1. Introduction

Choline is a nutrient that contributes to several metabolic processes, including lipid transport, cell signaling, cell membrane integrity, and biosynthesis of methylated compounds (¹,²,³). This vitamin is essential for the formation of endochondral bone, allowing the adequate proliferation of chondrocytes, bone elongation, and prevention of disorders in the paws, such as perosis (⁴). Additionally, choline acts with methionine as a lipotropic factor, improving lipoprotein synthesis and lipid-cholesterol transport, thereby preventing fatty liver syndrome (⁵,⁶,⁷).

In poultry nutrition, the requirement for this nutrient is met through the dietary utilization of products rich in choline. Some of these products are derived from selected plants, which exhibit a high content of esterified choline, along with bioavailability. According to Gupta et al. (⁸), some advantages of using vegetable choline, as an alternative of use of choline chloride, include high absorption efficiency, low hygroscopicity, low conversion of choline to trimethylamine (TMA), and high phosphatidylinositol and phosphatidylcholine (PC) content.

In research with broilers, it has been estimated that a plant-based product containing 1.6% PC has a choline bioequivalence of 2,520 g/kg (⁹). The present study hypothesized that another plant source with 3.2% PC could be utilized and would have at least twice the choline bioequivalence in broiler diets. Therefore, the objective was to evaluate the effects of dietary supplementation of two plant sources of PC on the performance and body composition characteristics of broiler chickens.

2. Material and methods

All procedures adopted in the current study were previously evaluated and approved by the ethics committee on the use of farm animals (Registration protocol: 07/2022), and were in compliance with the ethical principles of animal experimentation established by the Conselho Nacional de Controle de Experimentação Animal (CONCEA). Experiments were carried out in Viçosa, Minas Gerais State, Brazil (20°45’57.19” S, 42°51’35.42” W, and 682 m altitude).

2.1 Experimental design, diets, and animals

One-day-old male broiler chicks (Cobb 500) were used, with an initial weight of 46.1 ± 3.82 g. The birds were distributed in a completely randomized design with five treatments, twelve replications, and twenty birds per experimental unit. The experiment lasted 42 days. Three corn/soybean meal basal diets were formulated to meet the nutritional recommendations given by Rostagno et al. (¹⁰) according to the experimental phases (1 to 7, 8 to 21, and 22 to 42 days of age), except for choline levels (Table 1). For the formulation of the basal diets, a choline concentration of 440 mg/kg in corn and 2559 mg/kg in soybean meal was considered (¹¹). Therefore, the total level of choline in the basal diets was 550, 496, and 361 mg/kg of choline, respectively.

The plant sources of PC tested were Biocholine and Biocholine DS (minimum 1.6 and 3.2% PC, respectively, Nutriquest, Brazil). The experimental treatments consisted of Basal diets (BD)- diet without choline supplementation; BD + Biocholine (218, 197, and 143 mg/kg of diet, respectively); BD + Biocholine DS1 (146, 131, and 96 mg/kg of diets, respectively); BD + Biocholine DS2 (109, 98, and 72 mg/kg of diets, respectively); BD + Biocholine DS3 (87, 79, and 57 mg/kg of diets, respectively). The experimental treatments are illustrated in table 2. These levels of products supplementation considered the choline bioequivalence of 2,520 mg/kg for Biocholine and 3,780, 5,040, and 6,300 mg/kg of Biocholine DS1, Bicholine DS2 and Biocholine DS3, respectively, and the recommendation of supplementation given by (¹⁰) of 550, 496, and 361 mg choline/kg of diet, respectively. The addition of the products to the experimental rations was done in an on-top way.

During the research, a 24-hour light program was adopted from 1 to 14 days and then 18 hours of light until the end of the experiment. In addition, feed and water were provided ad libitum throughout the experimental period.

2.2 Evaluated parameters

2.2.1 Performance

The birds were weighed at 7, 21, and 42 days of age to evaluate performance parameters. Feed intake (FI), weight gain (WG), and feed conversion ratio (FCR) were measured. Mortalities were recorded daily throughout the study for corrections in performance parameters. The difference between the final weight and the initial weight determined WG. The FI was calculated as the difference between all the feed provided in the evaluated periods and the leftover feed in the feeders at the end of each period. Finally, the FCR was calculated as the ratio between FI and WG.

2.2.2 Carcass yield

At 42 days of age, two birds per experimental unit were slaughtered by electro narcosis to evaluate the carcass yield (CY, %), the yield of parts (%), and the relative weight of some organs. The CY was determined by the ratio of the carcass weight without viscera, head, feet, and neck to the live weight before slaughter; %CY = (Carcass weight x 100) / Live weight. The ratio between the weight of the evaluated part and the weight of the carcass without viscera, feet, head, and neck determined the yield of parts; % RPart = (Part weight x 100) / carcass weight, with breast yield (BY, %) and thigh plus drumstick yield (TDY, %) being evaluated. The relative weight of the organs was determined as the ratio between of the organ weight to the carcass weight, excluding viscera, feet, head, and neck. The formula used was: relative weight = (Organ weight x 100) / carcass weight. The relative liver weight (RLW) and abdominal fat (RWAF) were evaluated.

2.2.3 Body composition

Bird body composition was estimated by Dual Energy X-Ray Absorptiometry (DXA). At 42 days of age, a bird with the closest weight to the average weight of each experimental unit was chosen and slaughtered by cervical dislocation. The estimated values of fat tissue and lean tissue were used to determine the percentage of fat tissue and lean tissue according to the equations proposed by Schallier et el. (¹²):

• 1: Total Body Fat Percent = -1.288 + 0.806 x Percent Fat (DXA).

• 2: Percentage of total lean tissue = 19.95 + 0.805 x Percent lean (DXA).

2.3 Statistical analyses

Data were analyzed via one-way ANOVA using the GLM procedure of SAS (Statistical Analysis System, version 9.4). In addition, a comparison between treatment averages was performed using Tukey’s test. A significance level of 0.05 was applied.

3. Results and discussion

There was no effect of the treatments on the FI and WG of the birds in any of the phases studied (P > 0.05; Table 3). However, there was an effect of treatments on FCR from 1 to 21 days of age, and the birds of the basal diet presented the worst FCR in relation to the other treatments (P < 0.05).

There was no significant effect of treatments on carcass and parts yield and on the relative weights of abdominal fat and liver of birds at 42 days of age. Furthermore, no positive results were observed in body composition parameters with the supplementation of phosphatidylcholine sources (P > 0.05; Table 4).

The result found for the FCR in the phase from 1 to 21 days is in line with expectations since choline acts on lipid metabolism, promoting better use of dietary energy (¹³,¹⁴) and consequently leading to better performance results. On the other hand, no improvement was observed in FI and WG in any of the evaluated phases. According to Igwe et al. (¹), young birds are more demanding on choline as it is an essential nutrient for metabolic functions necessary for growth.

Unlike the current research, Khose et al. (¹⁵) found worsening in all performance parameters when diets were deficient in choline; however, their diets contained smaller proportions of sulfurcontaining amino acids, which could explain our result. Furthermore, Khosravinia et al. (¹³) found positive results for WG with no significant increase in FI. They reasoned that the lipotropic effect of choline may have improved dietary energy utilization and consequently promoted better WG.

Regarding carcass characteristics, it was expected that animals fed with BD would have higher percentages of body fat, since choline deficiency can house fat deposition in organs such as the liver and other parts of the carcass, since that it is an essential nutrient for lipid transport (¹³). As with the results for weight gain, the explanation for the lack of changes in carcass composition can be attributed to the amount of sulfur amino acid present in the diet, however, further studies are needed to corroborate our findings.

Research on the performance of broilers supplemented with choline shows controversial results, whether the source is organic or synthetic. These different results can be explained by the link between the metabolism of choline and that of sulfur amino acids (⁹,⁵,¹⁶,¹⁷,¹⁸). Supplementation does not promote any effect when animals are fed diets with a high content of sulfur amino acids since methionine can partially supply the choline deficiency, mainly in diets rich in corn and soybeans. Although the diets in the present study are deficient in choline, since it considers only the choline from corn and soybean meal, they are rich in methionine + cystine. This may explain the lack of positive results on WG and FI.

In research carried out by Lima et al. (¹¹), it was estimated from quadratic regression equations that the choline level that optimizes broiler performance was 1276 and 1010 mg/kg for phases 1 to 7 and 1 to 21 days of age, respectively. As previously mentioned, corn and soybean meal diets are very rich in choline, and although they were formulated according to Rostagno et al. (¹⁰), deficient diet choline levels are above those recommended by Lima et al. (¹¹). These data help to explain the lack of results in the current research and corroborate the hypothesis that the choline requirement is outdated and requires further studies.

4. Conclusion

In conclusion, supplementing with vegetable sources of phosphatidylcholine improves the feed conversion of broiler chickens from 1 to 21 days of age. Based on performance results up to 42 days of age, the Biocholine DS product, with twice the concentration of phosphatidylcholine compared to the Biocholine product, can be used with the bioequivalence matrix of 5.040 mg/kg in diets based on corn and soybean meal for broilers.

Acknowledgments

The authors thank Nutriquest Nutrição Animal for the financial support to carry out this work and CNPq for granting scholarship to the first author.

References

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