Genetic analysis of behaviors related to the solution of a detour learning task

A diallel cross involving five noninbred (purebred) lines of Japanese quail indicated that additive and nonadditive genetic effects had important influences on behaviors involved in a detour learning task. Social isolation for 3 hr was used to provide additional motivation which enabled detection of differences among strains. The percentage of quail, within purebred lines, that solved a 4-min detour task three or more consecutive times ranged from 52 to 72. Differences among purebreds were significant for most of the components of the learning task. Further, the data suggested strain differences associated with the successful attainment of the desired goal when there was a similar level of general activity.

Selection for body weight at eight weeks of age. 11. Ovulation and oviposition patterns

Two experiments were conducted to study oviposition patterns and ovarian activity at various physiological ages in S15 and S16 generation pullets from lines selected bidirectionally for high (HWS) and low (LWS) juvenile body weight. The fixed periods of lay for random samples of pullets from the date of first egg were 20, 40, 60, and 80 days in the first experiment and 40, 80, 120, and 160 days in the second experiment. HWS pullets matured significantly earlier than LWS pullets in both generations. The frequency and the percentage hen-day production (%HDP) of defective eggs were significantly greater in the HWS than LWS line in both generations. Delayed sexual maturity did not significantly change the pattern of defective egg production for a fixed period of lay. In the HWS line the %HDP of defective eggs progressively increased until about 40 days of lay and tended to decline thereafter, while in the LWS line the percentage decreased from 20 to 40 days and then stabilized. The frequency of normal unbroken eggs to 80 days of production did not differ among lines either in the S15 or S16 generation. When measurements were extended to 160 days of lay in the S16 generation HWS pullets produced significantly more normal eggs than LWS pullets. Possible effects of ovarian activity on the egg production pattern during the laying cycle are discussed. There was a significantly higher incidence of internal laying and atrecia of the growing follicles in the HWS than in the LWS pullets. Ovarian activity, evidenced by the number of developing and ruptured follicles, was significantly greater in the HWS than the LWS line, as was the incidence of ova developing in pairs. Product moment correlations and multiple regressions among the measurements of ovarian activity were calculated within lines. In the HWS line, 62.5% of the variation in %HDP of defective eggs could be accounted for by the %HDP of normal eggs and the number of developing follicles while in the LWS line these variables accounted for only 7.29% of the variation in %HDP of defective eggs.

A revised artificial insemination schedule for broiler breeder hens

Broiler type hens maintained in individual cages were artificially inseminated with either 0.023, 0.035, or 0.047 ml. of pooled semen. Insemination intervals were nine, nine, and ten days on a repetitive basis. This schedule was adopted because it allowed an extension of the conventional insemination interval and yet remained compatible with a five-day industrial work-week. The results demonstrated that maintaining broiler breeder hens in cages and utilizing artificial insemination as a means of obtaining fertile eggs were feasible. The data also indicated that extending the insemination interval to 10 days is possible providing the number of spermatozoa inseminated is increased.

Light effects during incubation on lines of White Leghorns selected for fast and slow hatching

Eggs from White Leghorn lines selected for fat and slow hatching time were incubated in continuous light and in unlighted incubators. The fast hatching line averaged 48 hours shorter in incubation time than the slow hatching line. The light treated eggs averaged five hours earlier in hatching time than the unlighted treatment. These two effects on hatching time, one genetic and one environmental, were completely additive. No effect of either treatment on hatchability was observed after all hatchable eggs had hatched.

Erythrocyte lifespan in dwarf and normal pullets from growth selected lines of chickens

Mean erythrocyte lifespan was estimated, using a 51Cr tagging procedure, in dwarf and normal sisters from lines selected for high and low body weight at eight weeks of age. Correlations between body weight, packed cell volume and erythrocyte lifespan were not significant. Significant differences were found among genotypes for body weight and packed cell volume, but not for lifespan of erythrocytes.

Selection for mating ability in Japanese quail

Results are presented for a replicated mass selection experiment for high and low cumulative number of completed matings. Through six generations of selection heritabilities of the selected trait averaged .07 for the high lines and .25 for the low lines. No correlated responses were noted for body weight at either 4 or 8 weeks of age, whereas the relationships of the selected trait with size of the cloacal gland and relative aggressiveness were positive.

Blood parameters of dwarf and normal pullets from growth selected lines before and after Escherichia coli challenge

Two experiments were conducted to study the hematological differences and the effect of challenge with Escherichia coli on the hemopoietic system among dwarfs and their normal sisters in lines selected for high and low juvenile body weight. Erythrocyte counts, packed cell volumes, and hemoglobin concentrations were significantly higher to dwarf than for normal pullets, while no such differences were noted for mean corpuscular volume, mean corpuscular hemoglobin and hemoglobin concentration. Dwarfs had a significantly lower erythrocyte sedimentation rate than normal pullets. The effect of challenge with E. coli was evident in all the groups. Body weight decreased and leucocyte counts increased significantly. Lymphopenia, accompanied by heterophilia and a consequent increase in H:L ratio was the conspicuous effect of the challenge with E. coli indicating a polymorphonuclear response. Forty-eight hours after challenge the differential response of lines and genotypes to heterophilia was uniform. The hematological data suggest that the dw gene may not contribute to resistance to bacterial diseases. Mortality and autopsy lesions data indicate that the dw gene had a deleterious effect in the low weight but not in the high weight line, suggesting that its influence on the traits measured is dependent upon the genetic background of the population.

Immune response to Escherichia coli

Chickens from a line artifically selected for lew level of plasma corticosterone (LPC) produced higher antibody titers, produced antibody earlier, continued the production of antibody longer, responded to lower dosages of antigen, and had greater body weight gain than those from a line slected for a high level of plasma corticosterone (hpc). the HPC line resisted Escherichia coli challenge and antigen more effectively than the LPC line. It appears that, although the HPC line is more effective in its defense against bacterial infections, the LPC line can be aided more by vaccines.

INTERRELATIONSHIP OF COMB LOCI AND MATING BEHAVIOR IN CHICKENS

Qualitative and quantitative data obtained from lines of chickens divergently selected for male mating ability and from the unselected randombred control population were used to evaluate the relationship of comb type alleles and mating behavior. An apparent antagonistic relationship was found between the rose (R) allele and low cumulative number of completed matings in the low mating line, while the opposite association was found for the pea (P) allele. No association was found between alleles of the rose and pea loci and mating ability in the high mating or control lines. An antagonistic relationship was indicated between the rough (He+) allele and a high cumulative number of matings. These results support the hypothesis that two genetical systems interact to influence the mating frequency of male chickens and further suggest that alleles of the rose, rough, and pea loci should not be used as marker genes to estimate genetic drift in random mating populations maintained by natural matings.