The effect of energy levels on the performance of naked neck, french hillbilly stone gray rolled chickens, in the starter phase^

Introduction

The production of hick chickens is a viable, profitable, easy-to-explore alternative, that could become an important activity for small and medium rural producers. This activity can contribute to increase family income, and it has grown in recent years in Brazil and elsewhere. As an alternative animal protein, hillbilly (country-, or peasant-type) chicken production has entered the market well, since these animals show superior traits as compared to regular, intensively-farmed broilers in terms of organoleptic characteristics that fulfill certain consumers' demands (Zanusso and Dionello, 2003).

Nutritional requirements are constantly re-evaluated in order to optimize dietary nutrients, since bird nutrition and feeding can show large variations due to the search of least production costs, and in agreement with the ongoing genetic improvements aiming enhance performance and competitiveness (Longo et al., 2001). Among then nutritional levels to be determined, dietary metabolizable energy (ME) levels out stand because of their great influence on feed intake, animal performance, carcass yield, and portion yields, carcass fat deposition and cost per unit of gain (Massi, 2007).

Considering that slow-growing chickens can potentially respond differently to ME levels, the need exists to investigate which is the best energy level, and its best ratios, as to maximize performance. With the above in mind, the objective of this study was to evaluate the effects of dietary ME levels on the performance of naked neck, French Hillbilly Stone Gray Rolled chickens, in the starting phase.

Materials and Methods

The study has performed in an experimental house located in Parauapebas City, PA, Brazil. One hundred and nine two (192) naked neck, French Hillbilly Stone Gray Rolled (Pedrês) chickens were housed at a stocking density of 6.4 birds/m².

chickens were allotted to 16-animal pens, under an intensive system. The experimental design was completely at random with 3 treatments and 4 repetitions each. Treatments (T) consisted of various dietary energy levels, i.e., T1: 3,000 Kcal ME/Kg; T2: 3,100 Kcal ME/Kg; T3: 3,200 Kcal ME/Kg. Experimental feed composition is shown in Table 1.

Table 1. Composition of the experimental feeds for starting chickens (1-28 days)

Ingredients	T1	T2	T3
Corn	58.83	56.54	54.25
Soybean meal	32.60	32.90	33.33
Plant oil	1.80	3.70	5.60
Meat meal	5.50	5.60	5.60
Calcium carbonate	0.37	0.36	0.35
Salt, NaCl	0.30	0.30	0.30
*Polimax F-1^()**	0.60	0.60	0.60
Total	100	100	100
Calculated nutritional composition
Met Energy, Kcal/Kg	3,000	3,100	3,200
Crude protein, %	22.00	22.00	22.00
Ether extract, %	4.89	6.70	8.51
Crude fiber, %	3.54	3.52	3.49
Mineral matter, %	5.31	5.31	5.31
Lysine, %	1.21	1.22	1.23
Calcium, %	1.00	1.00	1.00
Total phosphorus, %	0.68	0.68	0.68
Avail. phosphorus, %	0.48	0.48	0.48
Sodium, %	0.17	0.17	0.17

^{(*)Composition per Kg product: Vit. A - 1,835.000 IU; Vit. D3 - 335.000 IU; Vit. E - 2.835 mg; Vit. B1 - 335 mg; Vit. B2 - 1,000 mg; Vit. B6 - 335 mg; Vit. K3 - 417 mg; Vit. B12 - 2,500 μg; Biotin - 17 mg; Folic acid- 135 mg; Niacin - 6,670 mg; Selenium - 35 mg; Antioxidant - 2,000 mg; Calcium pantotenate- 1,870 mg; Copper - 1,000 mg; Cobalt 35 mg; Iodine- 170 mg; Iron 8,335 mg; Manganese - 10,835 mg; Zinc - 8,335 mg; Choline chloride 50% - 135,000; Methionine- 267,000 mg; Coccidiostat - 13.335 mg; Growth promoter- 16.670.}

Prior to experiment start, the house and equipment were washed and disinfected. The chickens were vaccinated in the hatchery against Marek's disease and fowl pox and, at day 7 of age, Newcastle disease vaccine was given. At arrival in the facilities, chickens were weighed as to form homogeneous experimental groups that were distributed among the pens in accordance with treatments and repetitions.

Water and feed were administered ad libitum during the entirety of the study. Pressure drinkers and cylinder feeders (15 kg capacity) were used. Heating was given by the means of 60W lamps during the early experimental days. Internal pen temperature was in accordance with ambient temperature and chicken behavior. A continued, 24 hour lighting program was given throughout the experimental period.

The variables studied included end weight, feed intake, weight gain, feed conversion rate, crude protein intake, ME intake, energy efficiency, and protein efficiency.

Performance data were recorded weekly, and analyzed for the cumulative 1-28-day of age period. in order to obtain body weight information, all birds in a pen were weighed as a pool, then every week. Weight gain was estimated by the difference between end weight and start weight. Feed intake was calculated by the difference between total feed consumed and feed leftovers at the end of each period. Feed conversion rate was calculated by the ratio of feed consumed and weight gain in the period. In order to estimate crude protein intake and ME intake (kg/bird) feed intake was multiplied times protein and ME concentration in the centesimal formulation of the feed. Protein efficiency and energy efficiency were calculated by the protein and ME intake to weight gain ratio.

Results were statistically analyzed using the ANOVA procedure for a completely-at-random model, with the "Statistical and Genetic Analysis System" (SAEG, 2007). Differences among means of the variables studied were compared using Tukey´s test (P<0.05).

Results and Discussion

Mean weight, feed intake, weight gain, and feed conversion rate in the starting phase (1-28 days of age) are shown in Table 2.

For feed intake and FCR no significant effects were found (P>0.05) among treatments. Our results differ from those of Pacheco (2004), who found a linear decrease in feed intake and improved FCR as energy levels increased (2,860, 2,920, 2,980, 3,040, 3,100, 3,160 Kcal/Kg) of two allow-growing chicken strains (Red label and Extra-Heavy [Label Rouge and Pesadão]), in the starting phase (1-14 days).

Table 2. Performance of naked neck, French Hillbilly Stone Gray Rolled (Pedrês) chickens fed 3 different energy levels, in the starting phase (1-28 days of age)

Variables	Treatments
T1	T2	T3	CV (%)
Mean weight (g)	463.75 ^b	570.50 ^a	537.75 ^ab	9.465
Feed intake (g)	875.25 ^a	984.00 ^a	927.75 ^a	13.691
Weight gain (g/bird/day)	15.28^b	19.10^a	17.91^ab	10.173
Feed conversion rate	2.06 ^a	1.82 ^a	1.85 ^a	10.349

^{Means followed by different small case letters in the lines show statistically-significant differences as per Tukey's test (P<0.05).}

A significant effect was seen for mean weight (P<0.05) and weight gain (P<0.05), where T2 (3,100 Kcal/Kg ME) had higher values as compared to T1 (3,000 Kcal/Kg ME), while no difference was found with T3 (3,200 Kcal/Kg ME). These results agree with those of Oliveira Neto et al. (2000) who reported improved weight gain and feed conversion rates in Hubbard broilers fed 3,232 and 3,224 Kcal/Kg ME, at 22 days of age. Xavier et al. (2008) found no significant effect on Cobb broiler performance fed various ME levels (2,850, 2,950, 3,000, 3,045 and 3,150 Kcal/Kg) in the starter phase.

With the energy levels studied, no significant effects (P>0.05) were found on crude protein intake, ME intake, protein efficiency or energy efficiency. Henrique (2010) stated that energy control is important not only because of its effects on growth rate, but also because of the negative effects of excess feed intake that can be rious for carcass quality due to increased fat deposition. Decreased dietary ME intake results in lower carcass fat levels. Therefore, low dietary energy levels seem to be a viable option to reduce production costs and improve carcass traits.

Table 3. Energy and protein efficiencies of naked neck, French Hillbilly Stone Gray Rolled (Pedrês) chickens fed 3 different starter diets (1-28 days of age)

Variables	Treatments
T1	T2	T3	CV (%)
Crude protein intake (g/bird/day)	6.87	7.73	7.28	13.69
ME intake (Kcal/bird/day)	93.77	108.94	106.02	13.69
Protein efficiency	0.45	0.40	0.40	10.35
Energy efficiency	0.16	0.17	0.16	10.34

^{Means show no statistically-significant difference as per Tukey's test (P>0.05).}

Conclusions

The ME level of 3,100 Kcal/Kg resulted in improved performance in naked neck, French Hillbilly Stone Gray Rolled (Pedrês) chickens in the started phase, while protein and energy efficiency remained unchanged.

Bibliography

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Massi PA. 2007. Energia metabolizável para frangos de corte de diferentes potenciais de crescimento criados em sistema de semiconfinamento. Seropédica. Rio de Janeiro. Universidade Federal Rural do Rio de Janeiro. Instituto de Zootecnia.

Oliveira Neto AR, Oliveira RFM, Donzele JL, Rostagno HS, Ferreira RA, Carmo HM. 2000. Níveis de Energia Metabolizável para Frangos de Corte no Período de 22 a 42 Dias de Idade Mantidos em Ambiente Termoneutro. Rev. bras. Zootec. 29(4):1132-1140.

Pacheco O. 2004. Efeitos de diferentes níveis de energia e proteína sobre o desempenho de frangos de corte de linhagens colonial. Disertação de mestrado em ciências veterinária, UFPR.

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Xavier SAG, Stringhini JH, Brito AB, Andrade MA, Mogyca NS, Café MB. 2008. Níveis de energia metabolizável em rações pré-iniciais para frangos de corte. R. Bras. Zootec. 37(1):109-115.

Zanusso JT & Dionello NJL. 2003. Produção avícola alternativa - análise dos fatores qualitativos da carne de frangos de corte tipo caipira. R. bras. Agrociência 9(3):191-194.

FB Tavares²*, MSV Santos¹, SS Vieira⁴,HC Soares⁵, JPB Loureiro³, EM Lima⁵^Project Financed by FAPESPA, ¹Professor Animal Husbandry Graduate Course, Federal Rural University of Amazonia, Parauapebas Campus, Brazil; ²Master Undergraduate Amazonia´s Animal Health and Production and Animal Husbandry Professional, Federal Rural University of Amazonia, Parauapebas Campus, Brazil; ³Masters Undergraduate Amazonia's Animal Health and Production; ⁴Scholarship Holder, PIBIC/CNPQ/UFRA; ⁵Academicians, Animal Husbandry Graduate Course, Federal Rural University of Amazonia, Parauapebas Campus, Brazil.