This study was designed to examine the influence of dietary protein and restricted feeding on body composition of Japanese quail at the onset of lay. The first experiment utilized five isocaloric diets containing either 26%, 24%, 20%, 16%, or 14% crude protein. Each diet was fed to three groups of quail: one group was fed <i>ad libitum</i>, a second group was fed 80% of <i>ad libitum</i>, and the third was fed 60% of <i>ad libitum</i> intake. Age at the onset of lay was successfully delayed. The quail fed the lower protein levels entered lay at later ages than those fed the high protein diets. Likewise, the restricted fed groups achieved lay at later ages than the <i>ad libitum</i> fed groups. Other traits examined in this experiment including body weight, breast weight, abdominal fat pad weight, carcass lipid and shank length produced inconsistent results. The final experiment incorporated identical diets and feeding regimes as the previous study. Age at the onset of lay was influenced by dietary protein level and feeding regime. The dietary protein level by feeding regime interaction was also significant. The groups fed the higher protein diet <i>ad libitum</i> tended to enter lay at younger ages than did the groups fed restricted amounts of the diets containing less protein. The other traits measured were more consistent than in the first experiment. The early maturing quail tended to enter lay with heavier body weights1 larger breast percentage and lower carcass lipid percentages. The last groups to achieve lay did so with lower breast weight percentages and higher carcass lipid percentages. Shank length, or skeletal growth, also may have been an important factor in the onset of lay. This effect was apparently independent of lean tissue. Adipocyte cellularity measurements were inconsistent. Body composition differences were apparent as age at the onset of lay was increased by dietary manipulations. It was speculated that early maturing quail reach oviposition when a minimum chronological age or "critical" lipid level was reached. The late maturing quail entered lay when a "critical" lean percent or skeletal size was attained. The intermediate maturing quail, like the late maturers, achieved oviposition when percent lean or skeletal size reached "critical" levels. Thus, one of these four factors appeared limiting for each group to achieve lay. The attainment of the critical level of the limiting trait allowed the quail to achieve sexual maturity. / M.S.

A genetic selection study to determine the effects on egg hatchability and subsequent chick performance of Japanese quail (Coturnix japonica) eggs incubated at 100 F dry bulb temperature (Control, Line C) when compared to other eggs incubated at 102 F (Selected, Line S) was conducted over 10 consecutive generations. Eggs from a randomly mated population (designated as Generation 0) of Japanese quail maintained at the Oregon Agricultural Experiment Station were randomly allocated to two treatment groups (Lines C and S) and incubated at the different temperatures in separate but identical Jamesway 252 machines. On day 14 of incubation all eggs were transferred to a common hatcher (98.5 F). Using family-based selection, the chicks that hatched from the two lines were subsequently used as breeders (25 paired matings per line) and the resulting eggs from each line incubated at their respective temperatures for 10 consecutive generations. Following the 10th generation percent egg fertility and percent hatch of fertile eggs were greater in Line C vs. Line S (p<O.O3 and p<O.0001, respectively). Embryo development time was shortened in Line S by 24 hours and mean 4- or 5- week body weights were greater (p<0.001) in Line S. Ten-day post-hatch mortality increased greatly in Line S vs. Line C after generation 6 (p<0.001) and hen-day egg production decreased after generation 4 in Line S vs. Line C (p<0.0001). The results indicate that embryo development time can be reduced by high temperature incubation, but at the expense of reproductive traits such as egg production, fertility, and hatchability of fertile eggs. / Graduation date: 2005