Weekly body weight and body weight gain
The weekly body weight (BW) and weekly body weight gain (BWG) of turkey poults from 0-8 weeks have been presented in Table 4 and 5 respectively. Data on BW and BWG changes indicated that there was no significant difference in average weekly BW and BWG of birds throughout experimental period except at 7
th week. T
2 and T
3 group birds had significantly higher (P<0.05) BW and BWG compared to the other two treatment groups at 7
th weeks of age.
Baker et al., (1996) noted that there was increase in BWG of chicken with increasing levels of digestible valine and the BWG was highest with supplementation of 1.06% digestible valine.
Alves et al., (2017) reported that BW in meat-type quails was highest when the digestible Val: Lys ratio was 0.80 followed by 0.85. In the present study, the valine percent in T
2 and T
3 was 1.21 and 1.25 and the digestible Val: Lys ratio in T
2 and T
3 as determined by digestibility coefficients was 0.82 and 0.85 and the body weight in T
2 followed by T
3 was apparently higher compared to the other treatment groups throughout the experiment.
Corzo et al., (2007) noted that broilers were more sensitive to L-valine supplementation pertaining to BWG better in the valine supplemented group. In the present study too, BWG was comparatively higher in all the valine supplemented groups compared to the control group during the entire growth phase.
Tavernari et al., (2013) observed that BWG was highest in broilers when the digestible Val: Lys ratio was 0.81. Similarly,
Alves et al., (2017) reported that BWG in meat-type quails was highest when the digestible Val: Lys ratio was 0.80 followed by 0.85. The digestible Val: Lys ratio in T
2 and T
3 were 0.82 and 0.85 in the present study.
Weekly feed conversion ratio and phase-wise feed conversion ratio
The weekly and phase-wise feed conversion ratio (FCR) of turkey poults are presented in Table 6 and 7, respectively. Results indicated that there was no significant difference in FCR of birds during the entire experimental period except at 7
th week and FCR was significantly better (P<0.05) in T
2 and T
3 as compared to T
1 and T
4 group. Results indicated that there was no significant difference in FCR of birds during 0-4 weeks and during 4-8 weeks of age. However, when FCR was calculated during 0-8 weeks of age, significantly better (P<0.05) FCR was observed in T
2 and T
3 than T
1 and FCR of T
4 group was comparable to that of T
1, T
2 and T
3.
Corzo et al., (2007) noted that broilers were more sensitive to L-valine supplementation pertaining to FCR as FCR was better in valine supplemented group. Similarly, in the present study, FCR was comparatively better in all the valine supplemented groups compared to the control during different phases of growth.
Alves et al., (2017) reported that FCR in meat type quails was better when digestible Val: Lys ratio was 0.80 followed by 0.85. In the present study, the Val: Lys ratio in T
2 and T
3 was 0.82 and 0.85. Further, the FCR in T
2 followed by T
3 was better compared to the other treatment groups during the entire growth phase. The better FCR in valine supplemented groups compared to the control group may be due to better amino acid balance resulted in better protein accretion in the body.
Humoral immune response
Data on humoral immune response revealed that HA titre was significantly higher (P<0.05) in T
3 as compared to T
1 and T
2 treatment groups and numerically higher than T
4 treatment groups (Table 8). Similarly, IgG response was better in T
3 group as compared to the other treatment groups 8 weeks of age. In addition, HA, IgG and IgM titre values in 0.04%, 0.08% and 0.12% L-valine supplemented groups were apparently higher than the control group. This agrees with the results obtained by
Daware et al., (2018) who noted that dietary supplementation of L-valine @ 0.01, 0.04, 0.08 and 0.12% in broilers resulted in higher ND titres compared to control. In the same experiment, it was also observed that 0.08% dietary valine supplementation elicited significantly higher ND titre compared to control. Branched chain amino acids (BCAA) including valine, isoleucine and leucine have the greatest potential to modulate immune responses among the amino acids in broilers
(Konashi et al., 2000) and play critical role in regulation of immunity against diseases in humans and in animals
(Nie et al., 2018).
Carcass quality traits
Results pertaining to the yield of cut-up-parts of the carcass at 8 weeks of age have been expressed as a percent yield of the eviscerated weight of the carcass in Table 9. Breast percent was significantly higher (P<0.05) in the T
3 as compared to T
1 and T
2 and numerically higher than the T
4 group. Statistical analysis of the data revealed there was no significant difference observed in other cut-up-parts among the different treatment groups. The present findings are similar to
Daware et al., (2018) who also reported that dietary supplementation of L-valine in broiler diet did not affect eviscerated yield but supplementation of 0.04, 0.08 and 0.12% L-valine in broilers significantly improved (p<0.05) breast yield in broilers at the end of sixth week of age. Similar to present findings, there was significantly higher breast yield and breast meat weight by dietary valine supplementation in broiler diet
(Nascimento et al., 2016).
Chemical composition of breast (Pectoralis major) muscle
Results pertaining to yield of proximate analysis of breast muscle of the carcass at 8
th week of age are presented in Table 10. Per cent crude protein level in breast muscle of turkey poults were significantly higher (P<0.05) in T
3 as compared to T
1 and numerically higher than T
2 and T
4 treatment groups. These results may be because serum concentration of triiodothyronine (T
3) increased significantly on L-valine supplementation compared to the control group
(Azzam et al., 2015; Carew et al., 1998). Thyroid hormones are recognised as the key metabolic hormones of the body, with triiodothyronine (T
3) being the most functionally active form. The serum concentration of thyroid hormones is associated with protein synthesis and energy production
(Hornick et al., 2000; Smith et al., 2002).