % (Table 1, 3). The low transportation crating densities may have resulted in cold stress in broilers due to relatively lower metabolic heat production. These two factors therefore interact in such a way that the longer transportation of broilers under lower numbers of birds per crate resulted in depletion of muscle glycogen, an increase in the pH_u of the meat associated with an increase in water binding capacity and a reduction in drip loss %, particularly in colder environments (Zhang et al., 2009; Dadgar et al., 2012; Sowinska et al., 2013). Similarly, dos Santos et al. (2017) compared two transportation distances (15 and 90 km) in two different seasons (Rainy: 25°C+67% RH and Dry: 19°C+44% RH) in Brazil and reported higher pH_u and lower drip losses in birds subjected to long-term transportation in both seasons. Furthermore, Yalçin and Güler (2012) reported a significant decrease in meat thawing and cooking loss % with the increase in transportation distance from 65 to 165 km in Turkey. Delezie et al. (2007) reported no effect of different crating densities on drip loss of meat.

The present experiment showed significantly (P<0.05) higher marinade uptake in the meat of birds slaughtered on farm without transporting, whereas marinade uptake was lowest in birds transported for 240 km (Table 3). However, non-significant differences were observed within different crating densities. Reduction in marinade uptake with the increase in transportation distance may be due to higher WHC of meat with higher pH_u (Le Bihan-Duval et al., 2001), as shown in Table 1. The muscle-bound water content will be higher in meat having lower drip losses and there will be less space for new water molecules to add to muscle structure during marination. Furthermore, the results of marinade retention % also confirm the above-mentioned findings. The higher (P<0.05) marinade retention observed in longer transportation birds may be due to low pH_u, which increases the water binding capacity of meat (Van Laack et al., 2000; Huff-Lonergan and Lonergan, 2005). Owens and Sams (2000) also reported that 3 h transportation of male turkeys caused a significant increase in breast pH and marinade retention and reduction in cooking losses. Among different crating densities, the higher marinade retention in birds transported at lower crating densities could be attributed to chilling/cold stress due to lack of metabolic heat accumulation inside crates. The cold stressed birds had relatively higher ultimate pH (as shown in Table 1) and WHC (Dadgar et al., 2012). However, no previous studies have focused on the effect of crating densities on marinade retention, but an increase in water retention capacity of meat in birds transported at low ambient temperature has been reported by Bianchi et al. 2007.

A gradual decrease in shear force (N/cm²) was observed with the increase in transportation distance (Table 3). Lower pH_u in the control group may have caused inhibition of proteolytic enzymes resulting in more drip loss % and higher shear force (Khan and Cohen, 1977). Similar findings were also reported by dos Santos et al. (2017), who observed a significant decrease in shear force with the increase in transportation distance of broilers. Our experiment revealed an increase in shear force of broilers at a transportation distance of 160 km compared to 80 and 240 km. Similarly, Ehinger (1977) also reported that broiler meat tenderness and WHC were reduced after 2 h of transportation but improved after 4 h of transportation. Among different crating densities, the shear force of marinated breast meat was higher in the birds transported at 15 birds per crate (Table 3). The differences in marinade retention in different crating densities (Table 3) may have resulted in variation in shear force of marinated breast samples only. The treatments with higher marinade retention showed lower shear force (Table 3). A similar decrease in meat shear force due to the enrichment of muscle water content was also reported by Silva et al. (2011).

The current study demonstrated that transportation of broilers is associated with economic losses due to depression in meat quality and physical appearance. However, the cooking characteristics of the birds transported for longer distance during winter were improved. Thus, the meat from birds subjected to long-term transportation can be used for further processing operations. Similarly, the birds transported at crating density of 15 birds per crate had better physical appearance and those transported at 10 birds per crate had better yield and tenderness. Thus, transportation at a crating density of 12 birds per crate (0.042 m²/ bird) during the winter season is recommended for producing meat with better physical appearance, yield, and tenderness.

Acknowledgments

The authors express thanks and appreciation to Birds Inn Poultry for allowing on-farm experimentation and Ms. Aisha Shoukat and Mr. Muhammad Waseem (Seasons Foods Pvt. Ltd.) for making necessary arrangements regarding transportation of birds.

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