M. J. Zuidhof

Growth, efficiency, and yield of commercial broilers from 1957, 1978, and 2005

The effect of commercial selection on the growth, efficiency, and yield of broilers was studied using 2 University of Alberta Meat Control strains unselected since 1957 and 1978, and a commercial Ross 308 strain (2005). Mixed-sex chicks (n = 180 per strain) were placed into 4 replicate pens per strain, and grown on a current nutritional program to 56 d of age. Weekly front and side profile photographs of 8 birds per strain were collected. Growth rate, feed intake, and measures of feed efficiency including feed conversion ratio, residual feed intake, and residual maintenance energy requirements were characterized. A nonlinear mixed Gompertz growth model was used to predict BW and BW variation, useful for subsequent stochastic growth simulation. Dissections were conducted on 8 birds per strain semiweekly from 21 to 56 d of age to characterize allometric growth of pectoralis muscles, leg meat, abdominal fat pad, liver, gut, and heart. A novel nonlinear analysis of covariance was used to test the hypothesis that allometric growth patterns have changed as a result of commercial selection pressure. From 1957 to 2005, broiler growth increased by over 400%, with a concurrent 50% reduction in feed conversion ratio, corresponding to a compound annual rate of increase in 42 d live BW of 3.30%. Forty-two-day FCR decreased by 2.55% each year over the same 48-yr period. Pectoralis major growth potential increased, whereas abdominal fat decreased due to genetic selection pressure over the same time period. From 1957 to 2005, pectoralis minor yield at 42 d of age was 30% higher in males and 37% higher in females; pectoralis major yield increased by 79% in males and 85% in females. Over almost 50 yr of commercial quantitative genetic selection pressure, intended beneficial changes have been achieved. Unintended changes such as enhanced sexual dimorphism are likely inconsequential, though musculoskeletal, immune function, and parent stock management challenges may require additional attention in future selection programs.

Omega-3-enriched broiler meat: 3. Fatty acid distribution between triacylglycerol and phospholipid classes

Consumers are becoming more aware of the effect of the food they eat on their health. One of the ways they hope to reduce their risk of cardiovascular disease is by consuming more foods enriched with n-3 polyunsaturated fatty acids (PUFA). Due to the high content of alpha-linolenic acid (LNA), dietary flaxseed is a good source for increasing n-3 PUFA in poultry meat. A study was conducted with 2 primary objectives: to establish the distribution of n-3 PUFA between triacylglycerol (TAG) and phospholipid of broiler chicken breast and thigh meat and to determine the duration of dietary flaxseed supplementation required to ensure a level of n-3 PUFA of 300 mg per 100 g of meat necessary to label meat as a source of n-3 PUFA. This experiment was conducted as a 2 x 8 factorial, with 2 dietary levels of ground flaxseed (10 and 17%) and 8 durations of dietary flaxseed before processing [0 (control), 4, 8, 12, 16, 20, 24, and 35 d]. A total of 128 Ross x Ross 308 mixed-sex broilers were evaluated to 35 d of age. Breast and thigh meat fatty acid composition was analyzed on duplicate samples of ground meat pooled from 8 birds per treatment. Broken-stick analysis was used to estimate the duration required to achieve 300 mg of n-3 PUFA per 100 g of breast meat. Results clearly indicated that LNA was mainly deposited in the TAG fraction of both breast and thigh meat. Enriching the chicken breast meat with 300 mg of n-3 PUFA per 100 g of meat was achieved in 11.3 and 26.2 d with a 17 and 10% level of flaxseed in diet, respectively. Although a significant increase of n-3 long-chain PUFA (20:5n-3, 22:5n-3, and 22:6n-3) was found in the phospholipid and TAG fraction of both tissues, the concentration of these functional components was low. More than 95% of n-3 PUFA enrichment was due to LNA.

Omega-3-enriched broiler meat: 2. Functional properties, oxidative stability, and consumer acceptance

Consumers are becoming more aware of the impact on their health of the food they eat. One of the ways they hope to reduce their risk of cardiovascular disease is by consuming more foods enriched with polyunsaturated fatty acids (PUFA), particularly n-3 fatty acids. Flaxseed is a good source for increasing the n-3 PUFA in poultry meat because of the high content of alpha-linolenic acid. A study was conducted to identify an optimal process to enrich of broiler diets with n-3 PUFA by using 2 levels of flaxseed fed for various times before processing. The acceptability of broiler meat functional properties was tested to ensure that further processing efficiencies would not be compromised by the enrichment strategy. This experiment was conducted as a 2 x 8 factorial, with 2 dietary levels of ground flaxseed (10 and 17%) fed for 8 lengths of time before processing [0 (control), 4, 8, 12, 16, 20, 24, and 35 d]. Of 650 Ross x Ross 308 mixed-sex broilers reared in this study, 128 were used to evaluate breast and thigh meat functional properties, oxidative stability, and sensory analysis. No statistical interactions were found between treatments for chicken breast meat quality traits. The duration of feeding flaxseed strongly affected meat quality parameters. In particular, feeding flaxseed for 16 d resulted in a final pH of 5.65, compared with 5.93 in the control. The lower ultimate pH found in animals fed flaxseed affected meat cooking loss, drip loss, and shear value (P < 0.0001). Shear value significantly increased after 16 d of feeding flaxseed (P < 0.0001). Susceptibility to oxidation increased in both breast and thigh broiler meat with the duration of feeding flaxseed. Enriching the diet for less than 16 d did not result in perceivable sensory defects. Duration of flaxseed feeding significantly affected the color characteristics, functional properties, and oxidative stability of broiler meat.

Omega-3-enriched broiler meat: 1. Optimization of a production system

Consumer awareness of the health benefits of n-3 fatty acids is growing and is driving consumer demand for enriched food products. Enrichment of meat with n-3 fatty acids is an opportunity for the broiler production sector to add value to their product, but enrichment can increase the cost of production. A study was conducted to determine an optimal production strategy for n-3 enrichment of broiler meat using ground full-fat flaxseed. Low and high levels of dietary flaxseed (10 and 17%, respectively) were fed to broilers for 8 lengths of time (0, 4, 8, 12, 16, 20, 24, or 35 d) before processing at 35 d. Increasing the level or duration decreased feed intake, BW, and the percentage yield of carcass and breast. Flaxseed level and duration of feeding increased feed conversion ratios and the cost of production. Feeding flaxseed at 10 and 17% increased breast n-3 fatty acid levels by 7.65 and 13.70 mg/100 g of meat per day, respectively. In breast meat, the threshold level of 300 mg/g, required in Canada for labeling foods as a source of n-3 fatty acids, was reached at 12.1 and 24.1 d in the high and low flaxseed treatments, respectively. This was due primarily to a tripling of alpha-linolenic acid (18:3n-3) levels in the breast meat. Levels of the long-chain n-3 fatty acid eicosapentaenoic acid increased significantly in the breast meat with increased level and duration of flax feeding, indicating that birds were able to desaturate and elongate alpha-linolenic acid to eicosapentaenoic acid. To minimize cost, while achieving adequate breast meat n-3 enrichment, carcass weight, and meat yield, feeding 10% flaxseed for 24.1 d before processing is recommended as an optimal breast meat n-3 enrichment strategy. The optimal thigh meat n-3 enrichment strategy was to feed 10% flaxseed for 4.54 d before processing.

Comparative feeding value of extruded and nonextruded wheat and corn distillers dried grains with solubles for broilers

The feeding value of extruded and nonextruded wheat and corn distillers dried grains with solubles (DDGS) for broilers was evaluated in 2 experiments. In experiment 1, male broilers (n=360) housed in battery cages were fed assay diets that included either 15 or 30% wheat or corn DDGS (extruded or not) in relation to a basal diet from d 21 to 28. Birds were killed on d 28 and ileal digesta was collected to establish the apparent ileal digestibility (AID) coefficients of energy and nutrients for test ingredients using the difference method based on 5 cages of 8 birds per diet. In experiment 2, a 42-d study compared the growth performance of broilers fed phase diets including 0, 5, or 10% wheat or corn DDGS, based on 4 pens of 55 birds per diet×sex combination. Diets within phase were formulated to have a similar content of AME, CP, and digestible lysine. Breast meat weight and yield were determined on d 37 by sampling 5 birds per pen. In experiment 1, at 15% inclusion, AID coefficients of most amino acids were higher for corn DDGS than for wheat DDGS (P<0.05). At 30% inclusion, however, there were fewer differences in AID between corn and wheat DDGS. Twin-screw extrusion increased the AID of AA in both corn and wheat DDGS by 10 to 34% (P<0.05). In experiment 2, there was no adverse effect of including corn or wheat DDGS at up to 10% of the diet on pen average daily weight gain, feed disappearance, feed efficiency, breast meat weight, or yield. In conclusion, extrusion increased the feeding value of DDGS. The AID coefficients for amino acids were similar between corn and wheat DDGS. We also confirmed that either corn or wheat DDGS can be included at up to 10% of wheat-based broiler diets without affecting growth performance or breast meat yield.

Effect of holding temperature, shackling, sex, and age on broiler breast meat quality

Antemortem holding temperature and flapping can affect broiler pectoralis major (referred to as p. major) meat quality. The influence of environmental temperature 12 to 14 h before processing and antemortem handling on p. major functional properties and color was tested at multiple processing ages in a 3 × 2 × 5 factorial design study. At 28, 35, 42, 49, and 56 d of age, mixed-sex broilers were crated and held in one of 3 target temperature treatments: heat (30°C), thermoneutral (21°C), or cool (7°C). Following feed withdrawal, birds were transported to a processing facility where either a long (120 s) or short (<10 s) shackling treatment was imposed. Sex was determined at processing. Lightness, redness, and yellowness values were measured at deboning [4.50 to 8.25 h postmortem (PM)] and at 24 h PM. Ultimate pH was measured at 24 h PM. Drip loss, cook loss, and Allo-Kramer shear force were determined at 72 h PM. Ultimate pH was highest in the cool treatment, with no difference between heat and thermoneutral treatments (5.97 vs. 5.87 and 5.90, respectively; P = 0.0004). Ultimate pH correlated negatively with drip loss (r = -0.47; P < 0.0001). Drip loss was lowest in the cool treatment, with no difference between the heat and thermoneutral treatments (2.06 vs. 2.24 and 2.19%, respectively; P = 0.007). The p. major from broilers in the heat treatment had higher Allo-Kramer shear force values than those in both the thermoneutral and cool treatments (4.64 kg/g vs. 4.21 and 4.21 kg/g, respectively; P = 0.023). With the exception of 49 d, broilers subjected to the long shackling treatment had higher redness values at deboning than broilers subjected to the short shackling treatment; by 24 h PM only the 28-d broilers subjected to the long shackling treatment had higher redness values. Higher hue angles at deboning and 24 h PM were observed in the short treatment compared with the long treatment (65.58 vs. 57.46 and 68.48 vs. 63.31, respectively; P < 0.0001), indicating that p. major from long-shackled broilers were redder in appearance. Ultimate pH was lower in female broilers than in male broilers (5.87 vs. 5.96, respectively; P < 0.0001) and subsequent drip loss was higher in females compared with males (2.34 vs. 1.99%, respectively; P < 0.0001). Although temperature and handling before slaughter affected p. major color and texture traits, the differences may not be large enough to have commercial significance. Differences in p. major quality attributable to sex of the bird may have greater commercial significance than previously reported.

Nutritive value of single-screw extruded and nonextruded triticale distillers dried grains with solubles, with and without an enzyme complex, for broilers

The nutritive value of triticale distillers dried grains with solubles (DDGS) for broilers was investigated in 2 experiments. In experiment 1, four hundred male broilers housed in battery cages were fed diets including 15 or 30% triticale DDGS (extruded or not) or a basal diet, supplemented with or without a multi-enzyme complex from d 21 to 28. Birds were killed and ileal digesta was collected on d 28 to establish the apparent ileal nutrient digestibility (AID) coefficients for both assay diets and DDGS as test ingredients based on 5 cages per diet. In experiment 2, a 42-d performance study compared growth phase-specific diets formulated to similar levels of AME, CP, and digestible lysine with graded levels (0, 5, or 10%) of triticale DDGS inclusion based on a minimum of 4 pens per diet x sex combination. Breast muscle weight and percentage yield were determined on d 37 by sampling 5 birds per pen. In experiment 1, there was a significant (P < 0.05) DDGS level of inclusion x enzyme interaction for CP, lysine, methionine, tryptophan, isoleucine, histidine, and phenylalanine, such that the AID increased with enzyme supplementation based on 15% but not 30% DDGS inclusion. At 15% DDGS inclusion, enzyme supplementation increased the AID of these nutrients in DDGS between 6 and 19 percentage units. Extrusion of triticale DDGS increased (P < 0.05) the AID of GE, CP, methionine, tryptophan, branched-chain amino acids, and phenylalanine between 3 and 8 percentage units. In experiment 2, feeding up to 10% triticale DDGS had no adverse effect on feed intake, weight gain, or feed efficiency of broilers compared with controls over the 42-d study. Feeding up to 10% triticale DDGS did not affect breast weight or yield on d 37. In conclusion, feed enzyme complex supplementation and extrusion both increased the nutritive value of triticale DDGS for broilers. Triticale DDGS can be fed at up to 10% of practical broiler diets without adverse effect on performance and breast muscle yield.

Characterization of energetic efficiency in adult broiler breeder hens

This trial characterized residual feed intake (RFI) and residual maintenance requirement (RME(m)) as measures of energetic efficiency in broiler breeder hens. The RFI was defined as the difference between observed and expected ME intake and RME(m) as the difference between observed and expected maintenance requirements. A total of 600 Ross 708 1-d-old pullets were placed in floor pens. At 16 wk, 144 hens were caged and randomly assigned to 1 of 2 feed allocation treatments (72 birds each). The control treatment had feed allocated on a group basis (GRP) following the standard BW target. A second treatment had feed allocated on an individual-bird basis (IND) and followed the same BW target as GRP. Sexual maturity age, egg and chick production, and several feed conversion ratios were correlated to standardized efficiency indices of RFI (SRFI) and RME(m) (SRME(m)) in each treatment. Greater SRFI and SRME(m) values described a greater energetic efficiency. Residual feed intake was more variable in IND than GRP hens (P < 0.001). The variability of RME(m) did not differ between treatments (P = 0.14). The SRFI was positively correlated to egg production in the GRP hens (r = 0.31), but negatively correlated in IND hens (r = -0.40) and was correlated to feed conversion per chick only in the GRP-based feed allocation (r = -0.44). The SRME(m) correlated strongly to egg production (r = 0.64), chick production (r = 0.64), and feed conversion per chick (r = -0.59) in both feed allocation treatments. Feed intake confounded the RFI calculation, which limits the value of RFI as a selection criterion in meat-producing animals. The independence of RME(m) from feed intake is desirable for energetic efficiency assessment in selection programs because consistent values can be obtained across different management schemes. Hens with lower maintenance requirements (greater RME(m) efficiency) partitioned more energy toward reproduction than did high-maintenance hens. The RME(m) methodology provided an unbiased estimate of energetic efficiency by adjusting the maintenance requirement for the effect of dietary thermogenesis.

Characterization of the n-3 polyunsaturated fatty acid enrichment in laying hens fed an extruded flax enrichment source

The time required to reach a plateau of n-3 polyunsaturated fatty acid (PUFA) concentration in plasma and egg yolk and dynamics of the enrichment process were examined in laying hens. A group of 75 Lohmann White Leghorn layers (65 wk) were fed one of 3 diets: control, moderate, or high n-3 PUFA-enriched diet for 18 d. Diets provided similar ME and CP and contained 0, 7.5%, or 15% LinPRO (source of n-3 PUFA), respectively. Prior to dietary treatment, baseline values were established for the BW, fatty acid composition in egg yolk on a whole-egg basis, and in plasma. These measurements were repeated at 6, 12, and 18 d of feeding. Enzymatic conversion rates of linolenic acid (LNA) to long-chain fatty acids were calculated. Data were analyzed with Proc Mixed of SAS, and broken stick analysis was used to determine n-3 PUFA plateau using the NLIN procedure of SAS (P < 0.05). The total egg yolk n-3 PUFA reached a plateau of 343.7 mg/egg and 272.9 mg/egg after 6.6 and 5.9 d on the high and moderate diets, respectively. In blood plasma, the n-3 PUFA concentrations reached saturation in 7.2 d with 0.93 mg/mL and 0.67 mg/mL on high and moderate diets, respectively. The transfer efficiency of total n-3 PUFA from the diet to the egg yolk was calculated as 55.6% in control birds, 30.5% in moderate birds, and 22.2% in high birds, demonstrating reduced transfer efficiency of n-3 PUFA as inclusion in the feed increases. Final egg yolk n-3 PUFA concentrations had a CV of 16.5% compared with 28.5% for plasma. After 12 d, the long-chain n-3 PUFA [eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA)] were significantly higher in egg yolk from hens on the moderate and high enriched diets compared with those from hens fed the control diet, whereas in plasma values did not differ. Broken stick analysis of egg enrichment indicated that high birds reached the target threshold of 300 mg of total n-3 PUFA/egg in 5 d. A significant increase in EPA, DPA, and DHA and reduction in arachidonic acid content in egg yolks from hens fed enriched diets compared with the control diet confirms competition for enzymes during postabsorptive modification of these fatty acids. This work contributes to the understanding of individual hen effects on n-3 PUFA absorption and the effect of level of dietary enrichment with an extruded flax product on final yolk n-3 PUFA concentration.

Arsenic Species in Chicken Breast: Temporal Variations of Metabolites, Elimination Kinetics, and Residual Concentrations.

Background: Chicken meat has the highest per capita consumption among all meat types in North America. The practice of feeding 3-nitro-4-hydroxyphenylarsonic acid (Roxarsone, Rox) to chickens lasted for more than 60 years. However, the fate of Rox and arsenic metabolites remaining in chicken are poorly understood. Objectives: We aimed to determine the elimination of Rox and metabolites from chickens and quantify the remaining arsenic species in chicken meat, providing necessary information for meaningful exposure assessment. Methods: We have conducted a 35-day feeding experiment involving 1,600 chickens, of which half were control and the other half were fed a Rox-supplemented diet for the first 28 days and then a Rox-free diet for the final 7 days. We quantified the concentrations of individual arsenic species in the breast meat of 229 chickens. Results: Rox, arsenobetaine, arsenite, monomethylarsonic acid, dimethylarsinic acid, and a new arsenic metabolite, were detected in breast meat from chickens fed Rox. The concentrations of arsenic species, except arsenobetaine, were significantly higher in the Rox-fed than in the control chickens. The half-lives of elimination of these arsenic species were 0.4–1 day. Seven days after termination of Rox feeding, the concentrations of arsenite (3.1 μg/kg), Rox (0.4 μg/kg), and a new arsenic metabolite (0.8 μg/kg) were significantly higher in the Rox-fed chickens than in the control. Conclusion: Feeding of Rox to chickens increased the concentrations of five arsenic species in breast meat. Although most arsenic species were excreted rapidly when the feeding of Rox stopped, arsenic species remaining in the Rox-fed chickens were higher than the background levels. Citation: Liu Q, Peng H, Lu X, Zuidhof MJ, Li XF, Le XC. 2016. Arsenic species in chicken breast: temporal variations of metabolites, elimination kinetics, and residual concentrations. Environ Health Perspect 124:1174–1181; http://dx.doi.org/10.1289/ehp.1510530