M. S. Lilburn

Standardized Ileal Amino Acid Digestibility of Plant Feedstuffs in Broiler Chickens and Turkey Poults Using a Nitrogen-Free or Casein Diet

The standardized ileal amino acid digestibility (SIAAD) of 5 plant-based ingredients was determined in 5- and 21-d-old broiler chicks and turkey poults. Two diets (N-free diet, NFD, and a highly digestible protein diet 10% casein, HDP) were fed to determine ileal endogenous amino acid flow, and each was used for endogenous amino acid correction for the plant-based ingredients. The plant-based ingredients evaluated were 2 samples of corn distillers dried grains with solubles (light and dark DDGS), canola meal, corn, and soybean meal. Each diet was fed for 5 d to 6 replicate cages containing 30 or 8 birds, which were sampled on d 5 or 21, respectively. For chicks, apparent ileal amino acid digestibility increased with age for all the feed ingredients. After standardization, SIAAD increased with age when chicks were fed DDGS and corn, but not soybean meal or canola meal. For all the feed ingredients evaluated, SIAAD values for both methods of standardization were not different at d 5. However, the HDP method resulted in greater SIAAD values for most of the amino acids in light DDGS, canola meal, and corn (d 21). In poults, the apparent ileal amino acid digestibility values increased with age for all the feed ingredients except the dark DDGS and canola meal. After standardization, there was no effect of age on amino acid digestibility in all the feed ingredients evaluated, with the exception of corn. Within a particular age (d 5 or 21), both methods of standardization resulted in similar amino acid digestibility values except for corn, for which the SIAAD values were greater (NFD method) in 11 amino acids. Results from this study showed that age-appropriate endogenous amino acid standardization is necessary and, in some cases, results in no age-associated differences in amino acid digestibility. With the exception of corn, standardization of amino acid digestibility with ileal endogenous amino acid flow from birds fed an NFD or HDP did not differ for most plant feedstuffs.

Comparative proteomic characterization of the sarcoplasmic proteins in the pectoralis major and supracoracoideus breast muscles in 2 chicken genotypes

The selection processes that have resulted in broiler (meat) and leghorn (eggs) chickens have had very different effects on the pectoralis major and supracoracoideus muscles. The objective of this study, therefore, was to analyze the one-dimensional proteomic profiles of sarcoplasmic protein fractions isolated from the p. major and supracoracoideus muscles collected from 10 chicks from each genotype to compare developmental differences. The sarcoplasmic protein fraction was analyzed by SDS-PAGE. The mean band percentages were analyzed using a mixed model, with strain and muscle type as main effects. Six bands were found to be significantly different across the 2 strains. Strain differences in glycogen phosphorylase, enolase, elongation factor 1, creatine kinase, fructose-bisphosphate aldolase, and glyceraldehyde 3-phosphate-dehydrogenase suggest a genotype-specific shift in energy metabolism during breast muscle growth and development.

Effect of recycled litter on immune cells in the cecal tonsils of chickens

This experiment was conducted to study selected aspects of the gut immune response in broiler chicks reared on fresh or recycled litter that were fed diets with and without subtherapeutic antibiotic supplementation. All of the chicks were reared in pens that contained either fresh pine shavings (fresh litter) or litter that was recycled for 3 consecutive flocks (recycled litter). The experiment was a 2 × 2 factorial arrangement of treatments with 4 replicate pens (n = 4) per treatment. At 10 and 35 d of age, the cecal tonsils were analyzed for intestinal immune measurements. The cecal tonsils of birds reared on recycled litter had increased IL-1 mRNA (P < 0.01) and a lower percentage of CD4(+)CD25(+) cells at 10 and 35 d of age when compared with those of chicks reared on fresh litter. Birds fed diets supplemented with bacitracin had a reduction in CD4(+) cells (P = 0.01) at 10 d of age when compared with that of chicks that were not fed the antibiotic. The combination of bacitracin supplementation and fresh litter resulted in an approximate 10-fold increase in IL-10 mRNA (P = 0.01) at 10 d of age when compared with that of the unsupplemented chicks in fresh litter. Among those chicks that were not supplemented with bacitracin, the recycled-litter treatment resulted in 25-fold (P = 0.01) and 39-fold (P = 0.02) higher IL-4 mRNA levels at 10 and 35 d of age, respectively, when compared with those of the chicks reared on fresh litter. In conclusion, the intestinal immune response of birds reared on recycled litter is skewed toward an inflammatory response, whereas the fresh litter treatment was skewed toward an anti-inflammatory response. Bacitracin supplementation did not interact with the litter type to alter IL-1 mRNA levels in cecal tonsils, suggesting the low efficiency of bacitracin in alleviating the inflammatory response induced by recycled litter.

The morphological, material-level, and ash properties of turkey femurs from 3 different genetic strains during production

Femoral fractures are observed in selective-bred commercial turkeys; however, the etiology of such fractures is unknown. The current study investigated the whole bone morphological, material-level mechanical, and bone ash properties to determine the effect of selective breeding on bone strength. Femora from 3 divergent strains of turkeys, a commercial line, a different selectively bred heavy line (F-line), and a lighter age or weight matched random-bred line (RBC2/R-EQ, respectively), were compared. Bone geometric properties were measured with micro-CT and bone mechanical properties were measured using 3-point bending tests. Whole bone ash quantities were also recorded. Statistics were run using a general linear model multivariate ANOVA (GLM ANOVA). Results showed that at similar ages, the faster growing birds (commercial and F-line) had femurs twice the size of the RBC2 line as measured by cross-sectional area as early as 8 wk into the study. The femurs of the commercial and F-lines also exhibited as much as 20% greater mechanical strength than femurs from the RBC2 line at 16 and 20 wk of age as measured by properties such as elastic modulus and ultimate tensile strength. However, at similar BW, the slower growing R-EQ line had higher mechanical properties than the other lines, with the elastic modulus being 40% greater and the ultimate tensile strength being 37% greater at weights equivalent to those of the commercial and F-lines at 12 wk of age. Moreover, it was observed that the morphological properties (i.e., cross-sectional area, moments of inertia) are largely governed by BW, as there is little difference in the amount gained per week of age across the different lines. Conversely, the mechanical properties, as well as the related ash content, appear to be governed at least in part by time. Therefore, whereas modulation of bone geometry is the key responder for changes in BW, sufficient time for matrix mineralization or maturation or both to occur is also essential for mechanical competence of bone.

Feed restriction delays developmental fast skeletal muscle myosin heavy chain isoforms in turkey poults selected for differential growth

Genetic selection has been very successful at significantly increasing BW and breast muscle proportion in commercial broiler and turkey strains. The mechanisms of breast muscle growth in poultry and the interactive effects of nutritional status and selection are not fully understood. The hypothesis underlying the current study is that feed restriction, simply as a vehicle for controlling early growth, would delay the temporal expression pattern of neonatal (nMyHC) and adult (aMyHC) fast skeletal muscle myosin heavy chain (MyHC) isoforms in the pectoralis major muscle of turkey poults. The poultry growth model used to evaluate this hypothesis consisted of a randombred control turkey line (RBC2) that represents commercial turkeys of the 1960s and a line developed from the RBC2 by selection for BW at 16 wk of age (F line). The F line has significantly heavier breast muscles than the RBC2 concomitant with increased BW, but the proportion of breast muscle relative to BW is similar. A quantitative indirect ELISA using fast skeletal MyHC isoform specific monoclonal antibodies revealed no significant line differences in the temporal expression of posthatch fast skeletal muscle MyHC in ad libitum fed poults. Feed restriction, however, altered the temporal expression patterns of nMyHC and aMyHC in both F line and RBC2 poults compared with the poults fed ad libitum.

The effects of genotype on embryonic development in eggs from divergent turkey genotypes

Unique turkey genotypes and reciprocal crosses of these lines were used to study the relationship between egg size, posthatch growth potential, and selected aspects of embryonic development. A line of turkeys selected for increased egg production (E), its randombred control line (RBC1), a line selected for increased 16-wk BW (F line), and its randombred control line (RBC2) were the pure lines used in each of 2 experiments. In experiment 1, a sample of E-line hens were mated to either E line (E/E) or RBC1 toms (RBC1/E), and RBC1 hens were mated to RBC1 toms (RBC1/RBC1). Egg weight at set and at 25 d of incubation was significantly lower in the E/E and RBC1/E crosses compared with that of the RBC1/RBC1 eggs. On d 21 and 25 of incubation and at hatch, the yolk-free wet embryo weights of E/E and RBC1/E embryos were similar, and both weighed significantly less than the RBC1/RBC1 embryos (P ≤ 0.001). Similar observations were observed for the residual yolk sac weight at each of those developmental ages. In experiment 2, embryos from the F line, RBC2, RBC1, E, and 2 reciprocal crosses (RBC1/E, E/RBC1) were compared at various time points during the course of incubation. Egg weight was consistently highest in the F line and lowest in the E line and intermediate in the RBC1 and RBC2 lines. Egg weight followed the maternal genotype in the E/RBC1 and RBC1/E reciprocal crosses. On embryonic d 19, 23, and 26, the order of yolk-free weight embryo weights followed closely the pattern observed for egg weight. In summary, egg weight and embryonic development is largely controlled by the maternal genotype. This should be considered when making inference to posthatch selection effects on embryonic development.

A comparison of long bone development in historical and contemporary ducks

The selection for growth and carcass traits in poultry meat species has contributed to increased interest in understanding and characterizing skeletal growth as the birds struggle to balance skeletal development with increased BW and muscle mass. The objective of this study was to compare the physical characteristics and mineralization of the tibia and femur from commercial Pekin ducks representing circa 1993 and 2010 commercial strains. In 1993, the femur and tibia were collected from 8 ducks at 11 ages between 11 and 53 d. A similar study was done in 2010 in which the femur and tibia were collected from 8 ducks at 12 sample ages between 10 and 49 d. All bones were weighed and the length and width at 50% of length were measured. Each bone was subsequently cut into epiphyseal (top 25% of length) and diaphyseal (midregion at 50% of length) sections. Each bone segment was extracted with ether, hot weighed, and ashed. The 2010 contemporary ducks reached market weight faster than the 1993 ducks. Therefore, statistical comparisons were made at common BW as well as at common ages. The mean tibia length of the 2010 duck was 0.75 cm greater (P < 0.05) at similar ages and similar BW. The percentage ash in the diaphyseal region of the tibia was 3% greater (P < 0.05) in the 2010 versus 1993 ducks. The percentage epiphyseal ash in the femur was 10% lower (P < 0.01) at 10 d and 14 d in the 2010 ducks but there were no significant differences by 18 d of age. The lower epiphyseal ash values at both younger ages and smaller BW in the 2010 contemporary ducks suggests that it is critical to monitor those factors that influence bone mineralization in contemporary ducklings that can achieve market BW at earlier chronological ages.

Intestinal physiology and regulatory T cell response to immediate or delayed access to feed and water in Pekin ducklings

This study investigated the effects of delayed access to feed and water on early duckling growth, selected aspects of intestinal physiology, and immune responses. Ducklings were assigned to one of 2 experimental groups. In one treatment group (referred to as the fed group), feed and water were provided beginning on d 0, and in the other treatment group (referred to as the withheld group), feed and water were withheld until d 2. The ducklings in the withheld treatment had lower BW at 2 and 6 d posthatch than ducklings in the fed group. At 8 d posthatch (6 d postfeeding), the BW of the ducklings in the withheld group was comparable to the BW of the 6-d-old ducklings in the fed group. At 2 d posthatch, withheld ducklings had lower absolute and relative duodenum plus pancreas weight than fed ducklings. At 8 d posthatch (6 d postfeeding), withheld ducklings had higher absolute and relative duodenum plus pancreas weight than fed ducklings at 6 d posthatch. At 2 d posthatch, mucin 5B mRNA content was approximately 2 times lower in withheld ducklings (P = 0.09) than in fed ducklings. At 6 d posthatch, mucin 5b mRNA content was approximately 2.5-fold higher in withheld ducklings (P = 0.07) than in fed ducklings. Delayed access to feed and water increased the CD25(+) cell number in the cecal tonsil at 2, 6, and 8 d posthatch. The IL-10 content of CD25(+) cells was higher in the withheld ducklings than in the fed ducklings at 2 and 6 d posthatch. In conclusion, delaying access of ducklings with no experimental pathogen infection to feed and water has no long-term effects on early growth parameters, intestinal physiology, and immune responses.

Effect of age and body weight on plasma concentrations of luteinizing hormone in turkey hens before and after photostimulation

The independent effects of age and body weight (BW) on photostimulatory response in turkey breeder hens were studied by measuring changes in plasma luteinizing hormone (LH; ng/mL) before and 3 d after photostimulation. The study was conducted with hens from two BW groups at 24-25, 27-28, and 31-32 wk of age. There was approximately a 1-kg difference in BW between groups within an age. Six hens per BW and age group were cannulated (jugular vein) and serially sampled during each of two 6-hr periods. Samples were collected at 10-min intervals. The two sampling periods were the last 6 hr of the short-day photoperiod (SD) and the same period during the third long day after photostimulation (LD). The photostimulatory response (PR) or difference between the SD and LD baseline LH concentrations was greatest in the 24-25-wk-old hens. The PR was unaffected by hen BW at any age. The baseline LH concentration during the SD photoperiod declined as hens aged. After photostimulation, baseline LH and LH peak amplitude concentrations were higher in 24-25-wk-old hens compared with the older ages. The number of LH peaks increased after photostimulation, but there were no significant effects attributable to age or BW within an age. In conclusion, the PR was affected by hen age but not hen BW or BW within a particular age.

Multivariate evaluation of 1-dimensional sarcoplasmic protein profile patterns of turkey breast muscle during early post-hatch development

Proteins are the main participants in metabolic pathways. However, the analysis of protein abundance patterns associated with those pathways is complicated by the large number of proteins involved. In this study, the objective was to present the application of principal component analysis (PCA) to permit the visualization of developmental proteomic patterns of sarcoplasmic proteins found in breast muscle. Different turkey genotypes and nutritional regimens were used to potentially increase the variability within the sarcoplasmic protein profile. Sarcoplasmic protein fractions from turkey breast muscle samples were collected at 6 ages between 7 to 24 d. Breast muscle samples were collected from 2 distinctly different turkey lines. The poults within each line were either ad libitum or restrict fed. Proteomic PCA plots showed a visual developmental pattern from 7 until 17 d. Multivariate ANOVA highlighted the effect of time point and feeding regimen among profile patterns. The use of different genotypes and feeding regimens influenced variability, which was measured by mean Euclidean distances and ellipses of the PCA plots. These treatment effects, however, did not mask the developmental patterns. After 17 d, the proteomic patterns converged, suggesting that a level of biological stability was achieved regardless of the genotype or treatment. The developmental pattern obtained by the PCA methodology can aid in the planning of more efficient experimental designs so the developmental stage of individuals can be more accurately assessed.