Effects of nanocalcium carbonate on egg production performance and plasma calcium of laying hens
The taste of eggs, the amount of valuable nutrients they contain and their low price cause eggs to be one of the most important human foods. Egg shell quality is a vital factor for the industry, and calcium is the primary element influencing this (Lavelin, Meiri, & Pines, 2000). A series of documented studies have shown that calcium sources affect both hen performance and egg quality (Nys, 1999; Richter, Kiessling, Ochrimenko, & Ludke, 1999; Roland & Bryant, 2000; Boorman & Gunaratne, 2001; Kibala, Rozempolska‐Rucinska, Kasperek, Zieba, & Lukaszewicz, 2015; : Swiatkiewicz, Arczewska‐Włosek1, Krawczyk, Puchała, & Józefiak, 2015). It is noticeable that about 95% of the dry egg shell is calcium carbonate (Pavlovski, Vitorovic, Skrbic, & Vracar, 2000). Therefore, the diet of laying hens must contain adequate calcium in a form that can be utilized efficiently (Roberts, 2004a); Roberts, 2004b . Oyster shell and calcium carbonate are two important sources to supply calcium in laying hen diets but they differ in solubility, biological usage and price (Leeson & Summers, 1969). A large number of studies have investigated the effect of different calcium levels and sources on egg production, egg shell quality and egg internal quality. Meyer, Baker, and Scott (1973) compared oyster shell, egg shell, pulverized limestone and limestone grit as calcium supplements in laying hens and observed that use of oyster shell, egg shell and limestone grit gave higher egg shell quality. Lichovnikova (2007) showed that oyster shell had the best effect on egg shell quality in comparison with fine limestone, coarse limestone and egg shell as calcium sources. Pelica et al. (2009) showed that using 4.5% of calcium in laying hens diet positively affected performance and egg quality in comparison with other Ca levels. In the recent years, many strategies have been used to decrease mineral supplementation. Application of nanotechnology as a noble strategy increasing the bioavailability of minerals particularly calcium by enhancing its surface area which could result in an increase in its absorption and utilization (Vijayakumar & Balakrishnan, 2014). Studies have shown that nanoparticles are stable under high temperature and pressure and could be easily absorbed in the digestive system; therefore, minerals nanoparticles are more effective at lower levels than their conventional forms (Swain, Rajendran, Rao, & Domonic, 2015). Zha, Xu, Wang, and Gu (2007) reported that supplementation of rats diets with 200 ppb nano‐Cr enhanced the Cr digestibility and absorption. Research shows that due to small size and unique physical properties of nanoparticles, these feed additives could have better bioavailability and interaction with other feed components (Sahoo, Swain, & Mishra, 2014). Inclusion of NCC to diets as a calcium source could reduce calcium supplementation leading to reduction in calcium content in faeces and finally decreasing its negative impact on environment particularly in large poultry housing systems. As there is no evidence in the literature regarding the effect of NCC on production performance of laying hens, our study was conducted to evaluate the effects of nanocalcium carbonate (NCC) instead of calcium carbonate (CC) on egg production performance, egg shell quality, tibia thickness and plasma calcium in laying hens.