Genetic correlations between six- and seven-week-old broilers.

The genetic relationship between carcass traits in broiler chickens at 6 and 7 weeks of age was determined. Two-hundred and sixteen male broilers from 42 sires and 108 dams with 2 full sibs/dam were slaughtered at 41 and 48 days of age. One offspring per dam was slaughtered at each age. Means of 41-day-old birds are presented first and 48-day-old birds second: live weights 1435, 1872 g; carcass weights 877, 1200 g; abdominal fat weights 23.4, 41.7 g; percent abdominal fat/live weight 2.04, 2.22; percent abdominal fat/carcass weight 3.30, 3.47. Genetic correlations between weeks were: .58 (live weight), .66 (carcass weight), .48 (abdominal fat), .45 (% abdominal fat/live weight), and .42 (% abdominal fat/carcass weight). Records obtained on 6-week-old full sibs might be useful in a selection program to improve traits in 7-week-old birds.

Genetic variation of body temperature of Coturnix coturnix in two ambient temperatures.

Coturnix quail were placed in an environmental chamber maintained at 21 degree C. and rectal temperatures taken. The birds were subjected to an abrupt change to 36 degree C. and the temperatures taken hourly for eight hours and at 25, 38 and 72 hours. Females had higher temperatures than males. When birds were moved to 36 degrees C. their temperatures rose rapidly and then dropped to a level higher than when birds were in the 21 degrees C. chamber. The genetic and total variation estimated from the analysis of variance method decreased under this sudden thermal stress condition. Birds kept in 36 degrees C. for three weeks were shifted to 21 degrees C. Their body temperature dropped sharply and then increased to a level lower than that obtained in the 36 degrees C. environment. The genetic variation was essentially zero when shifted to a lower temperature while the total variation increased.

Relationship between fat in breast and thigh muscles and skin with abdominal fat from mated and unmated female Coturnix quail.

Coturnix quail chicks were hatched from randomly selected eggs and grown to adulthood. Forty-two mated and 13 unmated females were killed at 107 days of age. Correlations between abdominal fat and fat measured at different locations (breast, thigh, crop collar) were high. Percentage thigh fat was 1.3 times that of breast fat. There was no difference (P greater than .05) between mated and unmated female quail for percentage fat and moisture content of breast muscle and skin and percentage fat content of thigh muscle. A highly significant difference was found for percentage fat and percentage moisture content of wet thigh skin between mated and unmated birds. The phenotypic correlation between percentage moisture and fat content in the breast muscle was -.76 and was -.94 in the breast skin in both mated and unmated females. Coturnix quail may be used as a pilot animal in body composition research provided due caution is taken because of the difference between species.

Heritability and genetic correlations of body weight and surgically removed abdominal fat in Coturnix quail.

Thirty-seven male Coturnix quail were weighed (99 g) and anesthetized. The leaf fat (1.35 g) was surgically removed from these birds at 58 days of age. Ten days later, they were single-pair mated and produced 141 male and 137 female offspring. The offspring weighed 107 g (males) and 114 g (females) at 58 days of age and had 2.53 g (male) and 1.31 g (female) of leaf fat. Estimates of heritability of body weight were .74 +/- .21 (sire-son regression), .69 +/- .22 (sire-daughter regression), .67 +/- .18 (full-sib analysis for males), and .73 +/- .18 (full-sib analysis for females). Heritability estimates of leaf fat were .71 +/- .33 (sire-son regression), .58 +/- .34 (sire-daughter regression), .65 +/- .18 (full-sib analysis for males), and .33 +/- .17 (full-sib analysis for females). Genetic correlations between body weight and leaf fat using the sire-offspring relationship were .77 +/- .10 and .74 +/- .22 for sons and 1.01 and .90 +/- .06 for daughters when estimated by arithmetic and geometric methods, respectively. Corresponding genetic correlations from the full-sib analyses were .82 +/- .08 (males) and .55 +/- .21 (females). Environmental correlations were .80 +/- .11 (males) and .87 +/- .47 (females), and phenotypic correlations were .82 +/- .09 (males) and .64 +/- .28 (females). Males had the highest percent of fat (2.5%) as compared with females (1.2%), a reversal of the broiler chicken relationship. The surgical technique developed in this experiment might be used for estimating abdominal fat in young chicken broilers. It was concluded that Coturnix quail could be used as a pilot animal in abdominal fat research provided due caution was taken of the differences between the two species.

Body and abdominal fat weight reduction upon feed withdrawal in coturnix quail.

Coturnix quail are used for human consumption, and loss of live weight prior to slaughter must be minimized. Feed, but not water, was withdrawn from 49-day-old, male Coturnix quail for times (treatments) of 0, 6, 12, 24, and 48 hr. Number of quail per treatment ranged from 24 to 26. Body weight decreased as length of feed withdrawal increased, but the difference between treatments 12 and 24 was not significant (P greater than .05). The largest loss in abdominal fat weight (1.10 g) and percentage abdominal fat of body weight (.91%) was between Treatments 0 and 48. The lack of significance (P greater than .05) among Treatments 0, 12, and 24 indicates stability of abdominal fat during 24-hr feed withdrawal. These results indicate that body weight is affected more than abdominal fat weight by feed withdrawal in processing quail.

Heritability of live and abdominal fat weights in Coturnix quail.

Twenty-seven single-pair matings of Coturnix quail produced 48 sons and 50 daughters. Parents and progeny were reared under similar conditions and killed at 58 days of age. Live and abdominal fat weights were obtained. Heritability estimates from parent-offspring regressions ranged from .05 to .72 (live weight), .49 to .80 (abdominal fat weight), and .45 to .88 (percent abdominal fat/live weight). The high heritabilities for live weight (except sire-daughter regression) and for abdominal fat in Coturnix quail indicate that a selection method could be used to reduce fat and increase live weight.

Genetic variation of abdominal fat, body weight, and carcass weight in a female broiler line.

Pedigreed matings in a commercial purebred female broiler selection line produced 311 males and 341 females, which were slaughtered at 50 days of age. Coefficients of variation of abdominal fat weights were higher than live and carcass weights. The coefficient of variation was reduced when abdominal fat was regressed on live weight or when percentage of live or carcass weight was used. Leaf fat was approximately two-thirds and gizzard fat was approximately one-third of the total abdominal fat. Heritabilities for abdominal fat were high, and the genetic correlations between the fat and live or carcass weights ranged from .43 to .50 in males and .32 to .40 in females. The phenotypic correlations between fat and live weight were reduced when abdominal fat weight was subtracted from live weight, showing that the part-whole relationship between abdominal fat included in live body weight increased the correlations. The heritabilities indicate that it should be possible to reduce abdominal fat by selection, and the genetic correlations signify that a method has to be devised to increase body weight while simultaneously reducing abdominal fat weight.

Abdominal and carcass fat in five broiler strains.

Ten males and 10 females from each of five commercial broiler strains were weighed and slaughtered at 55 days of age. Over all, mean live body weight was 2112 g for males and 1702 g for females and abdominal fat was 2.9% (males) and 3.3% (females). Mean total fat in whole bird was 13.4% (males) and 15.1% (females). There were no statistically significant differences between strains at the 5% level. Correlation coefficients with percent abdominal fat were .29 for body weight (males) and .36 (females), for percent carcass fat .51 (males) and .77 (females), and for fat free carcass .26 (males) and .07 (females). Abdominal fat represented 22% of the total fat for males and females. The results obtained were similar to those found previously in this laboratory with one strain of broilers.

Comparison of predicted with actual body weight selection gains of Coturnix coturnix japonica.

Results of nine generations of individual selection for six-week large and small body weight of Japanese quail (Coturnix coturnix japonica) are reported. The objectives of this study were three-fold: 1) To estimate genetic variation of body weight of Coturnix quail at six weeks; 2) To predict selection gains when selecting on an individual basis for large and small body weight; and 3) To conduct a selection program for large and small females and males, respectively, with greater response in the positive direction. Generally the actual gain was predicted more accurately in the females than in the males.