Body weight gain
Feeding BPD did not change pullets BWG during 16-18 woa (Table 1). When pullets fed with BPD and different nutrient density layer diets, the layer diet containing 2500 or 2600 kcal ME/kg with 17.0 or 18.0% CP (T0 to T3) maintained BWG than 16.0 (T4) or 15.0% CP (T5). The BPD did not support layers BWG when subsequently fed with low CP (16.0 or 15.0%) during 19-40 woa. Decreasing dietary CP (12.0, 14.0 and 16.0%) lowered (p<0.02) layers BWG
(Novak et al., 2008) indicating role of dietary CP level in maintaining optimal WG during laying corroborates with the present findings. It confirmed that the BPD supported achieving BWG in layers fed with 2500 or 2600 kcal ME/kg with 18.0 or 17.0% CP during 19-40 woa but did not support BWG in layers subsequently fed with a low CP (16 or 15%) layer diet.
Feed consumption
Feeding same BPD to all groups (T0 to T5) did not change FC of pullets (Table 1) during prelay (16-18 weeks). Feeding different nutrient density layer diets (19-40 weeks) with same BPD indicating layer dietary CP and Ca levels did not change layers FC, but dietary ME changed FC (Table 1). The BPD maintained layers FC fed with
BIS (2007) specifications layer diet (T0) during 19-40 woa. Layers’ FC predominantly depends on dietary ME and require to adjusting dietary CP and ME because altering CP level without considering ME may result in nutrient imbalance
(Harms et al., 2000). Birds did regulate their FC according to energy level (
Zhang and Kim. 2013). Different dietary CP levels did not affect FC with isocaloric diet confirmed by
RamaRao et al., (2011). Different layer dietary CP
(Ribeiro et al., 2016) and Ca (Sudaryati, 2006) levels did not influence FC. Therefore, dietary ME affects laying hen’s FC. This study indicated that the higher dietary ME lowers FC and vice-versa in White Leghorn layers. Layers can be fed a 2600 kcal ME/kg diet with 18.0% CP and 3.0% Ca during 19-40 woa when fed with BPD to maintain FC.
Calcium, protein and energy intake
Daily CaI, PI and MEI during 16-18 and 19-40 woa are depicted in Table 2. Feeding of same BPD resulting similar FC in all groups did not influence pullets daily CaI, PI and MEI during 16-18 woa. Feeding of 3.0% layer Ca (T0 and T1) significantly (p<0.01) decreased CaI in layers (19-40 woa) than 4.0% (T2 to T5). Among T0 and T1, higher ME (2600 kcal/kg in T0) significantly (p<0.01) decreased FC than 100 kcal/kg less dietary ME (2500 kcal/kg in T1) leads to significantly (p<0.01) higher CaI in T1 than T0 indicating ME and Ca levels and proportion of FC govern layers CaI. Dietary ME in T2, T3, T4 and T5 was similar to T1 (2500 kcal/kg), which did not change FC and, thus, layers daily CaI.
RamaRao et al., (2013) recommended 3.68 g Ca/bird/ day in White Leghorn layers during 21-72 weeks of age reared in tropics without use of prelay Ca. Recently,
Lonkar et al., (2022a; 2022b) found that 2.5% prelay Ca supported 3.0% layer Ca for better productive performance, indicating best prelay Ca decreases layer Ca requirement.
Different layer CP (18.0, 17.0, 16.0, or 15.0%) feeding (Table 2) indicated that layers PI decreased with a reduction in CP from 18.0 to 15.0%. Further, PI changes with FC and FC is influenced by layer diet ME.
Bouvarel et al., (2011) also suggested that layer’s PI is determined primarily by ME that influences FC.
The present study indicated that 2500 or 2700 kcal ME/kg diet did not affect daily MEI in layers (Table 2). However, higher dietary ME caused lower FC and vice-versa. The ME levels influenced the FC without affecting daily MEI in layers.
Jeroch (2011) reported that laying hens can adjust their daily energy intake by increased FC corroborates with present findings.
Total egg number per hen
Significantly (p<0.01), lower TEN (Table 3) was recorded in T4 and T5 than T0 and other groups (T1, T2 and T3). Control T0 recorded the highest TEN than others. Feeding of low CP (T4: 16.0% and T5: 15.0% CP) led to fewer egg production while higher CP (T0, T1 and T2: 18.0% and T3: 17.0% CP) did not affect TEN. Layers from T4 and T5 produced 11.91 and 12.45 fewer eggs than control T0. Similarly,
Shim et al., (2013) and
Ribeiro et al., (2016) reported that feeding of low CP in layers decrease egg production. It was also found that the change in either ME or Ca level in layer diet did not affect the EN corroborates with
Harms et al., (2000); Zhang and Kim (2013) and
Sudaryati (2006) who found that dietary ME did not affect egg production. Feeding BPD (16-18 woa) and different layer diets (19-40 woa) indicated that a BPD supported egg production for 18.0 or 17.0% than 16.0 or 15.0% CP.
Williams et al., (2000) suggested that higher EP could be associated with positive energy and protein balance during the prelay period. Moreover, present result indicated that the layers can also be fed 17.0% CP (1% lower than
BIS 2007 specification) diet (19-40 woa) when fed with a BPD (16-18 woa).
Hen day egg production
Change in dietary ME from 2600 to 2500 kcal/kg, CP from 18.0 to 17.0% and Ca from 3.0 to 4.0% in laying diet among T0, T1, T2 and T3 did not show a significant difference (p<0.01) in HDEP during 17-40 woa (Table 3). Inclusion of low CP in layer diet from T4 (16.0%) and T5 (15.0%) resulted in a significant decrease (p<0.01) in HDEP.
Shim et al., (2013) confirmed feeding low CP in layers decreases egg production.
Harms et al., (2000) and
Zhang and Kim (2013) reported that dietary energy did not affect EP.
Sudaryati (2006) reported that the dietary Ca did not significantly affect EP. It is recommended to use BPD along with
BIS (2007) specifications layer diet to support good HDEP. Moreover, the BPD allowed to reduce layer CP by 1.0% (18.0 to 17.0%).
Feed efficiency
Inclusion of low CP (T4: 16.0% and T5: 15.0% CP) significantly (p<0.01) resulted in poor FCDE (Table 3) than higher CP (T0, T1 and T2: 18.0% and T3: 17.0% CP). The 17.0% CP (T3) lower than BIS (2007) (18.0%) in T0 layer diet was supported by BPD for maintaining FCDE. The best (p<0.01) feed efficiency was recorded at 18.0% dietary CP
(Ribeiro et al., 2016), while poor feed efficiency was recorded at 15.05% CP
(Shim et al., 2013). The FCDE was not affected by 3.0 or 4.0% of Ca in layer diet.
Performance efficiency index and egg feed price ratio
The BPD feeding with
BIS (2007) specification layer diet (T0) improved PEI than others (Table 4). Layers fed with low (16.0% and 15.0%) CP (T4 and T5) decreased PEI than others. Higher EN and less FC in layers fed with
BIS (2007) specification layer diet (T0) numerically increased EFPR (Table 4).
Lonkar et al., (2022a) reported better PEI and EFPR by feeding best prelay with
BIS (2007) layer diet and economical in White Leghorn layers corroborates with present findings.