Estimation of factors associated with the occurrence of white striping in broiler breast fillets.

Broiler breast fillets are sometimes characterized grossly by white parallel striations in the direction of the muscle fibers, and the condition is referred to as white striping. Depending on the severity of white striping, fillets can be classified as normal (NORM), moderate (MOD), or severe (SEV). The present study was intended to determine the factors associated with the occurrence of white striping in broiler breast fillets. Broiler birds (59 to 63 d) of 4 different commercial high-yielding strains (both males and females) fed with industrial type or phase-feeding regimens, were processed and ready-to-cook carcass weight was recorded. The carcasses were deboned at either 4 or 6 h postmortem. Fillets were scored for the degree of white striping at 24 h postmortem, and dimensions of fillets (length, width, cranial thickness, and caudal thickness), pH, color (L*, a* and b* values), cook loss, and Meullenet-Owens razor shear energy (MORSE) values were determined. About 55.8% of the birds used in the study showed some degree of white striping with MOD and SEV categories as 47.5 and 8.3%, respectively. Higher degrees of white striping were significantly (P < 0.05) related to higher cranial fillet thickness and ready-to-cook weights. The occurrence of SEV degrees of white striping was accompanied with increased b* values or yellowness of the meat. The growth differences in strains could influence the incidence of this condition, but feeding regimens and chill hour during processing did not. In addition, the degree of white striping did not show any significant (P > 0.05) relationship between various meat quality parameters such as pH, L*, a*, cook loss, and MORSE. In conclusion, the results of this study suggest that there is a greater chance of higher degrees of white striping associated with heavier birds, but the condition is not related to any major changes in cooked meat quality.

Influence of growth rate on the occurrence of white striping in broiler breast fillets.

White striping refers to the occurrence of different degrees of white striations on broiler breast fillets and thighs of larger broilers, yet little is known about its causes. Thus, the objective of the study was to estimate the occurrence of normal (NORM), moderate (MOD), and severe (SEV) degrees of white striping with respect to the growth rate of broilers and to compare their proximate composition without the confounding effect of diet. Straight-run 1-d-old chicks (n = 280) were randomly assigned to either a low- (LED) or high-energy (HED) diet (5 replicates of 28 birds/dietary treatment). Birds were processed at 54 d of age, and live weight, deboned fillet weight, and occurrence of white striping were recorded. As expected, birds fed the HED had lower (P < 0.05) feed conversion ratios than birds fed LED (2.08 vs. 2.28). Also, HED-fed birds had heavier P < 0.05) live and fillet weights when compared with the LED-fed birds. A greater (P < 0.05) percentage of breast fillets from LED-fed birds were scored NORM, whereas HED-fed birds produced a greater (P < 0.05) percentage of SEV fillets. Fillet weight and yield (percent of live weight) increased (P < 0.05) as the degree of white striping increased from NORM to SEV. Additionally, NORM fillets had greater (P < 0.05) lipid and lower (P < 0.05) protein content when compared with SEV fillets. Also, NORM fillets had greater (P < 0.05) percentages of SFA than SEV fillets; however, proportions of all monounsaturated fatty acids, as well as linoleic and linolenic acids, were greater (P < 0.05) in SEV than NORM fillets. These results suggest that an increased growth rate results in increased occurrence of higher degrees of white striping in broiler breast fillets, and the various degrees of white striping are associated with differences in chemical composition of breast fillets.

Phase feeding in a big-bird production scenario: effect on growth performance, yield, and fillet dimension.

Phase feeding (PF) has been effective at maintaining broiler growth while reducing production cost, but the effect on different broiler strains and sex has not been assessed. An experiment was conducted using 4 commercial broiler strains grown up to 63 d of age (n = 1,440), comparing a PF approach to an industry-type diet. At d 17, birds began either the industry or PF regimen. The industry regimen consisted of average industry nutrient levels with periods from 17 to 32 d, 32 to 40 d, 40 to 49 d, and 49 d to the end of trial. For PF, diets were prepared that contained Lys, sulfur amino acids, and Thr levels matching the predicted requirements for birds at the beginning (high nutrient density) and end (low nutrient density) of PF. Pelleted high and low nutrient density diets were blended to produce rations containing amino acid levels that matched the predicted PF requirements over 2-d intervals. Weight gain, feed intake, and feed efficiency were calculated through d 58. Birds were commercially processed at 59, 61, or 63 d; yield and fillet dimensions were measured. Phase feeding did not effect weight gain or feed intake of broilers during the overall growth period (17-58 d). For most strains, PF did not effect final BW, yield, or fillet dimensions. However, strain and sex had greater effects on growth performance, yields, and fillet dimensions. Strains B and D had greater breast yield than strains A and C. Reduced feed costs ($0.01 to $0.04 per kilogram of gain, depending on strain) were observed for all strains with PF for the overall growth period (17-58 d). Therefore, potential savings on feed costs are possible for all strains used in this study with the incorporation of the PF regimen.

Phase feeding in a small-bird production scenario: effect on growth performance, yield, and fillet dimension.

Phase feeding (PF) has been effective at maintaining broiler growth while reducing production cost, but the effect on different broiler strains grown in a small-bird production scenario has not been assessed. Three strains of commercial broilers were fed a diet containing average industry nutrient levels from 0 to 18 d. From 18 to 32 d, birds were fed either diets with average industry nutrient levels or diets with phased levels of amino acids. For PF, diets were prepared that contained Lys, sulfur amino acids, and Thr levels matching the predicted requirements for birds at the beginning (high nutrient density) and end (low nutrient density) of PF. Pelleted high and low nutrient-density diets were blended to produce rations containing amino acid levels that matched the predicted PF requirements over 2-d intervals, and diets were switched every other day during PF. Treatments were replicated in 6 pens; each pen contained 15 males and 15 females. Weight gain, feed intake, and feed efficiency were calculated. All birds were commercially processed; yield and fillet dimensions were calculated. Differences among strain BW were noted on d 0, 18, 32, and at processing. Males weighed more than females on d 18 (excluding strain C), 32, and the day of processing. Weight gain was affected by strain (P < 0.05) but not by feeding regimen in the overall growth period (18-39 d). Feed efficiency was improved by PF in strains B and C during the overall growth period. Fillet yield was improved with PF for strain B, and there were no significant differences between PF and industry fillet yields for the other 2 strains. Phase feeding had no effect on fillet dimensions, and there was little effect of strain. These results suggest that different strains may vary in their response to PF, although performance was similar or better in PF birds compared with birds fed the industry diet, regardless of strain.

Small bird programs: effect of phase-feeding, strain, sex, and debone time on meat quality of broilers.

Phase-feeding (PF) has been effective in maintaining broiler growth while reducing production cost, but the effect on different broiler strains grown in a small-bird production scenario has not been assessed. The objective of this study was to evaluate 3 commercial broiler strains typically used in a small-bird production scenario to assess the effect of various debone times and PF on yield and meat quality. Birds (n = 1,080) were fed either diets with average industry nutrient levels or diets with phased levels of amino acids. In total, 540 birds were commercially processed at 40 and 42 d of age. Breast fillets were harvested at 2, 4, and 6 h postmortem (PM). Muscle pH was measured at the time of debone and fillet dimensions, instrumental color (L*, a*, and b*), and pH were measured at 24 h PM. Fillets were cooked to 76°C and cook loss was calculated, followed by Meullenet-Owens Razor shear (MORS) analysis. Phase-feeding, strain, and sex had little effect on fillet yield, but deboning at 2 h PM resulted in a higher fillet yield compared with that of later debone times. Strain, sex, and debone hour had significant effects on fillet dimensions, with strain A producing longer and wider fillets than strains B and C. Males had larger fillets than females (longer and wider), whereas deboning early resulted in significantly thicker fillets compared with those of later deboning. There were no differences in fillet dimensions due to PF, however, uniformity was improved. The PF treatment did not affect pH, color, cook loss, or MORS energy. Deboning at 2 h PM resulted in higher MORS energy, indicating decreased tenderness in 2 of the strains, whereas in one strain, tenderness was not affect by debone time. Results of this study suggest PF does not adversely affect yield or meat quality of broilers in small-bird programs but strain, sex, and debone time can affect quality. Results also suggest that strain can effect tenderness of breast fillets when deboned prerigor.

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

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* 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.