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This study investigated the influence of different particle sizes of limestone in Golden Montazah layers diets on physical and mechanical properties of egg production, eggshell quality and breaking strength of tibia from 32 to 44 weeks of age. Limestone consisted of fine (F> 0.6 mm) and coarse (C>2.8mm-4.5mm). All hens take a basal ration of the same composition. The differences between the four equal groups were in the replacement percent of fine pulverised limestone by granular limestone, of coarser particle size. The control group takes the basal diet with only pulverised limestone as a calcium supplement. In the diet ration of the second group, 60% of the pulverised limestone was replaced with granular limestone, in the third group percent 80 % and in the last group 100% of fine limestone replaced with coarse particles of limestone. Significantly higher breaking force (31.69N), shell weight (5.65 g), shell thickness (0.46 mm) were found for eggs from the fourth group of hens than for eggs from the control group (29.46 N; 5.33 g ; 0.37 respectively). Tibia breaking strength was significantly higher (350.66 N) than those in control group (252.82 N). The results obtained in our investigation showed some possibilities of eggshell quality improvement using limestone of coarser particle size as a Ca supplement in the hen diet. Replacing 60-100% of fine limestone by coarser particle size limestone had positive effects on eggshell quality. INTRODUCTION ptimize the machines design and the effective utilization of the machines used in the transportation, processing, packaging and storage of agricultural products, the physical and mechanical properties of agricultural (animal and plant) materials must be known. 1 Senior Researcher, Agricultural Engineering Research Institute (AEnRI), Agricultural Research Center (ARC), Dokki. Egypt. 2 Researcher, Animal Production Research Institute, (ARC), Dokki. Egypt. O Misr J. Ag. Eng., 36 (4): 1303 1318 BIOLOGICAL ENGINEERING Misr J. Ag. Eng., October 2019 1304 To preserve eggs during transport from farm to market, eggshells must be strong enough to prevent cracking (Altuntas and Sekeroglu 2008). Eggshell strength has-been described using various variables such as thickness of eggshell, shell stiffness and rupture force. Eggshells must be strong enough to prevent broking in order to preserve the embryo until hatching. (Altuntas, E. 2010). The various egg physical properties such as egg mass and volume, surface area, shell thickness and weight affect the mechanical properties of chicken eggs. The quasi‐static, undestructive compression of an egg between two parallel steel plates is a common technique for the measurement of the shell strength of a chicken egg. The strongest correlation was found between the physical and the mechanical properties of chicken eggs (De Ketelaereet et al. 2002). Calcium is one of the essential minerals in poultry nutrition. In addition to its vital functions as the main component of bone structure and participation in acid-base balance and enzymatic system, calcium is the also the main component of the eggshell. It is estimated that each egg contains 2.2g of calcium, present mainly in the eggshell. Ca supplementation is a key for eggshell quality, each eggshell contains up to 3g of Ca, so the diet of hens must contain adequate amount of Ca in efficiently utilizable form (Roberts 2010). Mineralized eggshell is formed of calcium carbonate (96%); the remaining components include organic matrix (2%), magnesium, phosphorus, and a variety of trace elements The eggshell membranes will secreting and assembling during approximately one hour, resulting meshwork of interlaced fibers is composed of roughly 10% collagen and 70–75% other proteins and glycoprotein’s containing lysine-derived cross-links which are organized into morphologically distinct inner and outer sheets that enclose egg albumen Egg size and the eggshell thickness are strongly related to each other (Hincke et al. 2012). While egg weight increases during the production period, eggshell thickness and breaking strength usually decrease. Eggshell quality depends on egg size and weight. Egg properties such as SI and shell thickness affect the proportion of damaged eggs during handling and transport (Anderson et al. 2004). These physical properties of eggs, and their resistance to damage through mechanical shock, can be characterized by measures such as rupture force, specific deformation, rupture energy and firmness (Altuntas and Yıldız, 2007). Calcium BIOLOGICAL ENGINEERING Misr J. Ag. Eng., October 2019 1305 supplementation is required in animal feeds, as most consist of grains and it's by products, which have very low calcium. Adequacy of the recommended quantities of dietary Ca for layers is still being studied. (Castillo et al. 2004). perceiving the valid NRC recommendations (1994) contradictory, carried out a research establishing the effect of 5 levels of Ca (from 2.93% to 4.82%) on production and quality of egg shell in a modern layer hybrid –white eggs, to determine the biologically optimal level to realize maximum production and egg shell quality. Based on research results, the authors reported that under given conditions, biologically optimal level of Ca necessary to realize the maximum production was 4.38%, for maximum egg shell quality 4.64%, and economically optimal level for maximum profit was 4.35% of Ca in diet. Many researchers in their studies start with the assumption which is becoming scientific proven fact, that the adequate Ca nutrition of laying hens does not include only the enough level of Ca in diet, but also enough source and particle size of Ca. Namely, it is considered that Coarser particles of Ca source are retained longer in the gizzard and are slowly being degraded and absorbed during this longer passage through digestive tract, whereas the smaller Ca particles pass faster through the digestive tract and therefore they get degraded/absorbed partially (Svihus, 2011). Limestone is the principle supplemental Ca source used in laying hen rations due to its abundant natural reserves, low cost and easy incorporation into layer feeds. Different aspects of shell quality were reported to be improved by the partial replacement of limestone with oyster shells in the diet (Roberts, 2010). Many factors influence eggshell quality, including the age of hens, strain of bird, nutrition, ambient conditions and diseases. About 95 % of the dry eggshell is calcium carbonate and, because of that, laying hens have a high dietary calcium requirement for shell calcification. The main source of calcium in hen diets is pulverized limestone. However, eggshell formation usually occurs at night when the hen is not eating, and satisfaction of needs is not adequate. It has been suggested that calcium absorption might be more sustained if the hen is given access to particulate calcium which might persist for longer in the gut after eating ceases (Roberts 2010). Coarser particle size of limestone led to an increase the soluble Ca at the end of BIOLOGICAL ENGINEERING Misr J. Ag. Eng., October 2019 1306 eggshell calcification in laying hens (Zhang and Coon, 1997). Replacing 50 % of ground limestone by coarse particle size limestone was found to be quite adequate in order to optimize eggshell quality (Lichovnikova (2007) recommended supplying two-thirds of the Ca in the diet as coarse particles to ensure eggshell quality in the last third of the laying period. (Zhang and Coon 1997) concluded that coarser particle size limestone with lower in vitro solubility was retained in the gizzard for a longer time, which may increase Ca retention. The change in the particle size of calcium sources has been studied with some positive results for the quality of eggshell (Lichovnikova, 2007; Skřivan et al., 2010) and bird bones when coarser particles of calcium sources are offered in the rations. (Saunders-Blades et al., 2009) presented the positive effects on eggshell quality in hens receiving a diet in which 60 % of pulverized limestone was replaced by two granular forms of limestone. By substituting 60 to 80% of lime with Coarse size lime particles in mixtures for nutrition of older layers, positive effects on the egg shell quality can be realized. (Skrivan et al., 2010) showed some possibilities of eggshell quality improvement using limestone of coarser particle size as a Ca supplement in the hen diet. Replacing 60-80 % of pulverised limestone by coarser particle size limestone had positive effects on eggshell quality. A slower solubilisation of sources of Ca would make Ca available during the time eggshell calcification and diminish bone Ca and p mobilization (Skrivan et al., 2010). Wang et al., (2014) Was writing a report that limestone with a Coarse particle size provided for Productive performance superior, egg quality and bone characteristics and is more suitable than oyster shell for practical applications in laying ducks. The aim of the present study was to compare the effects on egg production, eggshell and bone qualities using diets with different amounts of fine limestone replaced by coarse particles limestone at peak. MATERIALS AND METHODS The experimental work was done at El-Fayoum Research Station, Animal Production Research Institute, ARC, MOLAR The physical and mechanical properties of eggshells and bones were carried out at the Agricultural Engineering Research Institute, Agricultural Research Center, Ministry of Agriculture, Egypt. One hundred and twenty eight 32 BIOLOGICAL ENGINEERING Misr J. Ag. Eng., October 2019 1307 weeks old Golden Montazah chickens were randomly allocated to four groups (32 pullets per group were divided into four replicates) and housed in cages individually from 32 to 44 weeks of age. The differences between the groups were in the replacement percent of fine pulverized limestone by granular limestone of coarser particle size. The two particle sizes of limestone grit were o

misr journal of agricultural engineering

EFFECT OF LIMESTONE SIZE PARTICLES ON IMPROVING EGGSHELL AND BONE PHYSICAL AND MECHANICAL CHARACTERISTICS AT THE PEAK OF EGG PRODUCTION IN GOLDEN MONTAZAH CHICKEN