COMPARATIVE STUDY OF BODY

Transcription

1 01998 Applied Poultry Science, Inc COMPARATIVE STUDY OF BODY CHARACTERISTICS OF DIFFERENT STRAINS OF BROILER CHICKENS A. A. ELFADIL Department of Animal and Poultry Science, Ontario Agricultural College, University of Guelph, Guelph, ON NlG 2W1, Canada J.-P VAILLANCOURT Department of Food Animal and Equine Medicine, College of Vetennay Medicine, North Carolina State University, 4700 Hillsbourough St., Raleigh, NC I. J. H. DUNCAN' Department of Animal and Poultry Science, Ontario Agricultural, College, University of Guelph, Guelph, ON NlG 2W1, Canada Phone: (5I9) , Exi FM: (519) Primary Audience: Broiler Breeders, Researchers DESCRIPTION OF PROBLEM Severd studies have demonstrated that cellulitis lesions in broiler chickens are m dy I other study has also established a significant association between cellulitis and the Drevalence of scratches [4].sifificant associations bemeen abdominal skin 1 To whom correspondence should be addressed

2 ELFADIL et al. Research Report 269 ported [5]. Experimental and field studies have demonstrated the importance of direct contact between Escherichia coli and scratches in the pathogenesis of cellulitis [4,6]. Improvement in productivity over the past 30 yr is an indication of the profound and rapid changes that have occurred in the genetics of broiler chickens [I. Such changes have resulted in the marketing of numerous strains of birds with various phenotypic particularities. Certain body characteristics may particularly predispose some strains of broilers to abdominal skin scratches and cellulitis. To investigate this hypothesis, this study first established the relationship between body weight and total skin surface area (TSSA) and abdominal skin surface area (ASSA), then compared different strains of broiler chickens regarding body weight, conformation of the abdomen, and length of the legs. MATERIALS AND METHODS Data for this study were collected from two experiments conducted consecutively during the period January-April In the first experiment, 30 male, 3-wk-old birds that had died from llflip-over'' disease were examined. Birds that die from "flip-over" are usually in good body condition and hence were regarded as appropriate for this experiment. Al thebirds were from the same origin, includmg their genetic line. The experiment was designed to investigate the associations between two dependent variables, TSSA (excluding head and legs below the intertarsal joints) and ASSA (the area lying between the sternum, vent and backbone), and three independent variables, abdominal circumference (the length around the abdomen passing the uropygial gland and tip of the sternum), length of the abdomen (the length between the tip of sternum and the vent), and body weight [8]. The data were statistically analyzed using backward stepwise regression [9, lo]. In the second experiment, 60 live male, Cwk-old birds (30 birds each from two different Strains A and B) were randomly selected from two floors in one barn. Strains A and B were selected because they were considered by poultry professionals to be different in their body characteristics. Body weight, abdominal circumference, and length of shank (the length between the bottom of the leg and the intertarsal joint) were measured to investigate the difference between the two strains. Since these birds were kept alive, ASSA was estimated from body weight using the regression equa- tion from the first experiment. The two-sample t-test was used to compare means of the body characteristics for the two strains [ll]. RESULTS AND DISCUSSION EXPERIMENT 1 Although all birds were of the same age, their body characteristics were quite variable (Table 1). The TSSA was positively associated with body weight (PS.OOO1). No significant association was observed between TSSA and TABLE 1. Descriptive statistics of body characteristics of 30 male, 3-wkold broiler chickens that died of "flio-over" I VARIABLE I MEAN I STANDARD 1 MINIMUM 1 MEDIAN I MAXIMUM I DEVIATION Skin areaa (cm2> Abdominal areab (cm') Body weight (g) Abdominal circumference' (cm) Abdominal lengthd (cm)

3 ~ 270 abdominal circumference, abdominal length, or ASSA. A good fit of the model was indicated by an adjusted R2 value of.9369 (Table 2). The ASSA was positively associated with body weight (PS.OO01). No association was observed between the ASSA and abdominal circumference, abdominal length, or TSSA. However, body weight did not explain as much of the variation in this surface area (adjusted R2 =.5033) (Table 2). The regression equation for the TSSA WaS: TSSA(~~~) = x Body weight (9) whereas the regression equation for the ASSA was: ASSA (cm2) = x Body weight (g) EXPERIMENT 2 Although body weight and the estimated ASSA of Strain B were higher than Strain A, no significant difference was observed between these two strains (Table 3). However, the abdominal circumference of Strain A was significantly greater than Strain B (P =.OOO4). Also, the length of the shank of Strain A was significantly shorter than Strain B (P =.0031) (Table 3). Although TSSA and its association with body we&t have been determined in other species of animals [12], this is the first reported study establishing the association between TSSA and ASSA and body weight in broiler chickens. The results show that among the factors examined, body weight is the only significant predictor for both TSSA and ASSA. However, the model for ASSA was less pre- BROILER BODY CHARACTERISTICS dictive than for TSSA, as indicated by the adjusted R2 ( vs ) (Table 2). This suggests that other factors not included in the model for ASSA are of more importance than body weight. It is also possible that more variability may have been introduced in the assessment of the ASSA versus the entire skin. The technique used was more consistent for the entire skin since there was no specific area to delimit. On the other hand, a large intercept was noticed in the equation for TSSA. This may indicate that this equation is valid for broiler chickens at least 3 wk old. When Strains A and B were compared, a significant difference was observed in abdominal circumference (P =.OOO4) and length of shank (P =.0031). These results are important because they indicate that conformation of the abdomen and length of the legs may differ enough between strains of birds to warrant further investigation with respect to any potential association these factors may have with conditions such as abdominal scratches and cellulitis in broiler chickens. Previous studies have demonstrated the important role of genetics in the strength of the skin as well as in the aggressiveness and nervousness of chickens [13, 14, 151. Such strain variations could possibly exacerbate the impact of phenotypic variations between strains. However, there was no significant difference in body weight and ASSA (calculated from body weight) for the two strains under study. This may be explained by the fact that all strains of broiler chickens are now selected for rapid growth. However, the results of this study indicate that even strains that do not differ sigdicantly in their body weight may differ sigzuficantly in other body characteristics. TABLE 2. Backward stepwise regression models of total skin surface areaa and abdominal skin surface areab with Dotential medictors VARZABLE COEFFICIEm STANDARD ERROR P-VALUE Body weight s.o001 Body weight I 5.o001

4 ELFADIL et al. Research Report 271 TABE 3. Descriptive statistics of body characteristics comparing two strains of 4-wk-old male broiler chickens I VARIABLE I MEAN I STANDARD I MINIMUM I MEDIAN I MAXIMUM 1 I I DEVIATION I 1 %e length around the abdomen, passing the uropygial gland and tip of the sternum. CONCLUSIONS AND APPLICATIONS 1. Body weight of broiler chickens is significantly associated with total and abdominal skin surface area. 2. Total and abdominal skin surface area could be estimated from body weight using the regression equation reported in this study. 3. Different strains of broiler chickens may have sigdkantly different body characteristics. 4. These characteristics may have an impact on conditions such as abdominal skin scratches and cellulitis. 1. Goodhope, RG., C. Riddell, and B. AUon, A descriptive study of cellulitis in Saskatchewan broiler chickens. 129th Annual A.V.M.A. Meeting, Boston, MA. 2. Messier, S., S. Quessy, Y. Robinwn, LA Devriese, and J. Hommez, Focal dermatitis and cellulitis in broiler chickens: Bacteriological and pathological findings. Avian Dis EUaW AA, J.-P. VaiUancourt, AH. Meek, RJ. Julian, and C.L Gyles, Description of cellulitis lesions and associations between celluhtis and other categories of condemnation. Avian Dis. 40: EUadil A.A., J.-P. Vaillancouri, AH. Meek, and C.L Gyles, 19%. A prospective study of cellulitis in broiler chickens in southern Ontario. Avian Dis REFERENCES AND NOTES 5. EUadil, A.A., J.-P. Vaillancourt, and AH. Meek, Impact of stochng density, breed, and feathering on the prevalence of abdominal skin scratches in broiler chickens. Avian Dis Peighambe S.M., RJ.Jl?ian, J.-P. Vaillancourt, and C.L Gyles, cellulitis: Experimental infections in broiler chickens. Avian Dis Norlh, M.O. and D. Bell, Broiler, roaster, and capon management. Pages in: Commercial Chicken Production Manual. 4th Edition. Van Nostrand Reinhold, New York, MI. 8. Birds were collected from a single farm the same day they had died and kept in a refrigerator for hr before being measured. Each bird was first weighed and

5 272 BROILER BODY CHARACTERISTICS then held in a horizontal position and the abdominal circumference and length were measured. The feathers were removed and the abdominal skin was dissected and laid down on a waxed paper with the subcutaneous side being in contact with the paper. The skin's contourswere marked on the waxed paper and cut. This paper was put on another waxed paper in order to reproduce the same surface without any subcutaneous tissues. This second waxed paper was weighed, and the area was determined using a standard paper which weighed 0.65 gm/loo an2, using the formula: ASSA (cm') = Weight of Waxed Paperweight of 1 cm' The remaining skin of the bird was then dissected (excludin the head and the legs below the intertam1 joints). &e abdominal skin was put in place and the area of the whole skin was determined in the same manner as above. 9. Snedecor, G.W. aad W.G. Cochran, Multiple Linear Regression. Pages33S373in: Statistical Methods. 8th Edition. Iowa State University, Ames, IA. 10. First, the total skin surface area was regressed on body weight, abdominal circumference, abdominal len h, and abdominal skin surface area. Second, abdominarskin surface area was regressed on body weight, abdominal circumference, abdominal length, and total skin surface area. The regression equation was calculated by the least squares method. 11. Snedecor, G.W. and W.G. Cocbran, The Comparison of Two Samples. Pages in: Statistical Methods. 8th Edition. Iowa State University, Ames, LA. 12. DeRoih, L and A. Bisaillon, Determination of body surface area in neonatal swine. Lab. him. Sci Kafri, I., DJ. Zelenka, J.A. Cherry, and P.B. Siege Skin breaking strength in chickens: Comparison among genetic combination. Poultry Sci % Granot, I., M. Pines, I. Plavnik, E Wax, S. Id@ and I. Bartov, Skin tearing in broilers in relation to skin collagen: Effect of sex, strain, and diet. Poultry Sci Muir, W.M., Purdue's "kinder, gentler chicken" moves into real-world test. S cia1 Report by Chris Sigurdson. Feedstuffs 67(3):472