Using different levels of energy in the diet of chicken slow-growing strain of rustic French Pedrês

This study aimed to evaluate the effect of the energy levels on growth performance and yield of the broilers Caipira French Pedrês, slaughtered at 77, 84 and 90 days old. We used 192 day old chicks, mixed, reared under intensive birds/m 2 density of 6.4. The experimental design was completely randomized with four replications of three treatments, the experimental unit being a box of 16 birds. Treatments were defined by the energy levels of the diets in the initial phase (1-28 days) and fattening (29 to 91 days) were: T1 - 3.000/3.100 kcal / kg, T2 –3.100/3.200 kcal / kg and T3 - 3.200/3.300 kcal / kg. The variables studied were average weight, feed intake, weight gain, feed conversion efficiency, protein efficiency ratio, carcass yield, prime cuts (breast, thigh on thigh),wings, back, head + neck and feet. The birds showed better growth performance and carcass yield and cuts when fed diets containing 3,000 kcal / kg of the initial phase and 3,100 kcal / kg in the final stage, can be slaughtered at 77 days old.


INTRODUCTION
The world population has adequate food habits that are based on natural products, which are considered healthier, which provides a constant expansion of poultry called alternative, from the creation of chicken and chicken (Vercoe et al., 2000). This alternative animal protein has cornered the market, showing that the birds obtained in this production system have superior qualities coming to the intensive system, as to its organoleptic characteristics, thus meeting some key demands of the consumer (Zanusso et. al, 2003).
The redneck chicken farming is a viable and economical production, becoming an important activity for small and medium farmers, allowing for the increase in family income and that has increased in recent years in Brazil. Displays features such as the use of family labor, the use of small areas of land and the large conversion capacity of grains and other plant products in meat and eggs.
In recent years occurred in the growth of knowledge of the nutritional value of feed ingredients and the nutritional requirements of animals in different production phases (Rostagno et. al 2007). These requirements are constantly reevaluated to allow optimization of the nutrients of the diets, since the nutrition and feeding of birds vary greatly due to a reduction in production costs or by genetic variations in constant search for better performance and greater competitiveness (Longo et. al, 2001). Among the nutritional levels to be determined, we can highlight the level of metabolizable energy of feed, due to its great influence on feed intake, animal performance, carcass yield and cuts, fat deposition in carcass and cost per unity gain (Massi, 2007).
Few studies on nutritional requirements have been carried out with slowgrowing birds. These birds may respond differently to energy levels when compared to industrial strains, it is necessary to investigate the level of metabolizable energy best suited to provide maximum performance. The objective of this study was to evaluate the effects of metabolizable energy levels and age at slaughter on growth performance and carcass characteristics of broilers Caipira French Pedrês (Gris Barre Cou Nu).

MATERIAL AND METHODS
The study was conducted in an experimental shed ceded to the Federal Rural University of Before the start of the experiment the shed and the equipment was cleaned and disinfected. In housing, 16 chicks were weighed evenly for the composition of the experimental plot, distributed in boxes according to the identification of treatments and replications.
The chicks in the hatchery were vaccinated against Marek's disease and fowl pox and received the vaccine against Newcastle toseven days old. Water and feed were provided ad libitum throughout the experimental period. We carried out the temperature management of the internal boxes, according to the temperature and the behavior of the chicks. Heating was provided by lamps of 60 W, connected during the first days of the experiment. The program light was continuous throughout the experimental period.
The variables studied for animal performance were average weight, feed intake, weight gain, feed conversion, crude protein, metabolizable energy consumption, energy efficiency and protein efficiency. Data were collected weekly and analyzed in a cumulative period of 28 and 29 will be 90 days old.
To obtain the body weight of each boxing birds were weighed weekly and the housing. Weight gain was calculated as the difference between final weight and initial weight. composition of the diet, respectively. The protein efficiency and energy efficiency were calculated by the ratio of protein intake and metabolizable energy for weight gain.
On completion of 77, 84 and 90 two-day old birds per pen were identified by means of flanges. After receiving a 12-hour fasting, birds were weighed and killed by bleeding following the procedure of plucking and gutting. The variables studied were carcass, prime cuts (breast, thigh on thigh), wings, back, head + neck and feet. The calculation of yield was done with the hot carcass weight.
Statistical analysis was performed using the ANOVA procedure with the "System for Statistical Analysis and Genetics" -SAEG (version 9.1). Differences between means of variables were performed using the Tukey Test adopting α = 0.05.

RESULTS AND DISCUSSION
The results of weight, weight gain, feed consumption and feed in the early phase (1-28 days old) and late (29-90 days of age) are shown in Table 3. reported higher rates of weight gain and feed conversion in chicks of Hubbard strain, those fed diets with 3.232 and 3.224 kcal / kg, 22 days old.
The survey results differ from those reported by Mendonça et al. (2008), who found no effect of dietary energy levels (2.600, 2.750, 2.900, 3.050, 3.200 kcal / kg ME) on the weight gain of males ISA Label in periods of 1 to 21 days of age reared under semi-confined . Xavier et al. (2008), analyzing the performance of chickens (Avian × Cobb) in the pre-start, no significant effect was observed with increasing levels of dietary metabolizable energy (2.850, 2.950, 3.000, 3.050 and 3.150kcal / kg).
To study the energy levels were not significant effects (p> 0.05) on the crude protein intake, energy intake, protein efficiency and energy efficiency of the birds (Table 4). Divergent results were reported by Oliveira et. al (2000), providing that a diet in a controlled manner and in equal amounts among treatments (2.850, 2.925, 3.000, 3.075, 3.150 kcal / kg), found that energy intake increased (p <0.01) linearly as that raised the level of the rations of MS, however no effect on crude protein intake of the birds.
Second Henrique (2010), control of energy intake is important not only for its effects on growth rate, but also negative effects of excessive drinking that can detract from the quality of housing by accumulation of fat. Reductions in levels of dietary energy lead to a lower accumulation of fat in the carcass. This assumes that the use of lower energy, it becomes feasible by reducing production costs and improves carcass characteristics. Sakomura et al. (2004) supplemental fat in the diet promotes an increase in caloric density, an effect extra calórico, which consists of increasing the availability of nutrients in feed ingredients, and an extra effect of fat metabolism that results in improved energy efficiency by increasing the net energy ration. According to Massi (2007), increased energy levels of the feeds include soybean oil has an effect extra calórico, thus providing greater availability of nutrients for the production, and in this case for meat production. However, when analyzing the data of the present study this result was not found.
The levels of metabolizable energy of feed and different ages at slaughter did not influence the carcass, breast, thigh on thigh-birds. These results indicated that the 77 days of age, regardless of level of metabolizable energy diet, the birds reached their maximum potential (Table 5). Mendonça et al. (2008), found similar results when testing the effect of metabolizable energy levels on the yield of noble cuts in males ISA Label. The results of this experiment are consistent with those observed by Mendes et al. (2004) they found no significant difference in carcass yield and cuts in Ross308 broilers when fed diets containing different levels of energy (2.900, 2.960, 3.020, 3.080, 3.140 e 3.200 kcal/kg).
In the review of performance of wings, back and feet of birds found that the levels of energy metabolizable feed and slaughter age were not significantly (p> 0.05) in the results. Neto etal., (2000) working with five levels of energy in the diet (3.000, 3.075, 3.150, 3.225 and 3.300 kcal / kg) for broiler chickens of Hubbard, found similar results where the absolute weights and cut yields were not affected by energy levels, with the exception of carcass yield, which varied (p<0.04) quadratically. Murarolli et al (2009), evaluating the yield of cuts (wing, drumstick + thigh, chest, head, foot and back) of female Cobb, who consumed diets with six levels of energy (3250, 3400, 3500, 2820, 2925, 3000 kcal / kg ) found no significant effect.

CONCLUSION
Birds of French lineage Caipira Pedrês (Gris Barre Cou Nu) showedbetter growth performance and carcass yield and cuts when fed diets containing 3.000 kcal / kg metabolizable energy in the initial phase and 3.100 kcal/kg in the final phase, may be slaughtered at 77 days of age.