In pursuit of a better broiler: carcass traits and muscle myopathies in conventional and slower-growing strains of broiler chickens

Can a mixture of Hermetia illucens and Tenebrio molitor meals be feasible to feed broiler chickens? A focus on bird productive performance, nutrient digestibility, and meat quality

Hermetia illucens (HI) and Tenebrio molitor (TM) meals have widely been used in broiler chickens, but their mixture has never been tested. This study investigated the effects of HI and TM meals - alone and as a mixture (MIX, 1:1) - on productive performance, nutrient digestibility, carcass traits, and meat quality of broiler chickens. After assessing the nutrient digestibility of the insect meals (72 26-day-old male broilers, 4 treatments, 9 cages/treatment, 2 birds/cage), a total of 420 1-day-old male broiler chicks were allotted to 7 diets for 37 days (6 pens/diet, 10 birds/pen): C (control), HI5 (5 % HI), HI10 (10 % HI), TM5 (5 % TM), TM10 (10 % TM), MIX5 (5 % MIX), and MIX10 (10 % MIX). In the whole experimental period, better feed efficiency was observed in TM5, TM10 and MIX5 than C, HI10 and MIX10 birds (P < 0.001). Overall, TM5 and MIX5 groups showed the highest slaughtering, ready-to-cook carcass, and chilled carcass weights, while the lowest values were observed in HI10 and MIX10 (P < 0.001). Meat pH and color were limitedly influenced by dietary insect meal inclusion, while higher breast cooking losses were observed in HI10 birds than C, HI5 and MIX5 (P < 0.001). Higher breast dry matter was observed in HI5 birds than TM5 and HI10 (P < 0.001), with the same broilers displaying greater breast crude protein than TM5 (P < 0.001). The highest and lowest percentage of monounsaturated and polyunsaturated fatty acids, respectively, were observed in TM10 birds, along with the lowest polyunsaturated:saturated fatty acids ratio (P < 0.001). The TM5, HI5 and HI10 meat displayed lower tenderness than C meat (P = 0.001), with lower juiciness and overall liking being also overall identified for TM5 (P < 0.05). In conclusion, including 5 % of TM and MIX meals in diets for broiler chickens improved growth performance and carcass traits, while the 10 % inclusion level of HI and MIX meals was associated with the worst outcomes. Including 10 % of HI meal or using TM meal (mainly 5 %) also worsened meat quality and consumer perception.

Gaping conditions of the Pectoralis minor (tenders) in commercial broilers: Prevalence, histology, and gene expression

Gaping is a recently described condition that affects the Pectoralis minor (tender) muscle of broiler chickens, characterized by post-mortem separation of myofiber that leads to meat depreciation and economic losses. In this study, we aimed at understanding prevalence, morphological features, and transcriptomics signatures of this poorly understood myopathy. Between July 2022 and January 2023, a total of 5,180 chicken tenders were collected from 32 flocks across two plants in the USA, handling light (2.7 kg) and heavy (4.1 kg) birds. The prevalence of moderate and severe gaping was 24.8 % and 53.7 %, respectively. The light bird plant had a lower prevalence of moderate gaping (P < 0.001), while the heavy bird plant had a lower prevalence of severe gaping (P < 0.001). Spaghetti meat prevalence from 8,000 fillets was 46.9 % for moderate and 8.3 % for severe cases, with no significant inter-plant differences. Use of peracetic acid treatment at the poultry plants significantly increased the prevalence of severe gaping. Physical and histological features, along with gene expression, were evaluated in 120 samples representative of three gaping severity tiers. Severely gaped tenders showed greater width compared to normal and moderately gaped tenders in both light and heavy birds (P < 0.05). An increase of 1 cm in tender width was associated with a 1.99-fold increase in the odds of classification into a more severe gaping category (95 % CI: 1.15 - 3.46). Affected muscles revealed histological evidence of myodegeneration, inflammation, and lipidosis with fibrosis. For one-unit increase in the myodegeneration score, samples had a 1.75-fold increase in the odds of being classified into a more severe gaping category (95 % CI: 1.37 - 2.23). Gene expression analysis using droplet digital PCR showed differential expression of 19 genes involved in oxidative stress response, cellular signaling, muscle development, and collagen formation between weight groups and myopathy categories. Notably, 21 out of 22 differentially expressed genes showed higher expression in light birds. This study provides the comprehensive description of gaping in broiler chickens and lays a crucial benchmark for assessment of future mitigating strategies.

Comparing commercial and slow-growing broilers in Thailand: growth, carcass quality, economics, and environmental perspective

Various aspects were compared of commercial and slow-growing broiler chickens in Thailand. In total, 416 one-day-old chicks of a commercial strain (COM) and a slow-growing strain (SG) were assigned equally to four experimental groups separated by strain and sex with 8 replications per group, using a 2 × 2 factorial in a completely randomized design. All birds were fed according to the recommended diets for each strain and sex, with the endpoint of the study at a final body weight of 2.5 kg/bird for each group. Growth performance parameters were assessed, and a separate digestibility study was conducted to evaluate nutrient intake, excretion, and retention, with a focus on assessing environmental impacts. The COM strain groups had a highly significant greater growth rate with lower feed intake and a better feed conversion ratio compared to SG strain groups, while the mortality rate did not differ between groups. The COM strain had a higher breast muscle yield, whereas SG produced significantly higher amounts of thighs and drumsticks. Furthermore, the feed ingredient ratios for energy (corn), protein (soybean meal), and phosphorus were lower in COM than for SG. The COM male broiler group had a significantly higher nitrogen digestion rate, with lower intake and excretion of nitrogen and phosphorus compared to SG. Economically, the COM strain groups had a lower feed cost than SG strain groups by approximately 16 % compared to SG, while the feed cost of COM was lower by 8 % in males and 23 % in females than for the equivalent SG groups. The interaction of strain and sex was highly significant in carbon emissions. The COM male group had lower carbon emissions compared to COM female, SG male, and SG female groups, which were 5.17 %, 11.73 %, and 31.25 %, respectively. In conclusion, raising commercial broiler chickens appeared to be more sustainable, effective and economic with a better environmental impact than raising slow-growing broiler chickens. This study did not evaluate welfare indicators, which should be addressed in future research.

Increased activity reduces the prevalence of woody breast in Ross 708 and Ranger Gold broilers

Woody or wooden breast (WB) is characterized by hardening and paleness of the Pectoralis major muscle and can affect up to 85% of broilers. We hypothesized that increased locomotor activity would lead to a lower prevalence of WB and increased tibia bone quality, with a greater effect on a faster growing than a slower growing broiler strain. Ross 708 (N = 188) and Ranger Gold (N = 213) broilers were raised in 3.05×3.05 m2 pens in groups of 23 to 24 and 26 to 27, respectively. Target ages for the Ross 708 and Ranger Gold birds were 42 and 56 d. There were 8 pens per strain: 4 assigned to an exercise treatment and 4 unexercised controls. An exercise regimen was applied for 10 min every hour for 6 h during each weekday with the goal of increasing frequency of standing and walking. A perch was placed between the feeder and drinker line in the exercise treatment pens to further promote broiler activity. WB severity was determined by palpation for all birds at the target age. Tibial bone mineral content (BMC) and bone mineral density (BMD) were measured using a dual-energy x-ray absorptiometry. The Fisher's Exact Test was used to determine treatment effects on the prevalence and severity of WB. Both prevalence (Ross 708: 77.5 vs. 90.5% control, P = 0.013; Ranger Gold: 57.9 vs. 76.4% control, P = 0.005) and severity (Ross 708: 12.9 vs. 24.2% control, P = 0.02; Ranger Gold: 4.7 vs. 0.02% control, P = 0.01) were reduced by treatment. The effects of strain, treatment and their interaction on tibial BMC and BMD were analyzed using linear mixed models. Only strain affected BMC (P = 0.003) and BMD (P = 0.03), with Ross 708 broilers having higher BMC (control: 3.246 g ± 0.061; treatment: 3.251 g ± 0.058) and BMD (control: 0.177 g/cm2 ± 0.002; treatment: 0.174 g/cm2 ± 0.002) values compared to Ranger Gold's BMC (control: 2.966 g ± 0.067; treatment: 2.987 g ± 0.064) and BMD (control: 0.168 g/cm2 ± 0.002; treatment: 0.168 g/cm2 ± 0.002) values. However, per unit of final body weight, Ranger Gold birds had a significantly higher BMC (P = 0.006) and BMD (P = 0.01) than Ross 708 broilers. Promoting broiler activity can reduce the prevalence and severity of WB prevalence in fast and slow growing broilers.

Review: Myopathies in broilers: supply chain approach to provide solutions to challenges related to raising fast growing birds

This review is a summary of a Poultry Science Association symposium addressing myopathies in broilers' breast meat, focusing on the interactions between genetics, nutrition, husbandry, and meat processing. The Pectoralis major myopathies (woody breast [WB]; white striping [WS]; spaghetti meat [SM]) and Pectoralis minor ("feathering") are described, followed by discussing their prevalence, potential causes, current and future ways to mitigate, as well as detection methods (in live birds and meat) as well as ways to utilize affected meat. Overall, breast myopathies remain an important focus across the poultry industry and whilst a lot of data and knowledge has been gathered, it is clear that there is still a lot to understand. As there are multiple factors impacting the occurrence of breast myopathies, their reduction relies on a holistic approach. Ongoing balanced breeding strategies by poultry breeders is targeting the longer-term genetic component but comprehending the significant influence from nongenetic factors (short-term solutions such as nutrition) remains a key area of opportunity. Consequently, understanding the physiology and biological needs of the muscle through the life of the bird is critical to reduce the myopathies (e.g., minimizing oxidative stress) and gain more insight into their etiology.

Significance of successive feeding of sources of n-3 fatty acids to broiler breeders and their progeny on growth performance, intestinal lesion scores, lymphoid organs weight and plasma immunoglobulin A in broiler chickens challenged with Eimeria

The study examined the effects of successive feeding of sources of n-3 PUFA to broiler breeders (BB) and their progeny in broiler chickens challenged with Eimeria. The BB were fed: 1) control (CON), corn-soybean meal diet, 2) CON + 1 % microalgae (DMA), as a source of DHA and 3) CON + 2.50% co-extruded full fat flaxseed (FFF), as a source of ALA. Eggs were hatched at 34, 44, and 54 wk of age. Posthatch treatments (BB-progeny) were: CON-CON, DMA-CON, FFF-CON, DMA-DMA and FFF-FFF with diets formulated for starter (d 1-10) and grower/finisher (d 11-42) phases. All chicks were orally challenged with Eimeria (E. acervulina and E. maxima) on d 10. Relative to CON, DMA and FFF increased concentration of n-3 PUFA by ≥ 2-fold in hatching eggs and progeny diets. There were no (P > 0.05) interactions between treatment and BB age on d 0 to 10 growth. In general, BB age affected (P < 0.05) growth performance throughout the study. In the starter phase, successive exposure to DHA and ALA improved FCR over CON-CON (P < 0.01). The interaction between treatment and BB age in grower/finisher was such that DHA exposure to younger BB resulted in poor growth performance (P < 0.05) relative to exposure to older BB. In contrast, exposure to ALA had similar (P > 0.05) growth performance irrespective of BB age. Moreover, successive exposure to ALA resulted in higher BWG, breast weight and lower FCR compared to successive exposure to DHA (P < 0.05). There were no (P > 0.05) interactions between treatment and BB age on the intestinal lesion scores, lymphoid organ weights and concentration of plasma immunoglobulin A (IgA). Successive exposure to DHA resulted in higher (P = 0.006) jejunal lesion scores than CON-CON birds. The results showed that successive exposure of DHA and ALA improved FCR relative to non-exposed birds in the starter phase. However, responses in the grower/finisher phase depended on n-3 PUFA type, with birds on successive ALA exposure supporting better growth and breast yield than birds on successive DHA exposure.

Transcriptomic Profiles of Pectoralis major Muscles Affected by Spaghetti Meat and Woody Breast in Broiler Chickens

Spaghetti meat (SM) and woody breast (WB) are breast muscle myopathies of broiler chickens, characterized by separation of myofibers and by fibrosis, respectively. This study sought to investigate the transcriptomic profiles of breast muscles affected by SM and WB. Targeted sampling was conducted on a flock to obtain 10 WB, 10 SM, and 10 Normal Pectoralis major muscle samples from 37-day-old male chickens. Total RNA was extracted, cDNA was used for pair-end sequencing, and differentially expressed genes (DEGs) were determined by a false discovery rate of <0.1 and a >1.5-fold change. Principal component and heatmap cluster analyses showed that the SM and WB samples clustered together. No DEGs were observed between SM and WB fillets, while a total of 4018 and 2323 DEGs were found when comparing SM and WB, respectively, against Normal samples. In both the SM and WB samples, Gene Ontology terms associated with extracellular environment and immune response were enriched. The KEGG analysis showed enrichment of cytokine-cytokine receptor interaction and extracellular matrix-receptor interaction pathways in both myopathies. Although SM and WB are macroscopically different, the similar transcriptomic profiles suggest that these conditions may share a common pathogenesis. This is the first study to compare the transcriptomes of SM and WB, and it showed that, while both myopathies had profiles different from the normal breast muscle, SM and WB were similar, with comparable enriched metabolic pathways and processes despite presenting markedly different macroscopic features.

Effect of light restriction on productive results and behavior of broiler chickens

The study aimed to evaluate the effect of light restriction (18L:6D vs. 14L:10D), genotype (A vs. B), and sex on performance, behavior, and meat quality, and the occurrence of wooden breast (WB) and white striping (WS) in broiler chickens. To this purpose 704 one-day-old chickens of 2 genotypes, half males and half females, were reared from hatching until slaughtering at 45 d of age in 32 collective pens (22 chickens per pen). Light restriction reduced growth rate and final live weight (LW), but improved feed conversion ratio (FCR) (P < 0.01) and reduced inactive behaviors of chickens (P < 0.001). Light restriction also reduced WS occurrence in breasts (89.5 to 64.6%; P < 0.001) and reduced meat shear force (2.64 to 2.20 kg/g; P < 0.05) and ether extract content (2.29 to 1.87%; P < 0.05). Regarding genotype, compared to genotype B, chickens of genotype A were heavier (3,242 g vs. 3,124 g; P < 0.01) with higher cold carcass weight and Pectoralis major muscle yield (12.9 vs. 12.0%; P < 0.001) and a higher FCR (1.63 vs. 1.61; P < 0.01). Finally, females had lower final LW (2,852 g vs. 3,513 g) and higher FCR (1.64 vs. 1.59) than males (P < 0.001), but a higher proportion of breast and P. major (P < 0.001), lower cooking losses (P < 0.001) and shear force (P < 0.01), and higher protein content (21.6 vs. 20.7%; P < 0.001). In conclusion, light restriction depressed growth, but was effective in decreasing WS occurrence and improved feed conversion. The decrease in inactive behaviors (sitting/laying) of light-restricted chickens can be positively considered in view of animal welfare.

Resiliency of fast-growing and slow-growing genotypes of broiler chickens submitted to different environmental temperatures: growth performance and meat quality

Growth performance and meat quality were assessed in 238 chicks of both sexes belonging to a commercial crossbreed (Ross 308), and 2 Italian local breeds (Bionda Piemontese-BP and Robusta Maculata-RM). The chickens were kept in 2 rooms at standard environmental conditions or under heat stress (+4.7°C on average) until slaughtering (42 d of age for Ross 308 and 99 d for RM and BP chickens). The Ross chickens showed the highest final live weight, feed intake, and daily weight gain, and the best feed conversion ratio compared to the local breeds (P < 0.001), with RM performing better than BP chickens. Thus, Ross chickens had the heaviest carcasses, the highest slaughter, and breast yields followed by RM and BP chickens (P < 0.001). At the pectoralis major (p. major) muscle, Ross chickens showed the highest pH, lightness, and yellowness, besides the highest cooking losses, whereas BP showed the highest redness (P < 0.001). Ross meat had higher water and ether extract contents, and lower crude protein content compared to BP and RM (P < 0.001), whereas no differences among genotypes were measured for the fatty acid profile. At the sensory analysis, Ross breasts had a higher juiciness compared to BP ones, besides a lower score for "brothy and chickeny/meaty" and a higher one for "wet feathers" compared to local breeds (0.05 < P < 0.001). The increase of the room temperature decreased growth performance and cold carcass weight (P < 0.001) compared to standard conditions, whereas the rate of α-linolenic acid in the meat increased (P < 0.01). The effect of a high environmental temperature on growth performance and slaughter and meat quality traits was more pronounced in Ross compared to BP and RM chickens (0.05 < P <0.001; significant interaction genotype × temperature). In conclusions, local chicken breeds showed lower performance and slaughter yield compared to the commercial genotype, but more favorable meat quality traits and higher resilience to the environmental heat-stress.

Transcriptomics reveals key genes responsible for functional diversity in pectoralis major muscles of native black Kadaknath and broiler chicken

RNA sequencing-based expression profiles from pectoralis major muscles of black meat (Kadaknath) and white meat (broiler) chicken were compared to identify differentially expressed genes. A total of 156 genes with log2 fold change ≥  ± 2.0 showed higher expression in Kadaknath and 68 genes were expressed at a lower level in comparison to broiler. Significantly enriched biological functions of up-regulated genes in Kadaknath were skeletal muscle cell differentiation, regulation of response to reactive oxygen, positive regulation of fat cell differentiation and melanosome. Significant ontology terms up-regulated in broiler included DNA replication origin binding, G-protein coupled receptor signaling pathway and chemokine activity. Highly inter-connected differentially expressed genes in Kadaknath (ATFs, C/EPDs) were observed to be important regulators of cellular adaptive functions, while in broiler, the hub genes were involved in cell cycle progression and DNA replication. The study is an attempt to get an insight into the transcript diversity of pectoralis major muscles of Kadaknath and broiler chicken.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03682-0.

Fast- and slower-growing broilers respond similarly to a reduction in stocking density with regard to gait, hock burn, skin lesions, cleanliness, and performance

There is an increasing trend toward broiler production systems with higher welfare requirements. Breed and stocking density are considered key factors for broiler welfare that are often specified as criteria for such higher welfare systems. However, it remains unknown how slower-growing broilers respond to a reduction in stocking density with regard to their welfare and performance, and whether this response differs from fast-growing broilers. Therefore, we compared fast- (F) and slower-growing broilers (S) housed at 4 different stocking densities (24, 30, 36, and 42 kg/m2, based on slaughter weight) and measured their welfare scores (i.e., gait, footpad dermatitis, hock burn, skin lesions and cleanliness), litter quality and performance. The experiment had a 2 × 4 factorial design with 4 replicates (pens) per treatment (32 pens in total). Thinning (15%) was done in a 50/50 male/female ratio at 38 (F) and 44 (S) d of age (estimated body weight of 2.2 kg). We hypothesized that breeds would respond differently to a reduction in stocking density. Contrary to our hypothesis, only one interaction between breed and stocking density was found on footpad dermatitis, indicating that fast- and slower-growing broilers generally showed similar responses to a reduction in stocking density. F broilers showed a steeper decline in the prevalence of footpad dermatitis with reducing stocking density compared to S broilers. Broilers housed at lower stocking densities (24 and/or 30 kg/m2) showed improved welfare measures, litter quality and performance compared to those housed at higher stocking densities (36 and/or 42 kg/m2). S broilers had better welfare scores (gait, footpad dermatitis and skin lesions), litter quality and lower performance compared to F broilers. In conclusion, reducing stocking density improved welfare of both F and S broilers, but more for F broilers in case of footpad dermatitis, and using S broilers improved welfare compared to F broilers. Reducing stocking density and using slower-growing broilers benefits broiler welfare, where combining both would further improve broiler welfare.

Comparison of carcass condemnation causes in two broiler hybrids differing in growth rates

Experimental studies concluded that genetic factors enabling fast growth rate might negatively affect broiler health and welfare. Recently, the proportion of slower-growing broilers has been increasing. However, studies of health in broilers with different growth rates in commercial systems are still scarce. This repeated cross-sectional study aimed to describe causes of carcass condemnations in two broiler hybrids with different growth rates, Ross 308, and Hubbard JA787, and to estimate the effect of hybrid. The study sample consisted of 63,209,415 broilers slaughtered in 4295 batches from 139 farms. All broilers were slaughtered from January 1st, 2015, to June 22nd, 2021, by the same company (Norsk Kylling). All causes of condemnation, except fractures, were more prevalent in Ross 308. The five most common causes (ascites, discolouration, hepatitis, small and skin lesions) were investigated in greater detail, and the effect of hybrid was assessed using mixed effects negative binomial models with the condemnation codes as outcome variables. For the five selected causes, variation in prevalence between slaughter batches was considerable for Ross and minor for Hubbard. The notable differences between hybrids in prevalence and causes of condemnation have important implications for animal health, welfare, economy, and sustainability in broiler production.

Dietary inositol-stabilized arginine silicate numerically reduced woody breast severity in male Ross 708 broilers without altering growth

The woody breast (WB) myopathy is an unintended outcome of fast broiler chicken growth and high breast muscle yields. Myodegeneration and fibrosis in the living tissue are results of hypoxia and oxidative stress driven by lack of blood supply to muscle fibers. The study aim was to titrate a vasodilator ingredient, inositol-stabilized arginine silicate (ASI), as a feed additive to improve blood flow and ultimately, breast meat quality. A total of 1,260 male Ross 708 broilers were assigned to: 1) a control basal diet, or the control diet plus increasing ASI: 2) 0.025% ASI, 3) 0.05% ASI, 4) 0.10% ASI, or 5) 0.15% ASI. At d 14, 28, 42, and 49, growth performance was measured on all broilers and serum from 12 broilers/diet was analyzed for creatine kinase and myoglobin presence. On d 42 and 49, 12 broilers/diet were measured for breast width, then left breast fillets were excised, weighed, palpated for WB severity, and visually scored for degree of white striping (WS). At 1 d postmortem, 12 raw fillets/treatment underwent compression force analysis, and at 2d postmortem, the same fillets were analyzed for water-holding capacity. mRNA was isolated from 6 right breasts/diet at both d 42 and 49 for qPCR quantification of myogenic gene expression. Birds fed the lowest dose of 0.025% ASI had a 5-point/3.25% feed conversion ratio reduction compared to birds fed 0.10% ASI over wk 4 to 6 and reduced serum myoglobin at 6-wk of age compared to the control. Breasts from birds fed 0.025% ASI received 42% greater normal WB scores at d 42 compared to control fillets. At d 49, breasts from broilers fed 0.10 and 0.15% ASI received 33% normal WB scores. At d 49, 0.025% AS-fed broiler breasts showed no severe WS. Increased myogenin expression was observed in 0.05 and 0.10% ASI breast samples on d 42 and myoblast determination protein-1 expression was upregulated in breasts from birds fed 0.10% ASI on d 49 compared to the control. Therefore, a dietary inclusion of 0.025, 0.10, or 0.15% ASI was beneficial in reducing WB and WS severity and promoting muscle growth factor gene expression at age of harvest without diminishing bird growth or breast muscle yields.

Breast muscle white striping and serum corticosterone reduced in broilers exposed to laser environmental enrichment

Genetic selection for breast yields and fewer days to market has inadvertent effects on broiler meat quality. Woody breast (WB) and white striping (WS) are pectoralis major myopathies prevalent in commercial broilers. Effects of voluntary exercise on these disorders, specifically, are unknown. A second-generation laser enrichment device shown to induce activity in Ross 308 and 708 birds was implemented using 1,360 Ross 708 broilers randomly assigned to laser enrichment or control for 49 d. Laser-enriched birds were exposed to 6-min laser periods 4 times daily. Seventy focal birds were gait and contact dermatitis scored weekly. Blood was collected wk 5 to 7 from 56 broilers for serum corticosterone, myoglobin, and troponin. Seventy broilers were sampled for breast muscle width, fillet dimensions, and WB and WS at wk 6 and 7. One and 2-day postmortem, fillet compression force and water-holding capacity were measured. Serum corticosterone was reduced by up to 21% in laser-enriched birds wk 5 to 7 (P < 0.01). Serum myoglobin was increased in laser-enriched broilers by 5% on wk 5 (P < 0.01) but increased in control birds wk 6 to 7 by up to 13% (P < 0.01). Serum troponin was reduced in laser-enriched broilers by 9% at wk 5 (P < 0.01). Laser exposure increased breast width and fillet weight at d 42 by 1.08 cm (P < 0.05) and 30 g (P < 0.05). At d 49, fillet height was increased 0.42 cm in laser-enriched birds (P < 0.05). Laser enrichment reduced severe WS incidence at d 42 by 24% (P < 0.05) and on d 49 by 15% (P < 0.10). Severe WB score was numerically reduced by 11% in laser enrichment on d 42 and 18% on d 49 (P > 0.05). Water-holding capacity was improved in laser-enriched breasts (P < 0.01) and expression of myostatin and insulin-like growth factor 2 were increased on d 49 (P ≤ 0.01. Laser enrichment reduced markers of stress and muscle damage while improving breast muscle quality and is therefore a potential effective enrichment for commercial broilers.

Carcass, visceral organ, and meat quality properties of two broiler hybrids differing in growth rates

This study aimed to determine the carcass, visceral organ, and meat properties according to the sex in slow growing broilers (SGB) and fast growing broilers (FGB). Six broilers from each genotype and sex group were slaughtered every week. It was determined that the difference between SGB and FGB in terms of carcass yield occurred at the highest level at 5 weeks and this difference continued until the age of 10 weeks. The weight percentages of all visceral organs examined in FGB were lower than in SGB. Higher values of pH, lightness, and cooking loss ​​were determined in breast and thigh meat of FGB compared with SGB (P < 0.05). The effects of genotype on protein levels of breast and leg meats were found to be insignificant. The fat level in breast meat was insignificant between genotypes after the fifth week of fattening period. There was no difference between the sexes regarding meat quality in both genotypes. When FGB and SGB were reared under the intensive conditions for 10 weeks, it was observed that visceral organs developed in harmony with body weight, especially in SGB during the 10 weeks of fattening period and SGB maintained their superiority in terms of meat quality.

Dietary vasodilator and vitamin C/L-arginine/choline blend improve broiler feed efficiency during finishing and reduce woody breast severity at 6 and 7 wks

Woody breast has become a considerable economic concern to the poultry industry. This myopathy presents rigid, pale breasts characterized by replacement of lean muscle protein with connective tissue, a result of hypoxia and oxidative stress in a metabolically starved muscle with inadequate circulation. Hence, the objectives were to supplement broiler diets with ingredients specifically aimed to improve circulation and oxidative status. About 1,344 male Ross 708 broilers were assigned to 1 of 4 diets: 1) a basal diet (control), 2) basal diet plus a blend of 0.2% supplemental L-arginine, 0.17% choline bitartrate, and 0.03% vitamin C (blend), 3) 0.1% vasodilator ingredient (vasodilator), or 4) 0.02% Astaxanthin ingredient (AsX). At d 14, 28, 42, and 49, performance outcomes were collected on all birds and serum from 16 broilers/diet (n = 64) was analyzed for creatine kinase and myoglobin. Once weekly beginning on d 28, a subset of 192 broilers were measured for breast width. On d 42 and 49, breast fillets from 16 broilers/diet (n = 64) were palpated for woody breast severity, weighed, and analyzed for compression force at 1-day postmortem and water-holding capacity at 2-day postmortem. mRNA was isolated from 15 breast fillets/timepoint for qPCR quantification of myogenic gene expression. Data were analyzed using Proc Mixed (SAS Version 9.4) with the fixed effect of diet. Feed conversion ratio was improved in the blend and vasodilator-fed birds d 42 to 49, each by over 2 points (P < 0.05). Breast width was increased in the control on d 42 compared to the vasodilator and AsX-fed broilers (P < 0.05). At d 42, there were 12% greater normal fillets in blend diet-fed birds and 13% more normal scores in vasodilator-fed birds at d 49 compared to the control. At d 49, myogenin expression was upregulated in the AsX diet compared to blend and control diets (P < 0.05), and muscle regulatory factor-4 expression was increased by 6.5% in the vasodilator diet compared to the blend and AsX diets (P < 0.05). Blend and vasodilator diets simultaneously improved feed efficiency in birds approaching market weight while reducing woody breast severity.

Polymorphisms of CRELD1 and DNAJC30 and their relationship with chicken carcass traits

Carcass traits play important roles in the broiler industry and single nucleotide polymorphism (SNP) can be efficient molecular markers for marker-assisted breeding of chicken carcass traits. Based on our previous RNA-seq data (accession number GSE58755), cysteine rich with epidermal growth factor like domains 1 (CRELD1) and DnaJ heat shock protein family member C30 (DNAJC30) are differentially expressed in breast muscle between white recessive rock chicken (WRR) and Xinghua chicken (XH). In this study, we further characterize the potential function and SNP mutation of CRELD1 and DNAJC30 in chicken for the first time. According to protein interaction network and enrichment analysis, CRELD1 and DNAJC30 may play some roles in chicken muscle development and fat deposition. In WRR and XH, the results of the relative tissue expression pattern demonstrated that CRELD1 and DNAJC30 are not only differentially expressed in breast muscle but also leg muscle and abdominal fat. Therefore, we identified 5 SNP sites of CRELD1 and 7 SNP sites of DNAJC30 and genotyped them in an F₂ chicken population. There are 4 sites of CRELD1 and 3 sites of DNAJC30 are associated with chicken carcass traits like breast muscle weight, body weight, dressed weight, leg weight percentage, eviscerated weight with giblet percentage, intermuscular adipose width, shank length, and girth. These results suggest that the SNP sites of CRELD1 and DNAJC30 can be potential molecular markers to improve the chicken carcass traits and lay the foundation for marker-assisted selection.

Factors Affecting Breast Myopathies in Broiler Chickens and Quality of Defective Meat: A Meta-Analysis

Fast-growing broiler chickens are subjected to breast myopathies such as white striping (WS), wooden breast (WB), and spaghetti meat (SM). Available studies about risk factors for myopathy occurrence often used flock data whereas a few reports evaluated chicken individual data. Thus, the present study aimed to elucidate the effect of growth and slaughter traits, besides sex and genotype on myopathy occurrence. Data were obtained from eight experimental trials, which used a total of 6,036 broiler chickens. Sex, genotype, daily weight gain, slaughter weight, and breast yield were evaluated as potential risk factors by logistic regression analyses. Then, the effects of myopathy and sex were evaluated on meat rheological traits (pH, colour, cooking losses and shear force). Based on a logistic regression, WS occurrence was associated with genotype, breast weight, and breast yield. Compared with chickens with intermediate breast weight and breast yield, higher odds of having WS were found in chickens with high breast weight (OR: 1.49) and yield (OR: 1.27), whereas lower odds were found in those with low breast weight (OR: 0.57) and yield (OR: 0.82). As for WB and SM, females had lower odds of having WB (OR: 0.55) and higher odds of showing SM (OR: 15.4) compared to males. In males, higher odds of having WB were found in chickens with a high daily weight gain (OR: 1.75) compared to those with an intermediate daily weight gain. In females, higher odds of having SM were associated to a high slaughter weight (OR: 2.10) while lower odds to a low slaughter weight (OR: 0.87). As for meat quality, only WB meat was clearly different for some technological and sensorial properties, which can play a major role also in meat processing. In conclusion, our analysis identified breast development as a potential risk factor for WS, while a high growth was the risk factor for WB and SM. A different probability of having WB or SM in females and male was found.

Multi-Omics Analysis of the Microbiome and Metabolome Reveals the Relationship Between the Gut Microbiota and Wooden Breast Myopathy in Broilers

Wooden breast (WB) is a widely prevalent myopathy in broiler chickens. However, the role of the gut microbiota in this myopathy remains largely unknown, in particular the regulatory effect of gut microbiota in the modulation of muscle metabolism. Totally, 300 1-day-old Arbor Acres broilers were raised until 49 days and euthanized, and the breast filets were classified as normal (NORM), mild (MILD), or severe wooden breast (SEV). Birds with WB comprised 27.02% of the individuals. Severe WB filets had a greater L* value, a* value, and dripping loss but a lower pH (P < 0.05). WB filets had abundant myofiber fragmentation, with a lower average myofiber caliber and more fibers with a diameter of <20 μm (P < 0.05). The diversity of the intestinal microflora was decreased in birds with severe WB, with decreases in Chao 1, and observed species indices. At the phylum level, birds with severe WB had a lower Firmicutes/Bacteroidetes ratio (P = 0.098) and a decreased abundance of Verrucomicrobia (P < 0.05). At the species level, gut microbiota were positively correlated with 131 digesta metabolites in pathways of glutamine and glutamate metabolism and arginine biosynthesis but were negatively correlated with 30 metabolites in the pathway of tyrosine metabolism. In plasma, WB induced five differentially expressed metabolites (DEMs), including anserine and choline, which were related to the severity of the WB lesion. The microbial-derived metabolites, including guanidoacetic acid, antiarol, and (2E)-decenoyl-ACP, which entered into plasma were related to meat quality traits and myofiber traits. In summary, WB filets differed in gut microbiota, digesta, and plasma metabolites. Gut microbiota respond to the wooden breast myopathy by driving dynamic changes in digesta metabolites that eventually enter the plasma.

Providing organic macro minerals and an elevated platform improved tibia characteristics, and increased locomotion and performance of fast- and slower-growing broilers

Improving leg health will support broiler health and welfare. Known factors to improve leg health are: replacing inorganic by organic macro minerals in the diet, providing environmental enrichments and using slower-growing broilers. However, it remains unknown how fast- and slower-growing broilers respond to a combination of providing organic macro minerals and an elevated platform as enrichment with regard to leg health. Therefore, the aim of this study was to identify whether a combined treatment of organic macro minerals and a platform affected leg health, tibia characteristics, behavior and performance of fast- and slower-growing broilers in a semicommercial setting. The experiment had a 2 × 2 factorial arrangement, with 12.800 fast-growing (Ross 308) and 12.800 slower-growing (Hubbard JA757) broilers that were randomly allocated to a control (i.e., inorganic macro minerals without enrichment) or adapted treatment (i.e., organic macro minerals and a platform). Broilers were housed in groups of 800 per pen (47.5 m²), with 8 replicates per treatment (total of 32 pens). Performance was measured weekly and over the total rearing period. Behavior was observed via scan sampling at a target weight of 0.6 and 1.9 kg for both breeds. Walking ability (gait score), footpad dermatitis, and hock burn were assessed in 10 broilers per pen just prior to slaughter weight. Leg disorders and tibia characteristics were assessed in the same broilers at slaughter weight (2.3 kg). Hardly any interaction effects between breed and treatment were found on leg health, tibia characteristics, behavior or performance, suggesting fast- and slower-growing broilers responded to the treatment similarly. The adapted treatment improved tibia characteristics, and increased locomotion and performance, but did not affect leg disorders, walking ability or contact dermatitis in both fast- and slower-growing broilers. The positive effects of the adapted treatment on tibia characteristics in both fast- and slower-growing broilers may improve leg health, although the current study did not confirm this for leg disorders, walking ability or contact dermatitis.

In pursuit of a better broiler: walking ability and incidence of contact dermatitis in conventional and slower growing strains of broiler chickens

In this study, the mobility, incidence, and severity of contact dermatitis and litter moisture content were assessed in 14 strains of broiler chickens differing in growth rate. The strains encompassed 2 conventional (CONV; ADG0-48 > 60 g/d) and 12 slower growing (SG) strains categorized as FAST (ADG0-62 = 53-55 g/d), MOD (ADG0-62 = 50-51 g/d), and SLOW (ADG0-62 < 50 g/d), with 4 strains in each category. A total of 7,216 mixed-sex birds were equally allocated into 164 pens (44 birds/pen; 30 kg/m2) in a randomized incomplete block design, with each strain represented in 8 to 12 pens over 2-3 trials. From each pen, 4 to 6 birds were tested in the latency-to-lie (LTL) and group obstacle tests 1 wk prior to the birds reaching 2 target weights (TWs) of approximately 2.1 kg (TW1: 34 d for CONV and 48 d for SG strains) and 3.2 kg (TW2: 48 d for CONV and 62 d for SG strains). The incidence of footpad dermatitis (FPD) and hock burns (HB) were evaluated a day prior to each TW. Litter moisture content was determined biweekly from d 14 to d 56. At TW1, CONV and SLOW had longer LTL than FAST birds. At TW2, CONV, MOD, and FAST birds had similar LTL. At both TWs, CONV birds were lighter than FAST birds in the group obstacle test, yet their number of obstacle crossings was similar. At TW1, CONV birds had greater incidence of FPD than FAST and MOD, while at TW2, CONV birds had greater incidence than the other categories. The incidence of HB in CONV and MOD was greater than SLOW birds at TW1, while at TW2, the incidence of HB was greater in CONV and FAST birds vs. MOD and SLOW birds. Litter moisture content was high in all categories from d 28 onward. Our results indicate that both BW and growth rate influence leg strength and walking ability, whereas the overall high litter moisture content and to a lesser extent growth rate influenced the incidence of contact dermatitis.

In pursuit of a better broiler: tibial morphology, breaking strength, and ash content in conventional and slower-growing strains of broiler chickens

This study was conducted to determine the differences in bone traits in 14 strains of broiler chickens differing in growth rate. The strains encompassed 2 conventional (CONV; ADG_0-48 >60 g/d) and 12 slower-growing (SG) strains classified as FAST (ADG_0-62 = 53-55 g/d), MOD (ADG_0-62 = 50-51 g/d), and SLOW (ADG_0-62 <50 g/d), with 4 strains represented in each SG category. A total of 7,216 mixed-sex birds were equally allocated into 164 pens (44 birds/pen; 30 kg/m²) in a randomized incomplete block design, with each strain represented in 8 to 12 pens over 2-3 trials. From each pen, 4 birds (2 males and 2 females) were individually weighed and euthanized at 2 target weights (TWs) according to their time to reach approximately 2.1 kg (TW1: 34 d for CONV and 48 d for SG strains) and 3.2 kg (TW2: 48 d for CONV and 62 d for SG strains). Tibiae samples were dissected, and length and diameter were recorded. Left tibiae were used for tibial breaking strength (TBS) at both TWs and tibial ash at TW2. At TW1, CONV birds' tibiae were narrowest and shortest (P < 0.001), yet had similar TBS compared to the other categories (P > 0.69). At TW2, category (P > 0.50) had no effect on tibial diameter, yet CONV birds had the shortest tibiae (P < 0.001). The CONV birds had greater TBS:BW ratio than FAST and MOD birds at both TWs 1 and 2 (P < 0.039) and similar ash content as the other categories at TW2 (P > 0.220). At 48 d of age, CONV birds had the greatest absolute TBS (P < 0.003), yet lower TBS:BW ratio than SLOW birds (P < 0.001). Tibiae from CONV birds were longer than MOD and SLOW birds, and thicker in diameter than the other categories, yet CONV birds had the lowest dimensions relative to BW (P < 0.001) at 48 d, indicating a negative association between accelerated growth and tibial dimensions. These results indicate that differences in functional abilities among categories may be due to differences in morphometric traits rather than differences in bone strength and mineralization.

Reliability of a White Striping Scoring System and Description of White Striping Prevalence in Purebred Turkey Lines

Simple Summary

A relatively recent issue in the turkey industry is white striping (presence of white striations on the surface of the breast fillets). This defect influences consumer acceptance and the nutritional value of the meat and, therefore, is of economic importance to the industry. This study is aimed to test the reliability of a white striping scoring system used by several observers and estimate the prevalence of this defect in modern turkeys. After a few training sessions, the scoring system was found to be moderately reliable within and between the six participating observers. We found that 88% of turkeys in the studied population had some degree of white striping, with most scores being of moderate-severe severity (Score 1 or 2). Furthermore, white striping severity was found to be associated with higher slaughter weight, breast weight, and breast meat yield. Future research is needed to evaluate the use of white striping information in turkey genetic selection programs, as a balanced approach is needed to avoid slowing gains in economically favorable traits, such as growth.

Abstract

To efficiently meet consumer demands for high-quality lean meat, turkeys are selected for increased meat yield, mainly by increasing breast muscle size and growth efficiency. Over time, this has altered muscle morphology and development rates, which are believed to contribute to the prevalence of myopathies. White striping is a myopathy of economic importance which presents as varying degrees of white striations on the surface of skinless breast muscle and can negatively affect consumer acceptance at the point of sale. Breeding for improved meat quality may be a novel strategy for mitigating the development of white striping in turkey meat; however, it is crucial to have a reliable assessment tool before it can be considered as a phenotype. Six observers used a four-category scoring system (0–3) to score severity in several controlled rounds and evaluate intra- and inter-observer reliability of the scoring system. After sufficient inter-observer reliability (Kendall’s W > 0.6) was achieved, 12,321 turkey breasts, from four different purebred lines, were scored to assess prevalence of the condition and analyze its relationship with important growth traits. Overall, the prevalence of white striping (Score > 0) was approximately 88% across all genetic lines studied, with most scores being of moderate-severe severity (Score 1 or 2). As was expected, increased white striping severity was associated with higher slaughter weight, breast weight, and breast meat yield (BMY) within each genetic line. This study highlights the importance of training to improve the reliability of a scoring system for white striping in turkeys and was required to provide an updated account on white striping prevalence in modern turkeys. Furthermore, we showed that white striping is an important breast muscle myopathy in turkeys linked to heavily selected traits such as body weight and BMY. White striping should be investigated further as a novel phenotype in future domestic turkey selection through use of a balanced selection index.

Characteristics of Broiler Chicken Breast Myopathies (Spaghetti Meat, Woody Breast, White Striping) in Ontario, Canada

Spaghetti meat (SM), woody breast (WB), and white striping (WS) are myopathies affecting breast muscle of broiler chickens, and are characterized by a loss of myofibers and an increase in fibrous tissue. The conditions develop in intensive broiler chicken production systems, and cause poor meat process-ability and negative customer perception leading to monetary losses. The objectives of the present study were to describe the physical and histological characteristics of breast myopathies from commercial broiler chicken flocks in Ontario, Canada, and to assess the associations between the severity of myopathies with the physical and histological characteristics of the affected breast muscle fillets. Chicken breast fillets (n = 179) were collected over 3 visits from a processing plant and scored macroscopically to assess the severity of myopathies, following an established scoring scheme. For each fillet, the surface area, length, width, thickness, weight, and hardness (compression force) were measured. A subset of 60 fillets was evaluated microscopically. Multinomial logistic regression models were built to evaluate associations between physical parameters and macroscopic scores. The odds of SM co-occurring with severe WB (SM1WB2) were significantly associated with increased fillet thickness (OR = 1.59, 95% CI 1.31–1.94) and weight (OR = 1.06, 95% CI 1.03–1.09). Histologically, myopathies had overlapping lesions consisting of polyphasic myodegeneration, perivascular inflammatory cuffing and accumulation of fibrous tissue and fat. The pairwise correlation between macroscopic and microscopic scores was moderate (rho 0.45, P < 0.001). This is the first study to characterize breast myopathies in Canadian broiler flocks. Results show that the morphologic and microscopic changes of fillets from this cohort are similar to data from other countries, and provide database to benchmark these parameters in future studies. Our standardized categorization can be applied to broiler breast fillets in other regions of the world.

Welfare and performance of slower growing broiler breeders during rearing

Current commercial strains of broiler breeders can only achieve an optimal reproductive performance under feed restriction. However, chronic feed restriction in broiler breeders is a welfare concern because of physiological and behavioral signs of hunger, lack of satiety, and frustrated feeding motivation. The objective of this research was to assess the welfare and performance of slower growing broiler breeders during rearing. A total of 360 broiler breeder chicks from 3 female strains (100 chicks per strain) and 2 male strains (20 and 40 chicks per strain) were raised in four identical pens per strain. Strain B and C pullets and X cockerels were slower growing strains, and strain A pullets and Y cockerels were intermediate growing strains. Birds were weighed and scored individually for footpad lesions, hock burns and feather coverage. Data were analyzed using generalized linear mixed models with pen nested in the models and age as a repeated measure. Compared to B and C pullets, strain A pullets grew faster, had poorer body weight uniformity, and started feed restriction 2 wk earlier to control growth rate. Strain A pullets also had higher feeding rate at 3 and 5 wk, higher water intake at 4 and 5 wk, and higher prevalence of footpad lesions at 6 wk than the other pullet strains. Fault bars in wing feathers (an indicator of chronic stress) were more numerous in A pullets than in B and C pullets. Our results indicate that pullets showed little feather coverage loss during early rearing and had good body weight uniformity and low cumulative feed intake at the end of rearing. Slower growing broiler breeders may still require some degree of feed restriction to control growth rate, and strains with lower feed restriction exhibited lower signs of feeding frustration and high body weight uniformity.