Abstract
This study was focused on analyzing the effects of dietary inclusion of raw chickpea seed as a replacement of soybean meal as a primary protein source on bone structure in broiler chickens. Broiler chickens (n = 160) received in their diet either soybean meal (SBM) or raw chickpea seeds (CPS) as a primary protein source throughout the whole rearing period (n = 80 in each group). On the 42th day randomly selected chickens from each group (n = 8) were slaughtered. Collected tibiotarsus were subjected to examination of the biomechanical characteristics of bone mid-diaphysis, microstructure of the growth plate and articular cartilages; the analysis of mineral content and crystallinity of mineral phase, and the measurements of thermal stability of collagen in hyaline cartilage were also carried out. The inclusion of chickpea seeds resulted in increase of bone osteometric parameters (weight, length and mid-diaphysis cross-sectional area) and mechanical endurance (yield load, ultimate load, stiffness, Young modulus). However, when loads were adjusted to bone shape (yield and ultimate stress) both groups did not differ. Mineral density determined by means of densitometric measurements did not differ between groups, however the detailed analysis revealed the differences in the macro- and microelements composition. The results of FT-IR and XRD analyses showed no effect of diet type on mineral phase crystallinity and hydroxyapatite nanocrystallites size. In trabecular bone, the increase of real bone volume (BV/TV) and number of trabeculae was observed in the CPS group. Total thickness of articular cartilage was the same in both groups, save the transitional zone, which was thicker in the SBM group. The total thickness of the growth plate cartilage was significantly increased in the CPS group. The area of the most intense presence of proteoglycans was wider in the SBM group. The structural analysis of fibrous components of bone revealed the increase of fraction of thin, immature collagen content in articular cartilage, trabeculae and compact bone in the CPS group. The dietary inclusion of CPS affected the thermal stability of collagen, as decrease of net denaturation enthalpy was observed. This study showed a beneficial effect of CPS on the skeletal development, improving the overall bone development and the microarchitecture of cancellous bone. It suggests that CPS can be a promising replacement for SBM in broilers feeding in the aspect of animal welfare related to the development of the skeletal system.