ISSUE FOCUS 46 FEED & ADDITIVE MAGAZINE July 2022 Bone Strength High temperature causes excretion of some minerals for example Ca, Fe, Zn, and leads to decrease bone strengthen. In chickens, bone mineralization as determined through dual-energy x-ray absorptiometry (DEXA) is positively correlated with bone breaking force (r = 0.58 to 0.68; P < 0.001) and bone ash weight (r = 0.73 to 0.99; P < 0.001). Higher increases in stress occur with smaller increases in ash content. Decrease in bone mineralization is accompanied by a decrease in bone breaking force and bone ash weight. Oil supplementation can affect the TBS and weight of dry and wet bone. It is unknown whether the potential effects of n-3 fatty acids on bone are due to specific longer chain derivatives, such as DHA and EPA or not. Thus, the differences in specific n-3 sources on bone have to be clarified. The highest dry bone weight, width and length of bone, maximum force for breaking bone and ash value obtained in the group fed by diet supplemented with zinc and vitamin E. In fact, the increase in thickness of the growth plate was proportional to DL-α-tocopheryl acetate dose. The thickness of the entire growth plate cartilage and of the lower hypertrophic chondrocyte (mineralized) zone was significantly wider in animals fed the greater level of vitamin E. The authors maintained that the increased thickness of the mineralized zone may be due to decreased cartilage resorption and phagocytic activity on the metaphyseal side. The lowest bone strengthen was observed in the group fed by diet supplemented with tallow. It seems that, high level of arachidonic acid in supplemented dietary with tallow, which is the precursor of PGE2 and may lead to decrease in bone formation, consequently decrease in bone strengthen (Watkins et al. ,1997). Our results are compatible with the results of Liu et al (2003). The highest bones strengthen, dry matter and ash content were observed in broilers fed by supplemented diet with zinc and vitamin E in normal temperature. Afterward the highest dry bone weight was observed in broiler under heat stress, but fed by diet supplemented by tallow. Higher growing rate in this group could be the reason of this fact. Feeding diet supplemented with zinc and vitamin E and diet supplemented with canola and fish oil in normal temperature resulted to maximum bone strength and ash content in broiler, respectively. It seems this high bone strength is because of high level of EPA, DHA, omega-3 and Zn in diet, which might increase Ca precipitation and collage formation. The lowest ash value and force for breaking bone were observed in broiler under heat stress, which fed by tallow. That would probably be due to high environmental temperatures and high omega-6 content in the diet. It might increase excretion some minerals and PGE formation, but decrease in collagen formation. CONSIDER TO DIETARY FAT, VITAMIN E, AND ZINC SUPPLEMENTATION In conclusion, the higher environmental temperature and feeding chickens with tallow lead to decrease in bone strengthen and in contrary supplementing diet with fish oil, zinc and vitamin E lead to increase in bone strength in broiler. References available upon request.
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