Long-term exposure of chickens to three levels of social stress

Cockerels were kept in environments characterized by high (HSS), medium (MSS), or low (LSS) levels of social stress for 3 or 4 months. Chickens raised in an environment of low light intensity (LSS) gained more weight than did those raised under natural lighting. Ability of chickens to produce antibody in response to antigen was greatly reduced, 2(15.4) in the LSS group to 2(3.4) in the HSS group, 1 day after chickens were moved from the LSS environment into the HSS environment. Normal responsiveness returned within 1 week. No long-term environments affected antibody production. After 3 months, chickens in the LSS environment had reduced weight gain and resistance to Escherichia coli infection compared with birds in the HSS environment. Chickens in the MSS environment, compared with those on the HSS and LSS environments, had greater weight gains, superior feed efficiencies, medium plasma corticosterone levels, a better negative correlation between antibody responsiveness and RBC antigens, and better resistance to Mycoplasma gallisepticum challenge. All parameters except antibody responsiveness were such that long-term exposure to HSS or LSS environments appears to be detrimental.

Dwarfism in diverse genetic backgrounds. 4. Effects of dietary energy

The interactions in the response of dwarf and normal genotypes to dietary energy were studied in lines of chickens divergently selected for high or low juvenile body weight. The genetic background of the dwarf genotype significantly affected body weights, egg production, and egg quality. The dietary energy levels used did not significantly affect these traits or the differences due to genetic background. Dwarf chickens were able to adapt to wide ranges of dietary energy when the diets contained sufficient crude protein.

The relationship between the dwarfing gene and E. coli infection in two populations of chickens

Resistance to an E. coli challenge was studied in the 6th, 7th, and 8th backcross generations after the introduction of the sex-linked recessive dwarf gene (dw) into two populations of White Plymouth Rock chickens that had undergone bidirectional selection for juvenile body weight. In the B6 and B8 generations, the dwarf genotype from the HW line had significantly higher mortality and/or heart lesions than the heterozygotes while the homozygous normal chickens were intermediate. No association between the dwarf allele and the incidence of E. coli infection was observed in the HW line in any generation, but genotypes in the LW lines were influenced by social environment in susceptibility to the E. coli challenge. Under low social strife, the dwarf and heterozygote genotypes were more susceptible than the normal genotype to the E. coli challenge, while under a high social strife there were no differences among genotypes. Since the genotypes in the LW line responded differently to the disease challenge than those in the HW line, it was concluded that a line-dwarf genotype interaction was present.

Fertility of chickens from lines divergently selected for mating frequency

Fertility comparisons of males under natural and artificial mating situations were made among lines of chickens selected for high and low mating frequency and the randombred population from which the selected lines originated. Although highly significant differences existed among lines for the frequency of sexual behaviors, there were no significant differences in fertility among lines either when males were with females for extended periods of time or when hens were artificially inseminated. Significant differences were found between mating systems for days to peak and duration of fertility.

Repeatabilities of feed and water consumption of growing chickens

Daily feed and water consumptions were obtained within 7-day periods for dwarf and normal males from lines selected for high and low juvenile body weight from 21 to 90 days of age. No significant differences were found among populations for the repeatabilities, and three measurements per week were sufficient to obtain an accurate estimate of feed and water consumption of growing chickens.

The effects of exogenous steroidal hormones on the testes of quail from selected high and low mating lines

Several steroid hormones were tested for their effects on the testes of lines of Japanese quail selected for high and low mating frequency. Estradiol benzoate and testosterone propionate caused a complete and partial regression of the testes, respectively, while dihydrotestosterone did not affect testicular weight. Spermatogenesis was adversely affected by both estradiol benzoate and testosterone propionate but not by dihydrotestosterone. Dihydrotestosterone caused a significant increase in the diameter of the seminiferous tubules while estradiol benzoate and testosterone propionate caused a significant decrease in tubular diameter. Significant line differences were found; the high mating line exceeded the low mating line for each of the treatments except extradiol benzoate. Extradiol benzoate caused testicular regression in both lines.

Antibody production and Escherichia coli resistance in socially stable flocks of dwarf and nondwarf chickens

Dwarf and normal pullets from lines that had undergone selection for divergence in juvenile body weight were maintained in cages as socially stable flocks. Antibody titers were measured at 6 and 14 weeks of age and an Escherichia coli challenge was administered at 16 weeks of age. There was a significant line by dwarf genotype interaction with dwarfs having lower antibody titers than normal pullets in the low weight line and higher antibody titers in the high weight line. The mortality of dwarfs from the low weight line to an Escherichia coli challenge was much higher than that of any other group. These results were consistent with those from previous experiments where the Escherichia coli challenge was given to hens in single cages.

Effects of early environmental stresses on chicken body weight, antibody response to RBC antigens, feed efficiency, and response to fasting

Stress early in life (SEL) by either overheating or water deprivation altered the responses of 4-to-18-week-old chickens selectively bred for high (HA) or low (LA) antibody response to sheep RBC. When unstressed, HA birds weighed more than LA birds. Following SEL, LA birds weighed more than HA birds. Antibody response following SEL was decreased in HA birds and increased in LA birds. Both SEL and adaptation to handlers (AH) decreased the deleterious effects of fasting on antibody response to RBC antigens. Chickens subjected to SEL had a lower rate of gain following fasting. Adaptation to handlers tended to increase antibody response more in HA than in LA birds, while SEL tended to increase antibody response more in LA than in HA birds. Feed efficiency (FE) was increased by AH. A SEL resulted in increased FE of unadapted birds and decreased the FE of AH birds.

Production and persistence of antibodies in chickens to sheep erythrocytes. 2. Resistance to infectious diseases

A line of chickens selected for ability to product high antibody titers to sheep red blood cells exhibited stronger antibody to Newcastle disease, was more resistant to Mycoplasma gallisepticum, Eimeria necatrix, a splenomeglia virus, and feather mites and less resistant to Escherichia coli and Staphylococcus aureus infection than a line selected for a lack of ability to produce antibody titers. A line of chickens selected for a nonpersistance of antibody titers to sheep red blood cells was relatively more susceptible to all infectious agents tested than a line selected for a persistence of atibody titers.

Cell-mediated immunity in Marek's disease virus-infected chickens genetically selected for high and low concentrations of plasma corticosterone

Lines of chickens genetically selected for high (HPC)-and low-plasma corticosterone (LPC) titers were assessed for cell-mediated immunity during Marek's disease tumorigenesis. Lymphocyte transformation (using phytohemagglutinin and 2,4-dinitrofluorobenzene-bovine serum complex) and mitogen-induced cellular cytotoxicity were evaluated with peripheral blood leukocytes. Chickens from the LPC line showed a greater lymphocyte transformation response than those from the HPC line. All tumor-bearing chickens demonstrated a markedly suppressed blastogenic response. Although the blastogenic response was suppressed in those chickens infected with Marek's disease virus but not having gross tumors when compared with the steroid level, this response was greater than that of chickens with tumors and less than that of normal controls. In comparison with LPC-line chickens, HPC-line chickens demonstrated a decreased mitogen-induced cellular cytotoxicity. A decreased mitogen-induced cellular cytotoxicity was observed in both steroid lines concomitant with the onset and severity of tumors. The impaired cell-mediated response observed in the HPC line was associated with an increased tumor incidence and a greater mortality than that observed in the LPC line. Metyrapone, a chemical which blocks adrenal corticosterone synthesis, transiently enhanced mitogen-induced cellular cytotoxicity and initiated tumor regression in chickens debilitated with Marek's disease tumors.

Adaptation of chickens to their handler, and experimental results

Chickens were adapted to their handler before the experiment. Adapted birds produced more antibody, had more blood protein, gained more weight, and were more resistant to Mycoplasma gallisepticum than unadapted birds. The antibody response to sheep red blood cells was not reduced for fasting for 48 hours in adapted birds but was in unadapted birds. Differences in antibody titers, blood protein, and weight gains between controls and birds fed 80 ppm of deoxycorticosterone could be demonstrated only with adapted birds.

Initial observations on the effect of corticosterone and inbred antibody competency in chickens on population development of the northern fowl mite

Roosters from a line artificially selected for high initial antibody response to sheep red blood cells were more resistant to development of populations of Ornitbonyssus sylviarum (Canestrini and Fanzago) than were birds selected for low antibody response. Oral administration of corticosterone to test chickens at doses ranging from 10 to 40 ppm did not affect mite development. The steroid regimen was shown to reduce lymphocyte and testes mass as well as total weight gain. Postmortem measurements were not different for the 2 inbred lines. Analysis of data indicated that antibody competency alone probably was not responsbile for the observed differences in mite populations.

The filling and emptying of the uterovaginal sperm-host glands in the domestic hen

In a series of three replicated experiments, dwarf hens were inseminated with semen of one phenotype (normal or dwarf) and then reinseminated 4 hr later with semen of the other phenotype. All eggs were pedigree-hatched for two weeks following the inseminations. Subsequent phenotypic determinations of the progeny demonstrated a preponderance of offspring from the latter insemination. The results suggested that spermatozoa sequentially filled the uterovaginal sperm-host glands which produced a permanent stratification of sperm cells, and mixing did not occur within a gland. Emptying of the host-glands appeared to follow a pattern of slow superficial leakage where spermatozoa from the second insemination were the first spermatozoa released, giving rise to the large number of progeny phenotypes from the second insemination. In addition, progeny phenotypes from the second insemination were predominant throughout the fertility period suggesting that the storage capacity of the uterovaginal sperm-host glands can exceed the functional life span of stored spermatozoa following a normal insemination.

Response to bidirectional and reverse selection for mating behavior in Japanese quail Coturnix coturnix japonica

Reported is a genetic analysis of mating behavior in male Japanese quail. Data were obtained from replicated experiments involving 12 generations of divergent selection for high and low cumulative number of completed matings (CNCM). No trait measured in the randombred control population changed significantly over time. Asymmetrical responses between the divergent lines were observed during various phases of selection. Reversed selection showed that additive genetic variance remains in the high lines. Small and unimportant were drift and error variances. Genetic and phenotypic relationships between CNCM and body weight were small but positive, while those between CNCM and relative aggressiveness were positive and intermediate. Also positive and intermediate were the correlations between CNCM and cloacal gland size.

Ultrastructural observations of the adenohypophyseal gonadotrophs from growth selected lines of chickens

The ultrastructure of adenohypophyseal gonadotrophs (GT-cells) from pullets of lines selected for high (HWS) and low (LWS) body weight was studied at various physiological ages. Increasing the photoperiod beyond 14 hours in a 24-hour cycle did not have a significant effect on the ultrastructure of GT-cells in either line. A qualitative analysis, based on the extent and complexity of the protein synthetic apparatus, suggested that the synthetic activity of gonadotrophs from HWS pullets was greater than that of LWS pullets at each of the ages studied. Although no significant differences were found in the frequency of pullets showing evidence of intracellular digestion of secretory products, the condition was more severe in the HWS than in the LWS females. Crinophagy tended to be positively correlated with cell activity in both lines. These observations suggest that selection for growth rate had a correlated effect on hypophyseal proteinaceous secretions. They also indicate that interactions between fluctuations in gonadotrophic cell activity, secreting mechanisms and neural thresholds for hormone action may be implicated in the manifestation of the erratic ovulation patterns.