Effect of phytase supplementation with graded crude protein levels on carcass characteristics of pratapdhan chicken

Introduction

Poultry farming is a rapidly evolving segment of the global agricultural landscape, representing a vital source of animal protein, income generation and rural development. Encompassing the breeding and management of domesticated birds such as chickens, ducks and turkeys, this sector caters to the escalating demand for meat and eggs driven by population growth and shifting consumer preferences worldwide (Mottet et al. 2007) [4] . The intensification of poultry production, characterized by advances in genetics, nutrition and health management, has transformed it into a cornerstone of food security, particularly in developing countries. A major concern in poultry nutrition is lowering protein and energy levels in feed to enhance sustainability and reduce production expenses. However, feeding birds with diets low in crude protein (CP) and metabolizable energy (ME) often leads to reduced growth rates, poorer feed efficiency and increased fat accumulation. Supplementing low-CP diets with essential amino acids can help maintain growth performance, even under challenging health conditions. Yet, according to Liu et al. (2017) [2] , precisely meeting the amino acid needs of poultry remains exact mechanism behind phytase's ability to enhance prececal amino acid digestibility (pcAAD) is not fully understood (Selle et al. 2006 [8,7,6] , complex and adjusting the balance between starch and protein in the diet might offer a more effective solution. Enzyme supplementation, particularly with phytase, is considered a promising approach to achieve this balance. Although the evidence shows that phytase consistently improves pcAAD. This improvement potentially allows for further reduction of dietary CP without compromising performance. Studies have demonstrated that phytase addition boosts body weight gain, overall carcass weight and breast muscle mass in broilers fed lysine-deficient diets (Selle et al., 2006; Walk and Rao et al. 2019) [8,12] . Moreover, phytase at 1,500 FTU/kg has been found to offset the negative effects on feed conversion ratio when broilers are given diets with CP lowered by 15 g/kg compared to standard protein levels. In summary, poultry farming remains integral to food and nutritional security globally and in India. Leveraging enzyme supplementation, particularly phytase, alongside judicious management of dietary protein offers promising pathways to enhance the productivity of indigenous breeds like Pratap Dhan. Such approaches not only improve growth performance and feed efficiency but also contribute to sustainable and economically viable poultry production systems. Continued research and development in these areas will be essential for meeting the rising demand for poultry products while addressing environmental and resource challenges.

Materials and Methods Experimental birds and diets

The present study was conducted using 200 day-old, straightrun Pratapdhan chicks obtained from the AICRP on Poultry Breeding, Rajasthan College of Agriculture, Udaipur. The chicks were randomly assigned to five dietary treatment groups, each with four replicates of 10 birds. They were reared under a deep litter system following standard management practices. The experimental diets aimed to evaluate the effect of phytase supplementation combined with graded crude protein levels on the growth and carcass traits of Pratapdhan chickens. The chicks were fed five different iso caloric experimental rations containing five different levels of crude protein viz. 19, 18 and 17%. The experimental diets comprised of Maize, Soyabean De Oiled Cake (DOC), De oiled Rice Bran (DORB), Rice bran oil, Dicalcium Phosphate and vitamin mineral premix as depicted in Table - At the end of the trial, eight birds from each treatment group were slaughtered to evaluate carcass traits. The parameters measured included live weight (g), dressed weight (g), dressing percentage, eviscerated weight and giblet weight. Additionally, two male Pratapdhan chickens from each treatment group were randomly selected at the end of the feeding trial. These birds were fasted for 24 hours with free access to water, weighed and then slaughtered to determine internal organ weights (heart, liver and gizzard) along with dressed weight. The organ weights were expressed as a percentage of live body weight.

Statistical Analysis

The observations recorded during the experiment was statistically analysed by using standard procedure for analysis of variance of CRD (Completely Randomized Design) as suggested by Snedecor and Cochran (1994) [10] .

Results and Discussion

All dietary treatments were formulated to be iso-caloric, with metabolizable energy values ranging from 2805 to 2811 kcal/kg of diet. However, the crude protein (CP) levels were adjusted to 20%, 20%, 19%, 18%and 17% in T 1 , T 2 , T 3 , T 4 and T 5 , respectively, with phytase supplementation included in treatments T 2 through T 5 . All other nutrients in the experimental diets were maintained within the normal recommended ranges across treatment groups (Table 1). The carcass traits are presented in Table 2 and illustrated in Figure 1. The data with respect to carcass traits of Pratapdhan chicks is presented in presented in Table 2 and depicted graphically in Figure 1. The parameters evaluated included live weight, dressed weight, eviscerated weight, dressing percentage, giblet weight and organ weights expressed as a percentage of live weight. At the end of the experimental period one male from each replicate was sacrificed to study carcass traits of Pratapdhan chicks, thus four birds from each treatment group were used for the carcass studies. The mean live weight values were 712.20±1.65, 771.93±0.91, 811.11±0.70, 740.71±0.63and 726.08±0.41 for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. The live weight was significantly highest in T 3 , followed by T 2 , T 4 and T 5 , with the lowest value observed in T 1 . The comparatively higher body weights observed in this trial may be attributed to the fact that slaughter birds were male chickens, which generally attain greater body mass than the combined average weight of mixed-sex flocks. Across treatments, the dressed weight averaged 621.25ᵇ±0.05 g, 619.00ᶜ±0.70 g, 728.82ᵃ±0.64 g, 614.75ᵈ±0.45 g and 611.00ᵉ±0.41 g for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. Significantly highest dressed weight was recorded in T 3 as compared to other treatment groups. The pronounced advantage observed in T 3 and T 1 reflects enhanced carcass yield and muscle deposition, most likely attributable to improved dietary nutrient assimilation and utilization efficiency. The mean eviscerated weights were 531.00±0.41g, 535.00±1.08g, 622.00±0.58 g, 542.00±0.71 g and 532.30±0.48g for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. The mean eviscerated weight was significantly highest in T 3 followed by T 4 , T 5 , T 2 and lowest in T 1 . However, the difference amongst T 5 , T 2 and T 1 was found to be nonsignificant.

The mean giblet weights were 48.44±0.82 g, 49.80±0.33 g, 55.92±0.31 g, 50.29±0.75 g and 43.15±0.68 g for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. Giblet weight was significantly highest in T 3 followed T 4 , T 2 , T 1 and lowest in T 5 . However, the difference between T 4 , T 2 and T 1 was found to be nonsignificant. The dressing percentage varied significantly among treatments, with mean values of 87.23±0.21, 80.19±0.08, 89.86±0.14, 83.00±0.10 and 84.15±0.60 for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. The highest dressing percentage was recorded in T 3 followed by T 1 , T 5 , T 4 and lowest in T 2 . The mean eviscerated percentages were 74.55±0.22, 69.30±0.09, 76.68±0.12, 73.13±0.15and 73.31±0.08 for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. The eviscerated percentage was significantly highest in T 3 followed by T 1 , T 5 , T 4 and lowest in T 2 while the difference in T 5 and T 4 was found to be non-significant. The mean heart weights expressed as a percentage of live weight, were 0.79±0.03, 0.74±0.04, 0.77±0.04, 0.74±0.03and 0.83±0.02 for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. The differences were found to be statistically non-significant. The mean liver weights were 2.72±0.21, 2.71±0.16, 2.73±0.15, 2.79±0.19and 2.77±0.15 for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. When expressed as a percentage of live weight, liver weight was highest in T 4 and T 5 , followed by T 3 and T 1 and lowest in T 2 . However, the differences among treatments were statistically non-significant. Evaluation of gizzard weight revealed mean values of 4.06±0.02, 3.18±0.06, 3.72±0.03, 3.73±0.06and 3.53±0.05 for T 1 , T 2 , T 3 , T 4 and T 5 , respectively. The gizzard weight was significantly highest in T 1 , followed by T 4 and T 3 and lowest in T 5 and T 2 . Differences between T 3 and T 4 were minor and statistically non-significant, suggesting similar gizzard development under these treatments. The findings of Kriseldi et al. (2021) [1] broilers were fed corn-soybean meal-based diets with either standard or increased nutrient density, supplemented with phytase at 4,500 FTU/kg. The increased nutrient density diets contained slightly higher levels of digestible amino acids (SAA, Lys, Thr, Val, Ile) and AMEn compared with the control diets. Phytase inclusion, alone or combined with higher nutrient density, significantly improved breast meat yield and overall carcass quality. These findings demonstrate that phytase can positively influence carcass characteristics, supporting both growth and meat accretion beyond its classical role in phosphorus and calcium utilization.

The results of this study are supported by the findings of Zeleke et al. (2022) [13] , who evaluated the effect of extracted phytase supplementation on Cobb 500 broilers were fed diets supplemented with phytase at 0, 300, 600 and 1200 FTU/kg for 42 days in a completely randomized design. The inclusion of phytase significantly influenced carcass characteristics, particularly dressed weight and breast weight, which were higher in birds fed phytase-supplemented diets compared to the control group. While most other carcass components remained similar among treatments, the improved dressed and breast weights indicate that phytase can enhance meat yield even under standard dietary conditions. These effects are likely associated with better nutrient utilization and protein efficiency mediated by phytase supplementation. Comparable results were observed by Sampath et al. (2023) [5] , where Ross-308 broilers were fed standard or phosphorusand calcium-deficient diets supplemented with graded levels of exogenous phytase (250, 500, 1000, 1500 and 3000 U/kg) from starter (1-7 d) to finisher (21-35 d) phases. Broilers receiving phytase-supplemented diets exhibited significant improvements in gizzard weight and breast muscle development, alongside enhanced carcass quality traits such as breast meat yield. These results indicate that phytase not only improves growth performance and nutrient utilization but also positively affects carcass and meat quality in Pratapdhan chicken, with 1000 U/kg or higher levels providing the most pronounced effects. A study by Mahmoud et al. (2024) [3] where Hubbard broilers were fed standard basal diets supplemented with graded levels of phytase (50, 75, 100, 150 and 200 g/ton) from day 1 to day 35. The inclusion of higher doses of phytase (150-200 g/ton) significantly improved carcass yield, breast meat protein percentage and reduced abdominal fat, while lower doses (50-100 g/ton) showed comparatively smaller effects. These findings confirm that phytase positively influences carcass characteristics and meat composition without compromising bird health. Vasanthi et al. (2023) [11] reported exceptionally high dressing percentages of 90.50% in Siruvidai males and 88.85% in females at 16 weeks of age under farm conditions. These values are comparable to those observed in the present study, although the birds evaluated belonged to different genetic groups. This indicates that high dressing yields can be achieved across diverse poultry types, while also reflecting the inherent variability in carcass traits among breeds. These findings suggest that while phytase can enhance certain carcass traits, the effects may vary depending on factors such as diet composition, phytase dosage and Pratapdhan chicken genetics.

Acknowledgement

AcknowledgmentThe authors are thankful to Head, Department of Animal Production and ICAR-AICRP on poultry breeding project for providing facilities during the experiment to carried out the research work.

References

1. Kriseldi R, Bedford MR, Dilger RN, Foradori CD, MacKay L, Dozier WA III. Effects of phytase supplementation and increased nutrient density on growth performance, carcass characteristics and hypothalamic appetitive hormone expression and catecholamine concentrations in broilers from 1 to 43 days of age. Poultry Science. 2021;100(12):101495.
2. Liu SY, Selle PH. Starch and protein digestive dynamics in low-protein diets supplemented with crystalline amino acids. Animal Production Science. 2017;57(11):22502256.
3. Mahmoud A, Khader N, Hegazy A. Dose dependent effect of phytase supplementation on hematological parameters, serum biochemical analysis, carcass characteristics and chemical meat analysis of Hubbard broiler chickens. Benha Veterinary Medical Journal. 2024;47(1):12-18.
4. Mottet A, Tempio G. Global poultry production: current state and future outlook and challenges. World's Poultry Science Journal. 2007;73(2):245-256.
5. Sampath V, Gao S, Park JH, Kim IH. Exogenous phytase improves growth performance, nutrient retention, tibia mineralization and breast meat quality in ross-308 broilers. Agriculture. 2023;13(10):1906.
6. Selle PH, Ravindran V. Microbial phytase in poultry nutrition. Animal Feed Science and Technology. 2007;135(1-2):1-41.
7. Selle PH, Cowieson AJ, Cowieson NP, Ravindran V. Protein-phytate interactions in pig and poultry nutrition: a reappraisal. Nutrition Research Reviews. 2012;25(1):117.
8. Selle PH, Ravindran V, Bryden WL, Scott T. Influence of dietary phytate and exogenous phytase on amino acid digestibility in poultry: a review. The Journal of Poultry Science. 2006;43(2):89-103.
9. Smith J, Jones M. Global trends in poultry production and consumption. Agricultural Reviews. 2021;42(3):201215.
10. Snedecor GW, Cochran WG. Statistical Methods. 8th ed. Ames, Iowa: Iowa State University Press; 1994.
11. Vasanthi B, Richard Churchil R, Omprakash AV, Karthickeyan SMK, Samuel Masilamoni Ronald B. Carcass characteristics of indigenous Siruvidai Chicken of Tamil Nadu raised under farm conditions. Indian Journal of Veterinary and Animal Sciences Research. 2023;52(1):16-24.
12. Walk CL, Rao SVR. High doses of phytase on growth performance and apparent ileal amino acid digestibility of broilers feed diets with graded concentrations of digestible lysine. Journal of Animal Science. 2019;97(2):698-713.
13. Zeleke NA, Abebe MG, Beker A, Zeryehun T, Yirgalem M. Effect of Supplementation of Extracted Phytase on Growth Performance and Carcass Characteristics of Broiler. Department of Animal Sciences, Wachemo University. 2022;23:27.