GENETIC ASSOCIATIONS OF UNCOLLECTABLE EGG PRODUCTION WITH OVULATION RATE, EGGSHELL DEPOSITION, AND ERRATIC TIMING OF OVIPOSITION IN WHITE LEGHORN HENS
Abstract
Possible genetic causes of uncollectable eggs (soft-shelled and shell-less eggs) were studied in a randombred flock of White Leghorn hens. One hypothesis stated that uncollectable eggs were formed when the ovulation rate exceeded the bird's ability to deposit sufficient shell on the egg. The genetic correlation between the number of uncollectable eggs (UC) and the number of ovulations (OV) was high and positive. The genetic correlation between UC and the average shell deposition per ovulation (SD) was small. The environmental correlation between UC and SD was large and negative. Thus, UC and SD were associated only through environmental influences. A second hypothesis proposed that erratic timing of ovulation was the cause of uncollectable eggs. The genetic correlation between the number of days when both a hard-shelled egg and uncollectable egg were laid (DO) and UC was very high. This high genetic correlation implied that the traits of DO and UC were controlled by the same genes. The environmental correlation between UC and DO was high and positive. Thus, uncollectable eggs appeared to be caused by the erratic timing of ovulation. The erratic nature appeared to be mainly under environmental control, due to the low heritability of DO.
Degree
Ph.D.
Subject Area
Genetics|Livestock
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