MACAÚBA MEAL LEVELS IN THE DIET OF NAKED NECK BROILERS

A total of 375-day-old naked neck chicks were distributed in a completely randomized design in five diets with 0, 2, 4, 6, and 8% macaúba meal levels to evaluate colonial broiler chickens. The data were submitted to linear or quadratic regression analysis according to the best fit for each studied variable using the statistical program SAS 9.0. Macaúba meal levels increased feed intake without influencing weight gain, resulting in worsening feed conversion and leading to a linear reduction in slaughter weight at 85 days and reduction in carcass yields due to higher abdominal fat deposition. Linear effects were found on the contents of a*, pH, ethereal extract, and ash in the breast and b*, moisture, ethereal extract, and ash in the drumstick + thigh. Thus, macaúba meal inclusion in the diet of naked neck broilers impaired performance by increasing diet intake, impairing feed conversion and reducing carcass yields. However, it favors breast, drumstick, and thigh colors because it is rich in carotenoids.


Introduction
The search for alternative foods that do not compete with human food is a significant challenge for animal farming.
Feeding represents the largest portion of production costs in poultry farming and, therefore, the use of quality alternative feeds and known compositions for the formulation of minimum cost feed allow a more economical adaptation to the producer. (1) In this sense, studies have been developed to update the nutritional values of foods commonly used in poultry feed and knowing the nutritional value of new foods. However, studies are still needed to demonstrate animal performance when replacing conventional feed with alternative nutrient sources.
Another major global concern is about clean and renewable energy production that can replace the use of oil derivatives. Among the various alternatives is biodiesel production and among the oilseed species that can be used to produce this biofuel is macaúba (Acrocomia aculeata). Macaúba has better yield conditions in Cerrado lands, where practically does not suffer from disease attack and has a high oil content. (2) Macaúba pulp accounts for around 45% of the fruit composition (3) and provides an orange-yellow oil rich in bioactive compounds and, in the fatty acid composition, high levels of oleic and palmitic acid. (4,5,6) Macaúba meal, a residue from the extraction of oil from fruit pulp, can be a viable co-product for animal feed. In studies on ruminant feeding, different authors have found that it is possible to replace conventional protein feeds such as soybean meal with macaúba meal or cake. (7,8,9,10,11) However, there is little information in the literature regarding the use of this food in the diet of broilers. Therefore, conducting the study may generate information on the effects of this food as an alternative food source on performance and carcass and indicate the best inclusion level to be used in practice. Therefore, this study was carried out to evaluate macaúba meal levels in the diet of colonial broilers in performance and carcass characteristics. A total of 375 day-old naked neck chicks, with a mean initial weight of 42.56±1.32 g, were distributed in a completely randomized design with five experimental diets (macaúba meal inclusion levels, %), five replications, and 15 animals per experimental unit.

Material and methods
Animals were housed in the same shed equipped with 25 boxes with internal measures of 1.75 × 2.40 m. Each box contained a suspended tubular feeder, an automatic pendant drinker, a 100W campanula, and approximately 6 cm of wood shavings.
The breeding system adopted was semi-intensive. The animals remained in confinement for up to 28 days and, after the initial phase, each box had access to a 60-m 2 paddock of Tifton grass during the day.
Macaúba meal was obtained by cold pressing the pulp to extract the oil and then drying the cake. Chemical composition and gross energy value of macaúba meal used in the formulation of experimental diets are shown in Table 1.
Experimental diets were formulated to meet the nutritional requirements of animals according to the linage manual (12) and growth phase, and each of them contained one of the following five macaúba meal levels: 0, 2, 4, 6, and 8% (Tables 2, 3, and 4).
The nutritional requirement in minerals and amino acids was met using mineral sources and industrial amino acids, aiming to maintain the minimum values obtained for diets free of alternative food in the different phases.
Humidity and maximum and minimum temperatures were measured during the experimental period by a digital thermohygrometer. The evaluated performance characteristics were weight gain, final weight, average feed intake, and feed conversion, measured from 1 to 28, 29 to 56, and 57 to 85 days old.
Animals were pre-slaughter fasted for 8 hours, weighed, stunned by electronarcosis, bled, and plucked at the end of the growth phase (85 days). The entire process was performed manually, and carcasses were not chilled. Carcasses were eviscerated and weighed to calculate carcass yield and fat percentage and then refrigerated. The measurements of pH were performed in the chest and drumstick muscles using a digital pH meter 24 hours after slaughter with the chilled carcasses. Subsequently, carcasses were packed in plastic bags and frozen at −20 °C. After 7 days, carcasses were thawed, ground, and homogenized for analysis of dry matter, ethereal extract, crude protein, and ashes, according to AOAC standards. (14) FERREIRA, M.W. et al.
Cienc. anim. bras., Goiânia, v.20, 1-12, e-52626, 2019 The color was determined with a Minolta colorimeter, which considers the coordinates L* (black/ white), responsible for luminosity, a* (green/red), related to red content, and b* (blue/yellow) related to yellow content. (15) Water retention capacity was determined according to the methodology described by Silva Sobrinho. (16) The data were submitted to linear or quadratic regression analysis, according to the best fit for each studied variable, using the statistical program SAS 9.0. (17)

Results
The average minimum and maximum temperatures registered during the experimental period inside the shed were 26 and 29 °C, respectively. No significant effects (P>0.05) of including different macaúba meal levels in the diets were observed on feed intake in the period from 1 to 28 days. However, a decreasing linear effect was observed on weight gain (Y = −18.488x + 1152.7; R 2 = 0.95) and an increasing linear effect on feed conversion, as shown in the equation Y = 0.0424x + 1.9456 (R 2 = 0.89) ( Table 5).
Macaúba meal levels did not influence (P>0.05) animal performance in the periods from 29 to 56 and 57 to 85 days, showing adaptation to the diet. However, an influence (P<0.05) of macaúba meal levels was observed during the accumulated experimental period (1 to 85 days), leading to linear increase in feed conversion (Y = 0.0218x + 2.3884; R 2 = 0.78) and a linear decrease on weight gain (Y = −24.8x + 314.4; R 2 = 0.810) and body weight at 85 days, as shown in the equation Y = −24.558x + 3187 (R 2 = 0.81).
Breast and drumstick + thigh yields were not influenced (P>0.05) by macaúba meal levels.
Luminosity (L*) of breast and drumstick + thigh was not influenced (P>0.05) by the inclusion of macaúba meal in the animal feeding (Table 7).
The yellow content (b*) in the drumstick + thigh increased linearly according to the equation Y = 0.0392x + 8.6055 (R 2 = 0.783) as macaúba meal levels were increased in the broiler diet.

Discussion
The range of temperature variation recorded in the experimental period is in accordance with the thermal welfare for broilers. (12) The negative effect on weight gain from 1 to 28 days may be related to the immaturity of the gastrointestinal tract in metabolizing nutrients contained in the experimental diets, considering that nutrient utilization is improved with the advancing age of animals as a function of higher production of digestive enzymes and increase in organ size. (18) The lack of effect on feed intake, associated with lower weight gain at 28 days, justifies the worsening in feed conversion during this period. Although there was no effect on feed intake, the availability of protein and amino acids, nutrients required in larger quantities in the initial phase of broilers, (13) may have been reduced, directly influencing performance.
Results showed that macaúba meal inclusion in the diet of naked neck broilers significantly compromises weight gain and, consequently, body weight at slaughter and feed conversion due to the high crude fiber content (28.540%). Fibers in non-ruminant diets affect the availability of other nutrients, influences the action on passage rate, (19) digesta viscosity, water retention capacity, and the performance in the bond with minerals and organic molecules. (20) The results for carcass yield are an indication of lower protein and amino acid availability of diets containing macaúba meal. This imbalance in protein utilization favored the deposition of adipose tissue such as abdominal fat, (21) and this excess influenced carcass yields, as abdominal fat is neglected in gutting, which is a problem for the poultry industry. (22,23) The effect of macaúba levels on a* content of breast cut is related to the influence of pH on light absorption, affecting myoglobin on green light absorption, making the meat appear less red. (24) A higher deposition of ethereal extract was observed in the breast section, which demonstrates the excess energy available, which contributes to ATP formation and, consequently, favored the deposition of glycogen reserve, which is related to the speed in the establishment of rigor mortis, (25) being closer to the pH range considered adequate between 5.70 and 5.96. (26,27) The absence of effect on drumstick + thigh pH was due to the dominance of type I muscle fibers presented in this section, resulting in lower glycolytic potential. (28) The increase in the deposition of ethereal extract in the breast and drumstick + thigh may be related to the fatty acid profile of macaúba meal. As observed by Nunes et al., (29) macaúba is rich in palmitic acid belonging to the group of saturated fatty acids, which have a higher influence on fat content in meat. (30,31) The higher moisture content in the drumstick followed an inversely proportional relationship between ethereal extract and moisture, as observed by Özdogan and Aksit, (32) who associated this relationship to the dietary lipid source.
Considering that there was an increase in the ethereal extract content of the breast and drumstick + thigh cuts, and that they constitute one of the organic fractions of the total composition, the relationship between proportion of organic/inorganic matter of carcasses when compared to an increase of macaúba meal levels justifies the lower gray values obtained for both cuts.
Knowing that pigmentation in poultry meat is strongly affected by carotenoid intake, (33) the increase in drumstick color b* suggests that macaúba meal inclusion in poultry diets increases pigmentation, which is a consumer-appreciated feature of free-range chicken meat.

Conclusion
Macaúba meal inclusion in the diet of naked neck broilers impaired performance by increasing dietary intake, impairing feed conversion and reducing carcass yields by increasing abdominal fat deposition. However, it favors breast, drumstick, and thigh colors, as it is rich in carotenoids.