BREEDING AND GENETICS Divergent Selection for Growth in Japanese Quail Under Split and Complete Nutritional Environments. 5. Feed Intake and Efficiency Patterns Following Nineteen Generations of Selection H. L. MARKS USDA, Agricultural Research Service, Southeast Poultry Research Laboratory, do University of Georgia, 107 Livestock-Poultry Building, Athens, Georgia 30602 (Received for publication August 6, 1990)
1991 Poultry Science 70:1047-1056 INTRODUCTION
relative growth rate are unknown. An understanding of the causes of these reciprocal shifts may provide insight into growth related mechanisms. The purpose of the present study was to examine changes in feed intake and feed efficiency accompanying changes in relative growth rate patterns prior to and following the age at selection in quail lines divergently selected for 4-wk body weight.
Divergent selection for 4-wk BW in Japanese quail under complete-diet (CD) and splitdiet (SD) environments resulted in dramatic shifts in BW during the first 11 generations (Darden and Marks, 1988a) and also during Generations 12 to 20 (Marks, 1991). Nestor et al. (1982) reported that selection under a CD also resulted in rapid initial responses to bidirectional selection for 4-wk BW in Japanese quail. Marks (1989) observed a continued MATERIALS AND METHODS response for high 4-wk BW in Japanese quail Because it was not feasible to obtain over 70 generations; however, responses decreased across generations. Selection for sufficient numbers of quail from a single hatch high 4-wk BW increased the relative growth for simultaneous evaluation under both selection environments, quail progeny from breedrate to 2 wk of age (Marks, 1978). Less clear, however, were changes that ers following 17 (S17) and 19 (S19) generations occurred in growth patterns from 4 wk of age of selection were used for evaluations under to maturity. Darden and Marks (1988a) found CD and SD environments, respectively. The that, during the period prior to selection (0 to 4 CD environment allowed quail to consume ad wk), the relative growth rates of quail in the libitum a standard 28% protein game bird diet, high (H) line were superior to those in me low whereas the SD environment allowed quail to (L) line; however, from 4 to 16 wk of age the self-select feed from two diets, one high in relative growth rates of L-line quail were two- protein (47% CP and 2,351 kcal/kg ME) and to fourfold higher man those of H-line quail. the other high in energy (9% CP and 3,332 Mechanisms responsible for these shifts in kcal/kg ME) (Darden and Marks, 1988a). 1047
Downloaded from http://ps.oxfordjournals.org/ at University of Bath, Library on June 29, 2015
ABSTRACT High (H) and low (L) quail lines divergently selected for 4-wk BW under complete-diet (CD) and split-diet (SD) environments were evaluated to examine changes in feed intake and feed efficiency before and after the age at selection. Progeny from the four quail lines (H-SD, L-SD, H-CD, L-CD) were fed the CD in Generation 17 and the SD in Generation 19. The BW of H-line quail were highest under their respective selection environments, and the BW of quail in the L lines were highest under reciprocal environments. However, the B W of the two H lines were similar as were those of the two L lines. Relative growth rates of Hline quail were superior to those of L-line quail for the first2 wk posthatch but L-line rates were superior after Week 4. However, the B W of H-line birds were always higher than for the L-line birds. Adjusted feed intake (grams of feed per 100 g of BW) values for the H lines were similar but lower than values for the L lines. Differences in adjusted feed intake between the H and L lines from 1 to 10 wk remained constant, although adjusted feed intake declined with age in all lines. Feed efficiencies (grams of gain + grams of feed) were superior in the H lines for Weeks 1 through 3 and superior in the L lines for Weeks 5 through 9. The same relative shifts between lines were observed in relative growth rates. Therefore, feed efficiency, in addition to feed intake, appears to play an important role in the divergence of BW in the H- and L-quail lines. (Key words: divergent selection, body weight, feed intake, feed efficiency, nutritional environments)
1048
MARKS
Experiment 1: Evaluation Under Complete Diet
Experiment 2: Evaluation Under Split Diet
Yijk = u, + Gi + Sj + r k + GSij + Gr^ + Srjk + GSrijk + e ^ where \i is me common mean; Gj is the effect of the i* genotype (line); Sj is the effect of the j 0 1 sex; rk is the effect of the k* replication; GSy is the effect of the interaction of the i^1 genotype with the j * sex; Gr^ the effect of the interaction of the i m genotype with the k * replication; and Srjk the effect of me interaction of the j * sex with the k01 replication; GSr is the interaction of the i* genotype with the j * sex with the k"1 replication, and e ^ is random error. Feed intake and feed efficiency data were analyzed by the same model with genotype as the only variable. The model for analyses of BW at slaughter and abdominal fat weights included line and sex as main effects, whereas the analyses for testes data included only line as a variable. The General Linear Model (GLM) procedure of the SAS Institute (1985) was utilized for the analyses with means compared by using Duncan's multiple range test. Statements of significance are P
1991 Poultry Science 70:1047-1056 INTRODUCTION
relative growth rate are unknown. An understanding of the causes of these reciprocal shifts may provide insight into growth related mechanisms. The purpose of the present study was to examine changes in feed intake and feed efficiency accompanying changes in relative growth rate patterns prior to and following the age at selection in quail lines divergently selected for 4-wk body weight.
Divergent selection for 4-wk BW in Japanese quail under complete-diet (CD) and splitdiet (SD) environments resulted in dramatic shifts in BW during the first 11 generations (Darden and Marks, 1988a) and also during Generations 12 to 20 (Marks, 1991). Nestor et al. (1982) reported that selection under a CD also resulted in rapid initial responses to bidirectional selection for 4-wk BW in Japanese quail. Marks (1989) observed a continued MATERIALS AND METHODS response for high 4-wk BW in Japanese quail Because it was not feasible to obtain over 70 generations; however, responses decreased across generations. Selection for sufficient numbers of quail from a single hatch high 4-wk BW increased the relative growth for simultaneous evaluation under both selection environments, quail progeny from breedrate to 2 wk of age (Marks, 1978). Less clear, however, were changes that ers following 17 (S17) and 19 (S19) generations occurred in growth patterns from 4 wk of age of selection were used for evaluations under to maturity. Darden and Marks (1988a) found CD and SD environments, respectively. The that, during the period prior to selection (0 to 4 CD environment allowed quail to consume ad wk), the relative growth rates of quail in the libitum a standard 28% protein game bird diet, high (H) line were superior to those in me low whereas the SD environment allowed quail to (L) line; however, from 4 to 16 wk of age the self-select feed from two diets, one high in relative growth rates of L-line quail were two- protein (47% CP and 2,351 kcal/kg ME) and to fourfold higher man those of H-line quail. the other high in energy (9% CP and 3,332 Mechanisms responsible for these shifts in kcal/kg ME) (Darden and Marks, 1988a). 1047
Downloaded from http://ps.oxfordjournals.org/ at University of Bath, Library on June 29, 2015
ABSTRACT High (H) and low (L) quail lines divergently selected for 4-wk BW under complete-diet (CD) and split-diet (SD) environments were evaluated to examine changes in feed intake and feed efficiency before and after the age at selection. Progeny from the four quail lines (H-SD, L-SD, H-CD, L-CD) were fed the CD in Generation 17 and the SD in Generation 19. The BW of H-line quail were highest under their respective selection environments, and the BW of quail in the L lines were highest under reciprocal environments. However, the B W of the two H lines were similar as were those of the two L lines. Relative growth rates of Hline quail were superior to those of L-line quail for the first2 wk posthatch but L-line rates were superior after Week 4. However, the B W of H-line birds were always higher than for the L-line birds. Adjusted feed intake (grams of feed per 100 g of BW) values for the H lines were similar but lower than values for the L lines. Differences in adjusted feed intake between the H and L lines from 1 to 10 wk remained constant, although adjusted feed intake declined with age in all lines. Feed efficiencies (grams of gain + grams of feed) were superior in the H lines for Weeks 1 through 3 and superior in the L lines for Weeks 5 through 9. The same relative shifts between lines were observed in relative growth rates. Therefore, feed efficiency, in addition to feed intake, appears to play an important role in the divergence of BW in the H- and L-quail lines. (Key words: divergent selection, body weight, feed intake, feed efficiency, nutritional environments)
1048
MARKS
Experiment 1: Evaluation Under Complete Diet
Experiment 2: Evaluation Under Split Diet
Yijk = u, + Gi + Sj + r k + GSij + Gr^ + Srjk + GSrijk + e ^ where \i is me common mean; Gj is the effect of the i* genotype (line); Sj is the effect of the j 0 1 sex; rk is the effect of the k* replication; GSy is the effect of the interaction of the i^1 genotype with the j * sex; Gr^ the effect of the interaction of the i m genotype with the k * replication; and Srjk the effect of me interaction of the j * sex with the k01 replication; GSr is the interaction of the i* genotype with the j * sex with the k"1 replication, and e ^ is random error. Feed intake and feed efficiency data were analyzed by the same model with genotype as the only variable. The model for analyses of BW at slaughter and abdominal fat weights included line and sex as main effects, whereas the analyses for testes data included only line as a variable. The General Linear Model (GLM) procedure of the SAS Institute (1985) was utilized for the analyses with means compared by using Duncan's multiple range test. Statements of significance are P
