Basic morphometry, microcomputed tomography and mechanical evaluation of the tibiotarsal bone of a dual-purpose and a broiler chicken line

Abstract

Continuous loading of the skeleton by the body's weight is an important factor in establishing and maintaining bone morphology, architecture and strength. However, in fast-growing chickens the appendicular skeleton growth is suboptimal making these chickens predisposed to skeletal mineralization disorders and fractures. This study compared the macroand microstructure as well as the mechanical properties of the tibiotarsus of a novel dualpurpose, Lohmann Dual (LD) and a highly developed broiler, Ross (Ross 308) chicken line. Eighty one-day-old male chicks of each line were grown until their body weight (BW) reached 2000g. Starting at the day of hatching, six birds of each line were sampled weekly. The weight, length and width of the tibiotarsus were measured and its mechanical properties (rigidity, M-Max and the M-fracture) were evaluated using the three-point bending test. Additionally, the mineral density of both, trabecular and cortical bone, the bone volume fraction, the trabecular number, thickness and separation plus cortical thickness of both chicken lines were analyzed using microcomputed tomography. The growth of the tibiotarsus in both chicken lines followed a similar pattern. At the same age, the lighter LD chickens had shorter, thinner and lighter tibiotarsi than those of Ross chickens. However, the LD chickens had a similar cortical thickness, bone volume fraction and similar mineral density of both trabecular and cortical bone to that of Ross chickens. Furthermore, the tibiotarsus of LD chickens was longer, heavier and wider than those of Ross chickens of the same BW. In addition the rigidity of the LD tibiotarsus was greater than that of Ross chickens. This suggests that the tibiotarsus of LD chickens had more bending resistance than those of Ross chickens of the same BW. Consequently, fattening LD chickens to the marketable weight should not affect their leg skeleton stability.

Differences in Tibia Shape in Organically Reared Chicken Lines Measured by Means of Geometric Morphometrics

“…Bone quality (i.e., mineralization and bone density) of slow-growing lines was higher than that of fast-growing ones [ 3 , 41 , 42 , 43 ]. The rigidity and consequently the bending resistance, of tibiotarsus in the Lohman Dual slow-growing line was greater than in Ross 308, a highly selected fast-growing line [ 2 ], confirming that skeleton stability is affected by weight gain.…”

“…All animals were apparently healthy and none of them showed evident leg pathologies all over the experiment, but it is rational that heavier chickens, characterized by a curved tibia , could be more prone to deformities or pathologies and more exposed to lameness risk [ 2 , 3 ].…”

“…When walking ability is reduced, animals are not suitable for rearing in open air; walking ability depends on genotype, weight, age, feeding, and housing [ 1 ]. It has been demonstrated that fast-growing broilers, if reared in organic system, are genetically prone to lameness and leg weakness [ 2 ]. There is a straightforward relationship between bone quality and growth rate in broilers [ 3 ].…”

“…The morphological approach is a more objective method used to detect bone anomalies, cause of lameness, and bone defects. To the best of our knowledge, previous studies relating fast growing and body weight to bone health and morphology used classic morphometrical approaches, such as the measure of bone length, weight, diameter [ 2 , 3 , 11 ], or analysis of radiographic images [ 12 ]. Most of previous studies considered the occurrence of skeletal anomalies and pathologies [ 11 , 13 , 14 , 15 ].…”

“…Most of previous studies considered the occurrence of skeletal anomalies and pathologies [ 11 , 13 , 14 , 15 ]. Significant differences were found in morphometric traits of tibio-tarsus in two different broiler strains (Ross and Lohman Dual) [ 2 ]. Rapid growth genotypes showed more tibia deformities, lack of mineralization, and reduced strength.…”