Energy and protein dilution in broiler breeder pullet diets reduced offspring body weight and yield.

The objective of the current research was to evaluate transgenerational effects of maternal dietary energy and protein on growth, efficiency, and yield of broiler offspring. A factorial arrangement of treatments consisting of high and low ME and CP levels fed during the rearing and laying phases was used. The study was a final 2 × 2 × 2 × 2 factorial arrangement of treatments, including broiler sex. Ross 708 broiler breeder pullets (n = 933) were fed diets containing 2,736 (HEREAR) or 2,528 kcal/kg ME (LEREAR) with either 15.3% (HPREAR) or 13.7% CP (LPREAR). From 25 wk, dams were fed a 15% CP laying diet containing 2,900 (HELAY) or 2,800 kcal/kg ME (LELAY). Following artificial insemination of the dams at 35 wk, eggs were collected for 1 wk, incubated, and pedigree hatched to preserve maternal identity. Broiler offspring were placed sex-separately into 32 pens, according to laying phase maternal treatments, with rearing maternal treatments nested within pens. Individual BW and pen level feed intake were recorded weekly. Broilers were processed at 40 d of age to evaluate yield. Maternal diet effects on offspring BW were sex dependent and transient. Female LPREAR × LELAY broilers had lower pectoralis major and carcass yield than HPREAR × LELAY females. Male HPREAR × HELAY broilers had increased breast yield (19.8%) compared with 18.4% in HPREAR × LELAY broilers. Carcass yield was lower in LEREAR × HPREAR broilers (63.7%) compared with HEREAR × HPREAR broilers (64.9%). LEREAR × HPREAR dams had the lowest ME to CP ratio (E: P) diets and highest rearing phase CP intake. Maternal diet did not influence offspring FCR. The most consistent contributor to increased BW was higher maternal dietary CP and ME during rearing. Low ME maternal laying phase diets increased BW of male offspring more consistently than of female offspring. Maternal nutrition also influenced broiler yield, and is thus economically important. Energy and protein dilution in broiler breeder pullet diets may have detrimental effects on offspring performance.

Effects of environmental temperature and dietary energy on energy partitioning coefficients of female broiler breeders.

With increasing disparity between broiler breeder target weights and broiler growth potential, maintenance energy requirements have become a larger proportion of total broiler breeder energy intake. Because energy is partitioned to growth and egg production at a lower priority than maintenance, accurate prediction of maintenance energy requirements is important for practical broiler breeder feed allocation decisions. Environmental temperature affects the maintenance energy requirement by changing rate of heat loss to the environment. In the ME system, heat production (energy lost) is part of the maintenance requirement (ME). In the current study, a nonlinear mixed model was derived to predict ME partitioning of broiler breeder hens under varied temperature conditions. At 21 wk of age, 192 Ross 708 hens were individually caged within 6 controlled environmental chambers. From 25 to 41 wk, 4 temperature treatments (15°C, 19°C, 23°C, and 27°C) were randomly assigned to the chambers for 2-week periods. Half of the birds in each chamber were fed a high-energy (HE; 2,912 kcal/kg) diet, and half were fed a low-energy (LE; 2,790 kcal/kg) diet. The nonlinear mixed regression model included a normally distributed random term representing individual hen maintenance, a quadratic response to environmental temperature, and linear ADG and egg mass (EM) coefficients. The model assumed that energy requirements for BW gain and egg production were not influenced by environmental temperature because hens were homeothermic, and the cellular processes for associated biochemical processes occurred within a controlled narrow core body temperature range. Residual feed intake (RFI) and residual ME (RME) were used to estimate efficiency. A quadratic effect of environmental temperature on broiler breeder MEm was predicted ( < 0.0001), with a minimum energy expenditure at 24.3°C. Predicted ME at 21°C was 92.5 kcal/kg; requirements for gain and EM were 2.126 and 1.789 kcal/g, respectively ( < 0.0001). Birds fed the HE diet were more efficient, with a lower RME than birds on the LE diet (-0.63 vs. 0.63 kcal/kg), translating to ME of 135.2 and 136.5 kcal/kg, respectively. In the current experiment, optimal biological efficiency was predicted at 24.3°C in feed-restricted broiler breeders fed the HE diet.

Effects of broiler breeder management on pullet body weight and carcass uniformity.

An experiment was conducted to study the effect of broiler breeder feeding management practices on pullet performance, BW uniformity, and carcass traits during rearing (to 22 wk of age). At 3 wk of age, 1,200 Ross 308 breeder pullets were assigned to one of 5 treatments: 1) control: standard mash diet, fed daily; 2) high fiber: mash diet containing 25% lower nutrient density, fed daily; 3) scatter: standard diet in pellet form scattered on litter, fed daily; 4) skip-a-day: standard mash diet, fed on alternate days; or 5) grading: standard mash diet, fed daily (birds sorted into low, average, and high BW groups every 4 wk). Birds on the high fiber treatment consumed more feed (P<0.0001) and had the highest feed conversion ratio (FCR; P<0.004) but the lowest ME to gain and CP to gain ratios (P≤0.002). Skip-a-day treatment pullets consumed more ME and CP than birds in any other treatment (P<0.001). Grading yielded the highest BW uniformity at 22 wk of age (CV=6.2%), while control and high fiber treatment groups were least uniform (CV>15%; P<0.0001). Skip-a-day feed restriction produced birds with the significantly lowest breast muscle and highest liver weight compared to all other treatments (P<0.05). Variation in shank length, chest width, and breast muscle was lowest in the grading treatment, whereas the CV for fat pad and liver was lowest in the skip-a-day treatment. In this trial, broiler breeder target BW profiles were achieved using combinations of quantitative and qualitative feed restriction, or preemptive management practices. Qualitative diet dilution and skip-a-day management did little to increase flock uniformity relative to the control during the most intense period of feed restriction (7 to 19 wk). Scatter feeding increased flock uniformity to a small degree, whereas grading yielded the highest increase in BW and carcass trait uniformity.

Effect of maternal dietary energy and protein on live performance and yield dynamics of broiler progeny from young breeders.

The objective of this research was to evaluate effects of female broiler breeder dietary ME and CP during rearing and dietary ME during early lay on broiler offspring performance and carcass yield dynamics. A factorial arrangement of treatments, with 2 ME levels, and 2 balanced protein levels from 3 to 24 wk, followed by 2 ME levels in the lay diets, and in the broilers, 2 sexes. A total of 1,635 broilers were housed in 32 pens, with 8 replicate pens according to maternal laying diet and sex. Maternal pullet diets were nested within pen (n = 9 to 14, depending on hatch rate). The broilers originated from 384 Ross 708 hens, which had been fed diets containing high (2,736 kcal/kg, HEREAR) or low ME (2,528 kcal/kg, LEREAR) combined with either high (15.3%, HPREAR) or low balanced protein (13.7% CP, LPREAR). Equal numbers of hens from each pullet treatment were then fed either a high (2,900 kcal/kg, HELAY) or low ME diet (2,800 kcal/kg, LELAY) containing 15% CP. Broilers were hatched from eggs collected at 28 wk of age, and fed identical diets. Broilers were individually weighed weekly. Serial dissections were conducted to evaluate yield breast muscle and abdominal fatpad dynamics. At 39 d, 180 broilers were processed to measure carcass yield. Female progeny of hens with the lowest CP intake during rearing (HEREAR × LPREAR) were lighter from 22 to 36 d of age than female offspring from hens that consumed more CP as pullets. We predicted the heaviest female progeny would result from an ME:CP ratio of 18.25 kcal/g in maternal pullet diets (P = 0.0063). Broiler breast yield increased when maternal EM:CP ratio increased after switching from pullet to laying diets. Hens fed HEREAR were fatter and had fatter progeny than LEREAR. Maternal diet, even during the pullet phase, influenced progeny growth and yield.

Effect of age at photostimulation on sexual maturation in broiler breeder pullets.

Genetic selection programs in broiler stocks have contributed to changes in the responsiveness of the broiler breeder female to nutritional factors. A study was conducted to investigate the effect of photostimulation (PS) age on sexual maturity traits in current broiler breeder pullets. Seven hundred twenty Ross 308 pullets with full access to feed to 1 or 3 wk of age were divided among 8 environmental rooms to 16 wk of age. At this time, 128 pullets (64 per initial feeding treatment) were randomly assigned to individual cages in 8 rooms with 16 pullets per room. Pullets were PS at 17 (PS17), 19 (PS19), 21 (PS21), or 23 (PS23) wk of age by increasing the day length from 8L:16D to 16L:8D (multiple steps). Each hen was dissected on the morning after first oviposition (sexual maturity). Data were analyzed by 2-way ANOVA with additional analysis of covariance analysis done using sexual maturity on BW as a covariate. Sexual maturation occurred later with later PS ages. Rate of sexual maturation was accelerated at later PS ages, although age at PS did not affect variation in age at sexual maturity. Despite a 42 d difference in PS age between the PS17 and PS23 groups, only a 25 d difference existed in mean age at sexual maturity among these groups. Initial egg weight, breast muscle weight, frame size, and abdominal fat pad weight at sexual maturity increased in birds with later PS ages. Covariate analysis indicated that these effects were influenced primarily by increased age and BW at sexual maturity in later PS birds. Pullets PS at 17 wk of age had 11.0 large white ovarian follicles, compared with 14.9 in PS23 birds. Comparison to previous studies demonstrates that the years of genetic selection for growth traits have not changed the interval between PS and sexual maturation. Previous research published on this theme likely had a confounding effect of mean BW on estimates of variation at various PS ages. Photostimulating later presented advantages with regard to development of the reproductive tract; these effects were BW dependent.

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.

Effect of metabolic efficiency and intestinal morphology on variability in n-3 polyunsaturated fatty acid enrichment of eggs.

The effect of metabolic efficiency and associated gut characteristics of laying hens on the variability of transfer of dietary n-3 polyunsaturated fatty acids (PUFA) to the egg was examined in laying hens at 56 wk of age. An empirical energetics model was used to categorize individual hens into energetically efficient or nonefficient treatments based on residual maintenance ME requirement. Birds were then provided a diet containing an extruded flax product as a source of n-3 PUFA for 14 d. Egg traits were determined and yolks collected at 0 d and 14 d for measurement of fatty acid composition and variation in fatty acid levels within hen efficiency class. Gut length and duodenal histomorphometric indices were assessed after the 14-d experimental period. Efficient hens had a 96.01% rate of lay compared with 88.63% in nonefficient hens. After 14 d of feeding, the concentration of n-3 PUFA increased (151.6 vs. 315.8 mg/egg) in the egg yolk whereas n-6 PUFA, saturated fatty acids, and monounsaturated fatty acids were reduced (P < 0.001). Energetic efficiency had no additional effect on these measurements. However, egg yolks from efficient birds had less α-linolenic acid but more docosapentaenoic acid than nonefficient birds, suggesting a greater up-conversion of medium-chain (α-linolenic acid) to long-chain fatty acids (docosapentaenoic acid) in efficient birds. After 14 d, the CV for total n-3 PUFA in egg yolks from efficient hens was lower than that from nonefficient birds (11.1 vs. 21.4), indicating a more uniform level of enrichment. Furthermore, efficient hens had longer duodenal villi (P = 0.02), resulting in a greater absorptive villi surface area (0.13 mm(2)/villi) than in nonefficient birds (0.10 mm(2)/villi; P = 0.01). Increased uniformity of n-3 PUFA enrichment of table eggs could be possible through focus on metabolic efficiency and gut absorptive condition in laying hens.

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.

Effects of maternal energy efficiency on broiler chicken growth, feed conversion, residual feed intake, and residual maintenance metabolizable energy requirements.

This study investigated the effect of maternal energy efficiency on broiler chicken growth and energy efficiency from 7 to 40 d of age. Residual feed intake (RFI) and residual maintenance ME requirement (RME) were used to measure energetic efficiency. Residual feed intake was defined as the difference between observed and predicted ME intake, and RME(m) as the difference between observed and predicted maintenance ME requirements. A total of 144 Ross-708 broiler breeder pullets were placed in individual laying cages at 16 wk of age. Hens with the greatest RFI (n = 32) and lowest RFI (n = 32) values from 20 to 56 wk of age were selected (maternal RFI; RFI(mat)). Selected hens were retrospectively assigned to a high- or low-RME(m) category (maternal RME(m); RME(mmat)). At 59 wk, eggs were collected for 8 d and pedigree hatched. A total of 338 broilers grouped by dam and sex were raised in 128 cages where feed intake, BW, and temperature were recorded from 7 to 40 d to calculate broiler feed conversion ratios, RFI, and RME(m). The design was a 2 × 2 × 2 factorial with 2 levels of RFI(mat), 2 levels of RME(mmat), and 2 sexes. Neither the RFI(mat) nor RME(mmat) category affected broiler offpring BW or total conversion ratio. The high-RFI(mat) × low-RME(mmat) broilers had decreased growth to 40 d. Low-RFI(mat) × low-RME(mmat) broilers had a lower RME(m) (-5.93 kcal of ME/kg(0.60) per day) and RFI (-0.86 kcal of ME/d) than high-RFI(mat) × low-RME(mmat) broilers (RME(m) = 1.70 kcal of ME/kg(0.60) per day; RFI = 0.38 kcal of ME/d). Overall, hens with low maintenance requirements (low RME(m)) produced more efficient broilers when other efficiency related traits, represented in a lower RFI, were present. Exclusion of high-RFI × low-RME(m) hens from selection programs may improve energy efficiency at the broiler level. The RME(m) methodology is a viable alternative to evaluate energy efficiency in broilers because it avoids confounding environmental effects and allows measurement standardization.

A data envelope analysis to assess factors affecting technical and economic efficiency of individual broiler breeder hens.

This study evaluated the effect of feed allocation and energetic efficiency on technical and economic efficiency of broiler breeder hens using the data envelope analysis methodology and quantified the effect of variables affecting technical efficiency. A total of 288 Ross 708 pullets were placed in individual cages at 16 wk of age and assigned to 1 of 4 feed allocation groups. Three of them had feed allocated on a group basis with divergent BW targets: standard, high (standard x 1.1), and low (standard x 0.9). The fourth group had feed allocated on an individual bird basis following the standard BW target. Birds were classified in 3 energetic efficiency categories: low, average, and high, based on estimated maintenance requirements. Technical efficiency considered saleable chicks as output and cumulative ME intake and time as inputs. Economic efficiency of feed allocation treatments was analyzed under different cost scenarios. Birds with low feed allocation exhibited a lower technical efficiency (69.4%) than standard (72.1%), which reflected a reduced egg production rate. Feed allocation of the high treatment could have been reduced by 10% with the same chick production as the standard treatment. The low treatment exhibited reduced economic efficiency at greater capital costs, whereas high had reduced economic efficiency at greater feed costs. The average energetic efficiency hens had a lower technical efficiency in the low compared with the standard feed allocation. A 1% increment in estimated maintenance requirement changed technical efficiency by -0.23%, whereas a 1% increment in ME intake had a -0.47% effect. The negative relationship between technical efficiency and ME intake was counterbalanced by a positive correlation of ME intake and egg production. The negative relationship of technical efficiency and maintenance requirements was synergized by a negative correlation of hen maintenance and egg production. Economic efficiency methodologies are effective tools to assess the economic effect of selection and flock management programs because biological, allocative, and economic factors can be independently analyzed.

Effects of vitamin E and organic selenium on oxidative stability of omega-3 enriched dark chicken meat during cooking.

The influence of vitamin E and selenomethionine (SeMet) on lipid oxidation in frozen-raw and cooked omega-3 enriched dark chicken meat was evaluated. Feed was supplemented with 2 levels of vitamin E (250 and 50 IU/kg of feed) and selenium (0.1 mg of sodium selenite/kg of feed and 0.3 mg of SeMet/kg of feed). An extruded linseed product was used as the alpha-linolenic acid source. Fatty acid (FA) profile, oxysterols, and thiobarbituric reactive acid substances (TBARs) were analyzed in frozen-raw, boiled, pan-fried, and roasted meat. After 6 mo of storage, oxysterols in frozen-raw meat remained stable with either high or low levels of dietary antioxidants. During cooking, high levels of vitamin E reduced oxysterol formation, whereas high levels of SeMet were inconsistent and even increased oxysterols during roasting. TBARs in frozen-raw meat stored for 6 mo were inhibited by high levels of either antioxidant. Conversely, no protective effect during cooking was observed at this time of storage. After 12 mo at -30 degrees C no antioxidant protection was observed.

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.

Nonlinear mixed models to study metabolizable energy utilization in broiler breeder hens.

This study developed mathematical models to overcome limitations of linear models of energy partitioning in hens. The fit of 1 linear and 2 nonlinear models of ME intake (MEI) were compared, using empirical data of 288 caged broiler breeder hens from 20 to 60 wk of age. Pullets were individually caged at 16 wk and assigned to 1 of 4 feed allocation groups. Three groups had feed allocated on a group basis with divergent target BW: standard (STD), HIGH (STD x 1.1), and LOW (STD x 0.9). The fourth group had individual-based feed allocation (IND) and followed the STD BW target. The linear model expressed MEI as a function of BW(0.75), ADG, egg mass (EM), and temperature. Nonlinear mixed models employed a normally distributed term associated with hen metabolic BW, and exponential terms of ADG and EM, or Cobb-Douglas form interactions between terms. Fit was evaluated with the Bayesian information criterion and systematic bias was analyzed through linear regressions of observed versus expected values. The linear model estimated energy partitioned to maintenance and retention in the range of reported values in the literature. However, this model had the poorest fit (R(2) = 0.64) and exhibited a slope bias of 0.91 (i.e., MEI was overestimated at low values and underestimated at high values). The first nonlinear mixed model indicated that MEI partitioned to ADG was a factor of ADG(1.15), whereas the ME partitioned to EM was a factor of EM(1.12). This model had improved fit (R(2) = 0.71) relative to the linear model. The second nonlinear mixed model indicated that the energy requirement for ADG increased by 0.60% and the EM energy requirement decreased by 2.07% for each 1% increment in BW. This model further improved fit (R(2) = 0.75). Nonlinear mixed models reduced estimation bias by accounting for individual variation in maintenance energy expenditure. These nonlinear mixed models may be used to analyze energy partitioning in animals, to develop prediction equations of MEI, to evaluate individual efficiency for maintenance, and to assess diets regarding the slope of bias in coefficients of maintenance energy requirements.

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.

Effect of reducing body weight variability on the sexual maturation and reproductive performance of broiler breeder females.

A study was performed to assess the effect of reducing BW variability on sexual maturation and reproductive performance of broiler breeder hens. A total of 208 Ross 708 1-d-old pullets were randomly assigned at hatch to 1 of 2 feed allocation treatments starting at 16 wk of age when all birds were placed in individual cages. A control treatment had feed allocated on a group basis (GRP) and followed the recommended BW target. A second treatment had feed allocated on an individual bird basis (IND). By design, the BW of IND pullets converged at 20 wk. This design dictated that IND birds had a lower BW variability and a higher feed intake variability than GRP birds. Pullets were retrospectively classified into 3 initial (16 wk) BW categories: low, average, or high, using the mean+/-0.5 SD as threshold. After their first egg, 64 birds were killed and dissected for determination of fleshing, fatness, and reproductive morphology. Egg production traits were analyzed to 60 wk, when the remaining birds were killed and dissected. Reducing BW variability did not reduce variability of age, follicle numbers, and ovary and oviduct weight at sexual maturity. The IND feed allocation accelerated the onset of production of low BW birds, which increased total egg production (177 eggs) and average sequence length (3.9 d) with respect to GRP x low birds (163 eggs; 3.0 d). However, INDxlow hens produced more eggs<52 g than GRPxlow hens (22 versus 8 eggs). The IND treatment increased variability of ovary weight, large yellow follicle number, and large yellow follicle weight at 60 wk. Reducing BW variability increased variation in ovarian morphology at the end of production, which suggests that optimal BW for reproduction varied among birds. Correcting BW from 16 wk to reach the BW target primarily affected low initial BW pullets, which entered lay sooner and produced more eggs, although 91% of the additional eggs weighed<52 g.

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.

Effects of maternal energetic efficiency on egg traits, chick traits, broiler growth, yield, and meat quality.

This study assessed egg traits, chick traits, growth, yield, and meat quality characteristics of the offspring from broiler breeders classified by 2 measurements of energetic efficiency: residual feed intake (RFI), defined as the difference between observed and expected ME intake, and residual maintenance requirement (RME(m)), defined as the residual of the relationship between hen maintenance requirement and feed intake. A group of 72 pullets were placed in laying cages from 16 to 60 wk of age. Individual hen-based feed allocation was provided following a standard BW target. At 41wk, eggs from 8 d of production were collected and pedigree hatched. Chicks were assigned to 1 of 3 maternal RFI (RFI(mat)) categories: low, average, and high. A total of 366 chicks were placed in 36 floor pens, 6 per sex x RFI(mat) interaction, and raised to 38 d. At the end of the breeder experiment (60 wk), broilers were retrospectively assigned to a low or high maternal RME(m) (RME(mmat)) category. Low RFI(mat) broilers had greater 38-d BW than average and high RFI(mat) broilers. That was achieved through a greater BW gain and feed intake of low RFI(mat) broilers from 21 to 28 d. It was found that RFI(mat) had no effect on feed conversion, yield, or meat quality characteristics. Low RME(m) hens produced heavier eggs (62.3 g) and chicks (42.5 g) than high RME(m) hens (60.0 g; 41.0 g), but RME(mmat) did not affect broiler 38-d BW. High RME(mmat) broilers had greater breast yield (29.5%) and lower breast shear force (4.7 kg of force/g) than low RME(mmat) broilers (28.5%; 5.6 kg of force/g). The low RFI(mat) x high RME(mmat) broilers had the greatest growth to 38 d. It was found that RFI(mat) was inversely related to broiler growth, particularly when RME(mmat) was high. Although low maintenance requirements may be desirable for egg and chick production, hens with a high maintenance requirement produced broilers with greater breast yield and tenderness. Minimizing maintenance requirements may not be compatible with maximizing broiler performance and meat yield.

Effects of nutrient density and age at photostimulation on carcass traits and reproductive efficiency in fast- and slow-feathering turkey hens.

This study was conducted to compare BW gain, carcass composition, and reproductive fitness in fast- and slow-feathering turkey females between 29 and 56 wk of age. A total of 452 Hybrid standard fast-feathering (FF) and experimental slow-feathering (SF) hens (226/group) were fed either a control or a high-energy, high-protein diet. Birds were photostimulated at 29 or 31 wk. Data on BW and carcass characteristics (keel and shank, keel, breast muscle, fatpad, liver, ovary, and oviduct weight) and egg production were assessed. At photostimulation, FF birds had an increased shank length (2.6%) compared with SF birds. After photostimulation, FF birds were heavier than SF birds by 7.8%. Fast-feathering hens had greater ovary weight (49%), oviduct weight (52%), keel length (2.8%), and had one more large yellow follicle at the end of lay. The number of large yellow follicles was greater in birds photostimulated at 31 wk (8.3) compared with birds photostimulated 2 wk earlier (7.8). Absolute ovary weight and oviduct weight were increased by 21 and 18%, respectively, in birds photostimulated at 31 wk compared with 29 wk. These effects of delayed photo-stimulation were greater in SF birds. Ultimately, FF hens had a greater total hen-housed egg production (55 vs. 33%), peak egg production (76 vs. 68%), and laying sequence length (5.7 vs. 3.3 d). Although delaying photostimulation did not affect total egg production, it did reduce the number of double-yolked eggs. Nutrient density had minimal effects on production in this trial. These data indicate that despite having similar BW, fleshing, and conformation traits to FF birds, the SF strain had inferior reproductive efficiency traits. This problem will need to be remedied before an SF turkey strain can become commercially viable.

Reproductive efficiency and metabolism of female broiler breeders as affected by genotype, feed allocation, and age at photostimulation. 1. Pullet growth and development.

A 3 x 4 x 2 factorial design was carried out to determine the effect of 3 broiler breeder strains, 4 target BW profiles, and 2 photostimulation ages on pullet growth and development. A total of 560 pullets from each strain (Hubbard Hi-Y, Ross 508, and Ross 708) were reared on BW profiles that separated at 4 wk and converged at 32 wk of age as follows: standard (mean target BW profile of the 3 strains used), low (12-wk BW target = 25% lower than standard followed by rapid gain to 32 wk), moderate (12-wk BW target = 150% of standard followed by lower rate of gain to 32 wk), and high (12-wk BW target = 200% of standard followed by minimal growth to 32 wk). Birds were photostimulated at 18 (18WK) or 22 wk (22WK). During the prephotostimulation phase (2 to 18 wk of age), 4 birds were killed for each of the 12 interactions at 14-d intervals to characterize changes in carcass traits. After 18 wk (wk 20, 22, and 24), 4 birds from each of the 24 interactions were killed and dissected (n = 768). Growth rate restricted frame size (e.g., 18-wk shank length: low = 101.8; standard = 105.6; moderate = 109.5; and high = 112.3 mm). At 24 wk of age, the 22WK birds had similar amounts of breast muscle compared with 18WK birds, whereas the later photostimulated hens had heavier abdominal fat pads. Early photo-stimulation resulted in increased 24-wk liver weights in all strains, but the difference was greatest in Ross 708 birds. The 22-wk ovary weight was influenced by age at photostimulation in high (18WK = 17.3; 22WK = 1.6 g) and moderate (18WK = 14.1; 22WK = 1.1 g) birds. The more extensive feed restriction of LOW birds before 12 wk of age appeared to limit breast muscle and fat pad growth and slow reproductive tract development following photostimulation. Pullets on heavier BW profiles respond to early PS by developing the reproductive system at the expense of breast muscle and fat pad growth. Genetic strain modulates some of the effect of very different target BW profiles.