Growth performance, carcass traits and physical properties of chicken meat as affected by genotype and production system

Abstract. The results of this study constitute a part of a project aiming at developing a cross-breed suitable for an extensive rearing system, utilising local biodiversity. Hybrids from mating a commercial broiler's male component (C) with Green-legged Partridgenous (GP) or Sussex (Sx) hens were compared with Cobb broilers. The study included 720 chickens of 3 genetic groups. Up to the third week of age, all birds were fed with balanced mixtures recommended for broiler chickens. From the fourth week, the mixture was weekly reduced by 10 % for the birds kept extensively (E). The deducted part was replaced with wheat bran, and from the seventh week with wheat. E groups had access to runs and received green fodder. Birds were slaughtered in 12th week of life. Carcass yield, giblets and proportion of carcass elements were estimated along with meat traits. The body weight at the 6th, 9th, 12th week of rearing and dissection results indicated a good suitability of Cobb chickens for an extensive rearing system. Hybrids were characterised by a considerably smaller proportion of breast muscle and slightly bigger of thighs and drumsticks, compared with Cobb, which could result from their greater motor activity. Results obtained by C × Sx and C × GP chickens, such as final body weight, proportions of abdominal fat and carcass elements, and appropriate value of meat traits, point at the usefulness of these hybrids as a meat-type chicken under extensive housing conditions. Darker colour of chicken meat, derived from C cocks and Sx or GP hens crossbred, can constitute an indicator for their carcasses' identification on the market.

INCIDÊNCIA DA CLAUDICAÇÃO DE AVES EM DIFERENTES IDADES E AVIÁRIOS

A finalidade da criação de frango de corte é a alta produtividade da ave. O objetivo deste trabalho foi verificar a incidência da claudicação de aves em diferentes idades e aviários. O trabalho foi realizado em quatro aviários denominados A1, A2 A3 e A4, de uma granja comercial durante dois lotes de produção de frango de corte. Todos os aviários apresentavam dimensões similares, sendo que A1, A2 e A3 eram com ventilação forçada utilizando pressão positiva, enquanto o aviário A4 apresentava ventilação forçada com pressão negativa. Os aviários A1 e A4 possuíam cama reutilizada, o A2 tinha cama nova de pó de serragem, enquanto no A3 foi usada cama nova e casca de arroz como substrato. Foram registradas as condições de ambiência do alojamento (temperatura, umidade relativa e velocidade do ar). Para a avaliação da claudicação, as aves foram observadas visualmente, sendo atribuído o grau de gait score. Esta avaliação se deu em um total de 75 aves por aviário, nas idades de 25, 32 e 40 dias. Os resultados mostraram que houve interação das idades das aves em cada aviário sobre o gait score. O efeito da idade foi menos intenso nos aviários A1 e A2, entretanto, o efeito das idades nos aviários A3 e A4 se mostrou mais intenso, de modo que os níveis de gait score se diferiram para todas as idades. Todas as aves, independente dos aviários, apresentaram incidência de claudicação. A idade com menos problemas de claudicação foi aos 25 dias de idade, enquanto as aves dos aviários A3 e A4 apresentaram maior incidência de claudicação aos 40 dias de idade.

Genetic effects of polymorphisms in myogenic regulatory factors on chicken muscle fiber traits

The myogenic regulatory factors is a family of transcription factors that play a key role in the development of skeletal muscle fibers, which are the main factors to affect the meat taste and texture. In the present study, we performed candidate gene analysis to identify single-nucleotide polymorphisms in the MyoD, Myf5, MyoG, and Mrf4 genes using polymerase chain reaction-single strand conformation polymorphism in 360 Erlang Mountain Chickens from three different housing systems (cage, pen, and free-range). The general linear model procedure was used to estimate the statistical significance of association between combined genotypes and muscle fiber traits of chickens. Two polymorphisms (g.39928301T>G and g.11579368C>T) were detected in the Mrf4 and MyoD gene, respectively. The diameters of thigh and pectoralis muscle fibers were higher in birds with the combined genotypes of GG-TT and TT-CT (p<0.05). Moreover, the interaction between housing system and combined genotypes has no significant effect on the traits of muscle fiber (p>0.05). Our findings suggest that the combined genotypes of TT-CT and GG-TT might be advantageous for muscle fiber traits, and could be the potential genetic markers for breeding program in Erlang Mountain Chickens.

Effects of outdoor access days on growth performance, carcass yield, meat quality, and lymphoid organ index of a local chicken breed

An experiment was conducted to evaluate the effect of outdoor access days on growth performance, carcass yield, meat quality, and lymphoid organ index of a local chicken breed. In total, 864 twenty one-day-old male Suqin yellow chickens, with similar body weight (536±36g), were selected and raised in indoor floor pens that measured 1.42×1.42 m (2 m2, 18 birds/m2) in conventional poultry research houses (36 birds per pen). Two hundred and sixteen birds were allowed outdoor access treatments at 21, 28, 35, and 42 d of age, respectively (access to outdoor for 35, 28, 21, and 14 days, respectively). Each treatment was represented by 6 replicates (pens) containing 36 birds (216 birds per treatment). In the outdoor access treatment, the birds had an outdoor free-range paddock that measured 3×8 m (24 m2, 1.5 birds/m2). The body weight of birds at 56 d of age increased linearly with increasing outdoor access days (P<0.001), but there was no effect of the outdoor access days on the body weight at 42 d of age (P=0.161). The daily weight gain, daily feed intake, and feed per gain from 21 to 42 d of age were unaffected by outdoor access days (P=0.401, P=0.463, P=0.223, respectively). However, the daily weight gain and daily feed intake from 42 to 56 and from 21 to 56 d of age increased linearly with increasing outdoor access days (P=0.002, P<0.001; P=0.001, P=0.004; respectively), while the feed per gain tended to decrease linearly from 21 to 56 d of age (P=0.060). The mortality from 21 to 56 d of age was unaffected by outdoor access days (P=0.261). At 56 d of age, the breast yield increased linearly with increasing outdoor access days (P<0.001), while the foot yield decreased linearly (P=0.016). The light (L*) and red (b*) values of leg meat color increased linearly with increasing outdoor access days (P=0.032, P=0.013, respectively). The spleen: the body weight ratio showed a decreasing and then increasing quadratic response to increasing outdoor access days (P=0.047). The litter moisture content at 42 and 56 d of age increased linearly with increasing outdoor access days (P<0.001, P=0.013, respectively). The findings of this study suggest that increasing outdoor access days advantageously affects the body weight, daily weight gain, feed per gain and breast yield as well as the light (L*) and red (b*) values of leg meat color, while decreasing foot yield.

The influence of providing perches and string on activity levels, fearfulness and leg health in commercial broiler chickens

The aim of this study was to assess the effect of providing environmental enrichment in the form of perches and string on the behaviour and welfare of commercial broiler chickens. Houses containing ~23 000 broiler chickens were assigned to one of four treatments in a 2×2 factorial design. Treatments involved two levels of access to perches (P) (present (24/house) '+P' or absent '-P') and two levels of access to string (S) (present (24/house) '+S' or absent '-S'). All houses contained windows, and 30 straw bales were provided from day 10 of the rearing cycle. Treatments were applied in one of four houses on a single farm, and were replicated over four production cycles. Behaviour and leg health were observed in weeks 3 to 5 of the rearing cycle. Production performance and environmental parameters were also measured. There was an interaction between perches and age in the percentage of birds observed lying, with higher percentages of birds observed lying in the +P treatment than in the -P treatment during weeks 4 and 5. There was also a significant interaction between string and age in the percentage of birds observed in locomotion, with higher percentages observed in locomotion in the -S treatment than in the +S treatment during weeks 4 and 5. There was also an interaction between string and age in average gait scores, with lower gait scores in the +S treatment than in the -S treatment during weeks 3 and 5 but not within week 4. Daytime observations showed that perches and strings were used frequently, with one bout of perching occurring approximately every 80 s/perch, and one bout of pecking at string occurring every 78 s/string on average. There was a significant effect of age on use of perches (P<0.001) and string (P<0.001), with perching peaking during week 5 and string pecking peaking during week 3. We conclude that commercial broilers in windowed houses with access to straw bales display an interest in additional enrichment stimuli in the form of perches and string, and therefore that these stimuli have the potential to improve welfare. In addition, provision of string as a pecking device appeared to positively influence walking ability. However, this effect was numerically small, was only shown in certain weeks and was not reflected in the other leg health measure (latency to lie). The results also showed an apparent negative effect of string and perches on the activity levels of birds (recorded away from the immediate vicinity of these enrichments) towards the end of the production cycle. These results emphasise the need for further research into optimum design and layout of enrichment stimuli for modern broilers in windowed houses to ensure that their provision leads to clear welfare benefits.

Effects of different broiler production systems on health care costs in the Netherlands

This study analyzed the effects of different broiler production systems on health care costs in the Netherlands. In addition to the conventional production system, the analysis also included 5 alternative animal welfare systems representative of the Netherlands. The study was limited to the most prevalent and economically relevant endemic diseases in the broiler farms. Health care costs consisted of losses and expenditures. The study investigated whether higher animal welfare standards increased health care costs, in both absolute and relative terms, and also examined which cost components (losses or expenditures) were affected and, if so, to what extent. The results show that health care costs represent only a small proportion of total production costs in each production system. Losses account for the major part of health care costs, which makes it difficult to detect the actual effect of diseases on total health care costs. We conclude that, although differences in health care costs exist across production systems, health care costs only make a minor contribution to the total production costs relative to other costs, such as feed costs and purchase of 1-d-old chicks.

Comparison of meat quality characteristics and oxidative stability between conventional and free-range chickens

The aim of this research was to evaluate quality traits and oxidative stability of meat products from free-range (FR) and conventionally (C) raised chickens as they actually reach consumers in the Italian retail market. Free-range female and male chickens (n = 1,500 + 1,500), medium growing ISA strain, were raised under commercial conditions for 56 (1.8 kg of live weight) and 70 d (3.1 kg of live weight), respectively; C female and male birds (n = 5,000 + 5,000) were a fast growing hybrid (Ross 708) and were separately raised for 39 (1.9 kg of live weight) and 50 d (3.1 kg of live weight), respectively. A total of 96 chickens (equally divided by production system and sex) were slaughtered in 2 separate sessions to obtain the main 2 commercial categories (rotisserie and cut-up, respectively). After slaughtering, 12 carcasses of each treatment group were randomly selected and used to assess quality properties, chemical composition, and oxidation stability of breast and leg meat. The C birds had dramatic higher carcass and breast meat yield, whereas FR had higher wing and leg yields. The FR birds exhibited higher water holding capacity in both breast and leg meat. Although shear force did not differ in breast meat, legs from FR birds were tougher. Fatty acid composition of FR breast and thigh meat of both categories were characterized by a higher polyunsaturated fatty acid n-6-/n-3 ratio. In general, a low lipid oxidation level (peroxide value < 1.3 mEq O2/kg of lipid and TBA reactive substances < 0.2 mg malondialdehyde/kg of sample) was found in breast and legs, regardless of the commercial category. However, the C system significantly increased peroxide value in rotisserie thigh meat, whereas FR led to a significantly higher TBA reactive substances in breast meat. Our results demonstrated that free range can modify the properties of chicken meat and also highlighted the importance of the bird genetic background to select nutritional strategies to improve meat quality traits and oxidative stability in poultry.

Nutrient density and slaughter age have differential effects on carcase performance, muscle and meat quality in fast and slow growing broiler genotypes

1. A 2 × 2 factorial design was used to investigate the differences in carcase, muscle and meat characteristics between fast and slow growing genotypes fed on low nutrient (LND) or high nutrient diets (HND) at their respective slaughter ages. 2. The birds were randomly assigned to treatments with 5 replicates of 145 birds for Wens Yellow-Feathered Chicken (WYFC, 5·75 birds/m(2)) or 115 birds for White Recessive Rock Chicken (WRRC, 7·25 birds/m(2)), according to the commercial recommendations for the two breeds and were fed on HND or LND. Birds were slaughtered at 63 d and 105 d of age. 3. The results showed WRRC had higher carcase yield and meat yield than that of WYFC, lower fat content, higher moisture content and lower cooking loss. The meat from WRRC was less tender and contained lower levels of polyunsaturated fatty acids (PUFA). 4. Birds fed on HND had higher breast meat yield, myofiber area and protein content in the breast muscle and lower fat content than birds fed on LND. The thigh muscle of birds fed on HND had higher levels of PUFA. Age had a positive effect on carcase parameters, but a negative effect on pH, meat tenderness and cooking loss, and the two genotypes exhibited different responses to the influence of nutrient density and age. 5. Genotype and age had the largest effect on carcase performance and meat quality. LND benefited meat quality and WRRC had larger responses in meat yield and shear force when fed on HND.

Lisina digestível em dietas de baixa proteína para frangos de corte tipo caipira de um aos 28 dias

Avaliou-se a inclusão de diferentes porcentagens de lisina digestível em dietas de baixa proteína para frangos de corte tipo caipira, machos e fêmeas, com idade entre um e 28 dias. Utilizaram-se 792 machos e 792 fêmeas de linhagem comercial, de um dia de idade, distribuídos em delineamento inteiramente ao acaso, em esquema fatorial 2x6 (sexo x porcentagem de lisina digestível: 0,85; 0,90; 0,95; 1,00; 1,05 e 1,10%) com seis repetições de 22 aves. Não foi constatada interação (P>0,05) de sexo versus inclusão de lisina. Observou-se superioridade (P<0,05) dos machos em relação às fêmeas para todas as variáveis avaliadas. O ganho de peso dos frangos diminuiu linearmente (P<0,05) em função do aumento da porcentagem de lisina digestível na dieta e observou-se redução linear (P<0,01) nos consumos de ração e de proteína. O consumo de lisina digestível aumentou linearmente (P<0,01) em função do aumento de sua concentração na dieta. Não houve diferença (P>0,05) para conversão alimentar. Da composição centesimal da carcaça, apenas o percentual de matéria mineral foi influenciada (P<0,05) pela porcentagem de lisina digestível. Conclui-se que 0,85% de lisina para frangos tipo caipira de pescoço pelado atende à exigência nutricional de lisina digestível em dietas com baixa concentração proteica.

The effects of broiler chicken growth rate on valgus, varus, and tibial dyschondroplasia

An experiment was conducted to test the hypothesis that the growth rate of broilers influences their susceptibilities to bone abnormalities, causing major leg problems. Leg angulations, described in the twisted legs syndrome as valgus and bilateral or unilateral varus, were investigated in 2 subpopulations of mixed-sex Arkansas randombred broilers. Valgus angulation was classified as mild (tibia-metatarsus angle between 10 and 25°), intermediate (25-45°), or severe (> 45°). Body weight was measured at hatch and weekly until 6 wk of age. There were 8 different settings of approximately 450 eggs each. Two subpopulations, slow growing (bottom quarter, n = 581) and fast growing (top quarter, n = 585), were created from a randombred population based on their growth rate from hatch until 6 wk of age. At 6 wk of age, tibial dyschondroplasia incidences were determined by making a longitudinal cut across the right tibia. The tibial dyschondroplasia bone lesion is characterized by an abnormal white, opaque, unmineralized, and unvascularized mass of cartilage occurring in the proximal end of the tibia. It was scored from 1 (mild) to 3 (severe) depending on the cartilage plug abnormality size. Mean lesion scores of left and right valgus and tibial dyschondroplasia (0.40, 0.38, and 0.06) of fast-growing broilers were higher than those (0.26, 0.28, and 0.02) of slow-growing broilers (P = 0.0002, 0.0037, and 0.0269), respectively. Growth rate was negatively associated with the twisted legs syndrome and a bone abnormality (tibial dyschondroplasia) in this randombred population.

Níveis nutricionais de cálcio para aves de corte ISA Label criadas sob semiconfinamento

Determinaram-se os níveis nutricionais de cálcio (Ca) para aves, machos e fêmeas, da linhagem ISA Label, nas fases inicial (um a 28 dias), crescimento (28 a 56 dias) e final (56 a 84 dias). Foram realizados três ensaios, um para cada fase, e, em cada ensaio, 480 aves com idade correspondente à fase de criação foram alojadas em 24 unidades experimentais com áreas de abrigo e de pastejo. Foi utilizado delineamento inteiramente ao acaso, em esquema fatorial 4x2 (Ca e sexo), totalizando oito tratamentos com três repetiç ões de 20 aves. Avaliaram-se: ganho de peso (GP); consumo de dieta (CD); conversão alimentar (CA); teores de fósforo (PT), de cálcio (CaT) e de cinzas na tíbia (CT) e resistência à quebra óssea (RQO). Na fase inicial, recomenda-se 1,16% de Ca na dieta, para aves de ambos os sexos, na fase de crescimento, 0,78 e 0,88% de Ca para machos e fêmeas, respectivamente, e, na fase final, 0,69% de Ca na dieta para ambos os sexos.

Live performance, carcass composition, and blood metabolite responses to dietary nutrient density in two distinct broiler breeds of male chickens

A study was conducted to evaluate the effects of varying nutrient density with constant ME:CP ratio on growing performance, carcass characteristics, and blood responses in 2 distinct broiler breeds of male chickens (Arbor Acres, a commercial line, and Beijing-You, a Chinese nonimproved line). Experimental diets were formulated with high, medium, or low nutrient densities for 3 growing phases. Starter diets (1 to 21 d) contained 23, 21, and 19% CP with 3,059, 2,793, and 2,527 kcal/kg of ME; grower diets (22 to 35 d) contained 21, 19, and 17% CP with 3,150, 2,850, and 2,550 kcal/kg of ME; and finisher diets (36 to 42 d for Arbor Acres and 36 to 91 d for Beijing-You) had 19, 17, and 15% CP with 3,230, 2,890, and 2,550 kcal/kg of ME. Male hatchlings (216 of each breed) were randomly assigned to 6 replicates of 12 birds in each treatment. Arbor Acres broilers had better (P < 0.001) BW gain, feed conversion ratio (FCR), and carcass yield, but had greater (P < 0.001) abdominal and carcass fat deposition. In both breeds, the higher nutrient density increased (P < 0.05) BW gain, protein efficiency ratio, and energy efficiency ratio while decreasing (P < 0.05) feed intake and FCR. The breed differences were increased for FCR, protein efficiency ratio, and energy efficiency ratio in the starter period and decreased for carcass chemical composition, respectively, by higher nutrient density. These findings indicate that 1) genetic improvement has a significant effect on broiler responses to dietary nutrient density, 2) performance differences between breeds are lessened with diets of low nutrient density, 3) carcass quality differences are less when birds were fed diets of high nutrient density, 4) carcass composition is hardly modified by nutrient density and both breeds exhibit similar metabolite responses to dietary concentrations, and 5) optimal diets are deduced for these breeds for the 3 growing phases.