Big-bird programs: Effect of strain, sex, and debone time on meat quality of broilers

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1 Big-bird programs: Effect of strain, sex, and debone time on meat quality of broilers V. B. Brewer,* V. A. Kuttappan,* J. L. Emmert, J.-F. C. Meullenet,* and C. M. Owens * 1 * Department of Poultry Science, University of Arkansas, Fayetteville 72701; and Department of Animal Sciences, University of Illinois, Urbana-Champaign ABSTRACT The industry trend toward early deboning of chickens has led to the need to explore the effect on meat quality, including the effects of strain and sex. An experiment was conducted using broilers of 4 different high-yielding commercial strains chosen because of their common use in big-bird production. Of each strain, 360 birds were commercially processed at 59, 61, and 63 d of age in 2 replicates per day. Breast fillets were harvested at 2, 4, and 6 h postmortem (PM). Muscle ph and instrumental color (L*, a*, and b*) were measured at the time of deboning and at 24 h PM. Fillets were cooked to 76 C and cook loss was calculated, followed by Meullenet-Owens razor shear (MORS) analysis. Muscle ph significantly decreased over time as aging before deboning increased. Furthermore, L* values significantly increased as aging time increased, with the fillets deboned at 6 h PM having the highest L* Key words: strain, deboning, ph, color, shear value, followed by 4 h, and then 2 h PM. After 24 h, the fillets deboned at 6 h still had the highest L* compared with those deboned at 2 or 4 h PM. Fillets from strain B had the highest L* values. Fillets deboned at 2 h PM had significantly higher cook losses and MORS energy (indicating tougher fillets) than fillets deboned at 4 or 6 h PM, but there was no difference in cook loss due to strain at any deboning time. Fillets deboned at 4 h PM also had higher MORS energy than fillets deboned at 6 h PM, and differences in MORS energy among the strains were observed at 4 h PM. There was no difference in instrumental color values or cook loss due to sex. However, fillets of males had significantly greater MORS energy (tougher fillets) when deboned at 2, 4, and 6 h PM than those of females. Results of this study suggest that deboning time, sex, and strain can affect meat quality in big-bird market programs Poultry Science 91 : doi: /ps INTRODUCTION 2012 Poultry Science Association Inc. Received June 27, Accepted September 24, Corresponding author: cmowens@uark.edu The increasing demand for further-processed products, coupled with the preference of broiler breast meat in the United States, has led the poultry industry to produce larger, higher-yielding birds to meet these demands. In 2007, 57% of the broiler market was devoted to deboning carcasses for further processing, and although not necessarily all heavy broilers, many of the heavy broilers produced in the US will be used in this market (NCC, 2007). Also, to increase production efficiency, save energy, and reduce labor costs, processors are trending toward deboning carcasses immediately postchill, which can mean deboning the meat as early as 2 h postmortem (PM), often before the completion of rigor mortis. It is recommended that broiler carcasses be aged to at least 4 h PM to allow for rigor development and to prevent toughening; therefore, deboning immediately after leaving the chiller (e.g., 2 h postmortem) can have negative meat-quality implications, including decreased tenderness (Stewart et al., 1984; Lyon et al., 1985; Dawson et al., 1987). Tenderness plays a critical role in consumer acceptability of wholemuscle products. Lyon and Lyon (1990) reported that as time before deboning increased from 0 to 24 h PM, consumer acceptability of the meat texture increased, with fillets deboned at 0 and 2 h PM considered tough by a consumer panel, and samples deboned at 6 and 24 h PM considered slightly tender to moderately tender. Similar results were reported by Cavitt et al. (2005). Many factors can influence poultry meat quality, including sex and strain (Guhne 1970; Lyon and Wilson, 1986; Poole et al., 1999; Northcutt et al., 2001). Northcutt et al. (2001) reported no difference in breast fillet shear values between sexes; however, the evaluated birds were 51 d old, and it is not uncommon in industry today for broilers to be grown to 60 d of age or more and at a faster rate compared with 10 years 248

2 ago. Therefore, there could be a potential difference between sexes as birds age. These differences could be attributed to the difference in size of the fillet of males compared with females. In other research, Mehaffey et al. (2006) reported differences among 5 different strains for both postmortem ph at the time of deboning and shear values, suggesting variation in rigor development due to strain. Therefore, the purpose of this study was to evaluate several common (in 2008) high-yielding commercial broiler strains and the effect of deboning on breast meat from these strains at various times PM. In the current study, 4 commercial strains targeted for the big-bird debone market were grown to 8 wk of age and subsequently deboned at 2, 4, and 6 h PM. MATERIALS AND METHODS Experimental Design STRAIN EFFECTS ON MEAT QUALITY IN BIG-BIRD PROGRAMS To simulate a big-bird production scenario, 4 commercial broiler crosses were grown to between 59 and 63 d of age. Three of the strains (strains A, B, and D) used were bred to be high-yielding broilers for the debone market (big-bird programs), whereas one strain was bred to be a moderate-yielding classic type broiler (strain C). However, all of the strains used in this study are grown in current commercial big-bird market programs. In total, 1,440 birds (n = 360/strain) were grown in 6 replications. Equal numbers of males and females were used (180 males per strain and 180 females per strain). Two nutritional treatments were used in this study, a typical industry-type feeding regimen and a phase-feeding regimen (Brewer et al., 2009). Phase-feeding is a feeding regimen with the goal of more accurately targeting broiler nutrient requirements so that significant reductions to production costs can be achieved (Warren and Emmert 2000; Pope and Emmert, 2001; Pope et al., 2002; Brewer et al., 2006a,b). To assess growth performance, birds were individually weighed at 3, 17, 32, 40, and 49 d of age and at the time of processing (59, 61, and 63 d). Birds were processed in 2 on-farm replicates per day (480 birds/d). Birds were processed following a 10-h period of feed withdrawal on a commercial-style in-line system, including electrical stunning (11V, 11 ma, 11 s), scalding (2 min at 53.9 C), defeathering, and evisceration. Following evisceration, carcasses were placed in agitated immersion chill tanks for a total of 105 min to an endpoint temperature of 4 C. The chilling process included 15 min of prechill at 12 C followed by a 90 min chill at 1 C. After chilling, carcasses were well-packed and aged on ice until deboning at 2, 4, or 6 h PM. Ready-to-cook carcasses were weighed. Deboning was performed by 4 trained, experienced people. Butterfly breast fillets (pectoralis major) were harvested and weighed to assess yield, and were then immediately measured for muscle ph and color. Color and ph measurements were made at the time of deboning and at 24 h PM. Muscle ph was determined in right fillets using a Testo spear-tip probe and meter (model Testo 205; Testo Inc., Sparta, NJ). Color measurements (L*, a*, and b*) were also made at 3 locations on the dorsal side (bone side) of the right fillet using a Minolta colorimeter (CR-300; Konica Minolta, Ramsey, NJ), and all of the readings were averaged. Fillets were then placed in zip-sealable plastic bags, packed on ice, and held overnight in a 4 C cooler. On the day following the initial processing, butterfly fillets were split into single fillets. Muscle ph and color were again measured on the right fillet, whereas the left fillet was vacuum-packed and frozen (stored at 29 C) for later determination of cook loss and texture analysis. Fillet dimensions were only made on left fillets deboned at 6 h and at 24 h PM. Four measurements were made on each fillet using calipers, including length at longest point, width at widest point, cranial thickness at thickest portion of the fillet, and caudal thickness measured 2.5 cm from the bottom of the fillet (Mehaffey et al., 2006). Right breast fillets were removed from the freezer and allowed to thaw for 24 h before cooking. Fillets were weighed and cooked to an end-point temperature of 76 C according to methods described by Sams (1990) as modified by Mehaffey et al. (2006). Fillets were cooled to room temperature and reweighed to determine cook loss, an indicator of water-holding capacity (WHC). Fillets were then individually wrapped in foil and stored overnight in a 4 C cooler for texture analysis the following day. For texture analysis, the Meullenet-Owens razor shear (MORS) method was conducted to determine shear energy, or MORSE (Cavitt et al., 2005; Mehaffey et al., 2006), using a texture analyzer (model TAXT2; Texture Technologies, Scarsdale, NY). Whole fillets were sheared in 4 locations (crosshead speed of 5 mm/s) and the data was averaged for each fillet. Statistical Analysis The experiment was analyzed as a completely randomized design using the GLM procedure of SAS (SAS Institute, 2002). Factors considered included feeding regimen, strain, sex, and debone hour. Statistical analysis indicated that feeding regimen did not affect (P > 0.05) meat-quality results; therefore, feeding regimen was removed as a main effect and data was pooled by other main effects. Differences among treatment means were established using Duncan s multiple range test and means were considered significant at P < Correlation of fillet weight and dimension was considered significant at P < RESULTS AND DISCUSSION 249 Live weights at the time of processing were significantly affected by strain and sex (Table 1). Strain B

3 250 Brewer et al. Table 1. Live weight and yields of male and female broilers in a simulated big-bird market program Strain Sex Item A B C D Female Male Pooled SEM Live weight 1 (g) 3,028 b 3,260 a 3,014 b 3,093 b 2,906 y 3,303 x RTC yield 2 (%) 78.3 a 78.6 a 79.0 a 78.7 a 78.7 x 78.6 x 0.28 Fillet yield 3 (%) 22.1 b 23.5 a 22.2 b 23.4 a 23.2 x 22.5 y 0.06 Tenders yield 3 (%) 5.6 ab 5.6 ab 5.5 b 5.7 a 5.8 x 5.4 y 0.03 Total breast yield 3 (%) 27.7 b 29.1 a 27.7 b 29.2 a 29.1 x 27.8 y 0.07 a,b Values within a row within strain lacking a common superscript differ (P < 0.05); n = 360. x,y Values within a row within sex lacking a common superscript differ (P < 0.05); n = Live weight was taken immediately before processing. 2 RTC = ready-to-cook; the yield was calculated as a percentage of live weight. 3 Parts yields calculated as a percentage of the RTC weight. broilers were significantly heavier than broilers from strains A, C, or D. However, ready-to-cook yield as a percentage of live weight was not affected by either strain or sex. Strains B and D had significantly greater fillet yield than those of strains A and C (P < 0.05). Males of all strains had significantly greater live weights than females at the time of processing, but females had greater fillet yields than males. Young et al. (2001) also reported that females have greater fillet yields than males. The difference in live weight and fillet yield attributed to strain and sex has been thoroughly documented (Orr et al., 1984; Bilgili et al., 1990; Acar et al., 1991; Young et al., 2001; Mehaffey et al., 2006). There was no difference in live weight for birds processed at 2, 4, and 6 h PM, and fillet yield was not affected by debone hour (data not shown), which is consistent with Young et al. (2001) who also reported no difference in fillet yield when fillets were deboned at variable times postmortem (0, 2, 4, and 6 h). However, other studies reported decreases in fillet yield as aging times before deboning increased, likely because of increased moisture loss or proteolysis in the muscle (Mehaffey et al., 2006; Brewer, 2011). Differences in these studies may be attributed to the different size and age of birds or other conditions used in each study. Fillet dimensions were measured to understand the basic profile of the fillets for the different strains, therefore, data from fillets deboned at 6 h PM are presented (Table 2). Fillet dimensions were variable dependent upon strain. Strains C and D had longer fillets than strains B and A, whereas strain B fillets were only wider than strain A. In addition, strains B and D were thicker at the cranial measurement than strains A and C and thicker at the caudal end than strain A; only strain B was thicker than strain C. Therefore, in this study, it seems that fillets that had greater weights were also thicker, particularly at the cranial end (r = 0.84). Lubritz (1997) reported that increased fillet length, width, and thickness all significantly increased with fillet weight; however, fillet thickness had a much greater effect on weight than did length or width. Male fillets were longer, wider, and thicker than fillets of females, with the difference again associated with differences in fillet weight (Table 2). Mehaffey et al. (2006) reported some differences in fillet dimensions, but the dimensions were not related to fillet size (weight). However, in that study, broilers were smaller than in the current study and also yielded less breast meat. Muscle ph was measured to monitor PM metabolism (Table 3). For all strains and both sexes, the ph measured at the time of deboning decreased from 2 to 6 h PM, which would be expected as lactic acid levels in the muscle increase due to the breakdown of glucose through glycolysis (Lawrie, 1991). Strain A had a significantly lower ph at 2 h PM compared with those of strains B and C, yet for all strains, ph values measured at 2 h PM were in a narrow range of 6.3 to 6.4, typical values for that period. At 4 h PM, strain C had a Table 2. Fillet dimensions at 24 h postmortem (PM) of single breast fillets deboned at 6 h PM from male and female broilers in a simulated big-bird market program Item Strain A B C D Female Male Sex Pooled SEM Fillet weight 1 (g) 520 c 596 a 533 b 577 a 524 y 593 x 5.08 Fillet length 2 (cm) 18.9 b 19.1 b 19.5 a 19.5 a 19.0 y 19.5 x 0.05 Fillet width 2 (cm) 9.69 b 9.94 a 9.81 ab 9.77 ab 9.71 y 9.90 x 0.03 Cranial thickness 2 (cm) 2.68 c 3.06 a 2.68 c 2.86 b 2.74 y 2.91 x 0.02 Caudal thickness 2 (cm) 0.89 c 1.07 a 0.95 bc 1.03 ab 0.88 y 1.09 x 0.02 a c Values within a row within strain lacking a common superscript differ (P < 0.05), n = 360. x,y Values within a row within sex lacking a common superscript differ (P < 0.05), n = Fillet weight taken immediately after deboning, butterfly weight. 2 Dimensions measured at 24 h PM on single fillets deboned at 6 h PM.

4 Table 3. Meat quality of breast fillets deboned at 2, 4, or 6 h postmortem (PM) from broilers in a simulated big-bird market program Strain A Strain B Strain C Strain D Pooled SEM 2 h 4 h 6 h 2 h 4 h 6 h 2 h 4 h 6 h 2 h 4 h 6 h Quality STRAIN EFFECTS ON MEAT QUALITY IN BIG-BIRD PROGRAMS ph at deboning 6.30 b 6.04 d 5.88 e 6.40 a 6.10 cd 5.83 e 6.39 a 6.14 c 5.85 e 6.35 ab 6.05 d 5.80 e 0.01 ph at 24 h PM 5.76 bcd 5.80 abcd 5.81 abc 5.73 cd 5.76 bcd 5.81 ab 5.82 ab 5.77 bcd 5.85 a 5.78 abcd 5.73 d 5.85 a 0.01 L* at deboning 49.0 gh 50.1 ef 51.8 b 48.9 h 50.5 de 53.1 a 47.9 i 49.6 gf 51.1 cd 48.8 h 50.7 de 51.6 bc 0.08 L* at 24 h PM 51.1 d 51.9 abcd 51.6 cd 51.7 bcd 52.7 ab 52.7 a 50.9 d 51.3 cd 51.7 bcd 52.2 abc 52.3 abc 51.5 bc 0.08 Cook loss (%) 24.7 abc 23.6 abcd 23.0 bcd 25.4 a 25.2 ab 24.1 abcd 25.1 ab 22.0 d 22.3 d 24.4 abc 23.5 abcd 22.8 cd 0.19 Shear energy (N/mm) a de def a bc ef a ef ef ab cd f 2.14 a i Values within a row lacking a common superscript differ (P < 0.05); n = higher ph than those of strains A and D, but it was similar to that of strain B. At 6 h PM, however, there was no significant difference in ph among the strains, nor were there differences in ph at any deboning hour between males and females of all strains (Table 4). In this study, although there were slight differences in ph observed among strains at 2 and 4 h PM, all of the strains examined in this study progressed through rigor at a normal pace with an approximate ph decline of 0.25 to 0.3 ph units from 2 to 4 h PM. Furthermore, BW and breast yield had no consistent effect on PM muscle metabolism (ph). There have been a variety of conclusions drawn about the effect of BW on PM ph. In contrast to findings in this study, Berri et al. (2001) concluded that larger birds that have greater breast yield progress through rigor more slowly than birds that yield less. Berri et al. (2001) used smaller birds from a slow-growing genetic line. Mehaffey et al. (2006) showed that there were differences in the progression of rigor (indicated by ph) due to strain at both 2 and 4 h PM among 5 commercial broiler strains, but there was no consistent relationship with breast yield or BW. Color (L* value) was measured in this study because it is an important consideration for consumer satisfaction, and previous reports have indicated that color can be affected by strain, age, and sex (Froning, 1995). There was no difference in L* values measured at the time of deboning among strains A, B, and D (Table 3), but strain C had a significantly lower L* value at 2 h PM compared with the other strains and a significantly lower L* value at 4 h PM when compared with strains B and D. These differences were not related to BW or fillet yield. There have been conflicting reports about the effect of body size and fillet yield. Santiago et al. (2005) concluded that higher breast yield can also cause higher L* values, whereas Mehaffey et al. (2006) reported no difference in color for strains with higher breast yield. There was no difference in color values measured at 24 h PM for all strains, excluding strain B whose 2 h fillets had lower L* values than the 6 h fillets when measured at 24 h PM (Table 3). Sex did have an effect on color in this study (Table 4). Fillets of females processed were all lighter in color than fillets of males when color was measured at the time of deboning. However, at 24 h PM, there were no significant differences in L* values between the sexes at any deboning hour. For all strains used in this study, color changed as fillets aged from 2 to 6 h PM as indicated by higher L* values at 6 h PM than 2 h PM. Mehaffey et al. (2006) reported similar results. This change is likely related to changes in ph and water-holding capacity that occurs during rigor development. These results would indicate that color is not negatively affected by deboning fillets prerigor and that strain does not have a major effect on breast meat color. Water-holding capacity was measured because it can affect color and tenderness of fillets (Jeffery, 1983), and in this study, WHC was determined by cook loss. Strain and sex had no effect on WHC, indicated by no

5 252 Brewer et al. Table 4. Meat quality of breast fillets deboned at 2, 4, or 6 h postmortem (PM) from male and female broilers in a simulated bigbird market program Female Male Quality 2 h 4 h 6 h 2 h 4 h 6 h Pooled SEM ph at deboning 6.35 a 6.09 b 5.81 c 6.37 a 6.07 b 5.87 c 0.01 ph at 24 h PM 5.78 b 5.73 c 5.80 b 5.76 bc 5.79 b 5.86 a 0.01 L* at deboning 48.9 e 50.5 c 52.2 a 48.4 f 49.9 d 51.6 b 0.08 L* at 24 h PM 51.6 ab 52.2 a 51.8 ab 51.4 b 51.9 ab 52.0 ab 0.08 Cook loss (%) 24.3 ab 23.5 bc 22.7 c 25.5 a 23.7 bc 23.4 bc 0.19 Shear energy (N/mm) b d e a c d 2.14 a e Values within a row lacking a common superscript differ (P < 0.05); n = 240. significant differences in cook loss at any given deboning hour (Table 3 and Table 4, respectively). With all strains, there was a trend for slightly more cook loss in fillets deboned prerigor (Table 3); yet, cook losses were only significantly greater for strain C at 2 h PM compared with 4 and 6 h PM. Mehaffey et al. (2006) reported greater cook loss in fillets deboned at 2 h PM compared with fillets deboned at 4 h PM from 7-wkold broilers. Northcutt et al. (2001) reported greater cooked yield (lower cook loss) in fillets deboned later PM; fillets deboned at 0 h PM had significantly lower cooked yield compared with those deboned at 2, 4, or 6 h PM (which were not different). This higher cook loss in earlier deboned fillets may be attributed to smaller interstitial spaces in the muscle for water storage due to sarcomere shortening that can occur due to prerigor deboning (Papa and Lyon, 1989). In this study, there was no consistent relationship between WHC and fillet yield. Mehaffey et al. (2006) also found that there was no relationship between yield or strain and WHC. Texture of meat is a major aspect of consumer acceptability (Lyon et al. 1985). Meullenet-Owens razor shear energy was measured in this study as an indication of tenderness. If fillets are removed from the skeleton before the completion of rigor (around 4 6 h PM in broilers), this allows for shortening of the sarcomeres, and results in tougher fillets (Lyon et al., 1985; Papa and Fletcher, 1988; Papa and Lyon, 1989; Sams and Janky, 1991). In this study, fillet ph (measured at the time of deboning) indicates that fillets deboned at 2 h PM are in an earlier stage of rigor than the 4 h PM fillets, and fillets deboned at 4 h PM are in an earlier stage of rigor than fillets deboned at 6 h PM. As a result, in this study, fillets deboned at 2 h PM were tougher than fillets deboned at 4 and 6 h PM for all strains as indicated by higher MORS energy (Table 4 and Figure 1). There was no difference in MORS energy among strains at 2 h PM; therefore, all fillets deboned at 2 h PM in this study would be considered slightly-to-moderately tough by consumers (Cavitt et al., 2005). Interestingly, strains A and C reached a tenderness equivalent to 6 h PM by 4 h PM, as indicated by no significant difference in MORS energy between 4 and 6 h PM deboned fillets. Conversely, strains B and D still had significant decreases in MORS energy from 4 to 6 h PM, suggesting that there may still have been sufficient biochemical activity (e.g., sufficient adenosine triphosphate levels) when these strains were deboned at 4 h PM. At 6 h PM, there was no difference in MORS energy among strains. Interestingly, strains B and D also had significantly larger fillets compared with those of strains A and C. Furthermore, males in this study also had a larger fillet size than their female counterparts, and males of all strains had higher MORS energy than female counterparts of the same strain. Lyon et al. (1992) also reported that fillets from males were tougher than fillets from females. In both cases in this study, the differences in tenderness in strains with larger fillets and fillets from males (larger fillets) were not related to phd. However, muscle ph and shear force are not always strongly correlated (Stewart et al., 1984; Sams and Janky, 1986; Liu et al., 2004), especially within a given time point. Mehaffey et al. (2006) reported weak correlations between ph and shear force, especially at 4 h PM. Stewart et al. (1984) suggested that ph and tenderness is not a cause-effect relationship, rather ph is an indicator of rigor development (e.g., adenosine triphosphate levels). It is possible that tenderness could be related to fillet size or its interaction with rigor development. In a study by Mehaffey et al. (2006), fillets deboned from 7-wk-old broilers had higher MORS energy values than fillets deboned from 6-wk-old broilers. This could be attributed to increased fillet weight (size) from 6 to 7 wk. Northcutt et al. (2001) also reported that Warner Bratzler shear values generally increased as the bird age increased (indicating tougher meat). Mehaffey et al. (2006) also found differences in tenderness among strains deboned at 2 and 4 h PM, but there was no consistent relationship between shear energy and fillet size characteristics. However, there were very few differences in various fillet dimensions among strains, indicating consistency across strains. Differences between these studies may be related to the size of the birds used (or strains) as larger birds ( 3 kg) were used in the current study, compared with smaller birds ( 2.6 kg) used in previous studies. Differences in tenderness within one deboning hour among strains could be attributed to increased myofibrillar diameter of the higher-yielding strains used in this study due to increased fillet size or sarcomere shortening due to deboning. Werner et al.

6 STRAIN EFFECTS ON MEAT QUALITY IN BIG-BIRD PROGRAMS 253 Figure 1. Meullenet-Owens razor shear (MORS) energy of fillets deboned at 2, 4, and 6 h postmortem from broilers in a simulated big-bird market program. a f Values lacking a common letter differ (P < 0.05); pooled SEM = (2008) did report that turkeys with greater myofibrillar diameter had higher shear forces. Smith (1963) reported that heavier chicken strains had greater myofibrillar diameters than strains with lighter BW at 10 wk compared with 1 d of age. Burke and Henry (1997) reported similar results, indicating increased muscle mass is related to increased fiber diameter. In red meat, it has been reported that muscle fiber size and tenderness are strongly positively correlated (Tuma et al. 1962; Crouse et al. 1991). Therefore, this could potentially be a cause for toughening of broiler breast fillets of larger strains and male birds that have significantly greater breast muscle mass. Another potential explanation could be that birds with larger muscle mass still had sufficient adenosine triphosphate levels (in muscle) at 4 h PM to allow for contraction or sarcomere shortening compared with the strains with smaller muscle mass. It is not likely that collagen (or increase in heat-stable collagen) is the cause of tenderness differences due to the relatively young market age of these broilers. However, further investigation is needed to determine the causes for these differences in tenderness. Often, these high-yielding birds are deboned for further-processed markets, and because the poultry industry is trending toward early deboning, it could be detrimental that these strains have tougher meat than strains that yield less, especially if fillets are marketed as nonmarinated (i.e., portioned only). Sometimes, but not always, fillets harvested from these larger birds typically have some sort of further processing (i.e., marination); therefore, many of these problems with increased shear energy, indicating tougher meat, can be alleviated (Kuttappan et al., 2009). Conclusion In conclusion, data from this study suggest that strain and sex do effect meat quality of high breastyielding broilers in big-bird programs. Strain has little effect on color and WHC, but strain does affect fillet yield, dimension, and tenderness. Two strains that had greater breast weight, yield, and fillet dimension also had tougher meat at 4 h PM. However, by 6 h PM, these differences in tenderness were not detected. Fillets from male broilers were also greater in weight and dimension than those of females and were significantly tougher (P < 0.05) at all deboning hours than females. Although strain and sex do affect meat-quality parameters, these parameters are most affected by the time PM that meat is removed from the bone. ACKNOWLEDGMENTS The authors are appreciative for the support of Cobb- Vantress Inc. (Siloam Springs, AR) and the University of Arkansas Division of Agriculture (Fayetteville, AR) throughout this project. REFERENCES Acar, N., E. T. Moran Jr., and S. F. Bilgili Live performance and carcass yield of male broilers from two commercial strain crosses receiving rations containing lysine below and above the established requirement between six and eight weeks of age. Poult. Sci. 70: Berri, C., N. Wacrenier, M. Millet, and E. Le Bihan-Duval Effect of selection for improved body composition on muscle and meat characteristics of broilers from experimental and commercial lines. Poult. Sci. 80:

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