Incubation Conditions and Integrity in Pekin Ducks Ozan Akkus 1, Co-PI; Todd Applegate 2, Co-PI; Serife Agcaoglu 1 1 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA 2 Department of Animal Sciences, Purdue University, West Lafayette, IN 47907,USA Introduction Curved rib syndrome is a skeletal condition where the ribs and keels are malformed. The curvature of the ribs is random in malformed ducks whereas ribs are in order in normal duck.the deformities are also evident at locations where ribs connect to the keel (Figure 1).The incidence of curved rib syndrome in ducks has increased in recent years, and is higher during the summer (70%) compared to winter (40%). However, the cause for this syndrome is not known. The objective of this study was to investigate the existence of cellular, compositional and/or structural abnormalities which lead to morphological deformities on keel and rib of Pekin ducks. Materials and Methods Day-old and adult Pekin ducks were visually examined and grouped as normal, unilaterally malformed and bilaterally malformed. Experiments were conducted to compare normal and malformed market age ducks in terms of keel and rib properties as well as side-to-side comparison within groups. First, ribs of malformed and normal dayold ducks were counted and were compared in terms of number of ribs and symmetry. Second, width and length of the keel and breast meat amount were compared using Student s t test. Significant difference and lack of symmetry were determined (Figure 2).Third, mechanical strength of ribs were assessed with three point bending test. The yield stress and Young s modulus of ribs were calculated by a customized MATLAB code. These properties were compared rib by rib using Mann Whitney non-parametric test. For example, strength of rib # 4 of normal ducks was compared with the strength of rib # 4 of malformed ducks (the number assigned to the rib increasing from the distal to the proximal.). Fourth, indentation strength of keels were measured at locations close to the deformity and compared with Mann Whitney non-parametric test (Mow et al., 1989). Fifth, proteogylcan content was extracted and quantified from keel and Mann Whitney non-parametric test was applied.(franzen et al., 1984) Last, hematoxylin and Eosin (H&E), PicoSirious Red and Safranin Orange/Fast Green were used in histology to observe cell shape, collagen distribution and cartilage,respectively. Both longitudinal and transverse sections were taken to investigate keel, rib and the connective tissue.
Results After evaluating the results, no statistically significant difference was observed between malformed and normal ducks in terms of the number of ribs. Also, malformed ones did not lack symmetry. There was significantly more breast meat at the left side of malformed ducks although both sides had comparable amount of meat in normal ones (Table 1). The left side of the keel was significantly wider than right side on malformed ducks at mid-length (Table 2). Increased meat amount could be due to wider available space for breast meat. Furthermore, there was a marginally significant difference in length between malformed and normal keels (P=0.061)(Table 2). Young s Modulus was greater in normal ducks for the ribs #3 (P=0008) and #4(P =0.027) and for other ribs were comparable. A similar result was observed for the yield stress. The difference was significant for rib #3 (P=0.013), #4 (P=0.045) and #5(P=0.037). In terms of indentation strength, normal and deformed keels were not different (P > 0.05). The left side was stronger in for normal ducks (P < 0.05). Proteoglycan content was not different for malformed and normal keels. No significant difference was observed in terms of appearance of cells neither in the keel and rib nor in connective tissue (Figures 6-8). Summary This research systematically studied the physical integrity and physiological aspects as related to malformations of the rib in Pekin ducklings. Notably, number and appearance of the ribs were similar indicating that it was not an effect of differentiation early in incubation. Rather, physical attributes to the keel (left) and ribs (# 3-5) were affected by the condition lending to a decreased modulus and strength, due plausibly to the asymmetry in keel width and resultant muscle mass. Histological examination has not revealed any apparent differences in proteoglycan content, mineral or connective tissue thus far. References Franzen A, Heinegard D. Extraction and purification of proteoglycan from mature bovine bone.biochemical Journal, 224:47-58. 1984. Mow VC, Gibbs MC, Lai WM, Zhu WB, Athanasiou KA. Biphasic indentation of articular cartilage- II. A numerical algorithm and an experimental study. Journal of Biomechanics, 22: 853-861. 1989.