Candling hatching eggs during incubation and breakout examination of the clear eggs or dead embryos are useful tools for hatchery managers to use in maintaining quality assurance and analyzing poor hatches. Other tools include monitoring the temperature of the egg storage room, incubator temperature, incubator humidity, shell quality, chick quality, hatching percentage, bacterial counts in air or on hatchery surfaces, and egg moisture loss during incubation. This publication illustrates various conditions that may be seen in eggs during candling and describes how to identify infertile eggs and early dead embryos during breakout. It is best used in conjunction with Common Incubation Problems: Causes and Remedies (ANR Publication 8127) and the video Hatching Egg Breakout (ANR Video V86-W) (see "For More Information" at the end of this publication). This publication also contains a glossary of technical terms.
Three experiments were conducted to determine whether dim light is interpreted by Japanese quail as subjective day or night, and whether this interpretation depends upon absolute light intensity. Birds were exposed to 24-h days consisting of either bright light (2500-3000 lx) with dim light (0.5-5 lx) or dim light with darkness. Locomotor activity was higher in the brighter photophase, whether it was bright light or dim light, indicating that the birds interpreted the brighter phase as daytime. Dim light produced daytime activity levels when paired with darkness, but it produced nighttime activity when paired with bright light, indicating that activity rhythms are determined by relative not absolute light intensity. Similarly, photostimulation, as measured by growth of the cloacal protrusion area (CPA), depended upon photic context, not absolute light intensity. CPA growth occurred when birds were exposed to 16 h of dim light with 8 h of darkness (16dm:8dk) but not when exposed to 10 h of bright light with 14 h of dim light (10bt:14dm). Constant dim light was stimulatory regardless of previous dim light context. Photostimulation appears to depend upon subjective interpretations of day and night rather than solely upon light intensity.
Chickens of various Oriental breeds (Shamo and Aseel) and crossbreeds in California's Central Valley were observed to have an unusual skin condition and feather loss. The appearance of white plaques on the comb, face, and/or ear lobes was followed by feather loss starting at the caudal base of the comb and progressing down the neck. Although the cocks were affected first, the condition spread to the hens paired with those cocks. The birds showed no other signs of illness. The affected areas were scraped and biopsied. The samples were examined histologically and by culturing on Sabouraud's dextrose agar and dermatophyte test medium. Microsporum gallinae, the causative agent of favus (avian dermatophytosis), was identified by the histological and mycological tests.
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