Research Note: Preliminary assessment of the impact of dietary yeast products on egg production and cecal microbial profiles of laying hens.

The objective of the current study was to conduct an initial comparison of commercial yeast products in layer hen diets on egg production parameters and the corresponding impact on the cecal microbiota. A short-term feeding study was conducted with 35 laying hens receiving either a control, or 1 of 4 different yeast fermentation products, Immunowall, Hilyses (both from ICC, São Paulo, Brazil), Citristim (ADM, Decatur, IL), and Maxi-Gen Plus (CBS Bio Platforms, Calgary, Canada) with 7 hens per treatment from 40 to 46 wk of age. At the end of the trial, hens were euthanized, the ceca removed and prepared for denatured gradient gel electrophoresis (DGGE) microbial compositional analyses. Although initial shell weight and shell thickness were similar among the treatment groups, hens fed Hilyses had lower shell weight and thickness at the end of the experiment. The most predominant DGGE bands with the strongest intensity were identified as Lactobacillus species and excised double bands were identified as Bacillus, Clostridium, or Lachnospiraceae. In this short-term feeding trial, the commercial yeast products tested had little effect on egg production and shell quality, and only moderately impacted the composition of mature layer hen cecal microbiota.

Review: Current challenges in poultry nutrition, health, and welfare.

The poultry industry has benefited greatly from advances in genetics, nutrition, housing and management strategies. Geneticists have made welfare and health traits important components of selection programs, and in general, modern, high-producing poultry are healthier than 30 years ago. However, increased productivity means that the birds are closer to their physiological limits, and nutrition, environment and management have become increasingly important. The move away from in-feed antibiotic growth promotors has resulted in challenges in maintaining gut health and consequently, bird performance. However, as the industry adapts to production without the use of antibiotic growth promotors, long-term benefits may be realized due to a reduction in antimicrobial resistance. Intensive selection for meat yield and efficiency are associated with an increased risk of muscle myopathies that affect bird health and meat quality. As genetic selection increased broiler production traits, it became necessary to restrict parent stock nutrient intake in order to prevent excessive muscle and fat deposition, reduce metabolic disease, and maintain ovarian control. With continued selection for broiler production traits, the degree of restriction implemented has become a welfare issue. Additionally, recent research suggests that highly efficient broiler lines may have limited fat deposition and therefore energy reserves to support sexual maturation and egg production, especially if typical broiler breeder BW targets are maintained. A re-examination of broiler breeder feeding programs is necessary to maintain productivity and welfare. Modern laying hens are capable of laying cycles in excess of 100 weeks of age. This has reduced the use of stress-inducing forced molting programs and reduces the total number of hens needed to meet the demand for egg production. The important role of the skeletal system in eggshell deposition demands that skeletal development during rearing be carefully managed to avoid shell and skeletal problems at the end of the production cycle. As the production potential of modern poultry continues to increase through genetic and genomic selection, even greater care must be paid in order to maintain bird health and welfare. The poultry industry has successfully faced many challenges in the past and is likely to overcome the existing challenges as well.

Protected biofactors and antioxidants reduce the negative consequences of virus and cold challenge while enhancing performance by modulating immunometabolism through cytoskeletal and immune signaling in the jejunum.

The aim of this study was to evaluate the effectiveness and mechanism of action of 2 feed additives in reducing the impacts of virus and temperature stressors. We determined the effects of protected biofactors and antioxidants (P(BF+AOx)), and protected biofactors and antioxidants with protected organic acids and essential oils (P(BF+AOx)+P(OA+EO)) on the immune and metabolic health of Ross 308 broiler chickens. These biofactors and antioxidants were derived from vitamins, and Aspergillus niger, Aspergillus oryzae and Bacillus subtilis fermentation extracts. All Ross 308 chickens were exposed to a double-dose of live bronchitis vaccine at d 0 and environmentally challenged by reducing the temperature from 32°C to 20°C at d 3 for 48 h. Control birds were fed without feed additives in the diet. Performance data and jejunum samples were collected to evaluate the effects of these treatments on growth, cytokine expression, and protein phosphorylation via kinome peptide array. ANOVA was used for statistical analysis of the performance and gene expression data (p-value of 0.05), and PIIKA2 was used for statistical evaluation and comparison of the kinome peptide array data. The P(BF plus;AOx) and P(BF+AOx)+P(OA+EO) treatments significantly increased bird weight gain and decreased feed conversion. The kinome peptide array data analysis showed increased activity of cytoskeletal, cell growth and proliferation proteins, and metabolic signaling in the jejunum of P(BF+AOx)+P(OA+EO) treated chickens. There was a significant decrease in IL-6 gene expression in the jejunum of P(BF+AOx)+P(OA+EO) samples compared to control at d 15. P(BF+AOx)+P(OA+EO) treatments in the jejunum showed strong immunomodulatory effects, perhaps to control inflammation. P(BF+AOx)+P(OA+EO) improves gut health via growth and metabolic signaling in the jejunum while inducing stronger immunomodulation.

Evolution of maternal feed restriction practices over 60 years of selection for broiler productivity.

The effect of commercial selection by poultry breeders on the growth, efficiency, and sexual maturity of broiler breeders was studied using 2 University of Alberta Meat Control strains unselected since 1957 and 1978 (AMC-1957 and AMC-1978, respectively) and 2 strains originating from the University of Arkansas; 1995 Random-bred (1995RB) and 2015 Random-bred (2015RB). A study with a 4 × 2 factorial arrangement was conducted with the 4 strains fed at either ad libitum, or restricted levels to achieve a current commercial breeder target BW profile. Growth rate, feed intake, feed efficiency, age at sexual maturity, carcass components, and body conformation were measured. To assess reproductive development, birds were assigned to 2 fates: dissected at photostimulation or dissected after the second oviposition. At 22.4 wk of age, the restricted-fed AMC-1957, AMC-1978, 1995RB, and 2015RB reached 100, 61, 46, and 38% of their ad libitum-fed counterparts' BW, respectively. During the rearing phase, the amount of feed needed to maintain restricted-fed birds on the target BW was 99.4, 57, 29.5, and 24.9% of their ad libitum-fed counterparts for AMC-1957, AMC-1978, 1995RB, and 2015RB, respectively. Feed restricted birds in the 2015RB had lower heat production relative to the AMC-1957 and AMC-1978, which shows that modern strains utilized feed more efficiently compared to the antique strains. This might be related to the increasing severity of feed restriction of broiler breeders over the past 60 years. Relative to AMC-1957 and AMC-1978 strains, the 1995RB and 2015RB strains had heavier breast muscle and lower fat pad weight. Although the pubertal threshold for age and BW have increased over the last 6 decades, changes in selection programs for feed efficiency have resulted in broiler breeders that prioritize nutrient allocation to growth and breast development rather than adipose storage. As a result, feed restricted modern broiler breeders may have marginally sufficient fat resources to support reproduction.

A protected complex of biofactors and antioxidants improved growth performance and modulated the immunometabolic phenotype of broiler chickens undergoing early life stress.

We evaluated the supplementation of a protected complex of biofactors and antioxidants [P(BF+AOx)] on growth performance, antioxidant activity, expression of immune-related genes, and immunometabolic phenotype of broilers submitted to early life stressors. The treatments were a nutritionally complete basal diet supplemented or not with P(BF+AOx) (Jefo Nutrition Inc., Saint-Hyacinthe, QC, Canada) from 1 to 14 d of age. 720 one-day old male Ross 308 chickens were placed into pens of 30 birds (12 replicates/treatment). Birds were double-vaccinated against infectious bronchitis (IB; MILDVAC-Ma5T) at the hatchery and submitted, on d 3, to an acute reduction on environmental temperature (from 32° C to 20°C) for 48 h. Feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) were calculated weekly. On d 7 and 15, samples were collected for expression of immune-related genes and kinome array analysis, and serum to evaluate the antioxidant status. Data were analyzed by ANOVA using SAS (SAS 9.4). From d 1 to 21 and d 1 to 28, the dietary supplementation of P(BF+AOx) significantly increased BWG (P < 0.05) by 3.6 and 3.8%, respectively, and improved FCR (P < 0.05) by 1.2 and 1.8%, respectively. From d 1 to 35, dietary supplementation enhanced BWG (P = 0.03) by 4%. Serum glutathione reductase activity on d 15 was higher in birds fed diets supplemented with P(BF+AOx) compared to the control diet-fed birds (P = 0.04). Dietary supplementation reduced the expression of IL-1ß (P = 0.03) in the lungs on d 7. On d 15, dietary supplementation increased the expression of IL-6 (P = 0.02) and IL-10 (P = 0.03) in the liver. It was observed that, via decreased phosphorylation, catalase was activated in the jejunum and liver, and the phosphorylation of immunoregulatory or proinflammatory proteins was decreased. Other important cellular signaling pathways were also changed in the liver and jejunum due to the supplementation. The supplementation of P(BF+AOx) improves growth performance by promoting a general anti-inflammatory and antioxidant response in chickens undergoing early life stress.

Effects of dietary calcium and available phosphorus levels and phytase supplementation on performance, bone mineral density, and serum biochemical bone markers in aged white egg-laying hens.

Exogenous phytase supplementation increases P and Ca availability to allow for the dietary reductions without negative consequences on productivity or skeletal health. Effects of a Buttiauxella sp. phytase (BSP) supplemented in available P (avP)-reduced and Ca-reduced diets on performance, BW, eggshell quality, serum biochemical bone markers, and bone densitometry were evaluated in egg-laying hens from 68 to 78 wk of age. One hundred hens were fed 1 of 5 diets (n = 20/treatment), including a positive control (PC) with 0.35% avP and 3.5% Ca, and the PC moderately reduced in avP and Ca levels by 0.187 and 0.159% of the diet (by 53 and 4.5%), respectively, (NC1) or severely reduced by 0.231 and 0.275% of the diet (by 66 and 7.9%), respectively, (NC2). Other diets were the NC1 or NC2 supplemented with BSP at 600 FTU/kg (NC1 + BSP or NC2 + BSP, respectively). Egg production and feed conversion ratio were maintained by NC1 but were 11.9% lower and 12.3% higher, respectively, with the NC2 than the PC, which was alleviated by supplemental BSP. Diet effects on FI and eggshell quality followed a similar pattern. Body weight was 2.9% lower for NC1, and 6.1% for NC2 than the PC; BSP alleviated the decreased BW. Serum pyridinoline (bone resorption marker) was 20 to 27% higher in NC2 hens than in the other groups, with no effects on other bone markers. Total and trabecular space bone mineral density in the proximal metaphysis were 8.4 and 15.2% lower for NC1, respectively, and 12.1 and 26.7% lower for NC2, respectively, than PC. Supplemental BSP completely alleviated the decreased bone densitometry measures in NC1, but only partially in NC2. The NC1 hens maintained performance but had decreased BW and bone quality; phytase supplementation restored productivity, BW, and bone quality. The Ca and avP deficiencies in the NC2 hens relative to other groups were partially alleviated by the 600 FTU/kg BSP.

The efficacy of 2 phytases on inositol phosphate degradation in different segments of the gastrointestinal tract, calcium and phosphorus digestibility, and bone quality of broilers.

The anti-nutritional effects of dietary inositol phosphates (IP6 through IP3) have been recognized in broiler chickens; however, inositol hexaphosphate (IP6) is more potent than the lower IP esters. The efficacies of 2 commercial phytases, a Buttiauxella sp. phytase (BSP) and a Citrobacter braakii phytase (CBP) at 500 and 1,000 FTU/kg, were studied on IP6-3 concentrations in the crop, proventriculus + gizzard, and distal ileum digesta, and ileal IP6 disappearance in broilers at day 22. Apparent ileal P and Ca digestibility, and bone quality at days 22 and 33 were also measured. Female Ross 308 broilers (n = 1,890; 30 birds × 7 diets × 9 replicates) were fed corn-soy-based crumbled diets. The 7 diets included a primary breeder recommendation-based positive control diet (PC); the PC marginally reduced in available P by 0.146% and Ca by 0.134% of the diet, (NC1) or moderately reduced by 0.174 and 0.159% of the diet, respectively (NC2). Other diets were the NC1 + BSP or CBP at 500 FTU/kg (NC1+500BSP and NC1+500CBP) and the NC2 + BSP or CBP at 1,000 FTU/kg (NC2+1,000BSP and NC2+1,000CBP). Each of the NC1 and NC2 had distal ileum IP6 disappearance similar to that of PC, but each had lower P digestibility and the majority of measured bone quality parameters than the PC. The ileal IP6 levels were decreased by 52.0 and 32.7% for NC1+500BSP and NC1+500CBP, respectively, relative to NC1 and by 73.6 and 50.9% for NC2+1,000BSP and NC2+1,000CBP, respectively, relative to NC2 (P < 0.001), with a similar effect for distal ileum IP6 disappearance. Overall, phytase in the NC diets increased P digestibility, and femur breaking strength and cortical bone mineral density at days 22 and 33. Overall, each of the phytases at each dose degraded IP6-3 across the gastrointestinal tract segments to increase P digestibility and the P and Ca utilization in bone. However, dietary BSP at 1,000 FTU/kg was most effective. Supplemental phytase degrades phytate to decrease the anti-nutritional effects in a dose- and phytase-dependent manner.

Energy partitioning by broiler breeder hens in conventional daily-restricted feeding and precision feeding systems.

An empirical linear mixed model was derived to describe metabolizable energy (ME) partitioning in broiler breeder hens. Its coefficients described ME used for total heat production (HP), growth (ADG), and egg mass (EM). A total of 480 Ross 308 hens were randomly and equally assigned to 2 treatments: precision feeding (PF) and conventional daily-restricted feeding (CON) from 23 to 34 wk of age. The PF system allowed birds to enter feeding stations voluntarily at any time, weighed them, and provided access to feed for 60 s if their BW was less than the breeder-recommended target BW. The CON birds were fed daily each morning. Energetic efficiency of hens was evaluated using residual feed intake (RFI), defined as the difference between observed and predicted ME intake (MEI). The energy partitioning model predicted (P < 0.05): MEI = A × BW0.67 + 1.75 × ADG + 0.75 × EM + ϵ. The coefficient A, a vector of age-specific HP, was 142 kcal/kg0.67/d; the energy requirement for growth and EM was 1.75 and 0.75 kcal/g, respectively. For the CON and the PF hens, respectively, MEI was 366 and 354 kcal/d (P = 0.006); RFI was -5.9 and 6.7 kcal/d (P = 0.009); HP% was 85.5 and 87.7 (P < 0.001); hen-day egg production (HDEP) was 65.5 and 55.2% (P < 0.001). Although the CON hens had higher MEI, the model predicted lower HP%; thus, CON hens had more nutrients available for egg production, increased egg production, and were more energetically efficient than the PF hens. The decreased egg production by the PF hens was likely due to these hens receiving production-related feed increases after an egg was laid. However, feed allocation increases for the CON hens resulted in increasing MEI for all CON hens at the same time. Therefore, the PF hens had lower MEI and lower HDEP than the CON hens.

Long-term effects of Buttiauxella sp. phytase on performance, eggshell quality, apparent ileal Ca and P digestibility, and bone properties of white egg layers.

Adequate dietary Ca and available phosphorus (avP) are essential to long-term egg production and bone health in laying hens. The effects of dietary Ca and avP levels and Buttiauxella sp. phytase (BSP) were studied in Lohmann LSL Lite hens from 30 to 70 wk of age (woa). Hens (n = 456; 4 per cage) were fed either a primary breeder recommendation-based diet (positive control; PC); the PC with avP and Ca levels reduced by 0.146 and 0.134% of the diet, respectively, without (NC) or with 300 FTU/kg BSP (NC+BSP). Egg production, BW, feed intake, FCR, and eggshell quality from 30 to 70 woa, and apparent ileal digestibility of P (AIDP) and Ca (AIDCa), and bone quality at 32, 48, and 70 woa were measured. The avP and Ca levels in the NC diet were not clinically deficient, as most parameters were unaffected by diet. Hen BW from 34 to 70 woa tended to be 2.9% greater (P = 0.076) for PC and NC+BSP compared to NC. Mid-diaphysis cortical bone mineral content (CBMC) tended to be 10% and 9% higher (P = 0.065) in the NC+BSP hens than in NC hens at 48 and 70 woa, respectively. AIDP of NC+BSP was 24% greater (P = 0.034) than of NC at 32 woa and tended to be 18% greater (P = 0.082) than AIDP of PC at 48 woa, and 25% lower than of NC and PC at 70 woa (P = 0.028). AIDCa was 25% lower for NC+BSP than PC at 48 woa only (P = 0.037). The avP and Ca sufficiency in the NC diet limited the opportunity to determine a phytase effect. Although the supplemental BSP tended to increase BW and 48 and 70 woa CBMC, and increased 32 woa AIDP, the efficacy of BSP could not be determined due to the lack of an NC effect on most parameters. Commercial laying hens can maintain health and productivity at lower than recommended levels of dietary Ca and avP; phytase supplementation may allow for even further reductions.

Influences of trace mineral nutrition and maternal flock age on broiler embryo bone development.

At hatch, the chick skeleton is a miniature of that of the adult bird. The hen deposits calcium, phosphorus, and trace minerals (copper, zinc, and manganese) along with vitamin D into the egg to allow development of the embryonic skeleton. The main source of calcium is the eggshell, whereas phosphorus, trace minerals, and vitamin D are mainly derived from the yolk. Calcium is absorbed from the eggshell and transferred to the embryo and yolk through the chorioallantoic membrane, whereas phosphorus and trace minerals are simultaneously mobilized by the yolk sac membrane. These processes start at day 12 of incubation and peak at around day 17. While the eggshell provides a steady supply of calcium until 19 d of incubation, phosphorus and trace mineral reserves decrease considerably and minimal skeletal development occurs in the last 3 d of incubation. Whether the low levels of phosphorus and trace minerals at late incubation prevent further bone growth, or some other biological control exists preventing further mineralization towards hatching is unknown. Maternal transfer of minerals and the influence of trace mineral form in the hen diet to advance the state of skeletal development at hatch have received increased research attention. Minimal effects on yolk mineral composition and bone growth were observed in the offspring of hens fed different forms of trace minerals. Embryos from young hens had inferior bone development towards the end of incubation and at hatch relative to chicks from older hens. This effect is likely a consequence of limited egg nutrient resources in eggs from young hens. The influence of maternal nutrient transfer on embryonic bone development has been clearly established. However, attempts to increase the state of skeletal development at hatch through increasing egg mineral content have met with limited success. The focus of this paper is the relationship between skeletal mineralization of the chicken embryo throughout incubation and egg mineral supply.

Physiological response of broiler embryos to different incubator temperature profiles and maternal flock age during incubation. 1. Embryonic metabolism and day-old chick quality.

Broiler strain, maternal age, and incubation temperature influence embryo metabolism. Hatching eggs were obtained from young (Y; 28 to 34 wk, $\bar{\rm x}$ = 31.2 wk), mid (M; 36 to 45 wk, $\bar{\rm x}$ = 40.5 wk) and old (O; 49 to 54 wk, $\bar{\rm x}$ = 51.4 wk) Ross 708 (n = 88; Experiment 1) and Ross 308 [(n = 45; Experiment 2: (Y; 25 to 34 wk, $\bar{\rm x}$ = 30.5 wk), (M; 35 to 44 wk, $\bar{\rm x}$ = 40.2 wk), and (O; 49 to 54 wk, $\bar{\rm x}$ = 51.6 wk)] breeders. Eggs were stored for 2 to 4 d (18°C, 73% RH), and incubated for 14 d at 37.5°C and 56% RH. At 15 d (E15), 8 fertile eggs per flock age were incubated in individual metabolic chambers at 36.0, 36.5, 37.0, or 37.5°C until E21.5. Each temperature was repeated one additional time. O2 consumption and CO2 production were used to calculate embryonic heat production (EHP). Embryo temperature was measured as eggshell temperature (EST). Initial egg weight was used as a covariate; significance was assessed at P < 0.05. In Ross 708, daily EHP tended to be higher in M and O than Y treatments at E16; EHP of M was higher than Y and O eggs at E18; M and O were higher than O eggs at E19. Incubation at 37.0°C resulted in the highest EHP from E15 to E21, except at E17. Embryos at 37.5°C had reduced EHP beyond E17. Daily EST from E15 to E21 was higher at 37.5 and 37.0°C than at 36.0 and 36.5°C. In Ross 308, daily EST was highest at 37.5°C except at E20. Incubation temperature and EST were highly correlated (R2 = 0.90 to 0.89; P < 0.001). Ross 708 chicks were longer and hatched earlier at 37.0°C than at 36.0 and 37.5°C. EST and EHP increased with incubation temperature in Ross 708. In Ross 308, maternal flock age and incubation temperature did not impact EHP. However, EST was highest at 37.5°C except at E20. Ross 708 was more sensitive to incubation temperature than Ross 308.

Opportunities for exercise during pullet rearing, Part II: Long-term effects on bone characteristics of adult laying hens at the end-of-lay.

Osteoporosis in laying hens has been a production and welfare concern for several decades. The objective of this study was to determine whether differing opportunities for exercise during pullet rearing influences long-term bone quality characteristics in end-of-lay hens. A secondary objective was to assess whether differing opportunities for exercise in adult housing systems alters bone quality characteristics in end-of-lay hens. Four flock replicates of 588 Lohmann Selected Leghorn-Lite pullets were reared in either conventional cages (Conv) or an aviary rearing system (Avi) and placed into conventional cages (CC), 30-bird furnished cages (FC-S), or 60-bird furnished cages (FC-L) for adult housing. Wing and leg bones were collected at the end-of-lay to quantify bone composition and strength using quantitative computed tomography and bone breaking strength (BBS). At the end-of-lay, Avi hens had greater total and cortical cross-sectional area (P < 0.05) for the radius and tibia, greater total bone mineral content of the radius (P < 0.001), and greater tibial cortical bone mineral content (P = 0.029) than the Conv hens; however, total bone mineral density of the radius (P < 0.001) and cortical bone mineral density of the radius and tibia (P < 0.001) were greater in the Conv hens. Hens in the FC-L had greater total bone mineral density for the radius and tibia (P < 0.05) and greater trabecular bone mineral density for the radius (P = 0.027), compared to hens in the FC-S and CC. Total bone mineral content of the tibia (P = 0.030) and cortical bone mineral content of the radius (P = 0.030) and tibia (P = 0.013) were greater in the FC-L compared to the CC. The humerus of Conv hens had greater BBS than the Avi hens (P < 0.001), and the tibiae of FC-L and FC-S hens had greater BBS than CC hens (P = 0.006). Increased opportunities for exercise offered by the aviary rearing system provided improved bone quality characteristics lasting through to the end-of-lay.

Opportunities for exercise during pullet rearing, Part I: Effect on the musculoskeletal characteristics of pullets.

Increased load-bearing exercise improves bone quality characteristics in a variety of species, including laying hens. Providing increased opportunities for exercise during the pullet rearing phase, a period of substantial musculoskeletal growth, offers a proactive approach to reducing osteoporosis by improving bone composition. The main objective of this study was to determine whether differing opportunities for exercise during rearing influences pullet musculoskeletal characteristics. Two flock replicates of 588 Lohmann Selected Leghorn-Lite pullets were reared in either standard, conventional cages (Conv) or an aviary rearing system (Avi) from day-old chicks until 16 wk of age. The keel bone and the muscles and long bones of the wings and legs were collected at 16 wk to measure muscle growth differences between rearing treatments and quantify bone quality characteristics using quantitative computed tomography (QCT) and bone breaking strength (BBS) assessment. Keel bone characteristics and muscle weights were adjusted for BW and analyses for QCT and BBS included BW as a covariate. At 16 wk of age, rearing system had an effect on the majority of keel bone characteristics (P < 0.05). The length of the keel metasternum, caudal tip cartilage length, and the overall percentage of cartilage present on the keel at 16 wk was greater in the Avi pullets compared to the Conv pullets (P < 0.01). Wing and breast muscle weights of the Avi pullets were greater than the Conv pullets (P < 0.001), but leg muscle weights were greater in the Conv pullets (P = 0.026). Avi pullets had greater total bone density, total cross-sectional area, cortical cross-sectional area, total bone mineral content, and cortical bone mineral content than Conv pullets for the radius, humerus, and tibia (P < 0.001). Avi pullets had greater BBS compared to the Conv pullets for the radius, humerus, and tibia (P < 0.01). Increased opportunities for exercise offered by the aviary rearing system increased muscle and bone growth characteristics in pullets at 16 wk of age.

The effect of maternal canthaxanthin supplementation and hen age on breeder performance, early chick traits, and indices of innate immune function.

Hen age and nutrition influence chick innate immunity. The immunomodulatory antioxidant carotenoid canthaxanthin is transferred from the hen diet to the egg. Antioxidants could protect the chick from bactericidal oxidative species produced by the immune system. Broiler breeder hen diets were supplemented with 0 (Control), 6 (Low), or 12 (High) mg/kg canthaxanthin. Chick early growth and ex vivo innate immunity were measured at 31 to 33 (Early), 45 to 47 (Mid), and 57 to 59 (Late) wk of hen age. Escherichia coli (E. coli) bactericidal capacity, phagocyte activation (number of phagocytes containing at least one E. coli), phagocytic capacity (number of phagocytes containing one or more E. coli), and oxidative burst at 1 and 4 d of age were determined. Egg and chick liver canthaxanthin and chick plasma total antioxidant capacity were measured. Differences were considered significant at P ≤ 0.05. Breeder productivity was greatest for the Low hens; diet did not affect egg yolk, albumen, or shell proportions. Egg canthaxanthin increased with maternal supplementation and plateaued after 28 days, but was not affected by hen age. Chick liver canthaxanthin increased with maternal supplementation, but decreased as hens aged. Hen diet did not affect broiler chick performance to 21 days of age. Maternal canthaxanthin at 6 mg/kg increased chick E. coli bactericidal capacity and d 1 oxidative burst; phagocytosis was unaffected. E. coli bactericidal capacity decreased as hens aged, but increased from 1 to 4 d, indicating maturation of chick innate immunity. Plasma total antioxidant capacity at d 1 increased with maternal canthaxanthin in chicks from Mid and Late hens. Canthaxanthin possesses immuno-modulatory and antioxidant properties, and hen age affected chick innate immune development. Single-comb White Leghorn hens were fed the same levels of canthaxanthin to determine the rate of incorporation into eggs. Egg canthaxanthin reached a plateau after 7 d. Canthaxanthin in the hen diet at 6 mg/kg resulted in the greatest positive effect on hen performance, with little effect on the chick.

MHC variability in heritage breeds of chickens.

The chicken Major Histocompatibility Complex (MHC) is very strongly associated with disease resistance and thus is a very important region of the chicken genome. Historically, MHC (B locus) has been identified by the use of serology with haplotype specific alloantisera. These antisera can be difficult to produce and frequently cross-react with multiple haplotypes and hence their application is generally limited to inbred and MHC-defined lines. As a consequence, very little information about MHC variability in heritage chicken breeds is available. DNA-based methods are now available for examining MHC variability in these previously uncharacterized populations. A high density SNP panel consisting of 101 SNP that span a 230,000 bp region of the chicken MHC was used to examine MHC variability in 17 heritage populations of chickens from five universities from Canada and the United States. The breeds included 6 heritage broiler lines, 3 Barred Plymouth Rock, 2 New Hampshire and one each of Rhode Island Red, Light Sussex, White Leghorn, Dark Brown Leghorn, and 2 synthetic lines. These heritage breeds contained from one to 11 haplotypes per line. A total of 52 unique MHC haplotypes were found with only 10 of them identical to serologically defined haplotypes. Furthermore, nine MHC recombinants with their respective parental haplotypes were identified. This survey confirms the value of these non-commercially utilized lines in maintaining genetic diversity. The identification of multiple MHC haplotypes and novel MHC recombinants indicates that diversity is being generated and maintained within these heritage populations.

Effect of hen age and maternal vitamin D source on performance, hatchability, bone mineral density, and progeny in vitro early innate immune function.

The metabolite 25-hydroxy vitamin D3 (25-OHD) can complement or replace vitamin D3 in poultry rations, and may influence broiler production and immune function traits. The effect of broiler breeder dietary 25-OHD on egg production, hatchability, and chick early innate immune function was studied. We hypothesized that maternal dietary 25-OHD would support normal broiler breeder production and a more mature innate immune system of young chicks. Twenty-three-week-old Ross 308 hens (n=98) were placed in 4 floor pens and fed either 2,760 IU vitamin D3 (D) or 69 µg 25-OHD/kg feed. Hen weights were managed according to the primary breeder management guide. At 29 to 31 wk (Early), 46 to 48 wk (Mid), and 61 to 63 wk (Late), hens were artificially inseminated and fertile eggs incubated and hatched. Chicks were placed in cages based on maternal treatment and grown to 7 d age. Innate immune function and plasma 25-OHD were assessed at 1 and 4 d post-hatch on 15 chicks/treatment. Egg production, hen BW, and chick hatch weight were not affected by diet (P>0.05). Total in vitro Escherichia coli (E. coli) killing by 25-OHD chicks was greater than the D chicks at 4 d for the Early and Mid hatches, and 1 and 4 d for the Late hatch. This can be partly explained by the 25-OHD chicks from the Late hatch also having a greater E. coli phagocytic capability. No consistent pattern of oxidative burst response was observed. Chicks from the Mid hatch had greater percent phagocytosis, phagocytic capability, and E. coli killing than chicks from Early and Late hatches. Overall, maternal 25-OHD increased hatchability and in vitro chick innate immunity towards E. coli. Regardless of treatment, chicks from Late and Early hens had weaker early innate immune responses than chicks from Mid hens. The hen age effect tended to be the greatest factor influencing early chick innate immunity, but maternal 25-OHD also increased several measures relative to D.

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.

Effects of corn source and exogenous enzymes on growth performance and nutrient digestibility in broiler chickens.

This study was conducted to investigate the effects of exogenous enzymes on growth performance, ileal digestible energy (IDE) and apparent ileal digestibility of CP and amino acids (AA) in broiler chickens fed corn-soy diets formulated using 3 different sources of corn (corn 1, corn 2, and corn 3). One-day-old male broiler chicks (n = 3,600) were allocated to 15 dietary treatments as 5 treatments for each corn as follows: positive control (PC) with no exogenous enzymes and adequate in all nutrients; negative control (NC) without exogenous enzymes and a 3% reduction in calculated ME relative to the PC diet; NC plus a commercial xylanase; NC plus a commercial mixture of xylanase, amylase, and protease; and NC plus a commercial mixture of xylanase and ß-glucanase. Enzyme products had no effects on performance variables, and in some instances, they had negative impacts. In most cases, there were no effects of enzyme products on IDE and digestibility of CP and AA in the starter and finisher phases. Effects of exogenous enzymes on ileal digestibility were mainly found in the grower phase, and these responses were mostly observed in birds fed corn 2 diets compared with birds receiving corn 1 or corn 3 diets. Although analyzed nutrient contents of 3 corn samples were similar, supplementing corn 2 diets with enzyme products was associated with greater responses on digestibility parameters. Factors related to diets (e.g., availability of substrates) and birds (e.g., enzymatic activities in the digestive tract) may have limited nutrient digestibility, and these limitations may have provided favorable conditions for exogenous enzymes to specifically work on their substrates in corn 2 diets in the grower phase. Effects of enzyme products on IDE and digestibility of CP and AA were not consistent and varied depending on corn sources, enzyme products, and dietary phases.

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.