Effects of dietary amino acid levels and ambient temperature on mixed muscle protein turnover in Pectoralis major during finisher feeding period in two broiler lines

Effects of finisher diet nutrients density and slaughter age on energy and protein efficiency, productive and economic performance and meat quality of broilers

BACKGROUND

The current broilers have been greatly optimized for weight gain and breast yield, which necessitates the provision of nutrients-dense diets for maximum potential.

OBJECTIVES

The current study aimed to evaluate the effect of finisher diet nutrients density (ND) on energy and protein efficiency, productive and economic performance and breast meat quality of broilers raised until different slaughter age.

METHODS

A total of 600 23-day-old broiler male chicks (Cobb-500) were assigned to 10 treatments with six replicates and 10 birds each. Experimental treatments were included factorial arrangement of five increment (2.5%) levels of finisher diet ND (92.5%, 95%, 97.5%, 100% and 102.5% as strain recommendation) and slaughtered at 38 or 46 days of age. The relative difference in the energy level of experimental diets was used to increase ND levels at the same ratio.

RESULTS

Feed intake (FI) and breast meat quality traits exception water holding capacity (WHC) were not affected by finisher diet ND. In response to increasing finisher diet ND, energy and protein efficiency, productive traits, bio-economic index (BEI) and breast relative weight (BRW) linearly improved. However, residual feed intake and breast meat WHC improved with a quadratic trend. By using broken-line regression analysis, the optimum dietary ND was obtained at 97.5%-102% of strain recommendation. Energy and protein efficiency, feed conversion ratio and BEI deteriorated by prolonging rearing period. The BRW, meat lightness (L*), redness (a*), hue angle (h*) and WHC values for the birds slaughtered at 46 days of age were significantly higher, and cooking loss was lower than those slaughtered at 38 days old.

CONCLUSIONS

Broilers during the finisher period are not able to regulate their FIs with diet ND. The energy and protein efficiency, productive and economic performance were reduced when broilers were fed diluted diet or the rearing period was prolonged.

Effect of an immune challenge and two feed supplements on broiler chicken individual breast muscle protein synthesis rate

Optimization of broiler chicken breast muscle protein accretion is key for the efficient production of poultry meat, whose demand is steadily increasing. In a context where antimicrobial growth promoters use is being restricted, it is important to find alternatives as well as to characterize the effect of immunological stress on broiler chicken's growth. Despite its importance, research on broiler chicken muscle protein dynamics has mostly been limited to the study of mixed protein turnover. The present study aims to characterize the effect of a bacterial challenge and the feed supplementation of citrus and cucumber extracts on broiler chicken individual breast muscle proteins fractional synthesis rates (FSR) using a recently developed dynamic proteomics pipeline. Twenty-one day-old broiler chickens were administered a single 2H2O dose before being culled at different timepoints. A total of 60 breast muscle protein extracts from five experimental groups (Unchallenged, Challenged, Control Diet, Diet 1 and Diet 2) were analysed using a DDA proteomics approach. Proteomics data was filtered in order to reliably calculate multiple proteins FSR making use of a newly developed bioinformatics pipeline. Broiler breast muscle proteins FSR uniformly decreased following a bacterial challenge, this change was judged significant for 15 individual proteins, the two major functional clusters identified as well as for mixed breast muscle protein. Citrus or cucumber extract feed supplementation did not show any effect on the breast muscle protein FSR of immunologically challenged broilers. The present study has identified potential predictive markers of breast muscle growth and provided new information on broiler chicken breast muscle protein synthesis which could be essential for improving the efficiency of broiler chicken meat production. SIGNIFICANCE: The present study constitutes the first dynamic proteomics study conducted in a farm animal species which has characterized FSR in a large number of proteins, establishing a precedent for biomarker discovery and assessment of health and growth status. Moreover, it has been evidenced that the decrease in broiler chicken breast muscle protein following an immune challenge is a coordinated event which seems to be the main cause of the decreased growth observed in these animals.

Protein turnover in pigs: A review of interacting factors

Protein turnover defines the balance between two continuous and complex processes of protein metabolism, synthesis and degradation, which determine their deposition in tissues. Although the liver and intestine have been studied extensively for their important roles in protein digestion, absorption and metabolism, the study of protein metabolism has focused mainly on skeletal muscle tissue to understand the basis for its growth. Due to the high adaptability of skeletal muscle, its protein turnover is greatly affected by different internal and external factors, contributing to carcass lean-yield and animal growth. Amino acid (AA) labelling and tracking using isotope tracer methodology, together with the study of myofiber type profiling, signal transduction pathways and gene expression, has allowed the analysis of these mechanisms from different perspectives. Positive stimuli such as increased nutrient availability in the diet (e.g., AA), physical activity, the presence of certain hormones (e.g., testosterone) or a more oxidative myofiber profile in certain muscles or pig genotypes promote increased upregulation of translation and transcription-related genes, activation of mTORC1 signalling mechanisms and increased abundance of satellite cells, allowing for more efficient protein synthesis. However, fasting, animal aging, inactivity and stress, inflammation or sepsis produce the opposite effect. Deepening the understanding of modifying factors and their possible interaction may contribute to the design of optimal strategies to better control tissue growth and nutrient use (i.e., protein and AA), and thus advance the precision feeding strategy.

A novel dynamic proteomics approach for the measurement of broiler chicken protein fractional synthesis rate

RATIONALE

The study of protein synthesis in farm animals is uncommon despite its potential to increase knowledge about metabolism and discover new biomarkers of health and growth status. The present study describes a novel dynamic proteomics approach for the measurement of protein fractional synthesis rate (FSR) in broiler chickens.

METHODS

Chickens received a 10 g/kg oral dose of ² H₂ O at day 21 of their life. Body water ² H abundance was measured in plasma samples using a portable Fourier transform infrared spectrometer. Free and protein-bound amino acids (AAs) were isolated and had their ² H enrichment measured by gas chromatography with mass spectrometry (GC/MS). Peptide ² H enrichment was measured by proteomics analysis of plasma and muscle samples. Albumin, fibrinogen and muscle protein FSR were calculated from GC/MS and proteomics data.

RESULTS

Ala appeared to be more enriched at the site of protein synthesis than in the AA free pools. Glu was found to be the AA closest to isotopic equilibrium between the different AA pools. Glu was used as an anchor to calculate n(AA) values necessary for chicken protein FSR calculation in dynamic proteomics studies. FSR values calculated using proteomics data and GC/MS data showed good agreement as evidenced by a Bland-Altman residual plot.

CONCLUSIONS

A new dynamic proteomics approach for the measurement of broiler chicken individual protein FSR based on the administration of a single ² H₂ O oral bolus has been developed and validated. The proposed approach could facilitate new immunological and nutritional studies on free-living animals.

The Relationship between Performance, Body Composition, and Processing Yield in Broilers: A Systematic Review and Meta-Regression

This study aims to model the relationship among performance, whole body composition, and processing yield through meta-regression. Scientific papers found in Scopus and Google Scholar were included if they reported results and variability values of an actual experiment in the three mentioned groups of variables using a single broiler genetic line. Weighted mean effect sizes were determined with a random model, the risk of bias was determined, and heterogeneity was considered an indicator of usefulness. Meta-regressions considered the effect sizes of the response variable and the percent change in one or more variables as predictors. A 78-row database was built from 14 papers, including nine factors tested on 22,256 broilers. No influencing bias was found, and the data was determined useful. Meta-regressions showed that the changes in body weight gain (BWG) are inversely related to the effects in feed conversion ratio (FCR) (p < 0.001) and that the changes in FCR and effects in protein-to-fat gain (PFG) are directly related (p < 0.001). The changes in PFG and the effects on carcass conformation or the market value of birds are directly related (p < 0.001). In conclusion, body composition predicts carcass conformation and its market value, supporting its use to predict the economic value of broilers.

Protease supplementation reduced the heat increment of feed and improved energy and nitrogen partitioning in broilers fed maize-based diets with supplemental phytase and xylanase

An experiment was conducted to explore the effects of digestible amino acid (dAA) concentrations and supplemental protease on live performance and energy partitioning in broilers. Ross 308 male broilers (n = 288) were distributed into 24 floor pens and offered 1 of 4 dietary treatments with 6 replicates from 1 to 35 d of age. Dietary treatments consisted of a 2 × 2 factorial arrangement with dAA concentrations (standard and reduced [34 g/kg below standard]) and supplemental protease (without or with) as the main factors. At 1, 15, 28, and 35 d of age, feed and broilers were weighed to determine live performance. From 20 to 23 d of age, a total of 32 birds (2 birds/chamber, 4 replicates) were placed in closed-calorimeter chambers to determine respiratory exchange (heat production, HP), apparent metabolisable energy (AME), retained energy (RE), and net energy (NE). From 29 to 35 d of age, supplemental protease in the reduced-dAA diet decreased broiler feed conversion ratio (FCR) by 5.6 points, whereas protease supplementation in the standard-dAA diet increased FCR by 5.8 points. The indirect calorimetry assay revealed that supplemental protease decreased (P < 0.05) the heat increment of feed (HIF) by 0.22 MJ/kg. Also, from 20 to 23 d of age, broilers offered the reduced-dAA diet with supplemental protease had a higher daily body weight gain (BWG) (+10.4%), N intake (+7.1%), and N retention (+8.2%) than those offered the standard-dAA with supplemental protease. Broilers offered the reduced-dAA without supplemental protease exhibited a 3.6% higher AME-to-crude protein (CP) ratio than those offered other treatments. Protease supplementation in the standard- and reduced-dAA diets resulted in 2.7% and 5.6% lower AME intake-to-N retention ratios, respectively, compared with the unsupplemented controls. Reduced-dAA increased (P < 0.05) AME intake (+4.8%), RE (+9.8%), NE intake (+5.8%), NE intake-to-CP ratio (+3.0%), and RE fat-to-RE ratio (+8.6%). Protease supplementation increased (P < 0.05) respiratory quotient (+1.2%) and N retention-to-N intake ratio (+2.2%), NE-to-AME ratio (+1.9%), and reduced HP (−3.6%), heat increment (−7.4%), and NE intake-to-N retention (−2.5%). In conclusion, protease positively affected FCR and energy partitioning in broilers; responses were most apparent in diets with reduced-dAA concentrations.

Exposure of broiler chickens to chronic heat stress increases the severity of white striping on the pectoralis major muscle

A study was conducted to evaluate the effect of cyclic or chronic heat stress (HS) on the incidence and severity of white striping (WS) and histopathological changes in breast muscle of broiler chickens. One hundred eighty 1-day-old male chickens were randomly assigned to three research groups: control (standard temperature throughout the experiment), cyclic HS (32 ºC between 0800 and 2000 h from day 21 until the end of the experiment), and chronic HS (32 ºC from day 21 onwards). Cyclic and chronic HS groups showed a significant (P < 0.05) decrease in body weight gain and feed intake and poor feed conversion ratio in grower, finisher, and overall period. Serum biochemical profile was not different among the groups except globulin and P which were significantly higher (P < 0.05 and P < 0.001, respectively), in cyclic and chronic HS groups. Overall, WS incidence was numerically higher in control birds followed by chronic HS and cyclic HS birds, respectively. The chronic HS group had a lower incidence of mild (score 1) and a higher incidence of severe (score 2) WS lesions compared to control and cyclic HS groups. Histopathological analysis revealed that broilers subjected to chronic HS showed increased severity of myodegenerative changes, perivenular CD3 + cell infiltration, and lipidosis compared to control group. However, control and cyclic HS groups were not different in terms of histopathological lesions. In conclusion, this study confirms that cyclic or chronic HS may adversely affect the growth performance and that chronic HS may increase the severity of WS in broiler chickens.

Review: Physiological growth trend of current meat broilers and dietary protein and energy management approaches for sustainable broiler production

The food production system needs to be sustainable including poultry sector to feed the increasing global population. An accepted economical and environmental approach of broiler production is to produce larger broilers faster while using less feed. Broiler production is aimed at producing consumable meat and meat products. The global broiler meat market has evolved over the years with increasing selection pressure shifted toward attaining yield characteristics for increased cut-up parts such as breast and thighs. There is a shift toward a big bird market in the U.S. with approximately 70% of the broiler meat produced from large birds (>2.72 kg). Genetic selection of broilers for quantitative traits such as growth rate and lean muscle mass without increasing the fat mass has altered broiler physiological homeostasis to adapt toward the larger rates of muscle protein turnover. Physiological stresses created due to selection pressures in broilers have produced several muscle myopathies including an emerging one called woody breast myopathy. The sustainable broiler production practice may require humane consideration of raising broilers in less stressful grow-out regimes that will have minimal impact on broiler metabolic health. Another sustainability approach of broiler production toward feed efficiency lies on understanding dietary formulation approach of amino acids and energy that promote optimal nutrient utilization and minimal nutrient output to environment while also fulfilling the growth demands and body composition changes associated with increased protein gain in current meat broilers brought by the genetic progress.

Woody breast myopathy broiler show age-dependent adaptive differential gene expression in Pectoralis major and altered in-vivo triglyceride kinetics in adipogenic tissues

A study was conducted to understand the differentially expressed genes in Pectoralis (P) major under woody breast (WB) myopathy condition in a high yielding broiler strain using RNA-sequencing at the growing (d 21) and finishing (d 42 and d 56) grow-out ages. Follow-up study was conducted to understand the in vivo triglyceride (TG) synthesis (d 49) occurring in adipogenic tissues using deuterium oxide (2H2O) as a metabolic tracer. Results indicated the top physiological systems affected in myopathy broiler were related to the musculo-skeletal system (d 21, 42, and 56) and cardiovascular system (d 42 and 56). Ubiquitin-specific proteases are expressed higher in myopathy broiler at d 21 (OTUD1) and d 42 (SACS) that potentially indicated higher degradation of muscle protein occurring at those ages. While genes related to transcription factors and muscle cell differentiation (ZNF234, BTG2) and muscle growth (IGF1) were upregulated with myopathy broiler suggesting concurrent muscle fiber regeneration. The downregulation of PYGB and MGAM genes related to carbohydrate transport and metabolism at d 42 potentially indicated nutrient-deficient state of myopathy affected fibers; whereas the nutrient-deficient physiological state of cells seemed to be counteracted by up-regulation of genes related to carbohydrate (ALDOB, GPD1L2) at d 56. There was a reduced (P < 0.05) in vivo TG synthesis in liver of the myopathy broiler (0.123 %/hr) compared to non-myopathy broiler (0.197 %/hr). The majority of TG synthesized in liver with myopathy broiler could conceivably be delivered to P. major (rather than to abdominal fat pad storage) to fulfil the increased energy need of muscle cells (via TG lipolysis and fatty acid [FA] oxidation). The increased utilization of FAs in the WB affected muscle could result in reduced secretion of FAs into blood circulation leading to sub-optimal availability of FAs for re-esterification for TG synthesis in liver. Results indicated that myopathy broiler at later age (d 56) of grow-out period were synchronously going through adaptive physiological processes of feedback responses to adverse cellular states.

Protein and Amino Acid Metabolism in Poultry during and after Heat Stress: A Review

This review examined the influence of environmental heat stress, a concern facing modern broiler producers, on protein metabolism and broiler performance, as well as the physiological mechanisms that activate and control or minimize the detrimental impacts of stress. In addition, available scientific papers that focused on amino acids (AA) digestibility under stress conditions were analyzed. Furthermore, AA supplementation, a good strategy to enhance broiler thermotolerance, amelioration, or stress control, by keeping stress at optimal levels rather than its elimination, plays an important role in the success of poultry breeding. Poultry maintain homeothermy, and their response to heat stress is mainly due to elevated ambient temperature and the failure of effective heat loss, which causes a considerable negative economic impact on the poultry industry worldwide. Reduced feed intake, typically observed during heat stress, was the primary driver for meat production loss. However, accumulating evidence indicates that heat stress influences poultry metabolism and endocrine profiles independently of reduced feed intake. In conclusion, high ambient temperatures significantly reduced dietary AA intake, which in turn reduced protein deposition and growth in broilers. Further studies are required to determine the quantity of the AA needed in warm and hot climates and to introduce genetic tools for animal breeding associated with the heat stress in chickens.

Effects of dietary energy levels on Pectoralis major mixed muscle protein turnover and body composition in two broiler lines housed in different grow-out environments

This study determined the Pectoralis (P) major mixed muscle protein turnover (PT) in two meat broiler lines, Line A and Line B, during the finishing grow-out feeding period (21-42 days) as affected by the dietary metabolizable energy (ME) levels and ambient temperatures. Experimental finishing diets consisted of 80, 90, 100, 110 and 120% ME of recommended nutrient guidelines for energy level. Fractional synthesis rates (FSR) or fractional degradation rates (FDR) were measured in P. major at day 36 and 42. Protein and fat mass gain were measured, and respective energy retention efficiencies as protein and fat (EREp and EREf) were determined. Metabolic heat production (HP) was also reported. Experimental feeding studies were conducted in cool season (24 hr mean: 69.91˚F and 63.98% RH) and in hot season (24 hr mean: 77.55˚F and 86.04% RH). Results showed that FSR or FDR values were not affected by dietary ME levels at day 36, whereas reduced FSR (p < .05) were observed at day 42 fed diets with reduced ME levels (≤100% ME) which could have resulted from greater maintenance energy requirement of maturing broilers at that age. Broilers fed reduced ME diets (≤100% ME) maintained protein mass (equivalent to broilers fed ≥100%-120% ME) by reduced FDR and increased feed intake. Grow-out ambient temperature did not affect FSR or FDR values across ME levels. Line B retained higher protein mass, lower fat mass and greater HP compared to Line A. This was followed by higher feed intake in Line B. Further, Line B exhibited higher EREp and lower EREf across dietary ME levels. In summary, PT homeostasis and body composition changes in broiler lines studied seemed to be regulated by the birds' intent to normalize energy intake as per physiological need by controlling feed intake.

Effects of dietary energy levels on performance and carcass yield of 2 meat-type broiler lines housed in hot and cool ambient temperatures

Two meat-type broiler lines, line A and line B were fed experimental diets from 22-42 d with objectives to determine the effects of dietary metabolizable energy (ME) levels on feed intake (FI), performance, body composition, and processing yield as affected by environmental grow-out temperatures. Two thousand fifty male chicks from line A and 2,050 male chicks from line B were reared in 90-floor pens, 45 chicks per pen utilizing primary breeder nutrition and husbandry guidelines for starter (1-10 d) and grower (11-21 d) phases. Experimental finisher diets consisted of 5 increasing levels of apparent nitrogen corrected ME (2,800, 2,925, 3,050, 3,175, and 3,300 kcal/kg set at 19.5% crude protein and 1.0% dLys at each level) to represent 80, 90, 100, 110, and 120% ME of Evonik AminoChick energy level giving 2 × 5 factorial design and were fed from 22-42 d. All other amino acid levels in diets were formulated to a fixed ratio of dLys level. There were nine replicate pens for each diet and each line. The experiment was conducted twice-once in hot season (barn averages: 77.55 ˚F and 86.04% RH) and another in cool season (barn averages: 69.91 ˚F and 63.98% RH) of the year. Results showed that FI and feed conversion ratios (FCR) decreased (P < 0.05) linearly (R² = 0.9) by 61.25 g and 0.073 units for every 10% increase in dietary ME for combined analysis of lines and seasons. The % fat mass of total body mass increased by 0.57%, whereas % protein mass decreased by 0.21% across ME levels (R² > 0.9). However, there was no difference (P > 0.05) in % weights (of live weight) for wings, breast filet, tenders, or leg quarters across ME levels for both lines except % fat pad that increased (P < 0.05) by 0.20% for each 10% increment in dietary ME level. Line B had higher cumulative FI, BW gain, % lean, and protein mass of body mass than line A in hot season (P < 0.05). Feed intake was not different between lines in cool season (P > 0.05), whereas higher BW and improved FCR were observed for line A. Line A had higher % fat mass in both seasons. In summary, performance and yield results as affected by dietary ME levels were line specific and were affected by grow-out seasons. The optimal dietary ME level for the ME range studied (2,800-3,000 kcal/kg) at a constant recommended amino acid level lies in determining the best performance and profitability indices by taking into account the grow-out production inputs and processing yield outputs.

Effect of digestible amino acids to energy ratios on performance and yield of two broiler lines housed in different grow-out environmental temperatures

Two broiler lines, Line A and Line B, were fed experimental diets from 22 to 42 d with objectives to determine effects of digestible amino acids (AA) to metabolizable energy ratios on feed intake (FI), performance, and processing yield. Experimental diets were formulated to 3,150 kcal/kg with 5 levels of digestible lysine (dLys)—80, 90, 100, 110, and 120% of recommended AA level giving g dLys/Mcal values of 2.53, 2.85, 3.17, 3.48, and 3.80, respectively. All other AA were formulated to a fixed ratio to dLys. A total of 4,050 chicks were utilized in each trial (9 replicate pens for each AA level and each line; 45 chicks/pen) conducted twice: one in hot environmental temperature (HT) (24 h mean ∼85.3 °F; 80.9% RH) and another in cool environmental temperature (CT) (24 h mean ∼71.6 °F; 61.7% RH). Results showed that FI was not impacted by dietary AA levels in HT for both lines. Higher FI (P < 0.05) was observed in CT for lower dietary AA levels (<100% AA level) for both lines, with overall higher FI occurring in Line B. Higher FI for Line B was also accompanied by higher body weight in HT and CT. Treatment diets had quadratic effects on average daily gain (ADG), feed conversion ratio (FCR), and processing yields (breasts and tenders) in both HT and CT, with broilers in CT performing better (P < 0.05). The optimal response values for ADG in HT and CT were 89.72 g and 113.44 g occurring at 120 and 109.5% AA level, respectively. The optimal response values for FCR in HT and CT were 1.79 and 1.58 occurring at 120 and 117.5% AA level, respectively. The optimal response values for breast meat yield in HT and CT were 575.9 g and 776.5 g occurring at 112.6 and 114.5% AA level, respectively. The optimal response values for tender meat yield in HT and CT were 119.8 g and 154.9 g occurring at 120 and 115% AA level, respectively. Line A had a higher breast and tender yield % (of live weight) for both environmental temperatures which correlated to body composition data with higher % protein mass and % digestible AA retention. In this study, findings indicated that effects of increased digestible AA density on FI, performance, and processing yield are specific to strain and grow-out temperature, but the optimum response was attained for both lines with diets containing 110 to 120% AA levels (3.48–3.80 g dLys/Mcal) during the 22 to 42 d finisher period.

In vivo collagen and mixed muscle protein turnover in 2 meat-type broiler strains in relation to woody breast myopathy

Two meat-type broiler strains, strain A and strain B, were reared in floor pens (25 birds/pen; 45 pens/strain) for pectoralis (P) major collagen and mixed muscle protein turnover (PT) study from 0-56 D using primary breeder nutrition and husbandry guidelines. Forty broilers (n = 10/strain for collagen PT; n = 10/strain for mixed muscle PT) were selected at each sampling age at day 21, 28, 35, 42, and 56 and infused with 1-¹³C proline (Pro) and ¹⁵N-phenylalanine (Phe) which are used as amino acid tracers for collagen and mixed muscle PT measurements, respectively. Muscle and plasma samples were collected, and enrichments of 1-¹³C Pro and ¹⁵N-Phe were determined using mass spectrometry. Fractional synthesis rate (FSR) and fractional degradation rate (FDR) were measured for collagen and mixed muscle using precursor-product principle. At day 42, after separating the sampled broilers as myopathy (woody breast [WB] score > 1) and nonmyopathy (WB = 0), plasma metabolites were screened for differential 3-methyhistidine (3-MH) expression for both strains. Data were analyzed using one-way ANOVA using t test. Results showed that collagen and mixed muscle FSR and FDR in pectoralis major decreased (P < 0.05) for both strains as the broilers aged. FSR for collagen and FDR for mixed muscle were higher for strain B than those for strain A (P < 0.05). Total collagen was higher (P < 0.05) for strain B. Differentially expressed 3-MH in plasma was higher (P < 0.05) for myopathy-affected broilers indicating greater muscle degradation occurring in myopathy-affected broiler types for both strains. 3-MH Expression in plasma was higher for strain B than for strain A. The research findings showing an increased collagen content per unit muscle weight in pectoralis major in strain B (than in strain A) could be due to higher mixed muscle FDR and increased collagen FSR occurring during the grow-out period. The increased degradation of muscle fibers and probable replacement of muscle-specific protein with connective tissue, mainly collagen, was an evident pathophysiological phenomenon occurring in myopathy-affected broilers.