Recent studies on fluctuating dental asymmetry have isolated single stressors as causative agents. Since most stressors are composite in nature, the present study was designed to determine the effects of the interaction of stressors in the induction of fluctuating dental asymmetry. Pregnant rats were assigned to one of six treatment groups and stressed with various combinations of heat, cold, noise and protein deprivation. The levels of fluctuating dental asymmetry were assessed and it was found that all protocols produced higher levels of asymmetry than found for control animals. Noise and reduced protein exhibited an additive effect and the interaction of stressors produced a reduction in litter size. Suggestions were offered for further research in this expanding field.
An experiment was conducted to measure the effects of exposure to heat or cold during incubation on the size of skeletal bilateral traits (face, wings, shank, tibia, and femur) and weights of heart and lungs of broiler embryos. Measurements were obtained at 10 and 18 d of incubation and at hatch on d 21. Treatments consisted of eggs incubated at 37.8 degrees C throughout (control; C), cooled to 36.9 degrees C for 6 h daily from d 0 to 8 (C0-8), heated to 39.6 degrees C for 6 h daily from d 0 to 8 (H0-8), cooled to 21.0 degrees C for 24 h on d 14 (C14), cooled to 36.9 degrees C for 6 h daily from d 10 to 18 (C10-18), and heated to 39.6 degrees C for 6 h daily from d 10 to 18 (H10-18). Although cooling and heating of eggs during incubation influenced growth of the skeletal traits on d 10 and 18, compensation generally occurred by the time of hatch. The developmental stability of bilateral traits varied with the specific trait, with those observed earlier in incubation tending to decrease by hatch.
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.
Comparisons of age, food intake, body weight and body composition at the onset of sexual maturity were made between dwarf and normal chickens from lines selected for high or low juvenile body weight. At the same age birds which had started to lay were significantly heavier and contained significantly more abdominal and carcass fat than those which were not laying. Differences between normal and dwarf pullets within lines varied with genetic background, indicating differences between lines in meeting a body weight or a body composition requirement, or both, for the onset of sexual maturity.
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)
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