Egg weight
Average EW (Table 1) from T5 fed with 18.0% CP, 2700 kcal/kg diet ME and 2.5% Ca in prelay diet significantly (p<0.05) increased at 40
th week end and numerically higher at 24
th, 32
nd and 36
th weeks end than control and other groups. Higher EW observed in T5 might be due to high prelay energy and protein. Feeding pullets with higher protein in prelay diet significantly improved EW.
(Joseph et al., 2000) (Joseph et al., 2000) reported that higher dietary CP caused higher EW mainly due to increased AW and it is also related to the quantity of protein consumed. Consumption of an extra 1.0 g of protein per day increases EW by 1.4 g
(Bouvarel et al., 2011). Sujatha et al., (2014) reported that high prelay energy and protein diet resulted in heavier eggs. Present study also confirmed that 18.0% prelay CP produced heavier eggs. In present study, two prelay Ca levels (2.0 and 2.5%) were studied with 2700 kcal ME/kg and 18.0% CP. EW was higher in 2.5% Ca group than 2.0% Ca. However,
Nagarajan (1997) reported 1.0, 2.0 and 3.5% prelay Ca in White Leghorn pullets did not improve EW. There might be a slight influence of higher prelay Ca on EW.
Shell thickness
Significantly (p<0.01) highest ST (Table 2) was recorded in T3 and T5 than other groups at 24
th week. The 28
th week ST was significantly (p<0.05) higher in T2, T3, T4 and T5 than T0 and T1. The 32nd week ST was significantly (p<0.01) higher in T3 and T5, followed by T4, T2, T0 and T1. The 36th week ST was significantly (p<0.01) higher T5 and T3 than T0, T1, T2 and T4. The 40th week ST was significantly (p<0.01) higher in T5 than T3 and T4. The ST did not differ significantly during the overall period (24-40 weeks of age) but numerically higher ST was observed in T3 and T5.
Inclusion of 2.0-2.5% prelay Ca significantly (p<0.01) increased ST than 1.0% Ca.
Leeson et al., (1986) indicated a small increase in Ca retention in response to increased diet Ca and low Ca diets (0.9-1.5%) had a deleterious effect on early eggshell quality even common 3.5% Ca included in layer diet. Increase in dietary Ca two weeks before the first eggs’ appearance is essential to enhance medullary bone formation and the first eggs’ shell
(Bouvarel et al., 2011). Pavlovski et al., (2012) recommended 2.5% Ca in the pullet’s diet before entering the laying phase. In the present study, 2.5% prelay Ca significantly (p<0.01) maintained higher persistence in ST. Therefore, it is inferred that the prelay diet should include 2.5% prelay Ca. The hens laying eggs with thick shells retained more Ca than hens laying eggs with thin shells
(Clunies et al., 1992). Results indicated that prelay diet should contain 2.0-2.5% Ca to improve ST.
Yolk weight
Significantly (p<0.01) lowest overall YW was recorded in T4 and T5 than control and other groups (Table 3). Higher decreasing trend of YW in T4 and T5 might be due to increasing trend of percent AW observed in T4 and T5 containing higher CP (18.0%) than control and other groups (16.0%).
Almeida et al., (2012) reported significant interaction between dietary energy and protein on yolk proportion.
Shi et al., (2009) reported significant negative correlations of EW with percent YW confirmed in present study. Feeding of 2700 kcal ME/kg diet, 18.0% CP and 2.0-2.5% Ca in prelay diet significantly reduced per cent YW.
Albumen weight
Significantly (p<0.01) highest AW was recorded in T4 and T5 followed by T0, T1, T2 and T3 during overall period (Table 3). Better overall AW was observed in 18.0% prelay CP (T4 and T5). These results suggested some scope for slightly changing albumen proportion through dietary manipulation, as
Novak et al., (2006) reported. The 18.0% prelay CP caused higher AW than 16.0% prelay CP agrees with
Joseph et al., (2000), who reported increase in AW by 18.0% CP. Further, they reported diversion of additional nitrogen in a higher CP diet (18.0%) into egg formation.
Shi et al., (2009) reported significant positive correlations between EW and AW percentage confirmed in present study. Higher prelay CP (18.0%) might improve AW.
Shell weight
The 2.0 (T2 and T4) to 2.5% (T3 and T5) prelay Ca significantly (p<0.01) increased (Table 3) overall SW than 1.0% prelay Ca (T0 and T1). However, significantly (p<0.01) better SW was observed in 2.5% prelay Ca (T3 and T5) than 2.0% prelay Ca (T2 and T4). Significant increase in SW might contribute to EW improvement which is in agreement with
Farooq et al., (2001), who reported positive correlations between EW, SW and ST. The EW was significantly increased due to higher prelay protein (18.0% CP), energy (2700 kcal ME/kg) and Ca (2.5%).
Joseph et al., (2000) reported significantly higher SW in 18.0% prelay CP diet. This confirmed the positive relation between SW and EW. It was concluded that 2.0-2.5% prelay Ca significantly (p<0.01) improved SW than 1.0% Ca.
Shape index
Feeding of different nutrient density prelay diets did not affect egg SI (Table 3). These findings agree with
Babiker et al., (2010). Results indicated that the different nutrient density prelay diets did not influence egg SI.
Yolk index
The overall YI did not differ significantly (Table 3).
Duman et al., (2016) reported a significant negative correlation between SI and YI. Results indicated that feeding of different nutrient density prelay diet did not influence YI.
Albumen index
Albumen quality is an important indicator of egg freshness
(Yildirim et al., 2018). The different nutrient density prelay diets did not affect AI (Table 3). Numerical increase in the AI in T5 might be due to a slight numerical increase in SI because AI increased with increasing SI and a significant (p<0.05) positive correlation was determined between SI and AI
(Duman et al., 2016). The AI of an egg is an indication of its protein content. Results indicated that feeding of 2700 kcal ME/kg diet, 18.0% CP and 2.5% Ca in prelay diet helps to increase AI.
Haugh unit
Overall HU (Table 3) was apparently increased in T4 and T5. Inclusion of 18.0% CP with 2.0-2.5% Ca in prelay diet improves HU compared to 16.0% CP with 2.0-2.5% Ca. The HU improvement from T4 and T5 might be due to improved egg size observed in present study. In contrast,
Sujatha et al., (2014) observed no effect of prelay protein, energy and Ca on HU in their studies. The HU considers EW and albumen height and compares egg protein quality
(Monira et al., 2003 and
Monika et al., 2021). Higher the HU, better the quality of the egg is. Haugh unit indicates albumin height of an egg that signifies the protein content of the egg.
