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J APPL POULT RES 2007. 16:613-622. doi:10.3382/japr.2006-00039
© 2007 Poultry Science Association
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Research Reports

Effects of Feed Withdrawal Periods on Carcass Yield and Breast Meat Quality of Chickens Reared Using an Alternative System

C. Contreras-Castillo*,1, A. A. Pinto{dagger}, G. L. Souza*, N. J. Beraquet{ddagger}, A. P. Aguiar*, K. M. V. A. B. Cipolli§, C. M. I. Mendes|| and E. M. Ortega#

* Departamento de Agroindústria, Alimentos e Nutrição, Escola Superior de Agricultura "Luiz de Queiroz" (ESALQ), Universidade de São Paulo (USP), Piracicaba, São Paulo, Brazil; {dagger} Departamento de Tecnologia de Alimentos, Universidade Estadual de Maringá, Paraná, Brazil; {ddagger} Centro de Tecnologia de Carnes (CTC), Instituto de Tecnologia de Alimentos (ITAL), Agência Paulista de Tecnologia do Agronegócio (APTA), Secretaria de Abastecimento e Agricultura do Estado de São Paulo (SAA), Campinas, São Paulo, Brazil; § APTA Regional do Leste Paulista, APTA, SAA, São Paulo, Brazil; || Korin Agropecuária Ltda., Ipeúna, São Paulo, Brazil; and # Departamento de Ciências Exatas, Matemáticas, ESALQ, USP, Piracicaba, São Paulo, Brazil

Correspondence: 1 Corresponding author: ccastill{at}esalq.usp.br


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The purpose of this work was to evaluate the effects of different feed withdrawal (FW) periods (3, 6, 9, 12, 15, and 18 h) on live broiler weight loss, dressed and chilled carcass yields, and chilled breast meat quality attributes of chickens reared in an alternative system, without the use of any antibiotics, growth promoters, coccidiostats, or ingredients from animal sources. Live weight loss and dressed and chilled carcass yields after FW were determined, and also fillet color, water-holding capacity (WHC), pH, shear value, cooking loss, and proximate composition, and a sensory analysis was conducted. Longer FW periods resulted in significant (P ≤ 0.05) increases in live broiler weight losses, from 1.3 to 5.3% in the 18-h period. The drops in dressed and chilled carcass yields became statistically significant at 12 h of FW, with dressed carcass yields of 65.2% after 3 h of FW and 63.8% after 12 h. Chilled carcass yields dropped from 68.8% after 3 h of FW to 67.0% after 12 h. Fillet color, as indicated by the L* values, became darker with longer FW periods, as shown by regression analysis. No statistical differences were observed for the a* values, b* values, WHC, cooking losses, and proximate composition of the fillets for the different FW periods. The Pearson correlation values showed a significant but low negative correlation between fillet pH and shear force, which varied with FW period. The highest carcass yields were obtained for broilers submitted to FW periods of between 3 and 9 h.

Key Words: feed withdrawal • alternative rearing • carcass yield • chicken • quality attribute


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The world food consumption pattern has changed over the last decades, with consumers becoming more and more aware of food quality attributes. Nowadays, quality attributes include not only nutritional and sensory aspects, but also food safety and environmental and animal well-being during rearing. Members of the industry have tried to maintain their markets by addressing these new consumer interests. The production of chickens reared without antibiotics is one of these options.

In Brazil, the designation "Alternative Certified Chicken" (Frango Alternativo) means that a chicken was reared without the use of feed antibiotics, coccidiostats, feed growth promoters, or feed ingredients from animal sources, was raised at a lower density, and met other restrictions required in the standards laid down by the Brazilian Alternative Aviculture Association (AVAL) [1].

Before slaughter, while the chickens are still on the farms, their feed is withdrawn and they are submitted to a feed withdrawal (FW) period that aims to reduce the gastrointestinal contents, and consequently fecal contamination of the carcass during transport and evisceration. Although 10 to 12 h of FW is sufficient to minimize carcass contamination and yield loss [2, 3], Brazilian industrial practice varies extensively. Eight hours has been suggested as the minimum time to empty the broilers’ gastrointestinal contents [2]. Weight loss by the birds during the period between FW and processing is referred to as live shrink or shrinkage [4]. After broilers have been without feed for more than 6 h, they begin to draw moisture and nutrients from their own body tissues, and this weight loss may then affect edible yield [5].The degree of shrinkage caused by FW (SFW) is affected by bird age, gender, diet density, house environmental control, ambient temperature, length of FW, transportation, and plant holding conditions [4]. Feed withdrawal periods are linearly correlated with carcass yields before and after carcass chilling [6].

Broiler dehydration during FW and transport, in addition to causing weight loss, may affect the physical and chemical characteristics of the meat. Several events preslaughter have an influence on poultry processing efficiency, including feed and water withdrawal, catching methods, the transportation system, distance to the plant, and plant holding time and conditions, which are all significant factors affecting poultry slaughter quality [7]. Because of the increase in volume of deboned chicken cuts and further processing, the effects of FW on fillet pH, tenderness, cooking weight loss, and chemical composition have become the focus of attention for several researchers [8, 9]. The objective of the current work was to define the best FW period for broilers reared in an alternative system, based on the broiler and carcass yields and fillet quality attributes.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
In this study, 540 male Cobb broilers were grown by Korin Agropecuária Ltda. in Ipeúna, São Paulo, Brazil, under normal commercial conditions. These broilers were reared in an alternative feed system, without the use of any feed growth promoters, coccidiostats, or feed ingredients from animal sources, in farms integrated with the company. The density on the rearing farms was 12 broilers/m2. The experiments were conducted during the winter (July and August). The FCR was 2.2, and the feed composition can be found in references and notes [10].

Approximately 12,000 broilers were grown on each farm. When the broilers were 46 d old, they were separated randomly into 6 treatment groups by using foot-band numbers and placed in different areas inside the farm. Feed was removed at 1500, 1800, 2100, 2400, 0300, and 0600 h to meet, respectively, 18-, 15-, 12-, 9-, 6-, and 3-h FW periods. At the beginning of FW, the lights were turned on at 1800 h and turned off at 0200 h, resulting in a total photoperiod of 14 h. Table 1Go shows the times of feeding under light for each of the FW time periods. They were fed with tube feeders and given water in bell drinkers ad libitum until 3 h before slaughter. They were placed into the coops for transport 90 min after water withdrawal, and the required time of FW was adjusted at the abattoir. For the 3-h treatment, FW coincided with water withdrawal. The number of broilers was 105 per treatment and 35 per replicate. In practice, the total number of broilers per treatment varied from 89 to 101 because during the collection, transport, hanging, and slaughter operations, many broilers lost their identification foot-bands. These broilers had their previous weights deleted from the data. The broilers were weighed before the beginning of each of the FW periods on the poultry farm. Feed withdrawal times included the transportation time (40 min) from the farm to the slaughterhouse. The experiment was replicated 3 times.


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  		Table 1. Feeding under light for each of the different feed withdrawal time
 
The broilers were transported from the farms to the slaughterhouse (±30 km) in plastic cages, each containing 9 broilers. As each FW period was reached, each broiler was weighed (WAFW, weight at FW) as quickly as possible (10 min) to determine the SFW. The broilers were immediately hung on shackles, electrically stunned (60 Hz, 50 V, 38 mA), and killed by severing the right carotid artery and jugular vein in a single cut. The broilers were left to bleed for 4 min and then scalded at 60°C for 60 s, mechanically defeathered, and manually eviscerated. Each carcass (excluding giblets, heart, feet, neck, lungs, and so on) was weighed again to determine the dressed carcass weight (DCW). The carcasses were then chilled in a 2-stage immersion cooler with precooler tap water at 14 to 17°C for 15 min, followed by chilling in ice slush at 0 to 4°C for 30 min. After the carcasses had dripped for 3 min while hung on shackles, they were weighed to determine the chilled carcass weight (CCW).

The pectoralis muscles were removed after 45 min of chilling and 5 min of dripping. The breast fillets (pectoralis major) were trimmed of excess skin, the wings were removed, and the fillets were packed into polyethylene bags, placed in insulated boxes, and covered with ice (2°C) for transport to the meat laboratories at ESALQ-USP and CTC-ITAL (~1 h). In the laboratories, the packed fillets were stored in refrigerated rooms at 2 ± 1°C for up to 24 h.

Carcass Yields
The percentages of weight loss during FW, and the dressed carcass yield (DCY) and chilled carcass yield (CCY) were calculated as shown below:


Formula

where WBFW is live broiler weight before FW, WAFW is live weight after FW, DCW is dressed carcass weight, and CCW is chilled carcass weight.

The results obtained were analyzed by AN-OVA and the Tukey test (P ≤ 0.05). The Tukey test was used to measure meaningful differences between FW times. Regression analysis was used to explain the relationship between FW time and yields and quality attributes.

Physical and Chemical Analyses
For each of the 3 replicates, 5 carcasses (10 fillets) were used to determine pH, water-holding capacity (WHC) and L* (lightness), a*(red-ness), and b*(yellowness) color values, and another 5 (10 fillets) were used to determine shear value, sensory analysis, and cooking loss. The pH was determined at 8 h postmortem with a penetration electrode [11] that was inserted in 4 different positions of the fillet.

Water-holding capacity was measured at 24 h postmortem according to the method of Grau and Hamm [12] as modified by Hofmann et al. [13]. It is based on weighing approximately 0.5± 0.005 g of muscle samples and placing them between 2 pieces of filter paper, which are pressed between 2 plates of Plexiglas until a pressure of 226.8 kg/in.2 is reached, which is maintained for 2 min. After pressing, the sample area (A) and total wet area (T) are measured with a planimeter to calculate the G value, where G = A/T.

Measurements of L*, a*, and b* were carried out at 8 h postmortem on the CIELab system [14]. The sample was placed on a white plate and the color measurement was carried out on the medial muscle surface, averaging 5 readings for each sample.

Breast fillets were prepared for shear value determinations and the sensory evaluation as follows: at 24 h postmortem, the fillets were wrapped in aluminum foil and cooked on a Sirman electric grill [15] to an internal temperature of 82°C, as measured by a Novus thermocouple with a 15-cm needle [16]. After cooking, the fillets were left to cool in a storeroom maintained at 5°C. They were then cut into 2 x 1 x 1 cm pieces [17]. The 2-cm dimension was length and the pieces were 1 x 1 cm in cross-sectional area. Shear force values were obtained with a Warner-Bratzler blade attached to a Stable Micro System TA-XT 2i Texture Analyzer [18]. The results were expressed as kilogram-force (kgf) per square cm.

Cooking weight loss was determined by using the cooking method described above, and each fillet was weighed before and after cooking. The weight losses were calculated as percentages. The proximate composition was determined according to AOAC [19], with the values expressed as percentages.

Sensory Analysis
A 9- to 11-person trained panel with good discriminatory ability (Psample ≤ 0.5), good reproducibility (Prepetitions > 0.05), and good agreement among panelists evaluated tenderness and juiciness. The analyses were conducted in individually equipped booths with a computer monitor, green illumination to mask color differences, and other required characteristics.

The samples were kept warm in an oven at 35 to 40°C until served. The warm samples were served monadically on white plastic plates with a slice of bread and with water for mouth rinsing. Six samples were served per session in a complete block statistical design. Samples from each treatment and all replicates were evaluated in 3 sessions. The intensity of each attribute was evaluated by using a nonstructured 10-cm scale, where the extremes were "little tenderness" to "much tenderness" and "little juiciness" to "much juiciness." The data were collected by using Compusense Five software [20].

Statistical Analysis
The data were submitted to ANOVA to allow measurement of the effects of FW time on live broiler yield, carcass yield, and quality attributes. The Tukey test (P ≤ 0.05) was used for multiple comparisons. Multiple regression and Pearson’s simple correlation were determined [21]. The SPSS software was used to analyze the data [22].


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Broiler and Carcass Yields
The data in Table 2Go show that the average chicken weights for the different periods of FW (WBFW) were not statistically different (P ≥ 0.05), indicating that the different batches of broilers used in the replicates of the study were similar. Statistical differences were observed for the average WAFW for the different FW times. Live SFW over the first hours of the FW periods was probably attributable to the loss of gastrointestinal contents, as shown previously [23]. A gradual and significant (P ≤ 0.05) increase in SFW was observed as the hours of FW increased (Table 2Go and Figure 1Go). Percentages of SFW increased linearly with time, from 1.51% at the FW period of 3 h to 5.32% at 18 h. The statistically significant difference between the 3- and 6-h values for SFW should be considered with caution. Because of the procedures of the company where the work was carried out, the lights of the aviary were turned off at 0200, resulting in the 3- and 6-h FW groups having the same time to feed under light (11 h), and therefore being virtually the same. This might explain why the CCY values did not differ between these 2 treatments, and DCY would similarly be explained. The higher SFW values at the 12-, 15-, and 18-h FW periods might be due to broiler dehydration and to the metabolism of body tissues to obtain energy for maintenance, as hypothesized by Salmon [24] for turkeys submitted to FW periods of longer than 24 h. These results are of the same magnitude as those reported by Lyon et al. [6], with values of 2.94, 4.32, and 5.61% for chicken FW periods of 8, 16, and 24 h. Bilgili [4] reported that SFW is usually linear with time, in the range of 0.18 to 0.42% of live BW per hour. Smidt et al. [25] also observed a gradual decrease in the percentage of full feed weight broilers for FW periods increasing from 2 to 40 h. Wabeck [2], Chen et al. [26], and Buhr and Northcutt [27] reported significant increases in the weight loss of broilers with prolonged FW times. The results of the current work confirmed these earlier studies.


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  		Table 2. Yields of broilers and carcasses in relation to feed withdrawal times1
 

Figure 1
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  		Figure 1. Regression for live shrinkage (%) and feed withdrawal time.

 
Figure 1Go shows the regression equation between the weight losses attributable to FW and FW times. The curve obtained could be represented by the equation:


Formula

where y is SFW and x is FW time. The R2 value was 0.62.

The DCY (Table 2Go) showed that through 9 h of FW, there was no influence of FW time, with yields ranging from 65.00 to 65.44%. The higher DCY found in this study for the 3- to 9-h periods conflict with those reported previously [2], suggesting that not only gastrointestinal contents are lost during long FW periods, as stated before. A more important effect could be attributed to the longer periods of feeding and drinking under light for these treatments. The broilers might have had an increase in BW high enough to overcome the loss from the gastrointestinal tract. After 12 h of FW, the yields of these carcasses fell significantly (P ≤ 0.05), to 63.00 to 63.80%, similar to the report by Benibo and Farr [28] that each increasing increment in FW period (10, 15, and 20 h) resulted in lower dry eviscerated carcass yield and CCY for male broilers. In the current study, there were no significant differences in DCY for FW times of 12, 15, and 18 h. As shown in Figure 2Go, good correlation existed between the CCY values and FW times, showing that as FW time increased, CCY decreased linearly (R2 = 0.96). Chilled carcass yields showed a similar pattern, with no differences in the yields for 3 to 9 h of FW, which ranged from 68.01 to 68.80%, but with yields significantly greater (P ≤ 0.05) than those observed between 12 and 18 h. The CCY in the 12- to 18-h period were in the range of 65.96 to 66.99%, with the value observed at 18 h (65.96%) being significantly lower (P ≤ 0.05) than that observed for the 12-h period (66.99%). These results conflict with an earlier report [27], which concluded that 0, 6, 12, 18, and 24 h of FW did not affect CCY. A 1.5% yield difference between 6 and 14 h has been reported [29], whereas in other work, 5, 3.1, 1.5, and 1.25% differences were observed between yields on turkey carcasses at 0 and 12, 14, 16, and 24 h, respectively [24]. In the current study, yield differences of up to 1.8, 2.4, and 2.8% were observed at FW times of 3 and 12 h, 15 h, and 18 h, respectively. The lower yields for broilers submitted to long FW periods might have been due to diminished water uptake during chilling. Thomson et al. [30] previously stated that smaller carcasses from more dehydrated live broilers absorbed proportionately more water than did heavier carcasses during chilling, which was confirmed by Smith et al. [25]. In the current study, the broilers had live weights greater than 2.5 kg and were submitted to water withdrawal only 3 h before slaughter; that is, the live broilers were not dehydrated and therefore the carcasses did not absorb much water during chilling, resulting in lower CCY. In other works, the lights have typically been on during the entire FW period; however, in the current study, we used a 20-h photoperiod. In this study the broilers submitted to 6- and 3-h FW periods were kept in the dark for 4 and 3 h, respectively. This resulted in an actual FW period of 7 h for both treatments, which might explain the higher than expected DCY and CCY for these treatments.


Figure 2
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  		Figure 2. Regression for chilled carcass yield (%) and feed withdrawal time.

 
pH
As shown in Table 3Go, the pH of the fillets at 8 h postmortem showed values that varied from 5.76 to 5.91. The pH of the 3-h FW period was not significantly different (P > 0.05) from the pH in any of the other periods. A similar pH range of 5.79 to 5.84 has been reported for FW periods of 3, 6, 12, and 18 h, and Kotula and Wang [31] suggested that 8 h of FW would determine the final pH. Other statistically significant differences observed among the pH values do not provide a clear picture of the possible influence of FW time on pH. In general, the results of the current study agree with those of other authors [31], and lead to the conclusion that pH is probably not affected by FW time. In the current work, the relationship between high 8-h postmortem pH values and lower L* values was not totally confirmed, because none of the chicken breasts presented a pH higher than 6.0.


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  		Table 3. Physical characteristics and pH of breast fillets of broilers submitted to different feed withdrawal times1
 
WHC and Color
The FW periods did not affect the WHC values of breast meat, which were in the range of 0.56 to 0.62 (Table 3Go). Similarly, no effect of FW periods on WHC or L* and b* values was reported for a 5-h FW and a 1.5-h transport [32].

The average values for L*, a*, and b* are shown in Table 3Go. Breast fillets were deemed to be of a light color when the L* value was higher than 50.0, whereas those with L* values below 45.0 were considered dark [33, 34]. However, Wilkins et al. [35] indicated that an L* value equal to 50.0 cannot be considered a limit, because consumers rejected breast meat only with L* values higher than 57.0. They also suggested that the incidence of pale, soft, exudative meat condition should be identified by the determination of WHC. According to the findings of these authors, all the breasts used in this study would be considered dark, because their L* values ranged from 38.08 to 41.52. Again, a clear picture of the effect of FW time on the L* values was not possible, but a linear regression showed that lower L* values corresponded to longer FW periods. The adjusted R2 was equal to 0.832 (Figure 3Go).


Figure 3
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  		Figure 3. Regression for L* (lightness) value and feed withdrawal time.

 
The correlation between L* and pH values was not significant, contrary to the findings of previous work [26]. The values for a* were inversely related to the L* values but also revealed no influence of FW time. In addition, no significant differences were observed among the b* values in relation to the FW periods.

The aforementioned results lead to the conclusion that broilers reared in alternative conditions may have darker breast fillets, and that the parameters a* and b* are not affected by the FW period, although a tendency was observed for lower L* values (darker) as the FW times increased (Figure 3Go).

Shear Values
The shear value (kgf/cm2) were not affected by FW periods (Table 3Go). Significant differences in the shear value of broilers fasted for different periods (0, 3, 6, and 18 h) were found in a previous study [31].

We must emphasize that although these alternatively reared broilers were deboned immediately after dripping, their shear values (2.67 to 3.45 kgf/cm2) were of the same magnitude as those reported for conventionally reared broilers deboned 4 h postmortem, which had shear values in the range of 1.82 to 2.19 kgf/cm2 [36]. However, comparisons of shear values obtained by different authors were difficult, because sample geometrical dimensions varied and very often the cross-sectional area of the sheared samples was not given. The average sensory scores for breast meat from the different treatments in this study were on the tender side of the nonstruc-tured scale.

Although the carcasses from this study were not aged because deboning was carried out immediately postchilling, the shear values of the breast fillets (2.7 to 3.5 kg) were close to those reported (2.5 kg) by Khan and Nakamura [37].

Cooking Weight Losses
No significant difference in cooking loss could be attributed to the FW periods (Table 3Go). Lyon et al. [6] reported that the main effect for FW of 0, 8, 16, or 24 h was not significant for cooking yield.

Correlations Between Quality Parameters
There was a positive correlation between cooking loss and pH value (Table 4Go). As the pH decreased, the quality of the final product increased because the cooking losses were less. The values for a* were inversely correlated with cooking losses, whereas the b* values were directly correlated with cooking losses.


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  		Table 4. Pearson’s correlation coefficient (r; above) and probabilities (below) for cooking loss, pH, shear force, and CIE values (L*, a*, b*)1
 
Shear values were highly significantly (P ≤ 0.008) inversely correlated with cooking losses, in disagreement with common knowledge that as meat loses water, it becomes tougher. Shear values were also highly significantly inversely correlated (P ≤ 0.001) with pH. This finding was in agreement with other studies [38, 39] indicating that meat with a low pH is less tender, but because r values were low (0.20 and 0.25, respectively), their practical use is questionable. Although the breasts were deboned immediately after passing through the cooler, the values shown in Table 3Go were lower; that is, they were tender in spite of not being aged prior to de-boning.

Proximate Composition and WHC
There was no influence of FW period on the fat (1.19 to 1.32%), protein (22.28 to 23.80%), and ash (0.98 to 1.14%) contents of the breast meat. Although the percentage of moisture was significantly smaller (P ≤ 0.05) for the 15-h period (74.24%), as compared with the 6-h period (75.74%), the 18-h value (74.5%) was not statistically different (P > 0.05) from the values determined for the shorter FW periods. From these results, it is not possible to establish a clear relationship between FW and muscle moisture content. Ngoka et al. [40] reported that feed withdrawal periods of longer than 15 h did not influence the proximate composition of turkey meat.

Sensory Analysis
Table 5Go shows the values for tenderness and juiciness of the cooked chicken breasts, as evaluated by trained panelists. Feed withdrawal time influenced only the tenderness scores of samples showing significant differences (P ≤ 0.05) for some FW periods. The meat of chickens with FW of 15 h was less tender than that from chickens with FW for shorter periods, but the 18-h FW period did not show any significant difference when compared with the 6-, 9-, 12-, and 15-h FW periods. There were no differences in juiciness for the different FW periods, so this attribute did not interfere with the tenderness scores.


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  		Table 5. Sensory analysis for tenderness and juiciness of breasts fillets as related to feed withdrawal times1
 

   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 
  1. The weight losses of live broilers were positively correlated with FW periods, confirming that increasing FW times will result in higher live broiler shrinkage.
  2. Higher yields for live broilers and carcasses can be obtained with FW times of between 3 and 9 h.
  3. The different FW periods did not affect the quality attributes.
  4. The breast meat of all treatments was considered tender after 24 h of storage in spite of the broilers having been deboned immediately after chilling and dripping.


   ACKNOWLEDGMENTS
 
The authors thank FAPESP (Fundação de Amparo de Pesquisa do Estado de São Paulo) for financial support (project no. 2003/ 07445-6) and Korin Agropecuária (Ipeúna, São Paulo, Brazil) for providing facilities in its abattoir.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. Demattê Filho, L. C., and C. M. I. Mendes. 2003. Frango orgânico—Definição, produção e mercado. CD-ROM in Resumo do Encontro Internacional dos Negócios da Pecuári (ENIPEC), A. C. Camacho, ed. Fed. Agric. Pecuária Estado Mato Grosso, Cuiabá, Brazil.
  2. Wabeck, C. J. 1972. Feed and water withdrawal time relationship to processing yield and potential fecal contamination of broilers. Poult. Sci. 51:1119–1121.[ISI]
  3. Veerkamp, C. H. 1986. Fasting and yield of broilers. Poult. Sci. 65:1299–1304.[ISI]
  4. Bilgili, S. F. 2002. Slaughter quality as influenced by feed withdrawal. World’s Poult. Sci. J. 58:123–130.[CrossRef][ISI]
  5. Northcut, J. K. 2000. Factors influencing optimal feed withdrawal duration. WebMD: http://pubs.caes.uga.edu/caespubs/pubcd/B1187.htm Accessed Feb. 2006.
  6. Lyon, C. E., C. M. Papa, and R. I. Wilson. 1991. Effect of feed withdrawal on yields, muscle pH and texture of broilers breast meat. Poult. Sci. 70:1020–1025.[ISI]
  7. Bilgili, S. F. 1995. Minimizing broiler reprocessing in the plant. Pages 13–15 in Proc. 30th Natl. Mtg. on Poultry Health and Processing, Ocean City, MD. Delmarva Poult. Ind., Georgetown, DE.
  8. Ali, S. A., A. P. Harrison, and J. F. Jensen. 1999. Effects of some ante-mortem stressors on peri-mortem and post-mortem biochemical changes and tenderness in broiler breast muscle. A review. World’s Poult. Sci. J. 55:403–414.[CrossRef][ISI]
  9. Berri, C. 2000. Variability of sensory and processing qualities of poultry meat. World’s Poult. Sci. J. 56:209–224.[CrossRef][ISI]
  10. Nutritional composition of the feed used at the different chicken growth stages: Corn grits (57.7 to 71.4%), dry soybeans (2.5 to 11.5%), soybean bran (36 to 13.4%), DL-met (0.08 to 0.05), L-Lys (0.03 to 0.12%), and micronutrient matrix composed of calcium, phosphorus, salt, vitamins, minerals, and part of the amino acids (3.0%).
  11. The potentiometer was a Digimed model DM2 (Digimed São Paulo, São Paulo, Brazil).
  12. Grau, R., and R. Hamm. 1953. Eine einfache Method zur Bestimmung der Wasserbendung in Muskel. Naturwissenchaft 40:29.[CrossRef]
  13. Hofmann, K., R. Hamm, and E. Bluchel. 1982. Neus über die Bestimung der Wasserbindung des Fleischwirtsch. Fleischwirtsch 62:87–94.
  14. The color was measured with a Minolta spectrophotometer, model CM-508d (Minolta, Sakai, Osaka, Japan) with the following parameters: 8 mm of diameter of the measuring area, 10° angle of observation, and illuminant D65 with the specular component. Comission Internacional d’le Ecleraige, 1986, CIE Central Bureau, Vienna, Austria.
  15. Model PDL, Sirman, Padova, Vêneto, Italy.
  16. Model 51, type K, Novus, Porto Alegre, Rio Grande do Sul, Brazil.
  17. Froning, G. W., and T. G. Uijttenboogaart. 1988. Effect of post-mortem electrical stimulation on color, texture, pH, and cooking loses of hot and cold deboned chicken broiler breast meat. Poult. Sci. 67:1536–1544.[ISI]
  18. Texture Technologies Corp./Stable Micro Systems, Godalming, Surrey, UK. Stable fitted with a 25-kg load cell (50-kg capacity) and blade speed of 200 mm/min so that the fibers were sheared perpendicularly to the blade of the texturometer.
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