J. Appl. Poult. Res.
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J APPL POULT RES 2006. 15:433-441
© 2006 Poultry Science Association
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Research Reports

Influence of Age and Sex on Footpad Quality and Yield in Broiler Chickens Reared on Low and High Density Diets

S. F. Bilgili1, M. A. Alley, J. B. Hess and M. Nagaraj

Poultry Science Department, Auburn University, Auburn, AL 36849-5416

1 Corresponding author: bilgisf{at}auburn.edu


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The effect of age and sex on live performance, processing yields, and footpad quality of broiler chickens was evaluated by rearing 2 commercial strain-crosses (SC) to 56 d of age on 2 diets varying in nutrient density. Each strain cross was placed in 10 replicate pens of 50 birds (25 males and 25 females per pen). Equally distributed among the replicate pens were high- and low-density starter (0 to 21 d) and grower (22 to 42 d) diets with a common finisher fed from 43 to 56 d to all birds. Body weights, adjusted feed conversion, and mortality were determined at 21, 42, and 56 d of age. Processing yields, foot weights, and yields, and the incidence and severity of footpad dermatitis were evaluated on d 35, 42, 49, and 56.

No differences (P > 0.05) were seen in mortality between the SC and diet density treatments throughout the course of the study. Strain-cross had a significant effect on body weights at d 21 and feed conversion at d 42, but no differences remained at d 56. Significant SC effects were present for carcass without giblets at d 35, 42, and 56. Diet density effects were limited to carcass without giblets at d 35 and abdominal fat content at d 56. As expected, females had higher abdominal fat yields than males at all ages examined.

Foot weight and yields were significantly affected (P < 0.05) by SC and sex at d 42, 49, and 56. As expected, foot weights increased with age. The proportion of birds with footpad dermatitis tended to increase until 49 d of age after which they started to decline. Male broilers had significantly higher incidence of footpad dermatitis than female broilers at d 49 and 56. Footpad dermatitis response to diet density and pigmentation of the feet was dependent on SC.

Key Words: broiler • foot • paw • footpad dermatitis • strain-cross


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The broiler industry continues to demand improvements in growth rate, feed efficiency, and product quality in commercially available strains or strain-crosses (SC) of broilers [1, 2, 3]. Market age, sex, and plane of nutrition are important determinants of expression of the genetic potential of SC under commercial conditions [4, 5, 6].

Chicken paws, or the portion of the chicken feet cut just below the spur, have proved to be a very profitable export item in recent years [7]. Chicken paws are valued by size: small (22 to 26 g), medium (27 to 35 g), and jumbo (36 to 45 g), as well as quality (A or B grade). Hence, there is a financial incentive to harvest high-quality paws during processing [8]. Footpad dermatitis can significantly reduce the saleable value of paws. This condition is characterized by inflammation and necrotic lesions, ranging from superficial to deep, on the plantar surface of the footpads. Progressing deep ulcers may lead to chronic abscessation and fibrosis of underlying synovial structures [9]. Broiler flocks affected with severe form of footpad dermatitis show leg abnormalities like limping and uncoordinated gait, which negatively influences their activity [10]. Birds may also show slower weight gain due to pain-induced reduction in feed intake [11]. It has been observed that severe footpad lesions are commonly associated with other types of dermatitis such as hock burns and breast blisters [9, 11]. The lesions are also implicated as a cause for impaired product quality, because they can serve as portal of entry for Staphylococcus aureus and other microorganisms [10, 12].

Limited research has been published on factors affecting the yield and quality of this unique product [13]. With the implementation of voluntary Animal Welfare Audit programs, in which paw lesions are documented and monitored, prevention of paw lesions in broiler chickens has become a priority for the broiler industry [14].

The objective of this study was to evaluate the influence of age and sex on foot weight, yield, and footpad dermatitis incidence in 2 commercially available broiler lines reared on diets differing in nutrient density.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
One thousand sexed broilers from 2 commercial SC (designated as A and B) were placed in an open-sided, naturally ventilated, concrete floor house containing new pine shavings as a bedding material. Each SC was assigned 10 replicate pens [15], in which birds in half of the replicate pens for each SC received a high-density feeding program, and the remaining half received a low-density program (Table 1Go). Both feeding programs consisted of a crumbled starter (0 to 21 d) and a pelleted grower (22 to 42 d) diet; all birds received a common pelleted finisher (43 to 56 d) diet. The starter birds were reared on a 23L:1D lighting program, in which they received feed and water continuously via tube feeder and bell drinker. All birds were weighed on a per-pen basis at 21, 42, and 56 d of age when average weight and feed conversion were determined [16]. Mortalities were recorded daily.


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  		Table 1. Nutrient composition of high- and low-density experimental diets1
 
Three males and 3 females were randomly chosen from each pen and processed on d 35, 42, 49, and 56 at the Auburn University Processing facility. At each age, feed was withdrawn approximately 10 h before processing. Carcass and fat yields as well as foot weights and yields [17] were determined after chilling based on SC, sex, and diet density. Footpad dermatitis incidence and severity were scored by a visual ranking system [18]. The feet were also scored visually for the presence or absence of melanin pigmentation. The data were analyzed using the GLM of SAS [19, 20]. Level of probability was set at P < 0.05. Percentage values were transformed to arc sin values before analysis.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Mortality was unaffected (P > 0.05) throughout the course of this trial (Table 2Go). Body weights were significantly affected (P < 0.001) by SC only at 21 d of age. However, SC by diet density interaction was significant for both female and male BW at 42 d of age, because only SC-B responded to high diet density (Figure 1Go). The SC effect for feed conversion was limited to d 42. Males responded favorably to high-density diets, but this was significant only at d 42. No other diet density effects were detected in live performance. Differences in live performance of broilers were mainly SC related and tended to favor SC-A. This was not surprising, because commercially available SC have been shown to vary in growth characteristics and their response to dietary nutrient density [21]. Processing yields of male and female broilers at d 35, 42, 49, and 56 are summarized in Table 3Go. Carcass without giblets varied by SC on d 35, 42, and 56. Diet density effects on chilled carcass yields were significant only at 35 d of age. As expected, abdominal fat yields increased with age, and males showed lower (P < 0.05) fat yields than females [22]. Birds reared on the low-density diet showed significantly reduced (P < 0.05) fat yields at d 56. This is consistent with the literature showing that abdominal fat deposition in broilers increases in parallel with increasing dietary energy and calorie:protein ratio [23, 24]. A significant sex by diet density interaction was detected for abdominal fat yield at d 42, with only males showing low abdominal fat deposition on high-density diets (data not shown). In a similar interaction at d 56, only males responded positively to high diet density with chilled carcass yield (Figure 2Go). As expected, significant differences in chilled carcass yields were observed for SC (d 35 and 56), diet density (d 35), and sex (d 49 and 56).


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  		Table 2. Influence of strain-cross and diet density on broiler performance
 

Figure 1
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  		Figure 1. Strain-cross by diet density interaction (P < 0.05) for male and female weights at 42 d of age. a–cMeans with different superscripts differ significantly.

 

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  		Table 3. Influence of strain-cross, diet density, and sex on processing yields
 

Figure 2
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  		Figure 2. Sex by diet density interaction (P < 0.01) for carcass without giblets (CWG) and lean carcass yields at 56 d of age. a,bMeans with different superscripts differ significantly.

 
Significant SC effects were present for foot weights (P < 0.05) and yields at 42, 49, and 56 d of age (Table 4Go). Males consistently attained significantly higher (P < 0.001) foot weights and yields than females regardless of age. Foot yields, calculated as a proportion of live BW, continued to decline after 35 d, as the feet approached their maximum size while the body continued to grow. Strain-cross by diet density and sex by diet density interactions were due to differing growth responses of SC (A > B) and sex (males > females) to high-density diets (data not shown).


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  		Table 4. Influence of strain-cross, diet density, and sex on foot parameters
 
The proportion of birds with melanin pigmentation was unaffected (P > 0.05) by diet density throughout the trial (Table 4Go). Only at d 56 was a sex effect detected, with females showing a significantly higher proportion of feet with melanin pigmentation than males (40.3 vs. 20.8%); SC differences in melanin pigmentation were only significant at d 42.

The incidence of footpad dermatitis varied between the 2 SC used in this study depending upon diet density and sex (Table 5Go). Significant SC by sex interactions were present for a proportion of birds with paw lesions at 35 d (Figure 3Go) and 42 d (Figure 4Go) of age. The susceptibility of males and females from both SC varied by age, with females of SC-B showing low incidence of mild and severe lesions at 35 d of age and males of SC-A showing low incidence of mild lesions at 42 d of age. Significant SC by diet density interaction for severe lesions at 42 d of age (Figure 5Go) indicated that susceptibility to footpad dermatitis may vary by SC. In general, the proportion of birds with mild and severe footpad dermatitis tended to increase until 49 d of age after which they started to decline. Female broilers had a significantly higher incidence of mild footpad dermatitis than male broilers at d 42 (56 vs. 33%), d 49 (61 vs. 39%) and at d 56 (51 vs. 29%; Table 5Go). However, males tended to have higher incidence and severity (P < 0.05) of footpad dermatitis than females.


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  		Table 5. Influence of strain-cross, diet density, and sex on the incidence of footpad lesions1
 

Figure 3
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  		Figure 3. Strain-cross by sex interaction (P < 0.05) for footpad lesions at 35 d of age. a,bMeans with different superscripts differ significantly.

 

Figure 4
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  		Figure 4. Strain-cross by sex interaction (P < 0.5) for footpad lesions at 42 d of age. a,bMeans with different superscripts differ significantly.

 

Figure 5
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  		Figure 5. Strain-cross by diet density interaction (P < 0.05) for footpad lesions at 42 d of age. a,bMeans with different superscripts differ significantly.

 
Research conducted with broilers and turkeys indicates that litter conditions (i.e., wet and caked litter) serve as a catalyst in the development of footpad lesions [25]. This study was initiated with fresh shavings as bedding material. As the birds aged, litter quality gradually deteriorated. Although no objective litter quality measurements were made in this study, a combination of factors, including the reduction in stocking density with weekly sampling (12.14 to nearly 6 birds per m2) and changes in environmental conditions, may have contributed to improvements in paw lesions after 49 d of age.

A higher proportion of birds reared on low-density diets did not have footpad lesions. This finding is consistent with an earlier study demonstrating the effect of high-density diets on footpad lesions [26]. Many nutritional factors, including level and type of CP, methionine, biotin, pantothenic acid, riboflavin, and zinc have been reported to affect footpad dermatitis in poultry [25, 26]. Although paws can be downgraded in the plant due to a multitude of causes (i.e., bruises, fractures, equipment mutilation, and cuticle remnants), footpad dermatitis continues to be the most common cause [27]. In addition to flock management and environmental control, optimal nutrition should receive equal consideration in maximizing paw quality in broilers [28, 29].


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

  1. The live performance and processing yields of broilers was influenced by strain-cross and diet density.
  2. Foot weights and yields were mainly influenced by strain-cross and sex, with males attaining higher weights and yields over females regardless of age.
  3. The proportion of birds with feet pigmentation was sex (females > males) and strain-cross dependent.
  4. Diet density had significant effects on the occurrence of footpad lesions regardless of age. The incidence of footpad lesions varied by sex (males > females) diet density (high > low) and strain-cross.


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

  1. Lilburn, M. S. 1989. The interaction of genetics and factors associated with commercial broiler production. http://www.novusint.com/Public/Library/DocViewer.asp?ID=66 Accessed February 7, 2006.
  2. Emmerson, D. A. 1997. Commercial approaches to genetic selection for growth and feed conversion in domestic poultry. Poult. Sci. 76:1121–1125.[Abstract/Free Full Text]
  3. McKay, J. C., N. F. Barton, A. N. M. Koerhuis, and J. McA-dam. 2000. The challenge of genetic change in animal production. Pages 1–7 in Proc. 27 Occ. Publ. Br. Soc. Anim. Sci., Edinburgh, UK.
  4. Leeson, S., L. Carson, and J. D. Summers. 1996. Broiler response to diet energy. Poult. Sci. 75:529–535.[Web of Science][Medline]
  5. Marks, H. L. 1996. Broiler genetics: Genetics x nutrition interactions. Watt Summit II, Univ. Georgia, Athens.
  6. Smith, E. R., and G. M. Pesti. 1998. Influence of broiler strain-cross and dietary protein on the performance of broilers. Poult. Sci. 77:276–281.[Abstract/Free Full Text]
  7. Christensen, H. 1996. PRESTO! An insatiable market in southern China and Hong Kong changes a chicken by-product into a snack food. Poult. Market. Technol. April/May: 38–41.
  8. Bilgili, S. F., and J. B. Hess. 1997. Maximizing chicken paw yield and quality. Meat and Poultry, May:54.
  9. Greene, J. A., R. M. McCracken, and R. T. Evans. 1985. A contact dermatitis of broilers—Clinical and pathological findings. Avian Pathol. 14:23–38.
  10. Hester, P. Y. 1994. The role of environment and management on leg abnormalities in meat type fowl. Poult. Sci. 73:904–915.[Web of Science][Medline]
  11. Martland, M. F. 1985. Ulcerative dermatitis in broiler chickens: The effect of wet litter. Avian Pathol. 14:353–364.
  12. McCullagh, J. J., P. T. McNamee, and H. J. Ball. 1997. Application of pulse field gel electrophoresis to the typing of Staphylococcus aureus isolates collected from broiler houses and hatcheries in Northern Ireland. Page 50 in Proc 11th Int. Congr. World Vet. Poult. Assoc., Budapest, Hungary.
  13. Brown, H. G., D. J. Zelenka, and L. Reinhart-Jones. 1996. Effect of breed, sex, age and size on quantity and value of chicken paws. Poult. Sci. 75(Suppl.):25. (Abstr)[Web of Science][Medline]
  14. National Chicken Council. 2005. National Chicken Council Animal welfare guidelines and audit guidelines. National Chicken Council, Washington, DC.
  15. Each strain-cross was placed in 10 replicate pens of 50 birds (25 males and 25 females). The pens were 1.70 x 2.30m in dimension with a final stocking density of 12.14 birds per m2.
  16. Male and female weights were determined separately on d 42 and 56, whereas a straight-run average weight was determined on d 21 due to the inability to distinguish between the sexes.
  17. The entire foot was removed after defeathering and weighed. Although the paw is the portion of the foot below the spur, the hock joint was chosen as the point of removal in order to maintain consistency.
  18. The visual ranking system used to score footpad lesions indicated a score of 0 for no lesion present, a score of 1 for a mild lesion (lesion ≤ 7.5 mm) and a score of 2 for a severe lesion (lesion > 7.5 mm).
  19. The statistical model consisted of a 2 x 2 factorial arrangement of strain-cross and diet density, with sex as a nested effect. Pen (strain-cross x diet density) was used as the mean square divisor to test the strain-cross and diet density effects and their interaction.
  20. SAS Institute. 1988. SAS/STAT users guide for personal computers, release 6.03. SAS Institute, Inc., Cary, NC.
  21. Moran, E. T., Jr. 1999. Live production factors influencing yield and quality of poultry meat. Pages 179–195 in Poultry Meat Science. R. I. Richardson and G. C. Mead, ed. Poultry Science Symposium Series, Vol. 25, CABI Publishing, Wallingford, UK.
  22. Deaton, J. W., and B. D. Lott. 1985. Age and diet energy effect on broiler abdominal fat deposition. Poult. Sci. 64:2161–2164.[Web of Science][Medline]
  23. Wiseman, J., and C. E. Lewis. 1998. Influence of dietary energy and nutrient concentration on the growth of body weight and of carcass components of broiler chickens. J. Agric. Sci. 131:361–371.
  24. Maiorka, A., F. Dahlke, E. Santin, and A. M. Kessler. 2004. Effect of energy levels of diet formulated on total or digestible amino acid basis on broiler performance. Brazilian J. Poult. Sci. 6:87–91.
  25. Mayne, R. K. 2005. A review of the aetiology and possible causative factors of foot pad dermatitis in growing turkeys and broilers. World’s Poult. Sci. J. 61:256–267.
  26. Bilgili, S. F., M. A. Alley, J. B. Hess, and E. T. Moran Jr. 2005. Influence of strain-cross, sex and feeding programs on broiler chicken paw (feet) yield and quality. Pages 342–349 in Proc. XVII European Symp. on Quality of Poultry Meat, Doorwerth, The Netherlands.
  27. Bowers, P., and S. Shane. 1997. Keeping chicken feet healthy. Poultry Magazine Dec/Jan:22.
  28. Bilgili, S. F., D. Zelenka, and J. E. Marion. 2003. Use of statistical process control to assure finished product standards for chicken paws during processing. Poult. Sci. 82(Suppl. 1):109. (Abstr.)
  29. Hess, J. B., S. F. Bilgili, and K. M. Downs. 2004. Paw quality: Putting your best foot forward. Proc. Georgia Poult. Symp., Athens, GA.



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