Abstract
Aims of the research were to devise a proteome map of the chicken Pectoralis superficialis muscle, as resolved by two-dimensional gel electrophoresis, and to characterize protein expression changes in the soluble protein fraction in commercial conditions due to age and to time in transit before slaughtering. Broilers were reared under commercial conditions until they reached a mean 1.8 kg and 36 d, or 2.6 kg and 46 d of age. Transport to the slaughterhouse took 90 or 220 minutes. Transport-induced stress was assessed from blood metabolites and leukocyte cell counts, revealing significant changes in albumin, glucose and triglyceride concentrations, in heterophils and leukocyte counts for chickens in transit for longer, and in glucose depending mainly on age. The sarcoplasmic protein fractions were extracted from a total of 39 breast muscle samples, collected 15 min post mortem, for analysis by two-dimensional electrophoresis.Image and statistical analyses enabled us to study the qualitative and quantitative differences between the samples. Twelve up- or down-regulated protein spots were detected (P < 0.05): 8 related to the age effect, 2 to time in transit, and 2 to the interaction between the two. Age and time in transit influenced the avian proteome regulating the biological processes linked to the cellular housekeeping functions, related mainly to metabolism, cell division and control of apoptosis. Principal component analysis clustering was used to assess differences between birds. Age difference discriminated between the chickens analyzed better than time in transit, which seemed to have less general impact on the proteome fraction considered here.Isolating and identifying the proteins whose expression changes in response to transport duration and age shed some light on the biological mechanisms underlying growth and stress-related metabolism in chickens. Our results, combined with a further characterization of the chicken proteome associated with commercial chicken slaughtering management, will hopefully inspire alternative strategies and policies, and action to reduce the impact of stress related to time in transit.
Highlights
Rapidly-growing chickens bred for meat have been intensively selected for over 60 years, aiming for high growth and feed conversion rates, and low slaughtering age
Blood metabolite analysis and leukocyte counts for these same broilers have already been reported by Yalçın and Güler [6], who analyzed three groups of broilers that had been transported for different periods of time, sampling the groups spending the shortest and longest time in transit (90 and 220 minutes) for proteomic analysis
Using a threshold of 0.05 < P < 0.10, the analysis indicated that older broilers in transit for longer had a higher content of two proteins involved in the energy metabolism pathway, while younger broilers showed no differences in relation to time in transit
Summary
Rapidly-growing chickens bred for meat have been intensively selected for over 60 years, aiming for high growth and feed conversion rates, and low slaughtering age. Many disorders and end-product defects have been associated with the birds’ accelerated muscle growth and inappropriate pre-slaughter management, including ascites, pulmonary hypertension, dehydration, PSE meat [3,4,5]. The distance they are carried from the farm to the slaughterhouse has been correlated with end-product quality parameters [6], showing a negative impact of transport-induced stress on meat pH and color. Hazard et al [16] used proteomic, transcriptomic, and metabolomic approaches to assess the molecular basis for muscle response to stress in chickens, reporting expression changes in 45 protein spots, found related mainly to the cytoskeletal structure or carbohydrate metabolism networks
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