Optimization of digestible valine requirements for growth performance, carcass and immunological parameters in commercial boilers

Introduction

In order to meet the growing demand for poultry products, worldwide poultry production has grown significantly over past 50 yrs. Feed constitutes around 70% of the overall expense of broiler production. Increasing concerns regarding environmental effects of farming, including nitrogen as well as phosphorus contamination, as criteria in feed formulation, feeding optimum, as well as balanced nutrients, have an essential role in precision nutrition. Corn, as well as SBM (soybean meal), contributes to majority of broiler chicken diets. Broiler chicks exhibit rapid growth and generally consume diets rich in protein or AA (ERS, USDA, 2001) [5] . Such diets' amino acid (AA) concentrations are insufficient to satisfy needs of today's rapidly increasing broilers in order for them to maximize their full genetic potential. In diets as per corn and SBM, valine is fourth limiting AA. Protein is a vital element of all animal tissues and significantly influences the growth performance of chickens (Kamran et al., 2004) [8] . If broiler diets lack this AA, growth performance would be hampered. The emphasis currently is on meeting the requirements of this AA in broiler diet as feed-grade valine became commercially available. In diets lacking animal protein ingredients, Val can be next-limiting to threonine. Its primary biological role is to aid in muscle protein synthesis, or growth performance. Val is also a limiting amino acid in broilers, and a minimum digestible Val to lysine ratio of 80% is recommended. As feed grade L-Val is now available, the feed industry has an opportunity to further lower the quantity of protein in the diet.

Materials and Methods

A six-week growth trial has been performed in commercial broilers using 250-day-old men broiler chicks (Ven Cobb-400) with five dietary treatments using a completely randomized design (CRD). Chicks been procured, their wings have been banded as well as weighed, and they were then randomly distributed to five treatments, each with ten replicates and 5 chicks in every replicate. Throughout experimental period, chicks have been raised in battery brooders with electrical heating under ideal brooding conditions. 1.

Experimental diets

Collection of data

Body weight of every bird has been once noted at the end of each phase, which included the pre-starter (0-14 days), starter (15-28 days), finisher phase (29-42 days), up to 6 weeks of age. Amount of feed consumed by every bird has been noted replicate-wise for each phase. The feed intake per unit body weight gain from 0 to 6 weeks of age has been utilized to compute feed conversion ratio (FCR) for each phase. In order to study the immunity parameters, ten blood samples have been randomly gathered from every replicate for each dietary group at 28 th and 42 nd days of life. The HI (heamagglutination inhibition) test was used to ascertain NDV-specific antibodies in the chicks' sera, which were then denoted as log2 titers (Allan et al., 1978) [1] . The measurement of CBH (cutaneous basophilic hypersensitivity) to PHA-P (phytohaemagglutinin phosphate) was used to assess CMI (cell-mediated immune) response. One bird has been selected at random from each replication on the 42 nd day of the trial to test the CMI. A micrometer was used to measure the thickness of web between 3rd and 4th interdigital spaces of left and right feet. Left web (control) had an injection of 0.1 ml of PBS (phosphate buffer saline), while right foot's web had an injection of 100µg of PHA-P suspended in 0.1 ml of PBS. A micrometer has been used to measure web thickness of both feet 24 hrs after injection, alongside the CBH has been then computed utilizing a formula (Edelman et al., 1986) [6] . In order to evaluate the giblets' characteristics (liver, heart, and gizzard) and the weight of their immune organs (spleen and bursa), which have been denoted in grams per kilogram of live body weight, 10 birds from every dietary group have been slaughtered at end of experiment. Data has been analyzed utilizing one-way ANOVA in 15th version of SPSS (Statistical Package for Social Sciences). Duncan's multiple range test (Duncan, 1955) [4] has been used to analyze differences between treatment means at p<0.05.

Results and Discussion

Growth performance Body weight gain Supplementation of digestible valine at 0.885, 0.787, & 0.712 percent throughout pre-starter, starter, as well as finisher phases, respectively (75 percent of digestible lysine), resulted in a statistically significant increase (p<0.05) in BWG during weekly, pre-starter, as well as finisher phases of commercial broilers fed corn-SBMbased diets (Table 2). Total body weight gain is significantly (p<0.05) greater in group fed diet having 0.826, 0.735, & 0.665 percent digestible valine (70 percent digestible lysine) in pre-starter, starter, as well as finisher phases, correspondingly. Lowest body weight gain was recorded at 0.708, 0.630, & 0.570 percent digestible valine (sixty percent of digestible lysine) fed diet than 100% Cobb recommended digestible valine 0.89, 0.81, & 0.73% fed group in pre-starter, starter, as well as finisher phases, respectively, in commercial broilers. This is contrary to results of Goodgame et al. (2011) [7] , who noted a rise in body weight gain by 0.90% and 0.84% dietary Val supplementation during 1-21d and 21-35 d of Cobb broilers.

Feed intake

Phase-wise feed intake demonstrated significant (p<0.05) rise in feed consumption throughout pre-starter phase in group T 2 broilers' diet, which included 0.89 percent digestible Val (75 percent of digestible lysine) (Table 2). Nonetheless, there has been no statistically significant difference (p>0.05) in feed intake throughout starter as well as finisher periods in commercial broilers provided with diets containing varying concentrations of digestible Val. Lowest cumulative feed intake was observed in broilers fed digestible Val as 0.708, 0.630, & 0.570 percent (60 percent of digestible lysine) throughout pre-starter, starter, as well as finisher phases, correspondingly, in group (T 5 ) in commercial broilers fed corn-SBM-based diets. These findings are from Rodehutscord et al. (2005) [9] . Some studies proposed that dietary Val supplementation has significantly (p<0.05) enhanced feed intake in commercial broilers (Corzo et al., 2007) [2] .

Feed conversion ratio (FCR)

Phase-wise FCR values in current research showed that significantly (p<0.05) better FCR has been seen in groups fed 0.767 percent digestible valine (65 percent of digestible lysine) throughout pre-starter and 0.630 & 0.570 percent digestible valine (sixty percent digestible lysine) throughout starter as well as finisher phase in commercial broilers (Table 2). This is in concurrence with results of Corzo et al.

(2004) [2] , Rodehutscord et al. (2005) [9] . The studies suggested that the 0.45% and 0.67% dietary valine supplementation significantly (p<0.05) improved FCR in commercial broilers. In present study, dietary valine of 0.826, 0.735, and 0.665% recorded poorer FCR throughout pre-starter, starter, as well as finisher phases, respectively, in broilers.

Carcass parameters (Giblet weights)

Liver weight has been "significantly (p<0.05) affected by dietary Val supplementation in broiler diets (Table 3). Lower liver weight has been noted in treatment group (T 4 ) supplemented with digestible valine" and sixty-five percent of lysine than in other dietary groups. This is based on results of Selvarasu et al. (2016) [10] Immune parameters "Supplementation of digestible Val in corn-SBMbased diets did not significantly (p>0.05) affect weights of bursa as well as spleen in" this current study (Table 4). Humoral immunity assessed in relation to antibody titers against NDV at 28 th day & 42 nd day has not been significantly (p>0.05) influenced by dietary variations in digestible Val. However, humoral immune response to NDV at 42 nd day on the supplementation of digestible Val at 0.708, 0.630, & 0.570 percent (60 percent of digestible lysine) in pre-starter, starter, as well as finisher phases, respectively, fed group showed higher antibody titer. However, variation in antibody titer values was observed at 28 th day and 42 nd day age in broilers fed different concentrations of digestible Val, but not statistically significant (p>0.05) among groups. CMI "(cell-mediated immune) response evaluated using DTH (delayed-type hypersensitivity) reaction to PHA-P, quantified by SFT (skin fold thickness) in broilers. No significant difference (p>0.05) has been seen in CMI response to PHA-P inoculation because of variation in digestible Val concentration in diet".

Conclusion

The findings of present study indicate that a digestible valine level equivalent to 70 percent digestible lysine throughout the pre-starter, starter, as well as finisher phases (0.826, 0.735, and 0.665%, respectively) is optimal for maximizing economic returns while maintaining growth performance, carcass quality, and immune function in fastgrowing commercial broilers.

Acknowledgement

AcknowledgementsThe present experiment was carried out on commercial broilers with financial support from M/s Evonik (SEA) Pvt. Ltd. Singapore, for which the authors are grateful.

References

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