PERFORMANCE RESPONSE OF BROILER CHICKENS TO THE REPLACEMENT OF SOYBEAN OIL AND ACIDULATED FATTY ACIDS BY LECITHIN IN THE DIET †

Facultad de Medicina Veterinaria y Zootecnia Universidad Michoacana de San Nicolás de Hidalgo, Michoacán, México. Departamento de Producción Animal: Aves, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Mexico City. Grupo Ragasa SA de CV. Av. Dr. José Eleuterio González 2815, Col. Mitras Norte, Monterrey, Nuevo León. Instituto de Investigaciones Agropecuarias y Forestales Universidad Michoacana de San Nicolás de Hidalgo. Email: josheca@hotmail.com *Corresponding author


INTRODUCTION
The inclusion of fats and oils in broiler chicken diets is a common practice because they provide essential fatty acids, improved the absorption of soluble nutrients in oil and increased the content of metabolizable energy (ME) in the diets (Hossain and Das, 2014).Feeding programs are established based on EM needs, so nutritional strategies are sought to optimize productivity considering economic and environmental aspects during the production cycle (Andreoti et al., 2004;Dozier et al., 2007).The ME level in the diet of broilers is one of the main factors related to the regulation of voluntary feed consumption, growth and feed conversion.In chickens fed at libitum, feed consumption increases or decreases either to low or high ME levels in diets (Cortes-Cuevas et al., 2018).
Soybean crude oil (SB) is used as a concentrated source of energy in balanced feeds for birds; however due to its cost, which has increased in the recent years because of biodiesel production (Cortes-Cuevas et al., 2018), profitable alternatives are being sought, such as acidulated oils of lower cost and acceptable nutritional quality (Barbour et al. 2006;Cuca et al., 2009;Cortes-Cuevas et al., 2018).Soybean acidulated oils (AFA) are by-products of the refining process of soybean oil for human consumption (Pardío et al., 2001).
On the other hand, lecithin is the main phospholipid of crude soybean oil, which is an alternative in the formulation of rations as a source of energy, phosphorus and choline (Menten et al., 1997).Due to the aforementioned, the aim of the present study was to evaluate the partial or total substitution of soybean oil (SB) and acidulated soybean fatty acids (AFA) by soybean lecithin (L) on the productive response amount of liver ether extract, and the liver and skin coloration from chickens feed with corn-soybean diets.

Birds husbandry
The study was carried out in an experimental poultry farm located in the municipality of Charo, from the Michoacan State, México at 1940 meters above sea level, with an average annual temperature of 18ºC and an average rainfall of 700 mm.A total of 2800 broiler chickens of the Cobb 500 strain, without sexing and from 1 to 42 days of age, were used (50 birds for each lot with a density of 10 birds x m 2 ).The birds were kept in 56 cement floors that had wooden litters.Water and feed consumption were ad libitum.
This experiment was conducted in compliance with poultry management guidelines of the Institutional Committee for care and use of experimental animals (CICUAE-FMVZ-UNAM) based of the Official Mexican Norm (NOM-033-SAG/ZOO-2014).All birds were orally vaccinated against the Newcastle disease (La Sota strain) at 8 and 24 days of age.
During the first week of life, the chickens had 18 hours of light; then they were maintained with a natural light photoperiod during the day and at night with artificial light (9 to10 PM, 1 to 2 AM and 5 to 6 AM).

Experimental design
A completely randomized design was used.It consisted in 7 treatments of 8 repetitions with 50 birds each.The treatments consisted of partial (25% and 50%) or total replacement of SB by L and AFA (Table 1).The diets used were in the form of mash.For each treatment, three feeding phases were employed (Starting 0-21, growth 22-35, finishing 36-42 days of age).In Table 2, only corn-soybean diets with 100% SB are shown per feeding phase and their calculated analyzes that covered the nutritional profiles indicated in the Manual Cobb (Cobb, 2015).

Statistical Analysis
The response variables were body weight (g), feed intake (g), feed conversion ratio (grams of feed/body weight), mortality (%), liver yellowness, skin yellowness and ether extract in liver (%) in function of the different inclusion levels of soybean (SB), acidulated fatty acids (AFA) and lecithin (L).The mortality results were transformed to arcsine and then was analyzed same that other parameters, but in the table are presented in percent of total mortality.The results obtained from the evaluated variables were analyzed in order to verify the fulfillment of the normality and homogeneity of variances assumptions, setting a 5% significance level for both tests.After that, the variables under study were analyzed according to a completely random design.When significant differences (P<0.05) were found among treatments, these values were subjected to a comparison of means using a Tukey test (SPSS V 17.0).

RESULTS AND DISCUSSION
The average results from broiler chickens of 1 to 49 days of age, corresponding to body weight, feed intake, feed conversion and mortality percentage are showed in the Table 4.It is possible to observe that there was no effect (P> 0.05) to the total or partial inclusion of SB or AFA by L (25% and 50%).
Table 5 shows the average yellowness data in the liver, carcass skin and the percentage of liver ether extract.
No differences were found between treatments (P>0.05),indicating that the partial or total substitution of SB and AFA by L did not affect the behavior of these variables.The results of this study observed throughout the productive cycle, partially corroborate the findings of Baião (2005), Peña et al. (2014), Vieria et al. (2015) and Cortes-Cuevas et al. (2018), who showed that AFA is a substitute for SB, as a good source of energy and poly-unsaturated fatty acids.However, other authors (Sizemore and Siegel 1993;Cortes-Cuevas et al., 2018) point out that this energy ingredient has a lower value of metabolizable energy on average (9.3% or 10%).In this study, liver yellowness and ether extract were similar, suggesting that the ME value in Kcal/kg used in the formulation of the experimental diets for SB 8850, AFA 8000 and L 6700 (representing 9.7% and 24.3% less with respect to SB) was adequate.
The ME value used for lecithin was similar to the one reported by Gaiotto et al. (2001) [6715 kcal/kg of ME], but it was different from the one found by Borsatti et al. (2018) [7051 kcal/kg of ME] and Peña et al. (2014) [7502 kcal/kg of ME] due to synergism of L with AFA and glycerol or to the variation between methods in the determination of metabolizable energy as indicated by Dourado et al. (2010).In our study, the partial substitution of AS or AFA by lecithin had no effect on the studied productive variables, indicating some synergism of lecithin with the other energy sources evaluated.However, Huang et al. (2007), when using a 75:25 ratio mixture of soybean oil and soy lecithin in the diet, found greater weight gain and better feed efficiency in broilers at 42 days of age.On the other hand, Dubey et al. (2014) included different proportions of soybean oil and soybean lecithin in the diets of six-week-old broiler chickens; where they detected greater weight gains in chickens that consumed a 50:50 ratio, without observing significant differences in feed consumption and feed conversion.
Regarding skin pigmentation, which is considered an important factor for consumers in some countries and recognized as a critical attribute of quality during the marketing of broiler carcasses (Castañeda et al., 2005;Liu et al., 2008), there were no differences when L was included as a partial or total replacement of SB and AFA.This information corroborates the findings of Cortes-Cuevas et al. (2018), who did not found differences in the yellowness of the skin with the use of AFA or SB.

CONCLUSION
From the data obtained under the experimental conditions used in this study, it is concluded that soy lecithin is an alternative energy source to soybean oil or acidulated fatty acids in diets as partial or total replacement (25%, 50% and 100%), without affecting the productive performance, liver ether extract, and the yellowness of liver and skin in broiler chickens of 42 days of age, fed with corn-soybean-based diets with nutritional profiles of commercial use.

Table 1 .
Experimental design of treatments

Table 2 .
Composition of the corn-soybean meal diets for the three feeding phases with soybean oil (100%).

Table 3 .
Inclusion (%) of soybean oil (SB), acidulated fatty acids (AFA) and lecithin (L) used in the treatments during the different feeding stages.
Performance response and laboratory analysesWeekly records of body weight, weight gain, feed intake, feed conversion and mortality percentage were recorded.At 42 days of age, two birds (male and female) were sacrificed per repetition (a total of 16 birds per treatment) in order to evaluate the percentage of liver fat(ether extract, AOAC, 2006).

Table 4 .
Average results of productive parameters in broiler chickens from 1 to 42 days of age.

Table 5 .
Ethereal extract and pigmentation of the birds slaughtered at 42 days of age.