Comparison of growth curves of weight selected populations of turkeys, quail, and chickens

The pattern of growth from hatch to sexual maturity was measured in quail, chicken, and turkey females using the Gompertz equation. Quails and chickens were selected for high or low immature BW and turkeys were selected for high BW. Quail and turkey species also included their respective randombred control populations. The chicken species included an F2 of the selected lines. Thus, there were considerable differences in BW not only among species but between lines within species. Differences were evident at hatch as hatch weights relative to asymptotic BW were greater for quail than chickens and turkeys. Age and BW traits associated with point of inflection (POI) were variable. Species differences appeared to be influenced by the selection scheme applied to the populations. Slope at POI was greatest in quail and the same for turkeys and chickens. Age at 90% of the asymptotic BW was generally greatest for chickens, intermediate for turkeys and lowest for quails. Selection age in relation to age at POI may contribute to the timing and magnitude of growth response observed.

Genetic factors accountable for line-specific DNA fingerprint bands in quail

DNA fingerprints, prepared from mixes of DNA of individuals sampled from lines of Japanese quail selected for high or low 4-week body weight, were used to evaluate the relative contribution of several evolutionary forces to genetic diversity among populations. Comparisons between lines--two replicates of each selection direction and a control unselected line--were used to determine the frequency of line-specific DNA fingerprint bands produced by each of three major evolutionary forces: 1) mutation; 2) genetic drift; 3) selection. The latter force is expected to generate line-specific bands only if there is linkage disequilibrium between DNA fingerprint loci and quantitative loci (QTLs) controlling body weight. Using probes 33.6 and R18.1, an average of 48.4 DNA fingerprint bands in each line were analyzed. On average, 27.8 bands were found to be line-specific among the 96.8 (2 x 48.4) bands analyzed in an average comparison between pairs of lines. Based on the frequencies of line-specific bands in each particular comparison, it was calculated that 21% of the line-specific bands were due to mutation, 11% due to a single genetic drift event, 11% due to selection, 21% due to the combined effects of genetic drift and selection, 22% due to double independent events of genetic drift, and 14% due to undefined factors. Although evidence was found for a high frequency of genetic changes attributable to genetic drift, and a higher than expected frequency of linkage disequilibrium, the emphasis of this report is on the methodology suggested rather than on the particular results.

Genetic-environmental interactions and antibody response in chickens to two antigens

Chickens from lines selected for either a high (HA) or low (LA) antibody response to sheep erythrocytes were either socialized, ignored, or stressed before being injected with two different erythrocyte antigens. Correlation between the antibody responses to the two antigens and the difference between the titers of the HA and LA lines was greatest when the chickens were socialized in an optimum-stress environment. The antibody responses of individual chickens to the two antigens was influenced by their heterophil/lymphocyte ratios.

Composition of eggs from dwarf and normal chickens before incubation and at hatching in lines selected for 56-day body weight

Comparisons of egg composition prior to incubation and when the chick had pipped through the shell were made for dwarf (D) and normal (N) chickens from lines selected for high (H) or low (L) body weight. Weight of moisture, ash, and fat decreased and nonlipid organic matter increased during incubation. The pattern for these components was the same on a percentage of egg weight basis except that there was no change in ash. Genotype by line interactions were significant for egg weight, moisture, ash, fat, and nonlipid organic matter before incubation and for all of these characteristics except fat at pipping. The interactions were due to values being lower for D than N in Line L, and D and N were similar in Line H. When egg component weights were expressed relative to egg weight, interactions were not significant prior to incubation but were present for moisture and fat at hatch. These data show that characteristics influenced by the sex-linked dwarfing gene are modified by the background genome.

Production traits and alloantigen systems in lines of chickens selected for high or low antibody responses to sheep erythrocytes

The selection of chickens for high (HA) and for low (LA) antibody titers to sheep erythrocytes has produced differences in the selected trait and in the correlated responses in body weight, egg production, and erythrocyte antigens. The response to selection continued through 14 generations. There was considerable divergence between lines for erythrocyte alloantigen systems, including the major histocompatibility complex. Females from Line LA were heavier as juveniles and lighter as adults, matured at a younger age, and had higher egg production than those from Line HA. There were no differences between lines for the incidence of defective eggs laid-except for the percentage of eggs with double-yolks, which was greater for Line LA than HA. The phenotypic correlations of antibody response with growth and with reproductive traits were very low; the genetic correlations were moderate to high for most of these traits.

DNA fingerprints of chickens selected for high and low body weight for 31 generations

Two lines of White Plymouth Rock chickens that have been divergently selected for 8-week body weight for 31 generations were compared for patterns of DNA fingerprints (DFP). Digestion of DNA with HinfI and hybridization to Jeffreys' minisatellite probe 33.6 resulted in DFPs that were relatively similar within lines (bandsharing = 0.50) and less similar between lines (bandsharing = 0.22). Analyses of scorable DFP bands produced by mixing DNA from individuals within lines indicated that 48% were line-specific. Causes for the differences in DFP patterns between lines and for occurrence of line-specific bands for the two lines divergently selected for body weight are discussed.

Response of White Leghorn chicks fed ascorbic acid and challenged with Escherichia coli or with corticosterone

This study was undertaken to assess the effects of dietary ascorbic acid on the growth and immunoresponsiveness of chickens when subjected to particular types of stress. White Leghorn chicks were fed diets containing no supplemental ascorbic acid, and ascorbic-acid diet (330 ppm) for 2 days or for 19 days before challenge. Then, half of the females were inoculated with Escherichia coli; half of the males were challenged with dietary corticosterone (30 ppm) for 12 days; and the remaining chicks were maintained as controls. These chicks, reared under "good" husbandry procedures, did not realize advantages in growth or feed efficiency due to the short- or long-term consumption of diets containing ascorbic acid. Incubation with E. coli resulted in considerably higher heterophil-to-lymphocyte ratios 24 h after inoculation, and E. coli-induced mortality was higher for pullets on short-term ascorbic acid than for those on long-term or no ascorbic acid. Dietary corticosterone caused differences in body weight and the relative weights of certain organs, regardless of dietary levels of ascorbic acid. The antibody response to red-blood-cell antigens from sheep was enhanced in unchallenged cockerels (no dietary corticosterone) fed ascorbic acid on a long-term basis, but dietary corticosterone overshadowed the advantageous effects of dietary ascorbic acid. These data showed that the effects of supplemental ascorbic acid on growth and on immunoresponsiveness were related to the quality of the husbandry, length of supplemental feeding, age of the chicks, endogenous-exogenous balance for ascorbic acid, and the relationship with corticosterone.

IgG and IgM responses in high and low antibody-selected lines of chickens

Kinetics of IgG and IgM as measured by 2-mercaptoethanol-resistant (MER) and susceptible (MES) antibodies to sheep erythrocytes, respectively, were determined as correlated responses in lines of chickens selected for high (HA) and low (LA) antibody response to sheep erythrocytes. Primary response patterns for total, MER, and MES antibody differed according to the genetic line. Total antibody increased rapidly, peaked, and persisted at moderate levels in line HA, whereas both peak and persistency were lower in line LA. Levels of MES peaked and then declined in line HA chickens but persisted at low levels throughout in line LA. Titers of MER antibody were considerably greater in line HA than in line LA both on an absolute basis and as a proportion of total antibody titer. Secondary total titers were greater at five days after injection than at three days and greater for line HA than for line LA chicks. The pattern observed for MER and MES in line LA was similar to that for total antibody, as was MER in line HA. For MES the pattern was reversed in line HA.

Effects of dietary corticosterone in young Leghorn and meat-type cockerels

1. Cockerels from meat-type (MT) and Leghorn (LG) stocks were fed on diets containing 0, 20, or 30 mg corticosterone/kg from 1 to 22 d after hatching. 2. Within MT and within LG stocks, responses to dietary corticosterone inclusion rates were similar; however, patterns differed between these major classes resulting in stock X diet interactions. 3. Traits responding to different inclusion rates of corticosterone in a dissimilar manner for MT and LG chickens included: immunoresponsiveness, body weight, efficiency of food utilisation, feathering; relative weights of liver, spleen, bursa, testes, breast and abdominal fat pad, as well as the proportion of liver lipid. 4. No differential responses occurred for relative adrenal weight, plasma xanthophyll concentrations, proportion of breast lipid and abdominal fat, or surface and cloacal temperatures. 5. Results indicated genetic differences in thresholds for response to corticosterone and in degree of response once thresholds were reached. Within populations, sensitivities varied between target organs.

Restricted feeding in early and late-feathering chickens. 3. Organ size and carcass composition

Carcass composition traits and weights and lengths of organs relative to body weight were measured in females from a broiler-breeder parent stock segregating for early and late-feathering alleles maintained under four feeding regimens. Feeding regimens consisted of ad libitum (AL), ad libitum restricted (ALR, feed restricted daily), and skip-one-day and skip-two-days (SOD and STD, given two or three times ALR allowance on Day 1 and not fed on the next 1 or 2 days, respectively). At 160 days of age, pullets on SOD and STD were changed to ALR feeding; daily feed allowances were increased to 135 g by day 180 and to 138 g on day 250. Organ growth and carcass composition were generally similar for early and late-feathering genotypes. Restricted feeding increased relative weights and lengths of segments of the gastrointestinal tract (GIT) and pancreas and reduced relative weights of the abdominal fat depot (AFD) and lipid contents of the liver, AFD, and total carcass. Relative weights of legs, breast, feathers, heart, and liver and carcass protein composition were not affected by feeding regimen. Relative oviduct and ovary weights were not affected, but number of rapidly developing follicles was higher for AL than restricted-fed hens. Relationships of most organs to total body weight changed little after sexual maturity. Relative weights and lengths of GIT decreased whereas breast, legs, and AFD increased. Feed-restricted chickens adapted to fasts by retaining GIT contents longer. Feeding regimen x age interactions were significant for esophagus, proventriculus, gizzard, shank, breast, legs, feathers, and AFD weights; esophagus, duodenum, jejunum, ileum, and shank lengths; and lipid contents of AFD and liver.

Restricted feeding in early and late-feathering chickens. 2. Reproductive responses

Reproductive traits of females from a broiler-breeder parent stock segregating for early and late feathering were measured under four feeding regimens. Feeding regimens consisted of ad libitum (AL, feed was always available), ad libitum restricted (ALR, feed restricted daily to control body weight), and skip-one-day and skip-two-days (SOD and STD, given two or three times ALR allowance on Day 1 and not fed on the next 1 or 2 days, respectively). At 160 days of age, pullets on SOD and STD were changed to ALR feeding, and daily feed allowances were increased to 135 g by Day 180 and 138 g by Day 250. Early and late feathering chickens responded similarly, except that hen-day ovulation rates, relative egg shell weights, and incidences of extracalcified and compressed eggs were greater for the former than the later. For most traits measured, differences among restricted feeding regimens were minor, but considerable differences were noted between them and the AL regimen. Females fed AL reached sexual maturity approximately 60 days earlier than those whose feed intake was restricted. Also, body weights at onset of lay were about 1,200 g greater for AL than for feed-restricted females. Percentages of hen-day ovulation, normal egg production, and duration of fertility were lower, whereas incidence of defective eggs was higher for AL than for feed-restricted chickens.

Gordon Memorial Lecture. The genetic-behavior interface and well-being of poultry

Marked changes have occurred in poultry production practices and in stocks bred for the production of meat and eggs. Of behavior pattern that originally favoured domestication, positive responses to humans and adaptability to environments are now most important. Development of specific strains for production of meat or eggs resulted in correlated responses in behavioural traits. Compared with egg strains, meat strains are docile and have excessive appetites, poor immunoresponsiveness and reduced motor ability. Genotype by environment interactions for behaviour limit inferences concerning responses of stocks across environments. Innate behaviour patterns and habituation processes can prevent some stimuli from causing physiological manifestations observed in general responses to stressors. Husbandry procedures should optimise phenotypic expressions of genetic potential to enhance well-being.

Restricted feeding in early and late-feathering chickens. 1. Growth and physiological responses

Broiler-breeder females from a parent stock segregating for early and late feathering were fed ad libitum (AL, feed was always available), ad libitum restricted (ALR, feed restricted daily to control body weight), skip-one-day and skip-two-days (SOD and STD, given two or three times ALR allowance on Day 1 and not fed on the next 1 or 2 days, respectively). At 160 days of age, pullets on SOD and STD were changed to ALR feeding, and daily feed allowances were increased to 135 g by Day 180 and 138 g by Day 250. Responses of early and late-feathering females were similar for traits measured. Generally, body weights of AL chickens increased to 4,600 g at 130 days of age and then reached a plateau. Body weights of feed-restricted groups were less than half of that of AL chickens by 160 days of age. Controlled release from feed restriction enabled chickens to reach a weight of approximately 3,200 g by Day 210. Daily feed consumption for AL chickens increased to about 220 g by 140 days of age and then decreased to approximately 150 g by Day 250; it eventually decreased to approximately 120 g by Day 350, where it reached a plateau. Mortality, plasma glucose levels, and surface and cloacal temperatures were lower for females whose feed was restricted than for those fed AL. Plasma protein levels were greater for STD than for AL, ALR, and SOD groups whereas plasma lipids were higher for AL and SOD than for ALR and STD groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular defense of the avian respiratory system: effects of Pasteurella multocida on respiratory burst activity of avian respiratory tract phagocytes

The respiratory tract of healthy chickens contain few free-residing phagocytic cells. Intratracheal inoculation with Pasteurella multocida stimulated a significant (P less than 0.05) migration of cells to the lungs and air sacs of White Rock chickens within 2 hours after inoculation. We found the maximal number of avian respiratory tract phagocytes (22.9 +/- 14.0 x 10(6] at 8 hours after inoculation. Flow cytometric analysis of these cells revealed 2 populations on the basis of cell-size and cellular granularity. One of these was similar in size and granularity to those of blood heterophils. Only this population was capable of generating oxidative metabolites in response to phorbol myristate acetate. The ability of the heterophils to produce hydrogen peroxide, measured as the oxidation of intracellularly loaded 2',7'-dichlorofluorescein, decreased with time after inoculation. These results suggest that the migration of heterophils, which are capable of high levels of oxidative metabolism, to the lungs and air sacs may be an important defense mechanism of poultry against bacterial infections of the respiratory tract.

Organ growth of selected lines of chickens and their F1 crosses to a common body weight or age

Organ growth of male chickens selected for high and low 56-day body weight and their reciprocal F1 crosses was compared at a common age (56 days) or at a common body weight (180 g). Organs that differed at a common body weight included weights of proventriculus, small intestine, lungs, feathers and abdominal fat and length of esophagus. Organ weights that differed at a common age included esophagus, gizzard, heart, liver, lungs, breast, legs, feathers and abdominal fat, and lengths of shank, esophagus and small intestine. Heterosis for most organs was less than 15%. Those exhibiting heterosis greater than 30% included weights of fat depots and feathers, plus lengths of the esophagus, small intestine and shank. Heterosis for these traits, however, varied depending on whether comparisons were made at common body weight or age. These results imply that biological functions of organs at specific ages may not reflect the situations at common body weights and suggest differences in resource allocations among populations.

Cellular defense of the avian respiratory system: protection against Escherichia coli airsacculitis by Pasteurella multocida-activated respiratory phagocytes

The concept of nonspecific cellular defense of the respiratory system of poultry against respiratory pathogens by "preventive activation" of avian respiratory phagocytes (ARPs) was tested in an in vivo protection trial. Chickens were stimulated intratracheally by Pasteurella multocida Choloral vaccine strain. Seven hours later, these and mock-inoculated control chickens were challenged with pathogenic Escherichia coli via the air-sac route. Stimulated chickens had a 25-fold-elevated number of ARPs compared with mock-inoculated control chickens. The proportion of active phagocytes and the phagocytic capacity of these cells was higher in the ARP populations of stimulated chickens than in the ARP populations of control chickens. In vivo protection against E. coli air-sac infection was demonstrated by reduction of morbidity and mortality rates, diminished weight loss, and lower scores of gross and histopathological lesions of P. multocida-stimulated chickens compared with mock-inoculated controls.

Environment-genetic influences on immunocompetence

The immunological responses of an animal are changing continually in response to perceived environmental changes. This is because the genetic background, the lifelong environment of animals and their interaction greatly influence immunological responsiveness. An animal's genetic background influences all factors related to immunocompetence. Among these are age of onset of immunocompetence, responsiveness to specific antigens, antibody titers, type of antibody and immune response, as well as the persistence of the responses. Defense by immunity must require considerable resources, because chickens with a high antibody response are smaller and have poorer feed efficiencies than those chickens whose antibody response is lower. An increase in the effectiveness of one defensive factor may result in reduced effectiveness of another factor. For example, chickens selected for a high antibody titer response to antigen have reduced effectiveness of macrophages. Environmental stresses influence the immune response. Stress at the time of the animal's contact with antigen results in a reduced antibody response. After the antibody response begins, stress has little effect. Stress promotes the sensitization of cell-mediated immunity but inhibits its effectiveness. A short-term stressor such as weaning is followed, in about 24 h, by a short period of reduced immunocompetence, even though lymphoid mass may be reduced. Reduced immunocompetence during stressful periods can be reduced by employing adrenal blocking chemicals, or by socializing animals to their handlers.