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Heat stress (HS) is one of the most challenging stressors to poultry production sustainability. The adverse effects of HS range from feed intake and growth depression to alteration of meat quality and safety. As phytase supplementation is known to improve nutrient utilization and consequently growth, we undertook the present study to evaluate the effects of dietary phytase on growth and meat quality in heat-stressed broilers. A total of 720 day-old hatch Cobb 500 chicks were assigned to 24 pens within controlled environmental chambers and fed three diets: Negative Control (NC), Positive Control (PC), and NC diet supplemented with 2000 phytase units (FTU)/kg) of quantum blue (QB). On day 29, birds were exposed to two environmental conditions: thermoneutral (TN, 25 °C) or cyclic heat stress (HS, 35 °C, 8 h/d from 9 a.m. to 5 p.m.) in a 3 × 2 factorial design. Feed intake (FI), water consumption (WI), body weight (BW), and mortality were recorded. On day 42, birds were processed, carcass parts were weighed, and meat quality was assessed. Breast tissues were collected for determining the expression of target genes by real-time quantitative PCR using the 2−ΔΔCt method. HS significantly increased core body temperature, reduced feed intake and BW, increased water intake (WI), elevated blood parameters (pH, SO2, and iCa), and decreased blood pCO2. HS reduced the incidence of woody breast (WB) and white striping (WS), significantly decreased drip loss, and increased both 4- and 24-h postmortem pH. Instrumental L* and b* values were reduced (p < 0.05) by the environmental temperature at both 4- and 24-h postmortem. QB supplementation reduced birds’ core body temperature induced by HS and improved the FCR and water conversion ratio (WCR) by 1- and 0.5-point, respectively, compared to PC under HS. QB increased blood SO2 and reduced the severity of WB and WS under TN conditions, but it increased it under an HS environment. The abovementioned effects were probably mediated through the modulation of monocarboxylate transporter 1, heat shock protein 70, mitogen-activated protein kinase, and/or glutathione peroxidase 1 gene expression, however, further mechanistic studies are warranted. In summary, QB supplementation improved growth performance and reduced muscle myopathy incidence under TN conditions. Under HS conditions, however, QB improved growth performance but increased the incidence of muscle myopathies. Therefore, further QB titration studies are needed.

The objective of this study was to determine meat quality distributions and assess hardness distributions in raw and cooked breast fillets with the woody breast (WB) condition, in addition to evaluating the relationship between water properties and WB severity. A total of 90 breast fillets were collected and categorized as normal (NORM), mild (MILD) and severe (SEV). Breast weight, drip loss, compression measurements, cook loss, shear and texture profile analysis (TPA) values were measured for each sample by fillet location (cranial to caudal) and sampling depth (cranial-superficial, cranial-internal, middle-superficial, and middle-internal) in the raw and cooked meat state. Low-field NMR relaxation measurements were also collected for both the raw and cooked fillets. Results indicate that severe WB expressed increased hardness, a higher water content (bound water and free water) and reduced meat quality attributes in raw and cooked meat. Breast fillet hardness and meat quality distributions were unevenly distributed between fillets, compression measurements were higher mainly in the cranial region, and progressively decreased toward the caudal region for both raw and cooked fillets. Shear force and energy values were higher in the cranial region than in the middle region, and TPA values were higher in superficial regions rather than internal portions. Additionally, low-field NMR could be used to predict WB through variation in water properties as thermal processing reduces water distributing abilities in affected fillets.

The objective of this study was to investigate the relationships between morphometric measurements and woody breast (WB) severity in breast fillets using image processing as an objective detection method for WB. Breast fillets were collected and categorized as normal (NORM), mild (MILD), moderate (MOD), and severe (SEV). Compression force and energy increased as WB severity increased alongside a decrease in severity through fillet regions (P < 0.05). Length and caudal thickness were highest in SEV and MOD groups (P < 0.05), and cranial thickness increased as WB severity increased (P < 0.05). The aerial area was the smallest in NORM fillets, while the planar area increased from NORM to MOD (P < 0.05). Fillet curvatures were highest in SEV and MOD fillets (P < 0.05). All measured parameters expressed strong correlation to WB scores (P < 0.05) except width. The results from this study may provide a basis for further assessment of the potential incorporation of these measurements into vision grading systems that may allow processors to sort fillets by WB severity in commercial plants.

The objective of this study was to explore the effect of woody breast (WB) on quality characteristics of chicken meatballs paired with the feasibility of its inclusion. Cook loss (CL), color (CIE L*, a*, b*), texture (hardness, springiness, chewiness and resilience), low-field NMR (bound water, immobilized water, and free water), microstructure, and sensory characteristics of chicken meatballs with different WB inclusion levels (0%, 25%, 50%, 75%, 100%) were analyzed. The results showed that the impairment of product quality traits such as CL, color, texture (hardness, chewiness), free water, microstructure, and sensory scores (appearance, organization, total score) increased as the percentage of WB meat increased in the product formulation, particularly when the WB incorporation level exceeded 25%. Indeed, cook loss, L*, a*, b* parameters, bound water, and immobilized water increased when the WB inclusion level was higher than 25% (P ≤ 0.05). However, free water, sensory characteristics, hardness, and chewiness parameters decreased (P ≤ 0.05). The microstructure of chicken meatballs also changed as the proportion of WB meat increased. Even though data suggest that the inclusion of WB meat up to 30% could be feasible to produce acceptable chicken meatballs, the optimal maximum incorporation rate of WB meat into chicken meatball recipes was 25% based on economic feasibility and final overall quality.

The objective of the present research was to assess the dietary supplementation of three formulations of essential oils (EO) in chickens under heat stress (HS). Day-of-hatch Cobb 500 chicks (n = 500) were randomly distributed into four groups: 1. HS control + control diets; 2. HS + control diets supplemented with 37 ppm EO of Lippia origanoides (LO); 3. HS + control diets supplemented with 45 ppm LO + 45 ppm EO of Rosmarinus officinalis (RO) + 300 ppm red beetroot; 4. HS + 45 ppm LO + 45 ppm RO + 300 ppm natural betaine. Chickens that received the EO showed significant (p < 0.05) improvement on BW, BWG, FI, and FCR compared to control HS chickens. Average body core temperature in group 3 and group 4 was significantly (p < 0.05) reduced compared with the HS control group and group 2. Experimental groups showed a significant reduction in FITC-d at 42 days, a significant increase in SOD at both days but a significant reduction of IFN-γ and IgA compared with HS control (p < 0.05). Bone mineralization was significantly improved by EO treatments (p < 0.05). Together these data suggest that supplemental dietary EO may reduce the harmful effects of HS.

The scope of this paper was to investigate the effects of water distribution differences on the quality and feasibility of chicken patties supplemented with woody breast (WB). Chicken patties, containing differing amounts of WB (0%, 25%, 50%, 75%, 100%) were analyzed using low-field NMR. Quality differences between chicken patties were further evaluated by combining lipid and protein properties, fry loss (FL), color (L*, a*, b*), texture (hardness, springiness, chewiness, cohesiveness, resilience), microstructure, and sensory characteristics. The results expressed that both lipid and protein oxidation increased and immobilized water in chicken patties can be converted to free water more easily with increasing levels of WB. Additionally, the free water ratio decreased, water freedom increased, and the bound water ratio increased (p < 0.05). Fry loss, color, texture (hardness, springiness, chewiness), microstructure, and sensory (character, organization, taste) characteristics deteriorated significantly when the WB inclusion level exceeded 25%. Particularly, characteristics of texture (chewiness and character) and sensory (character and organization) decreased significantly as WB inclusion increased past 25% (p < 0.01). Furthermore, fry loss, texture, and overall microstructure partially confirmed the moisture variation of chicken patties as the potential cause of the abnormal quality. Although the experimental data expressed that mixing to 35% WB inclusion was feasible, the practical and economic impact recommends inclusion levels to not exceed 30%.

Powered by consumer taste, value, and preferences, natural products including phytogenics and algae are increasingly and separately used in the food systems where they have been reported to improve growth performance in poultry and livestock. The present study aimed to determine the effects of a new feed additive, microencapsulated NUQO© NEX, which contains a combination of phytogenic and phycogenic, on broiler growth performance, blood chemistry, bone health, meat quality and sensory profile. Male Cobb500 chicks ( n  = 1,197) were fed a 3-phase feeding intervals; 1–14d starter, 15–28d grower, and 29–40d finisher. The dietary treatments included a corn-soy basal Control (CON), basal diet supplemented with NUQO© NEX at 100 g/ton from 1 to 28d then 75 g/ton from d 28 to 40 (NEX75), and basal diet supplemented with NUQO© NEX at 100 g/ton from 1 to 40d (NEX100). The NEX100 supplemented birds had 62 g more BWG increase and 2.1-point improvement in FCR compared with CON in the finisher and overall growth phase ( p  < 0.05), respectively. Day 40 processing body weights and carcass weights were heavier for the NEX100 supplemented birds ( p  < 0.05). The incidences of muscle myopathies were also higher in NEX treatments, which could be associated with the heavier weights, but the differences were not detected to be significant. The NEX75 breast filets had more yellowness than other dietary treatments ( p  = 0.003) and the NEX 100 treatment reduced the levels of breast filet TBARS at 7 days-post harvest ( p  = 0.053). Finally, both NEX treatments reduced the incidence of severe bone (tibia and femur) lesions. In conclusion, the supplementation of the phytogenic NUQO© NEX improved finisher performance parameters, whole phase FCR, processing carcass weights, and breast filet yellowness, at varying inclusion levels.

The goal of this research was to assess cyclic heat stress on gut permeability, bone mineralization, and meat quality in chickens. Two separate trials were directed. 320 day-of-hatch Cobb 500 male chicks were randomly assigned to four thermoneutral (TN) and four cyclic heat stress (HS) chambers with two pens each, providing eight replicates per treatment in each trial (n = 20 chicks/replicate). Environmental conditions in the TN group were established to simulate commercial production settings. Heat stress chickens were exposed to cyclic HS at 35 °C for 12 h/day from days 7–42. Performance parameters, intestinal permeability, bone parameters, meat quality, and leukocyte proportions were estimated. There was a significant (p < 0.05) reduction in body weight (BW), BW gain, and feed intake, but the feed conversion ratio increased in chickens under cyclic HS. Moreover, HS chickens had a significantly higher gut permeability, monocyte and basophil levels, but less bone mineralization than TN chickens. Nevertheless, the TN group had significant increases in breast yield, woody breast, and white striping in breast fillets compared to HS. These results present an alternative model to our previously published continuous HS model to better reflect commercial conditions to evaluate commercially available nutraceuticals or products with claims of reducing the severity of heat stress.

Breast myopathies have caused significant economic losses to the poultry industry over the last decade. The induction of woody breast (WB), white striping (WS), and spaghetti meat (SM) have caused textural issues, functional issues, and a decline in consumer acceptance. Of these three myopathies, WB causes the most pronounced effects on product quality and reduces functional use. Woody breast is also commonly associated with expansive breast meat growth/high performing broilers. However, progress in reducing these myopathies has been limited without hindering other aspects of poultry rearing. Generally, production performance reduces as myopathy occurrence or incidence reduces. This response is primarily driven by a reduction in final body weight rather than in a net myopathy reduction. For this reason, novel strategies for reducing myopathies are still being investigated. Therefore, this dissertation aimed to assess new technologies in these sectors to reduce or prevent the occurrence of breast myopathies in commercial broilers. Chapter 2 assessed the supplementation of guanidinoacetic acid (GAA) in poultry diets for reducing the occurrence of WB in commercial broilers. Supplementation of GAA was achieved through on-top additions of 0.06% and 0.12% of the diet. Results suggest that GAA can be used as a dietary source of breast myopathy reduction without suppressing body weight or broiler growth. The use of GAA in the diet also improved FCR in broilers at both supplied levels compared to the control diet. Data indicate that supplementation levels may be beneficial above those utilized in this experiment and optimizing levels should be investigated. Chapter 3 also assessed the use of GAA, but in formulation as a potential energy sparing ingredient while maintaining a reduction in breast myopathies. Supplementation was formulated as a 55 kcal/kg and a 110 kcal/kg reduction in energy. Results suggest that a 110 kcal/kg reduction of energy produced no differences in final body weight or body weight gain over the 49 day rearing period. Broilers also expressed no differences in carcass or part yields with or without the presence of GAA. In addition, meat quality differences were not present among treatments. However, GAA inclusion provided an improvement in feed conversion ratio and had a numeric shift in WB occurrence in broilers. The need to assess ingredient pricing and availability should be considered for GAA use as an energy sparing ingredient. Chapter 4 evaluated the use of a novel 0.9% in ovo feeding of nicotinamide riboside (NR), a vitamin B3 analog, to reduce the occurrence of WB in broilers. Three concentrations of NR were utilized in this experiment including: 250 mmol, 500 mmol, and 1000 mmol of the vitamin B3 analog. Results suggest that NR had little effect on performance or meat quality parameters yet improved final bird weight compared to the control. Optimizing the dosing level for WB reduction may not have been met in this study and should be further investigated for conformation. Changing to other forms of WB reduction, Chapter 5 evaluated the use of broiler stocking density as a combative measure. Three research accepted stocking densities were assessed to determine effects on meat quality. Results indicate that WB is reduced when stocking density is increased, but performance characteristics are reduced alongside a reduction in final body weight. Results also suggest that investigation into welfare limits and financial gain may be necessary to determine the most beneficial stocking density. Finally, Chapter 6 was conducted to understand statistical sampling needs to assess myopathies (specifically WB) for common broiler rearing experiments. There is a growing trend to include meat quality analysis in studies designed for nutritional, management, or physiological aspects. These types of studies typically use a low sample selection size per pen which have typically been adequate for analysis, such as yield. In opposition, myopathy occurrence in populations can vary and may require a larger sample size. Some studies conducted on performance characteristics have started assessing meat quality traits with limited samples and drawing conclusions that do not seem to match common practice. Meat quality based studies typically utilize a substantially larger sample size than those of performance-based experiments as variability is generally higher. Results indicated that sampling a larger proportion of the pen (up to 75%) would greatly reduce the variance present between samples and lead to a more accurate description of myopathies among treatments. Overall, this dissertation provided three new avenues for assessing WB in commercial broilers and potential ways to reduce occurrences. Limited results were present in WB reduction, but results indicate that differences in body weight were not as apparent as seen in previous studies. Suppressed growth comes at a significant price to the industry so finding nutritional or managerial strategies to reduce myopathies is very important. The need to better understand the relationship between each of the assessed strategies and WB are still necessary to improve breast product quality.

Through current trends in animal protein consumption, the United States poultry industry has seen a drastic rise in production and popularity. Over the last few decades, poultry meat has surpassed both beef and pork production to become the most widely consumed animal protein. This rise may be accredited to an increased transition to more health-conscious consumers. As more consumers purchase poultry as a lean source of protein, the need for a superior quality product is of great interest to poultry integrators. Relationships between commercial broiler lines have been well documented in previous years, but constant and intensive genetic selection in the poultry industry has morphed modern broiler lines to perform differently from those previously investigated. Therefore, the need to address the impact of genetic selection on broiler meat quality was of paramount importance. Chapter 2 characterized the growth performance of males and females from four modern broiler lines fed either a low- or high-density diet. Broilers reared for two processing weights were utilized and variation between the two were assessed. High yielding (HY) broilers produced the highest carcass, breast, and tender yields, whereas standard yielding (SY) broilers produced higher body weights, as well as wing and leg yields. Males produced higher final body weights than females, however, females produced higher carcass, breast, and tender yields. High density diets produced larger carcasses, breast, and tender yields while reducing total fat. Concurrent with Chapter 2, Chapter 3 evaluated these broiler strains for variation in meat quality characteristics. Birds were processed by weight to meet two distinct markets for big bird and small bird debone markets, respectively. High yielding strains produced an increased incidence of all myopathies in comparison to SY strains. Males produced longer and thicker fillets, had increased incidences of white striping, and higher cook loss. Females however, showed an increase in woody breast and spaghetti meat incidence, higher ultimate pH, lighter fillets, and decreased peak counts. Males of the small bird debone market had decreased tenderness than those from the big bird market. However, females had higher degrees of tenderness in the small bird market. Variation in carcass dimensions were observed as males expressed a decrease in breast width as carcass width increased while female breast width increased as carcass size increased. For both Chapters, strain and carcass size provided the main variation in samples. Thus, the assessment of specific markets provides opportunistic selection for integrators to assess for maximum return of investment when broilers are placed.