The effect of metabolizable energy levels on the performance of feathered-neck, gray master hillbilly chickens in the starting phase^

Introduction

The progress and competitiveness of Brazilian poultry industry have resulted in constant genetic improvement of poultry strains. Research is being conducted in order to find genotypes with superior traits, selecting not only the best performing birds, but also those with increased carcass/edible part yields (Stringhini et al., 2003).

Among food-producing species, broilers are distinguished for transforming plant products into high quality protein (Ramos et al. 2006). the production of hillbilly-type broilers is a highly promising sector lf alternative poultry production to fulfill the demand for tastier, firmed, enhanced flavored meat (Madeira et al., 2010). In addition to productive traits, the meat quality of chickens has become an important factor, since consumers demand good sensorial features such as meat appearance and consistency (Beraquet, 2000).

Evaluating different broiler strains is fundamental in order to have updated information about the productive traits that best fulfill consumers'''' demands (Mendes, 2001; Moreira et al., 2003). The energy level of the feed interferes directly with broiler performance (Mendes et al., 2004).

The objective of this study was to investigate the effect of dietary metabolizable energy (ME) levels on the performance of feathered-neck, Gray Master Hillbilly (French Exotic) chickens fed various ME levels in the starter phase.

Materials and Methods

The study was undertaken in an experimental house located in Parauapebas Show Park, State of Pará, Brazil. Us used 192 feathered-neck, Gray Master Hillbilly (French Exotic), as hatched, one-day-old chicks, reared under an intensive system.

The experimental design was completely at random, with 3 treatments and 4 repetitions of 16 birds each. Treatments (T) included various energy levels in the starter phase (1 - 28 days), i.e., T1: 3,000 Kcal ME/Kg; T2: 3,100 Kcal ME/Kg; T3: 3,200 Kcal ME/Kg. The feeds were prepared using conventional feedstuffs such as corn, soybean meal, soybean oil, meat meal, limestone, dicalcium phosphate, salt, vitamin/mineral premix.

Rations were formulated using the SuperCrac software (2008), aiming to fulfill birds'''' nutrient requirements (Table 1).

Table 1. % Composition and calculated analysis of the starter diets (1 - 28 days of age)

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
Limestone	0.37	0.36	0.35
Salt	0.30	0.30	0.30
Mineral/vitamin premix*	0.60	0.60	0.60
Total	100	100	100
Calculated analysis
Metabolizable 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
Available phosphorus, %	0.48	0.48	0.48
Sodium, %	0.17	0.17	0.17

^{(*)Composition per kg of product: Vit. A - 1,335,000 II; Vit. D3 - 300,000 II; Vit. E - 2,000 mg; Vit. B1 - 167 mg; Vit. B2 - 670 mg; Vit. B6 - 170 mg; Vit. K3 - 335 mg; Vit. B12 - 1,670 μg; Biotin - 7 mg; Folic acid - 67 mg; Niacin - 4,670 mg; Selenium - 35 mg; Antioxidant - 2,000 mg; Calcium pantotenate - 1,870 mg; Copper - 1,000 mg; Cobalt 17 mg; Iodine - 170 mg; Iron - 8,335 mg; Manganese - 10,835 mg; Zinc - 7,500 mg; Choline chloride 50% - 83,340; Methionine - 235,000 mg; Coccidiostat - 10,000 mg; Growth promoter - 10,000}

Once in the experimental house, chicks selected and weighed in order to obtain 16-bird-lots to be randomly distributed among the pens, in accordance with treatments and repetitions. The drinking water was given ad libitum. The drinkers were washed and refilled twice per day in order to prevent water intake s that could result in feed intake s. The feed was weighed once per week and offered ad libitum, feed in the feeders at all times. Twice per day, the feed in the feeders was mixed as to promote intake. Any litter particles were removed from feeders at this time.

Variables studied included start weight, end weight, feed intake (FI) daily weight gain (DWG), feed conversion rate (FCR), crude protein intake, protein efficiency, ME intake, and energy efficiency. Result statistical analysis was performed using the ANOVA procedure for a completely-at-random model, with the "Statistical and Genetic Analysis System" (SAEG, 2007). Differences among means were compared using Tukey´s test, at the 5% level.

Results and Discussion

End weight, DWG, and FCR were influenced by dietary Me levels, since birds receiving the diet with 3.200 Kcal ME/Kg yielded better results, but were not statistically different from those fed 3.100 Kcal ME/Kg (Table 2).

Table 2. Performance of feathered-neck, Gray Master Hillbilly (French Exotic) chickens fed various levels of Me in the starter phase (1-28 days of age)

Treatments	Start weight (g)	End weight (g)	Feed intake (g)	Weight gain (g/bird/day)	Feed Conversion Rate
T1 - 3,000 Kcal ME/Kg	35.00^a	615.75^b	1,074.00^a	20.74^b	1.85^b
T2 - 3,100 Kcal ME/Kg	34.75ª	655.75^ab	1,102.00^a	22.19a^b	1.77a^b
T3 - 3,200 Kcal ME/Kg	34.75ª	713.50^a	1,082.75^a	24.24ª	1.59ª
CV (%)	1.86	6.51	8.30	6.83	5.45

^{Means with different lower case letters in the columns are different, as per Tukey''''s test (P<0.05).}

Rocha et al. (2003) reported different results since their chickens fed two ME levels (2,850 and 3,000 Kcal/Kg) had no statistical differences in terms of WG, FI or FCR. On the other hand, Reginatto et al. (2000) used two ME levels (3,200 and 2,900 Kcal/Kg) and found that high ME diets resulted in increased WG (P<0.01), reduced FI (P<0.01) and, therefore, improved FCR (P<0.01) in broilers at 21 days of age.

Dietary energy levels did not influence crude protein intake, ME intake or energy efficiency. Nevertheless, protein efficiency was reduced as ME levels increased (Table 3).

Pacheco (2004), evaluated the effects of energy levels (2,800, 2,860, 2,920, 2,980 and 3,040 Kcal ME/Kg) and protein on the performance of Red Label (Label Rouge) and Super heavy (Pesadão) starting chickens, and concluded that all growing dietary ME levels resulted in improved energy/protein efficiency.

Table 3. Protein and energy efficiency of feathered-neck, Gray Master Hillbilly (French Exotic) chickens in the starter phase (1-28 days of age)

Variables	Treatments
T1 3,100 Kcal ME/Kg	T2 3,200 Kcal ME/Kg	T3 3,300 Kcal ME/Kg	CV (%)
Crude protein intake (Kg/bird/day)	8.44ª	8.66^a	8.51^a	8.30
Metabolizable energy intake (Kcal/bird/day)	115.07ª	122.01ª	123.74ª	8.26
Protein efficiency	0.41ª	0.39^ab	0.35^b	5.45
Energy efficiency	0.18ª	0.18ª	0.20ª	5.38

^{Means with different lower case letters in the columns are different, as per Tukey''''s test (P<0.05).}

Conclusions

The dietary level of 3,200 Kcal ME/Kg produced improved performance in the feathered-neck, Gray Master Hillbilly (French Exotic) chickens in the starter phase. Decreased protein efficiency were observed as dietary ME levels increased.

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EM Lima^1*, MSV Santos², SS Vieira³, FB Tavares⁴, LRO Sampaio¹, LTO Galvão⁵

^Project Financed by Pará State Research Protection Foundation ( FAPESPA); ¹Academicians, Animal Husbandry Graduate Course, Federal Rural University of Amazonia, Campus Parauapebas, Brazil; ²Professor Animal Husbandry Graduate Course, Federal Rural University of Amazonia, Parauapebas Campus, Brazil; ³Scholarship Holder, Pibic/CNPq/UFRA; ⁴Masters Undergraduate Amazonia´s Animal production and Health, Animal Husbandry Professional, Federal Rural University of Amazonia, Parauapebas Campus, Brazil; ⁵Animal Husbandry Professional Municipal Secretariat of Rural Production, Parauapebas, Brazil.