Proximal femoral head transcriptome reveals novel candidate genes related to epiphysiolysis in broiler chickens.

BACKGROUND: The proximal femoral head separation (FHS) or epiphysiolysis is a prevalent disorder affecting the chicken femur epiphysis, being considered a risk factor to infection which can cause bacterial chondronecrosis with osteomyelitis in broilers. To identify the genetic mechanisms involved in epiphysiolysis, differentially expressed (DE) genes in the femur of normal and FHS-affected broilers were identified using RNA-Seq technology. Femoral growth plate (GP) samples from 35-day-old commercial male broilers were collected from 4 healthy and 4 FHS-affected broilers. Sequencing was performed using an Illumina paired-end protocol. Differentially expressed genes were obtained using the edgeR package based on the False Discovery Rate (FDR < 0.05). RESULTS: Approximately 16 million reads/sample were generated with 2 × 100 bp paired-end reads. After data quality control, approximately 12 million reads/sample were mapped to the reference chicken genome (Galgal5). A total of 12,645 genes were expressed in the femur GP. Out of those, 314 were DE between groups, being 154 upregulated and 160 downregulated in FHS-affected broilers. In the functional analyses, several biological processes (BP) were overrepresented. Among them, those related to cell adhesion, extracellular matrix (ECM), bone development, blood circulation and lipid metabolism, which are more related to chicken growth, are possibly involved with the onset of FHS. On the other hand, BP associated to apoptosis or cell death and immune response, which were also found in our study, could be related to the consequence of the FHS. CONCLUSIONS: Genes with potential role in the epiphysiolysis were identified through the femur head transcriptome analysis, providing a better understanding of the mechanisms that regulate bone development in fast-growing chickens. In this study, we highlighted the importance of cell adhesion and extracellular matrix related genes in triggering FHS. Furthermore, we have shown new insights on the involvement of lipidemia and immune response/inflammation with FHS in broilers. Understanding the changes in the GP transcriptome might support breeding strategies to address poultry robustness and to obtain more resilient broilers.

Efeito de linhagem e sexo nas características geométricas ebiomecânicas de tíbias de frangos de corte / Effects of lineage and sex on geometrical and biomechanical properties of broiler chickens tibias

A criação intensiva de frangos de corte, aliada à nutrição e ao melhoramento genético com foco no ganho de peso, tem resultado em índices crescentes da incidência de problemas de pernas. Dentre as variáveis que podem contribuir para a ocorrência destes problemas, estão a linhagem e o sexo. Neste contexto, avaliaram-se propriedades geométricas e mecânicas de tíbias de frangos de corte, machos e fêmeas, de três linhagens comerciais no periodo final de crescimento, entre 21 e 42 dias. As características geométricas refletem a resposta adaptativa dos ossos, com relação direta entre suas dimensões e o peso vivo das aves. Quanto às características mecânicas obtidas de ensaios de flexão, observa-se o que o julgamento da robustez óssea pode levar a conclusões diferentes dependendo da variável mecânica considerada. Aves mais pesadas, com ossos maiores, suportam forças maiores na flexão. Entretanto, quando variáveis de resistência intrínsecas do material são consideradas, como resistência à flexão, observa-se que a linhagem mais pesada não apresenta resistência à flexão significativamente diferente das demais. O mesmo ocorre entre machos (mais pesados) e fêmeas. Logo, aves mais pesadas, com tíbias tão resistentes quanto às das aves mais leves, podem ser mais susceptíveis a problemas estruturais de pernas.(AU)

The intensive rearing of broilers, combined with nutrition and genetic improvement focused on weight gain has resulted in increasing rates of leg problems. Among the variables that may contribute to the occurrence of these problems are sex and lineage. In this context, the study evaluated the geometric and mechanical properties of the tibiae of broilers, male and female, from three commercial lines in the final growth stage, between 21 and 42 days. The geometric characteristics reflect the adaptive response of bone, with a direct relationship between their dimensions and the live weight of birds. As for the mechanical properties obtained from bending tests, it is observed that the evaluation of bone strength can lead to different conclusions depending on the mechanical parameter considered. Heavier birds, with larger bones, support more load in bending. However, when intrinsic strength parameters of the material are considered, such as bending strength, it is observed that the heavier line does not show significantly different values from the others. The same occurred among males (heavier) and females. Thus, heavier birds may be more susceptible to structural leg problems, as their tibias are as strong as those from lighter birds.(AU)

Efeito de linhagem e sexo nas características geométricas ebiomecânicas de tíbias de frangos de corte / Effects of lineage and sex on geometrical and biomechanical properties of broiler chickens tibias

A criação intensiva de frangos de corte, aliada à nutrição e ao melhoramento genético com foco no ganho de peso, tem resultado em índices crescentes da incidência de problemas de pernas. Dentre as variáveis que podem contribuir para a ocorrência destes problemas, estão a linhagem e o sexo. Neste contexto, avaliaram-se propriedades geométricas e mecânicas de tíbias de frangos de corte, machos e fêmeas, de três linhagens comerciais no periodo final de crescimento, entre 21 e 42 dias. As características geométricas refletem a resposta adaptativa dos ossos, com relação direta entre suas dimensões e o peso vivo das aves. Quanto às características mecânicas obtidas de ensaios de flexão, observa-se o que o julgamento da robustez óssea pode levar a conclusões diferentes dependendo da variável mecânica considerada. Aves mais pesadas, com ossos maiores, suportam forças maiores na flexão. Entretanto, quando variáveis de resistência intrínsecas do material são consideradas, como resistência à flexão, observa-se que a linhagem mais pesada não apresenta resistência à flexão significativamente diferente das demais. O mesmo ocorre entre machos (mais pesados) e fêmeas. Logo, aves mais pesadas, com tíbias tão resistentes quanto às das aves mais leves, podem ser mais susceptíveis a problemas estruturais de pernas.

The intensive rearing of broilers, combined with nutrition and genetic improvement focused on weight gain has resulted in increasing rates of leg problems. Among the variables that may contribute to the occurrence of these problems are sex and lineage. In this context, the study evaluated the geometric and mechanical properties of the tibiae of broilers, male and female, from three commercial lines in the final growth stage, between 21 and 42 days. The geometric characteristics reflect the adaptive response of bone, with a direct relationship between their dimensions and the live weight of birds. As for the mechanical properties obtained from bending tests, it is observed that the evaluation of bone strength can lead to different conclusions depending on the mechanical parameter considered. Heavier birds, with larger bones, support more load in bending. However, when intrinsic strength parameters of the material are considered, such as bending strength, it is observed that the heavier line does not show significantly different values from the others. The same occurred among males (heavier) and females. Thus, heavier birds may be more susceptible to structural leg problems, as their tibias are as strong as those from lighter birds.

Selecting appropriate bedding to reduce locomotion problems in broilers

Two experiments were carried out at the Poultry Sector of the School of Agrarian Sciences of the Federal University of Grande Dourados to evaluate the incidence of leg problems in broilers reared on two distinct types of bedding material: rice husks or wood shavings, both new and reused. In both trials, a randomized experimental design was applied in factorial arrangement (2 x 2 x 2) using two genetic strains (Cobb® or Ross®); two sexes (male or female), and two litter materials (rice husks or wood shavings). In each trial 1080 one day pullets were reared equally divided in the treatments. The birds were placed in 4.5 m² boxes at a density of 10 birds m-2. All birds were fed diets with equal nutritional density, and water was offered ad libitum. Feeds were divided in three phases: starter diet (1 - 21 days), grower diet (22 - 35 days), and finisher diet (36 - 45 days). On day 45, fifty birds were randomly selected in each experiment to evaluate flock leg problems. The following parameters were analyzed: gait score, incidence of valgus and varus disorder, footpad dermatitis, femoral degeneration, tibial dyschondroplasia, and spondylolisthesis. Ambient temperature during rearing and litter caking and moisture content were recorded in four boxes per treatment. The analytical hierarchy process was used to organize the data into specific criteria. Several criteria, related to the attributes that were determinant according to the statistical analysis, were chosen in order to provide the best input to the process. Results indicated that new wood-shavings bedding was the most appropriate bedding to prevent locomotion problems, followed by new rice husks, reused wood shavings, and reused rice husks. However, when leg problems were associated to sex and genetic strain, male Ross birds strain presented less problems when reared on new rice husks, followed by new wood shavings

Selecting appropriate bedding to reduce locomotion problems in broilers

Two experiments were carried out at the Poultry Sector of the School of Agrarian Sciences of the Federal University of Grande Dourados to evaluate the incidence of leg problems in broilers reared on two distinct types of bedding material: rice husks or wood shavings, both new and reused. In both trials, a randomized experimental design was applied in factorial arrangement (2 x 2 x 2) using two genetic strains (Cobb® or Ross®); two sexes (male or female), and two litter materials (rice husks or wood shavings). In each trial 1080 one day pullets were reared equally divided in the treatments. The birds were placed in 4.5 m² boxes at a density of 10 birds m-2. All birds were fed diets with equal nutritional density, and water was offered ad libitum. Feeds were divided in three phases: starter diet (1 - 21 days), grower diet (22 - 35 days), and finisher diet (36 - 45 days). On day 45, fifty birds were randomly selected in each experiment to evaluate flock leg problems. The following parameters were analyzed: gait score, incidence of valgus and varus disorder, footpad dermatitis, femoral degeneration, tibial dyschondroplasia, and spondylolisthesis. Ambient temperature during rearing and litter caking and moisture content were recorded in four boxes per treatment. The analytical hierarchy process was used to organize the data into specific criteria. Several criteria, related to the attributes that were determinant according to the statistical analysis, were chosen in order to provide the best input to the process. Results indicated that new wood-shavings bedding was the most appropriate bedding to prevent locomotion problems, followed by new rice husks, reused wood shavings, and reused rice husks. However, when leg problems were associated to sex and genetic strain, male Ross birds strain presented less problems when reared on new rice husks, followed by new wood shavings