Effect of Dietary Supplementation of L-Valine on Growth, Immunocompetence Traits, Carcass Quality and Meat Composition of Turkey Poults

Background: Valine is an important amino acid and its deficiency may result in reduced growth and immunity. However, studies in turkeys are limited. Hence a study was conducted to assess the effect of supplemental L-valine (L-val) on growth performance, immunocompetence traits, carcass quality and meat composition of turkey poults. Methods: Day old turkey poults (n= 96) were distributed into four dietary treatment groups:T 1 -basal diet, T 2 -T 1 +0.04% L-val, T 3 - T 1 +0.08% L-val , T 4 - T 1 +0.12% L-val, having three replicates of 8 birds each. Result: No significance difference observed in average weekly body weight (BW), body weight gain (BWG) and feed conversion ratio (FCR) of birds throughout experimental period except at 7 th week where T 2 and T 3 poults had a significantly higher (P<0.05) BW, BWG and significantly better (P<0.05) FCR. HA titre was significantly higher (P<0.05) in T 3 . Per cent breast weight was significantly higher (P<0.05) in T 3 . Percent crude protein level in breast muscle of turkey poults was significantly higher (P<0.05) in T 3 . Thus, supplementation of L-val @ 0.08% in turkey poults resulted in significantly better humoral immune response, higher percent breast yield and higher percent crude protein in breast meat.


INTRODUCTION
Turkey is a rapidly growing bird and requires more energy, protein, vitamins and minerals than chicken.The poultry industry has already been dealing with fluctuating spikes in the price of various feed ingredients.W hen the cost of protein-rich feed ingredients goes up, the reduction of dietary crude protein via the use of commercially available amino acids becomes an effective formulation strategy that can reduce diet costs, maintain broiler performance and not interfere with feed milling throughput.An effort to decrease production costs can be accomplished via supplementation with L-lysine, DL-methionine, L-threonine and L-valine.Reduction of dietary protein level and use of synthetic amino acids are often suggested to reduce the feed cost and also to contain the environmental pollution of nitrogen.
Valine is 4 th amino acid in corn and soybean meal-based diets (Baker et al. 2002;Corzo et al. 2007Corzo et al. , 2009;;Rostagno et al. 2011).Valine deficiency in broilers may result in reduced growth performance, carcass quality and immune response (Kumar et al. 2015;Nascimento et al. 2016;Kaplan and Yildiz, 2017) respectively.Studies have been conducted on dietary supplementation of L-valine in broilers performance (Corzo et al. 2007;Azzam et al. 2015) but such studies are lacking in turkeys.Hence, the present study was designed with the obj ective to study the effect of supplementation of L-valine on growth performance, immunocompetence traits, carcass quality and meat composition of turkey poults.
Effect of Dietary Supplementation of L-Valine on Growth, Immunocompetence Traits, Carcass Quality and Meat Composition of... Husbandry, DUVASU, Mathura after due approval of the IAEC on 96-day-old turkey poults.Feed prepared as per NRC, 1994 was procured from CARI, Izatnagar.

Experimental design
Ninety-six-day old straight run turkey poults were randomly distributed into four dietary treatments comprising three replicates and eight poults in each replicate.The feed was offered ad lib in different experimental groups.The birds were housed in deep litter system.Water was offered ad lib.The dietary treatments during the experimental period of 8 weeks were as follows-T 1 : Control basal diet as per breed requirement with no addition of L-valine.T 2 : Basal diet + 0.04% L-valine.T 3 : Basal diet + 0.08% L-valine.T 4 : Basal diet + 0.12% L-valine.

Nutrient composition
The composition of the basal diet (Turkey Starter) has been depicted in Table 1 and the amino acid composition of the basal diet has been portrayed in Table 2.The nutrient chemical composition of the experimental feed is given in Table 3.

Body weight and feed conversion ratio
Weekly body weight and replicate wise feed consumption was recorded.Thereafter, phase wise (0-4 weeks, 4-8 weeks and 0-8 weeks) body weight gain and phase wise feed conversion ratio were calculated at the end of the experiment.

Antibody response to goat red blood cells (GRBC)
The microtitre plate haemagglutination procedure as described by (Siegel and Gross. 1980) with slight modifications was followed to measure total HA antibody titres in turkey poults on day zero and day 5 th post injection with 1 ml of 1% (V/V) of GRBC suspension.

Immunization and harvesting of immune serum
1 ml of 1% (V/V) of GRBC suspension was injected to 8 poults of each treatment group.About 3 ml of blood on 0 and 5 th day post immunization (dpi) were collected from wing vein.The blood was endorsed to clot in an incubator having temperature of 37C for 1 hour.The blood was endorsed to retract after detaching it from sides of its container and left at 4C.Centrifugation of blood was carried out at 2000 rpm for 5-10 minutes as it facilitated rapid collection of serum.The antibody titre was determined by HA methods (Vander Zijpp, 1983;Siegel and Gross, 1980).Antibodies were determined by means of a mercaptoethanol (ME) HA test as per the method described by Martin et al. (1989) with slight modification.

Carcass quality traits
At the time of slaughter, 16 birds were taken at 8 weeks of age for studying various slaughter traits viz.pre-slaughter fasting shrinkage in live weight (%), dressing (%) and total ready-to-cook yield (%).

Proximate composition of breast (pectoralis major) muscle of turkey poults
At 8 weeks of age, 4 birds from each treatment group (2 male and 2 female) were sacrificed and there after fresh samples of breast (pectoralis major) was processed and analysed for moisture, crude protein (CP), ether extract (EE), total ash, calcium and phosphorous (AOAC, 1990).

Statistical analysis
The data pertaining to various parameters were analyzed statistically as per the standard procedure (Snedecor and Cochran, 1989) and difference between the treatment means were obtained by using Duncan multiple range test (Duncan, 1955).

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 BW G changes indicated that there was no significant difference in average weekly BW and BW G of birds throughout experimental period except at 7 th week.T2 and T3 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 BW G 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

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 T2 and T3 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   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 BW G better in the valine supplemented group.In the present study too, BW G was comparatively higher in all the valine Effect of Dietary Supplementation of L-Valine on Growth, Immunocompetence Traits, Carcass Quality and Meat Composition of...   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 T3 as compared to T 1 and T2 treatment groups and numerically higher than T 4 treatment groups (Table 8).Similarly, IgG response was better in T3 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 T3 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 signiûcantly 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, Effect of Dietary Supplementation of L-Valine on Growth, Immunocompetence Traits, Carcass Quality and Meat Composition of...  with triiodothyronine (T3) 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).

CONCLUSION
The present study indicated that dietary supplementation of L-valine @ 0.04% and 0.08% resulted in better growth performance.The present study also showed that dietary supplementation of L-valine @ 0.08% leads to better humoral immune response, an increase in per cent breast yield and percent crude protein level in breast meat.

Table 1 :
Alves et al. (2017)013)et (Turkey starter).Effect of Dietary Supplementation of L-Valine on Growth, Immunocompetence Traits, Carcass Quality and Meat Composition of... 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 BW G 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.

Table 3 :
Chemical composition of turkey starter feed.

Table 4 :
Effect of L-valine supplementation on the average weekly body weight (g) of Turkey poults during 0-8 weeks of age.

Table 5 :
Effect of L-valine supplementation on the average weekly body weight gain (g) of turkey poults during 0-8 weeks of age.

Table 2 :
Amino acid composition of basal diet (Turkey starter).

Table 6 :
Effect of L-valine supplementation on the weekly feed conversion ratio of turkey poults during 0-8 weeks of age.

Table 7 :
Effect of L-valine supplementation on feed conversion

Table 8 :
Effect of L-valine supplementation on the humoral immune

Table 10 :
Effect of L-valine supplementation on chemical composition of breast muscle (pectoralis major) of turkey poults at 8 weeks of age.

Table 9 :
Effect of L-valine supplementation on the cut up-parts of turkey poults at 8 weeks of age (% dressed weight).