Carcass traits of exotic french hillbilly broilers fed various energy levels

Introduction

Given the tremendous progress of poultry production, particularly in the broiler sector, the search of alternatives for formulating more efficient, lower cost diets is crucial, since feeding represents 70 - 80% of total broiler production cost. In this context, the effects of dietary energy levels on broiler performance are continually evaluated, due to their major impact on feed cost (Duarte et al., 2006). Reports exist in the literature showing that poultry performance is directly related with feed energy levels. Nevertheless, so far, limited research efforts have been done to determine the energy requirements of slow-growing chickens (Mendonça et al., 2008).

Nutrition plays a crucial role for poultry production success. Its objective is improving carcass yield, particularly breast meat yield. Several different papers have been published regarding dietary energy levels for broilers, aiming to obtain adequate requirements for improved yield (Barbosa et al., 2001). The purpose of this study was to evaluate the effects of dietary energy levels on carcass traits in French exotic hillbilly chickens .

Materials and Methods

The experiment was carried out in an experimental house, Federal Rural University of Amazonia (UFRA), located in Parauapebas, PA, Brazil. One hundred and ninety two (192) as hatched, one day old chickens of the above-mentioned lineage were reared under an intensive production system. The experimental design was completely at random, with 3 treatments and 4 repetitions each. The experimental unit consisted of on 16-bird pen.

Treatments included different energy levels in the feeds (starter, 1 - 28 days; grower, 29 - 90 days). Treatments were: T1, 3,000/3,100 kcal/kg ME; T2, 3,100/3,200 kcal/kg ME; T3: 3,200/3,300 kcal/kg ME. For preparation, conventional feedstuffs (i.e., corn, soybean meal, soybean oil, meat meal, limestone, dicalcium phosphate, sodium chloride and vitamin/mineral premix). When birds reached 77, 84, and 90 days, two birds per pen were identified, weighed, and killed. Studied variables included carcass yield, breast weight, thigh weight, leg weight, and relative weights of wings, back, feet, and head/neck. Results were statistically analyzed using the ANOVA procedure for a completely-at-random model with the Statistical and Genetic Analysis System (SAEG, 2007). Mean differences among variables were compared using Tukey's, at a significance level of 5%.

Results and Discussion

When looking at the effects of dietary energy levels, significant effects were found for carcass yield and relative breast weight in the chickens fed 3,100/3,200 kcal ME/kg, processed at 77 days of age, but they showed no statistically-significant differences when compared with T1, containing 3,000/3,100 kcal ME/kg (Table 1).

Regarding age at processing, significant effects were found for carcass yield, leg weight, and breast weight. With regard to carcass yield, it was observed that birds fed the diet containing 3,000/3,100 kcal ME/kg produced better results when processed at 84 days of age, with no statistically-significant difference with those processed at 77 days. Similar results were reported by Oliveira and Silva (2005), who undertook an experiment with the slow-growing strain ISA S757-N, showing that birds fed the highest energy levels (3,000 and 3,200 kcal ME/kg feed), had better carcass yield, breast yield, and thigh yield, when marketed at 80 days of age.

Chickens fed 3,000/3,200 kcal ME/kg had the best breast weight results when processed at 90 days of age, with no significant differences when compared with those processed at 77 days of age. Leg weight showed a significant effect in those birds fed 3,200/3,300 kcal ME/kg, processed at 90 days, with statistically-significant differences as compared with chickens processed at 77 and 84 days of age.

Table 1. Carcass yield, breast weight, thigh weight, and leg weight in French exotic hillbilly chickens fed rations containing various metabolizable energy levels and processed at 3 different ages

*Treatments*	*77 days*	*84 days*	*90 days*	*CV (%)*
Carcass yield
T1 - 3,000 and 3,100 kcal ME/kg	80.72^abAB	82.41^aA	84.10^aB	3.52
T2 - 3,100 and 3,200 kcal ME/kg	82.20^aA	82.35^aA	79.87^aA	7.20
T3 - 3,200 and 3,300 kcal ME/kg	76.42^bA	81.36^aA	80.37^aA	6.78
CV (%)	5.64	9.76	8.74
	Breast weight
T1 - 3,000 and 3,100 kcal ME/kg	23.20^abAB	21.60^aB	25.06^aA	9.10
T2 - 3,100 and 3,200 kcal ME/kg	24.26^aA	20.57^aA	23.27^aA	12.70
T3 - 3,200 and 3,300 kcal ME/kg	21.84^bA	22.35^aA	23.16^aA	5.82
CV (%)	5.69	12.82	7.07
	Thigh weight
T1 - 3,000 and 3,100 kcal ME/kg	13.65^aA	14.13^aA	13.76^aA	9.64
T2 - 3,100 and 3,200 kcal ME/kg	13.59^aA	13.73^aA	13.97^aA	8.25
T3 - 3,200 and 3,300 kcal ME/kg	13.73^aA	14.04^aA	13.85^aA	6.49
CV (%)	6.48	8.76	8.74
	Leg weight
T1 - 3,000 and 3,100 kcal ME/kg	12.82^aA	13.30^aA	13.56^aA	5.80
T2 - 3,100 and 3,200 kcal ME/kg	13.51^aA	12.88^aA	13.30^aA	11.27
T3 - 3,200 and 3,300 kcal ME/kg	12.60^aB	12.77^aB	13.62^aA	6.86
CV (%)	6.96	10.86	7.98

^{Means followed by different small letters within a column and capital letters in a line are statistically different as per Tukey's test (P<0.05).}

Takahashi et al. (2006) found different results, since they did not detect any statistical differences in the yield of commercial parts from Naked Neck or Paradise Pedrês billhilly chickens at 84 days of age, fed diets containing 2,800 and 2,900 kcal ME/kg.

When the effect of energy levels on part yields was evaluated, no differences were found in the relative weights of wings, back, feet, head/neck for the various energy levels (Table 2).

When market ages were studies, an effect was found in the relative weights of backs and feet of birds fed diets containing 3,000/3,100 kcal ME/kg. AS far as the relative weight of back is concerned, processing the birds at 84 days was better, with statistically-significant differences as compared with processing at 77 or 90 days of age. Feet showed better results when processing was practiced at 77 days of age, but n significant differences were found in the relative weights of feet in birds processed at 84 days of age. In agreement with Moreira et al. (2003), carcass yield and part yield variations in broilers of commercial genotypes observed in several studies have been attributed to differences in growth rate and processing age.

Table 2. Relative weights of wings, backs, feet, heads/necks of French exotic hillbilly chickens fed rations containing various levels of metabolizable energy, and processed at 3 different ages

Treatments	77 days	84 days	90 days	CV (%)
Wings
T1 - 3,000 and 3,100 kcal ME/kg	10.56^aA	10.65^aA	10.15^aA	6.29
T2 - 3,100 and 3,200 kcal ME/kg	10.63^aA	10.31^aA	10.31^aA	7.99
T3 - 3,200 and 3,300 kcal ME/kg	10.52^aA	10.57^aA	10.59^aA	3.52
CV (%)	6.12	6.57	5.10
	Back
T1 - 3,000 and 3,100 kcal ME/kg	18.60^aB	23.56^aA	18.58^aB	17.61
T2 - 3,100 and 3,200 kcal ME/kg	21.06^aA	21.53^aA	19.48^aA	8.69
T3 - 3,200 and 3,300 kcal ME/kg	21.69^aA	22.24^aA	19.68^aA	5.96
CV (%)	14.31	9.51	6.39
	Feet
T1 - 3,000 and 3,100 kcal ME/kg	4.87^aA	5.19^aAB	4.21^aB	13.04
T2 - 3,100 and 3,200 kcal ME/kg	4.72^aA	4.25^aA	4.24^aA	16.57
T3 - 3,200 and 3,300 kcal ME/kg	4.85^aA	4.70^aA	4.32^aA	13.29
CV (%)	11.60	25.00	11.63
	Head + Neck
T1 - 3,000 and 3,100 kcal ME/kg	11.95^aA	10.62^aA	11.33^aA	24.94
T2 - 3,100 and 3,200 kcal ME/kg	9.55^aA	10.31^aA	11.06^aA	11.85
T3 - 3,200 and 3,300 kcal ME/kg	10.76^aA	10.30^aA	10.99^aA	11.52
CV (%)	10.08	12.89	8.46

^{Means followed by different small letters within a column and capital letters in a line are statistically different as per Tukey's test (P<0.05).}

Conclusions

Dietary energy levels had no influence on the relative weights of thigh, legs, wings, backs, feet, or heads + necks of chickens processed at 77, 84, and 90 days of age. Birds fed the diets containing 3,000/3,100 or 3,100/3,200 kcal ME/kg showed the best carcass yield and relative breast weight results when processed at 77 days.

Bibliography

Barbosa MJB, Junqueira OM, Andreotti MdeO, Cancherini LC, Araújo LF. 2001. Desempenho e Rendimento de Carcaça de Frangos de Corte Submetidos a Diferentes Níveis de Treonina e Lisina, na Fase Final de Criação. Revista Brasileira de Zootecnia, 30(5):1476-1480.

Duarte KF, Junqueira OM, Filardi RdaS, Laurentiz ACde, Casartelli EM, Assuena V, Ribeiro PdeAP. 2006. Efeito de diferentes níveis de energia e de programas de alimentação sobre o desempenho de frangos de corte abatidos tardiamente. Revista Brasileira de Zootecnia 35(5):1992-1998.

Mendonça MdeO, Sakomura NK, Santos FR, Freitas ER, Fernandes JBK, Barbosa NAA. 2008. Níveis de energia metabolizável para machos de corte de crescimento lento, criados em semi-confinamento. Revista brasileira de Zootecnia 37(8):1433-1440.

Moreira J, Mendes AA, Garcia EA et al. 2003. Avaliação de desempenho, rendimento de carcaça e qualidade da carne do peito em frangos de linhagens de conformação versus convencionais. Revista Brasileira de Zootecnia 32(6):1663-1673.

SAEG - Sistema para Análise Estatística. 2007. Versão 9.1: Fundação Arthur Bernardes - UFV - Viçosa.

Takahashi SE, Mendes AA, Saldanha ESPB, Pizzolante CC, Pelícia K, Garcia RG, Paz ECLA, Quinteiro RR. 2006. Efeito do sistema de criação sobre o desempenho e rendimento de carcaça de frangos de corte tipo colonial. Arquivos Brasileiros de Medicina Veterinária e Zootecnia 58(4):624-632.

Carcass traits of exotic french hillbilly broilers fed various energy levels

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