Influence of body weight restriction in a body-weight-selected line of turkeys on response to challenge with Pasteurella multocida

Research Note: The effect of selection for 16-week body weight on turkey serum metabolome

The phenotype of modern commercial turkeys is substantially different than that of unselected, heritage turkey lines. These phenotypic changes have arisen from alterations in the genome/transcriptome, as well as the influence of many external factors on growth performance including nutrition, environment, and management. To investigate the phenotypic changes resulting from genetic selection for increased body weight, The Ohio State University maintains 2 unique genetic turkey lines: the randombred control (RBC2) line, which is comprised of genetics from 1960 era commercial turkeys and has been maintained without conscious selection for any trait; and the F line, which was originally selected from the RBC2 line and has been selected for increased 16 wk body weight for over 50 generations. This study used broad-spectrum mass-spectrometry profiling techniques to identify and quantify differences in the metabolome of the serum of F and RBC2 turkey lines. Serum samples from both F and RBC2 turkeys were subject to quantitative time of flight liquid chromatography tandem mass spectrometry analyses. Principle component analyses showed distinct populations of metabolites in the F vs. RBC2 serum, suggesting that increased body weight is associated with the accumulation of several metabolites. Comparing the spectral features to online databases resulted in the selection of 104 features with potentially identifiable chemical structures. Of these 104 features, 25 were found at higher levels in the serum of the RBC2 line turkeys, while 79 were found at a greater abundance in the F line turkeys. A more detailed analysis of these 104 features allowed for the putative identification of 49 compounds, which were clustered into 6 functional groups: 1) energy metabolism; 2) vitamins; 3) hormones and signaling molecules; 4) lipid derivatives, fatty acid metabolites, and membrane components; 5) amino acid/protein metabolism; and 6) microbial metabolites. Further validation and experimentation is needed to confirm the identity of these metabolites and understand their biological relevance and association with selection for increased body weight.

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.

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.

Lutein supplementation alters inflammatory cytokine production and antioxidant status in F-line turkeys

Effect of dietary lutein supplementation on turkey production parameters, cytokine production, and oxidative status during an acute phase response following lipopolysaccharide (LPS) injection was studied. One-day-old chicks were fed a basal diet supplemented with 3 levels (0, 25, or 50 mg/kg of feed) of lutein. At 50 d of dietary lutein supplementation, turkeys were injected or not injected with LPS. Increasing dietary lutein increased the liver and plasma lutein content in both LPS injected and uninjected groups. In the groups fed 50 mg of lutein, LPS treatment decreased the lutein content of both the liver and the plasma at 48 h post-LPS injection. In the groups fed 0 mg of lutein, LPS treatment decreased the BW gain and feed consumption at 24 and 48 h post-LPS injection. The feed intake and BW gain of the group fed 50 mg of lutein in the LPS injected groups were comparable to those of the group with no LPS injection at both 24 and 48 h post-LPS injection. Treatment with LPS increased IL-1β mRNA content (P = 0.01) in the group fed 0 mg of lutein. In the LPS injected groups, increasing dietary lutein to 50 mg decreased the IL-1β mRNA amount compared with the group fed 0 mg of lutein. In the LPS injected groups, increasing dietary lutein to 50 mg increased IL-10 mRNA content compared with the group fed 0 mg of lutein. Injection of LPS increased the thiobarbituric reactive substances content of the liver in the group fed 0 mg of lutein. Increasing dietary lutein to 50 mg decreased the thiobarbituric reactive substances content of the liver in the LPS injected groups. Dietary lutein supplementation decreased oxidative damage and inflammatory responses post-LPS injection by decreasing IL-1β production and increasing IL-10 production in turkeys.

Differential Effects of Sex and Genetics on Behavior and Stress Response of Turkeys

Three lines of turkeys were tested for response in T-maze and open-field tests during the first 8 d after hatch, and behavior was observed after catching, moving, and transport. They were also compared for corticosterone (CORT) levels and heterophil:lymphocyte ratios (H:L) at 15 wk of age in response to an Escherichia coli challenge followed by transport stress. Large commercial-(COMM) line birds were faster and more active in the T-maze at d 2 than egg-line birds. Male COMM-line birds were faster than male egg-line birds when tested in an open field at d 8. Egg-line birds had more sleeping behavior after moving to a new floor pen as compared with both an intermediate-sized line (F line) and the COMM line. Transport stress increased CORT levels in all 3 lines, and the increase was greater in males compared with females. The egg line had higher basal CORT levels (P = 0.03) and higher levels after transport (P < 0.0001). The H:L ratios were affected by both transport stress and line but not by sex. The H:L ratio was lower in the egg line as compared with both the F line and the COMM line (P < 0.0001), with the COMM line having the greatest increase in response to transport. These data, combined with those from previous studies of these lines, suggest that differences in activity of fast-growing turkeys may be used to select birds that are less susceptible to inflammatory bacterial disease and that the H:L ratio may be more useful than serum CORT in evaluating the deleterious effects of stress.

Stress-induced colibacillosis and turkey osteomyelitis complex in turkeys selected for increased body weight

Two stress models were used to induce colibacillosis and turkey osteomyelitis complex (TOC): Escherichia coli challenge following dexamethasone injection (Dex) and E. coli challenge preceding transport stress (Transport). A total of 160 birds from 3 lines of turkeys: a slow-growing line selected for egg production (Egg), a line selected for 16-wk BW (F line), and a Commercial line (Comm), were studied in a 3 x 3 x 2 (line x treatment x sex) factorial design. At 14 wk, the Dex group was treated with 3 injections of 2 mg of Dex/kg of BW followed by airsac challenge with 100 cfu of E. coli. The Transport group was given 5,000 cfu of the same E. coli and 8 d later was transported for 3 h and held for an additional 9 h in the transport vehicle. Controls of each line were neither stressed nor challenged with E. coli. Birds were necropsied 2 wk postchallenge. All birds were sexed, scored for airsacculitis (AS) and TOC, and knee synovia were cultured for E. coli. Percent mortality was unaffected by sex, was increased by the Dex treatment, and was higher in Dex-treated male Comm-line birds and Dex-treated female F-line birds compared with their respective nonchallenged controls. Both treatments increased AS scores, and scores of Dex-treated male Comm-line birds and female F-line birds were also higher compared with their respective controls. Male Comm birds under Transport had higher AS scores as compared with nonchallenged males and challenged females. The TOC incidence was increased by Dex only. There was no TOC in Egg-line birds, whereas TOC incidence approached significance in both Comm and F lines compared with the Egg line (P = 0.06). Males had twice as much TOC as females, and this approached significance in the F line (P = 0.06). There was a low level of TOC in male Transport birds of both large-bodied lines, whereas no female Transport birds had TOC lesions. Dex-treated male birds of both the F line and Comm line had significantly higher incidence of TOC compared with their respective nonchallenged controls. The challenge strain of E. coli was isolated from more knee cultures of both large lines compared with the Egg line. Isolation was increased by Dex and was higher in male Comm-line birds and both male and female F-line birds relative to their controls. The difference in disease resistance between these lines suggests that selection for fast growth of turkeys may affect the stress response, resulting in increased chronic bacterial disease such as TOC.

Stress response differences and disease susceptibility reflected by heterophil to lymphocyte ratio in turkeys selected for increased body weight

Three genetic lines of turkeys were compared for their responses to Escherichia coli challenge following dexamethasone injection (Dex) or E. coli challenge preceding transport stress (TS). The turkey lines were a slow growing line selected for increased egg production (Egg line), a fast growing line selected for increased 16-wk BW (F line), and a commercial line (Comm line). At 14 wk of age, the Dex group was treated with 3 injections of 2 mg of Dex/kg of BW followed by airsac challenge with 100 cfu of E. coli. The TS group was given the same E. coli challenge at 1 x 10(4) cfu/bird without Dex treatment, and was subjected to transport stress, including 12 h of holding time in a transport vehicle, 8 d after the challenge. All treated birds and untreated control birds were bled at the same time, which was 1 d after transport and 9 d after challenge with E. coli. The main effect mean (MEM) total leukocyte counts (WBC) and the percentages of eosinophils (Eos) and basophils (Baso) were the same for all 3 lines; however, the MEM percentages of heterophils (Het) and monocytes (Mono) and the heterophil/lymphocyte ratio (H/L) were lower and the percentage of lymphocytes (Lym) was higher in the Egg line compared with the 2 fast-growing lines. Both stress treatments increased WBC, Het, and H/L and decreased Lym in all 3 lines; however, these effects were significantly greater in both fast growing lines compared with the Egg line. Sixteen-week BW was unaffected by either treatment in the Egg line and was decreased by both treatments in the Comm line and by the Dex treatment in the F line. Main effect mean airsacculitis score (AS) was not affected by line and was significantly increased by TS and Dex treatments. Neither treatment affected AS of the Egg line birds, whereas Dex treatment increased AS of the F line, and both Dex and TS increased AS of the Comm line. Mortality was significantly higher in the Comm line compared with the Egg line and was intermediate in the F line. The differences between these lines in their disease resistance and physiological response to stress in 2 stress models suggests that increasing selection for BW of turkeys is accompanied by changes in the stress response resulting in increased susceptibility to opportunistic bacterial infection.

Increased mortality in turkeys selected for increased body weight following vaccination with a live Newcastle disease virus vaccine

Candidate male and female breeders from nine genetic lines of turkeys that were reared intermingled, with the sexes housed in different buildings on the same farm, were vaccinated with a live Newcastle disease virus vaccine (B1 type, LaSota) just prior to the commencement of egg production. In 1999, an average mortality for all lines of 5.8% occurred during the 10 days immediately following vaccination and the level of mortality varied among lines. Mortality was, in general, greater in large-bodied lines than in small-bodied lines. Affected birds exhibited gross multiple areas of focal necrosis in the liver and spleen and congestion of the heart and lungs. The percentage mortality occurring following similar vaccination in 2000 averaged 2.6 for the 10 days following vaccination and mortality was greater (P < or = 0.05) in one line (F line) than the other genetic groups and higher in females than in males. Mortality in the F line, selected for increased body weight and known to be susceptible to various diseases, averaged 15.1% for both years. Attempts failed in both years to isolate Pasteurella multocida or other bacteria. There was a positive correlation between increased body weight and increased mortality following vaccination with the live LaSota vaccine.

Variation in resistance to Pasteurella multocida among turkey lines

Previous research has shown that a line (F) of turkeys selected long-term for increased 16-wk body weight was more susceptible to challenge with washed Pasteurella multocida than a randombred control line (RBC2), the base population of F. A previous study also indicated that the mortality of the F line following challenge with P. multocida was similar to that of sire lines from two of the three major primary breeders. The purpose of the present study was to compare the resistance of the sire line from the third major primary turkey breeder (C) not previously studied with that of the F and RBC2 lines to determine whether there is variation in resistance among the sire lines from three major primary breeders. The sire lines from all three primary breeders were used in the production of commercial turkeys. Body weights of the F line were greater than those of the C line at the time of challenge with P. multocida. Both the C and F lines were heavier than the RBC2 line. The birds were challenged at 6 wk of age with a field isolate of washed P. multocida (1.2 x 10(7) organism per bird of capsular serogroup A and somatic serotype 3,4). Mortality was recorded daily for 14 d. Mortality following challenge with P. multocida was higher in the F line than in the C line, and both large-bodied lines had higher mortality than the RBC2 line. Based on the present results and those published in the literature, there may be variation in resistance among commercial sire lines from the three major primary breeders.

Effect of feed withdrawal or challenge with Pasteurella multocida on growth, blood metabolites, circulating growth hormone, and insulin-like growth factor-I concentrations in eight-week-old turkeys

The daily effects of feed withdrawal or a bacterial disease (Pasteurella multocida; PM) challenge was studied in a slow-growing line of turkeys. The following groups (n = 6 birds/group) were sampled for up to 13 d: untreated control (CON), 4-d feed withdrawal followed by refeeding (FAST), a group that succumbed within the first 2 to 3 d after PM challenge (E-DEAD), a group that succumbed 8 to 9 d after PM challenge (L-DEAD), a group that survived the PM challenge (SUR), and a group treated with both PM challenge and 4-d feed withdrawal followed by refeeding (FAST/CHAL). Daily feed intake and BW gains were markedly reduced in the E-DEAD and L-DEAD groups immediately and 3 d after PM challenge, respectively. Feed intake and BW gain between CON and SUR groups of turkeys were not different throughout the trial. The turkeys in the FAST group followed the expected feed withdrawal and refeeding patterns for feed intake and BW loss or gain. The FAST/CHAL turkeys consumed the minimal amount of feed to maintain BW after refeeding. Plasma uric acid sharply increased 1 d prior to death in both E-DEAD and L-DEAD groups of turkeys. Plasma uric acid also increased each consecutive day during fasting in the FAST and FAST/CHAL groups of turkeys. Plasma growth hormone was measured in only the CON and FAST groups and increased from about 40 to 85 ng/mL in the FAST group during fasting but returned to control levels within 1 d of refeeding. Circulating plasma insulin-like growth factor-I (IGF-I) decreased from about 17 to 5 ng/mL in the PM-challenged (E-DEAD, L-DEAD, and FAST/CHAL groups) and FAST groups. The concentration of IGF-I returned to prefeed withdrawal levels within 3 d of refeeding the FAST group of turkeys. It was concluded that 1) turkey poults that were not susceptible to the PM challenge generally maintained physiological functions at control bird levels, 2) susceptible turkey poults generally exhibited depressed feed intake and BW gains, and 3) poults challenged with both feed withdrawal and PM treatment responded differently than poults challenged with either feed withdrawal or challenge with PM. The depletion of energy intake and mobilization of energy stores in susceptible poults might have contributed to the rate at which PM caused the poults to die.