Effects of strain and rearing dietary regimens on brown-egg pullet growth and strain, rearing dietary regimens, density, and feeder space effects on subsequent laying performance

The objective of this experiment was to compare the growth and development of two brown-egg strains when grown on three different dietary regimens, i.e., a "normal" step-down protein (SDP) regimen, a step-up protein regimen with a low energy starter (SUPLES), and a step-up protein regimen with a high energy starter (SUPHES). The SUPLES and SUPHES feeding regimens resulted in significantly lower BW and feed conversion, shorter sternum length, and lower tibial breaking strength than the SDP regimen. The weights of the liver, spleen, and fat pad were not different among the three regimens. The high energy starter in the SUPHES regimen significantly reduced FC below that obtained with the SUPLES program. The SUPHES regimen significantly reduced total feed cost compared with the other two feeding regimens. Both step-up protein regimens reduced total protein, energy, Ca, P, lysine, and sulfur amino acid consumption. Because tibial breaking strength was also reduced by the step-up protein regimens, the data suggest that the levels of dietary Ca and P should be increased with these programs to compensate for the reduced consumption associated with them.

Egg characteristics, carbohydrate metabolism, and thyroid hormones in late chick embryos from different genetic lines

Functional eggshell qualities, thyroid hormones, and carbohydrate metabolism of chick embryos at the end of incubation were compared between a modern (Arbor Acres line) and a randombred control population (Athens-Canadian Randombred). Embryos from the Arbor Acres genetic line developed in larger eggs with more albumen and less yolk than Athens Canadian Randombred lines. Percentage shell and functional eggshell properties measured as eggshell conductance constants did not differ between genetic lines. On a relative basis, hearts were generally smaller and livers heavier in Arbor Acres than in Athens-Canadian Randombred birds. Heart and liver glycogen concentrations were greater in Athens-Canadian Randombred than in Arbor Acres embryos. However, blood glucose was greater in Randombred than in Arbor Acres embryos only at internal pipping, a time of hypoxia and hypercapnia. Blood plasma concentrations of thyroxine did not differ significantly between the modern and Randombred embryos at any stage examined. Modern broiler chick embryos possessed greater concentrations of triiodothyronine as well as greater triiodothyronine to thyroxine ratios than Randombred embryos at external pipping and hatching. It can be inferred from the data that chick embryos differ in their use of carbohydrate during late development between modern and Randombred genetic lines.

Relationship of sex, strain, and body weight to carcass yield and offal production in turkeys

Three strains of male and female market turkeys (British United Turkeys, Hybrid, and Nicholas) were grown under commercial contract production conditions and slaughtered at a range of BW (4,200 to 17,640 g) and age (13 to 22 wk) that covers the range of commercial market weights in use at the time of the study. During processing, the weight of blood, feathers, head, neck, feet plus shanks, heart, liver, gizzard, lungs, gastrointestinal tract, water uptake, hot and chilled carcass with fat pad, fat pad alone, tail, wings, drumsticks, thigh meat, Pectoralis major, Pectoralis minor, scapula meat, lower back, upper back with ribs, breast skin, thigh skin, thigh bone, and hind half (legs, thighs, and saddle) were determined. The data were subjected to least squares analyses using models that included strain and sex effects relative to live BW. Significant differences in yield between the sexes but not among strains were found for feet plus shanks, gizzard, hot and chilled carcass with fat pad, and scapula meat. Similarly, significant differences in yield among strains but not between sexes alone were found for blood, feathers, heart, and hind half. The relationships of live BW with all other variables showed both strain and sex differences in yield. Whereas whole carcass yield as a function of BW was affected by sex alone, most other components varied by both sex and strain. Thus, choice of strain, sex, and age at slaughter affect the projected production of edible carcass and offal components.

Growth, livability, and feed conversion of 1957 vs 1991 broilers when fed "typical" 1957 and 1991 broiler diets

The relative contributions of genetic selection and dietary regimen on the performance of broilers was assessed. Body weight, feed consumption, mortality (M), and the degree of tibial dyschondroplasia (TD) were measured in the 1957 Athens-Canadian Randombred Control (ACRBC) strain of broilers and in the 1991 Arbor Acres (AA) feather-sexable strain when fed "typical" 1957 and 1991 diets. Energy and protein levels, vitamin and mineral packs, and the coccidiostats used in the two dietary regimens were chosen to be representative of those in use by the industry for the two time periods. Eight treatment groups, i.e., two strains, two sexes, and two dietary regimens, were assigned into four blocks of eight litter floor pens for grow out. The 1957 diets were fed as mash, and the 1991 starter and grower diets were fed as crumbles and pellets, respectively. Feed consumption and BW were recorded at 21, 42, 56, 70, and 84 d of age, a period covering the normal marketing ages for the two broilers. Mortality and the cause of death was recorded daily. The incidence and severity of TD was assessed using a Lixiscope at 42 d of age. Average BW were 190, 508, 790, 1,087, and 1,400 g for the ACRBC on the 1957 diets vs 700, 2,132, 3,108, 3,812, and 4,498 g for the AA on the 1991 diets at 21, 42, 56, 70, and 84 d of age, respectively. The 1991 diets increased the BW of the AA by an average of 14% (20% at 42 d, but only 8% at 84 d) and of the ACRBC by 22%. The BW advantage for the 1991 diet over the 1957 diet for the AA was less for males than for females after 42 d of age, and the advantage decreased with age, probably due to the increasing incidence of leg problems. The M for AA was 9.1% vs 3.3% for the ACRBC at 42 d. Most of the ACRBC M occurred before 21 d, whereas M occurred throughout for the AA, with most after 21 d due to flip-overs and ascites. The feed conversion at 42 d for the ACRBC on the 1957 diet was 3.00 vs 2.04 for the AA on the 1991 diet. The AA on the 1991 diet had a 48.6% incidence of TD vs 25.6% on the 1957 diet. The ACRBC had approximately 1.2% TD on both diets. The TD was more severe with the 1991 diet.

A comparison of the immune performance of a 1991 commercial broiler with a 1957 randombred strain when fed "typical" 1957 and 1991 broiler diets

The general objective of the present study was to assess the contribution that changes in genetic selection and dietary regimen have made on the immune performance of broilers. Chicks were hatched from 1991 and 1957 strains and placed on diets thought to be typical of those fed during 1957 and 1991. Immune responses were measured as total, IgM, and IgG antibody production, macrophage, and natural killer (NK) cell functions. Significant differences were observed between strains in antibody production. For example, 1957 males fed 1957 diets had the highest total (P < .0001), IgM (P < .0016), and IgG (P < .015) anti-sheep red blood cell antibodies as compared with all other strain-diet-sex groups. Both strains behaved similarly in terms of inflammatory macrophage recruitment, substrate adherence potential, and in the phagocytosis of sheep red blood cells. A greater percentage of the 1991 strain birds exhibited NK cell activity than all other groups. These studies suggest that genetic selection towards enhanced performance traits has negatively influenced the adaptive arm of the immune system (antibody production) with little or no effect on the nonadaptive components (macrophage and NK functions).

Carcass composition and yield of 1991 vs 1957 broilers when fed "typical" 1957 and 1991 broiler diets

Whole carcass yield and the yield of parts (i.e., wings, saddle and legs, Pectoralis major, Pectoralis minor, breast skin, rack, abdominal fat pad, heart, and lungs), as well as whole carcass analysis for fat, moisture, and ash, were measured in the 1957 Athens-Canadian Randombred Control (ACRBC) and in the 1991 Arbor Acres (AA) feather-sexable strain, when fed "typical" 1957 and 1991 diets. Using the average of both sexes, the carcass weights of the 1991 birds on the 1991 diets were 4.4, 3.9, and 3.5 times heavier than those from the 1957 ACRBC on the 1957 diet at 43, 71, and 84 d of age, respectively. Birds fed the 1991 diets had significantly heavier carcass weights than those fed the 1957 diets. Hot carcass yield of the AA broiler (mean of both sexes) was approximately 6 to 7% higher at the same age than for the ACRBC. Water uptake in the carcass (following a 60-min immersion in ice water) was approximately 2 to 2.5% higher in the ACRBC than in the AA broiler. Yield of saddle and legs as a percentage of live BW was about 4% higher in the AA than in the ACRBC. Dietary regimen did not affect the yield of saddle and legs. Males had 2 to 3% more saddle and legs than the females. The yield of total breast meat for the AA was approximately 3% higher (mean = 16.9%) than for the ACRBC over both sexes and all ages. Breast yield on the 1991 diets was approximately 1.2% higher for the AA than for the ACRBC. Females had slightly higher breast yield (1%) than males. The AA broiler had consistently heavier fat pads and higher percentage carcass fat at the same age and on the same diet than did the ACRBC. The percentage carcass fat was significantly higher on the 1991 vs the 1957 diet and in females vs males. The male-female difference in percentage carcass fat increased with age. Heart and lung size as a percentage of live BW were lower in the AA than in the ACRBC.

Effects of genetic strain and light management on the reproductive performance of turkeys

The laying performance of six genetic strains of turkeys, which have been bred and maintained at the Ohio Agricultural Research and Development Center, Wooster, OH, was compared under three laying house lighting regimens over a period of 3 yr. Light Treatment 1 (L1) consisted of 14 h of continuous light (L) and 10 h of dark (D; 14L:10D) throughout the laying period. Treatment 2 (L2) consisted of 14 h of intermittent light (IL, 15 min L and 45 min D/h) followed by 10 h of continuous dark. The IL treatment was started following a period (6 wk) in which the hens were trained to use the trapnests. Thus, during the first 6 wk of their laying period, L2 hens were also provided 14L:10D. Treatment 3 (L3) hens were provided the same program as L1 for the first 14 wk of the laying period. They were then moved to a continuous period of 19L:5D for the remainder of the laying period. All eggs produced were recorded through 180 days after the first egg was laid. Traits studied included: the number of days to first egg after light stimulation; the number of eggs produced through 84, 120, and 180 days after the first egg was laid; the average clutch length; the maximum clutch length; the total days lost to broodiness; the rate of lay; and the effective length of the laying period. Highly significant differences (P less than or equal to .01) were observed among the strains used for all traits measured. Light treatments showed no significant effects on any trait measured. Thus, from the present studies, the delayed IL program provides an economically attractive management program for environmentally controlled turkey breeder houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic and phenotypic relationships in Japanese quail. 1. Body weight, carcass, and organ measurements

Live BW, carcass data, and organ data taken at 34 days of age on approximately 1,000 quail of both sexes from 110 sires and 290 dams were utilized to estimate genetic parameters from the initial generation of a selection study. The birds represented a sample of a line selected for high 4-wk BW. Data were analyzed using Henderson's Method 3 (MM3) and restricted maximum likelihood (REML) with and without a relationship matrix. The paternal half-sib heritabilities for body, carcass, and organ weights in Japanese quail were moderate to high for most traits studied, suggesting that selection to increase or decrease these traits should be successful. With the exception of BW, abdominal fat (AF), and heart weights, maternal half-sib heritability estimates were smaller than paternal half-sib estimates. Heritability estimates of traits adjusted for BW tended to be lower than counterparts not adjusted for BW. The genetic correlations of BW with the other carcass measurements were positive, and tended to be moderate to high. The correlation of BW with AF was .34, suggesting that selection for increased BW alone will lead to a bird with more abdominal fat. The correlations of AF with the other traits tended to be low to moderate in magnitude, with three of the correlations being negative, suggesting correlated responses with other traits when selecting for increased or decreased AF would be small. Genetic correlations among various muscle measurements were all positive and most were high in magnitude, indicating that traits easiest to measure and collect can be used in a selection process. The genetic correlations among the organ measurements were positive and moderate as were the correlations of organ weights with muscle weights. Negative genetic correlation estimates between AF and muscle measures were obtained from analysis when BW was a covariate. The REML heritability estimates were higher than MM3 estimates and REML genetic correlation estimates were less extreme than MM3.

Estimates of genetic parameters in turkeys. 3. Sexual dimorphism and its implications in selection procedures

Live, carcass, and skeletal data taken at 16 wk of age on 504 female and 584 male turkeys from 34 sires and 168 dams were utilized to evaluate sex differences in genetic parameter estimates. Data were transformed to common mean and variance to evaluate possible scaling effects. Genetic parameters were estimated from transformed and untransformed data. Further analyses were conducted with a model that included sire by sex and dams within sire by sex interactions, and the variance estimates were used to calculate genetic correlations between the sexes and genetic regression parameters. Heritability estimates from transformed and untransformed data were similar, indicating that sex differences were present in the genetic parameters, but scaling effects were not an important factor. Genetic correlation estimates from paternal (PHS) and maternal (MHS) half-sib estimates were close to unity for BW (1.14, PHS; 1.09, MHS), shank width (.99, PHS; .93, MHS), breast muscle weight (1.23, PHS; 1.04, MHS), and shank length (1.09, PHS; .97, MHS). However, abdominal fat (.79, PHS; .59 MHS), total drumstick muscle weight (.75, PHS; 1.14, MHS), rough cleaned shank weight (.78, PHS; not estimatable, MHS), and shank bone density (1.00, PHS; .53, MHS) estimates were somewhat lower. The estimates suggest that the measurement of these latter "traits" at the same age in the two sexes may, in fact, be measuring different genetic effects and that selection procedures in turkeys need to take these correlations into account in order to make optimum progress. The genetic regression parameters indicated that more intense selection in the sex that has the smaller genetic variation could be practiced to make greater gains in the opposite sex.

Infectious bursal disease virus variant from commercial Leghorn pullets

An infectious bursal disease virus (IBDV) was isolated from 39-to-43-day-old commercial leghorn pullets suspected of having infectious bursal disease (IBD). These chickens had been vaccinated with a commercial live IBDV vaccine at 28 and 35 days of age. An isolate designated IN was recovered using specific-pathogen-free (SPF) chickens and the BGM-70 established cell line. Experimental studies using SPF chickens vaccinated with either inactivated vaccines made from the vaccine strain used in the problem flock or a standard-type vaccine indicated no protection against the IN isolate. However, two variants and another standard-type vaccine induced protection against the IN isolate. Cross-neutralization tests indicated that the IN isolate differed antigenically from commercial vaccine strains and was related to the variant IBDV strains recently isolated from broilers. To our knowledge, this is the first report of a variant IBDV recovered from commercial layer chickens in the United States.

Effects of genetic strain, slow versus rapid-feathering maternal genotype, and cage density on the performance of Single Comb White Leghorns

Two hatches involving 11,158 pullets from 22 Single Comb White Leghorn strain crosses were used in these experiments: 13 from rapid-feathering (k+/-) and 9 from slow-feathering (K/-) dams, some of which shared common genetic backgrounds; and all from 5 homozygous k+ sire types. Birds were grown intermingled within hatch, and were subsequently caged in two laying houses, one with 30.5 cm x 40.6-cm cages and the other with 40.6 cm x 30.5-cm cages, at densities of three or four birds/cage. Data were collected by cage on hen-day rate of lay from 50% production to 52 wk of age; (HD%), number of eggs produced per hen housed (EHH), percentage mortality (%M) to 52 wk of age; 35-wk BW (BW35); egg weight (EW34), specific gravity (SG34), and percentage bloodspots (BS%34) at 34 wk of age. The effects of hatches or house (H), density (D), maternal feathering type (MFT), genetic strain within MFT (GS/MFT), bank level within house (BL/H), and all possible interactions were included in the analysis model. Hatch, house, and cage type were completely confounded, so no general conclusion can be made concerning the effects of the reverse and standard cages on performance. The H effects were significant for all traits except HD%. Cage D significantly affected all traits except SG34 and BS%34. Pullets housed at three/cage weighed 26 g less, produced 5.5 more eggs that were .3 g/egg lighter, laid at a 1.7% higher hen-day rate, and had 3.6 less %M from 20 to 52 wk of age than those housed at four/cage. The MFT significantly affected all traits except %M, SG34, and BS%34. The k+/- daughters from K/- dams weighed 34 g less, produced at a 2.8% lower HD%, laid 6.9 fewer eggs, which eggs averaged .6 g/egg less than the eggs from the k+/- daughters of the k+/- dams. Interactions were in general small and nonsignificant. However, the H x GS/MFT interactions were significant for HD%, EHH, BW35, %M, and EW34 (P less than .05); their significance is suggestive of the presence of genotype x environment interactions.

Effects on turkey mortality and body weight of type of beak trimming, age at trimming, and injection of poults with vitamin and electrolytes solution at hatching

This study was designed to determine the influence of: 1) age at and type of beak trimming (BT), and 2) injection of poults at hatch with 2 mL of a commercial mineral and vitamin solution versus noninjection of poults on the viability and growth rate of turkeys to market age. Mortality from 0 to 20 wk of age and BW at 8, 16, and 20 wk of age were recorded. At hatch, poults were BT 1.0 mm (Experiment 1) or 1.5 mm (Experiment 2) anterior to the nostril using an electric arc beak trimmer. In a second treatment (Experiments 1 and 2), one-third to one-half of the beak was removed at 11 days of age with a hot blade beak trimmer. In Experiment 1, offspring from three large-bodied crosses were used whereas in Experiment 2 birds were from a single large-bodied cross. The BT at 1.0 mm anterior to the nostril with an electronic beak trimmer (Experiment 1) increased mortality and decreased BW at 8, 16, and 20 wk of age relative to BT at 11 days of age with the hot blade beak trimmer. The BT at 1.5 mm (Experiment 2) at hatching did not affect mortality and reduced BW only at 8 wk of age relative to BT at 11 days of age. The use of an injectable commercial vitamin-mineral solution did not influence mortality in either experiment and significantly increased BW only at 8 wk of age in Experiment 2. The interactions of strain cross with either age of BT or injection vs. noninjection of poults were NS in Experiment 1.

Response of two lines of turkeys to challenge with Pasteurella multocida

Two lines of turkeys were challenged with Pasteurella multocida during three trials. The two lines were 1) a randombred control line (RBC1), and 2) a subline (E) of Line RBC1 selected for increased egg production. Each trial differed as to the age at which poults were challenged. In Trial 1, unvaccinated birds were subcutaneously inoculated with P. multocida at 6 wk of age. In Trial 2, poults vaccinated (on the back of the neck) at 7 and 9 wk of age with .5 mL of P. multocida bacterin and unvaccinated poults were challenged at 11 wk of age. Trial 3 was similar to Trial 2, except that poults were vaccinated at 8 and 10 wk of age and challenged at 12 wk of age. Line E had significantly (P less than .05) higher mortality than Line RBC1 (66.7 vs. 31.8%) in Trial 1. In Trials 2 and 3, unvaccinated birds of Line E had higher mortality than unvaccinated birds of Line RBC1; however, differences between lines were not significant in either trial. Significantly lower levels of mortality were observed for vaccinated poults than for unvaccinated poults in the second and third trials, where birds were vaccinated and challenged at older ages.

Estimates of genetic parameters in turkeys. 2. Body weight and carcass characteristics

Data were taken from 1,088 individuals--504 females (F) and 584 males (M)--produced by 34 sires and 168 dams from a randombred control line (RBC2) of turkeys maintained at the Ohio Agricultural Research and Development Center, Wooster, OH. Turkeys were used to estimate genetic and phenotypic parameters among 16-wk body weight and a number of body composition characteristics. Heritabilities (h2) were estimated from sire components of variance for 16-wk weights of muscles of breast (BM: F = .08, M = .35); thigh (TM: F = .12, M = .17); and drum (DM: F = .30, M = .44); weights of leaf fat (LF: F = .13, M = .51) and total abdominal fat (AF: F = .21, M = .55); and total percentage carcass fat (%F:F = .06, M = .24), percentage protein (F = .07, M = .20), and percent moisture (F = nonestimable, M = .11). The h2 of percentage carcass ash was nonestimable from both data sets due to negative estimates of the sire variance components. Due to the non-normal distributions of some of the fat measures, the fat measure data were converted to natural logarithms. Genetic estimates from the transformed data were similar to those from the nontransformed data. Genetic correlation (rG) estimates indicated a positive genetic association between body weight (BW) and all the fat characteristics measured. The BW was highly correlated with BM (F = .48, M = .86), TM (F = .81, M = 1.01), and DM (F = 1.04, M = .70). However, BW was correlated to a lesser degree with LF (F = .02, M = .27), AF (F = .25, M = .32), and %F (F = .93, M = .50). The BM was only moderately correlated with TM (F = .43, M = .28) and DM (F = .73, M = .27). The TM and DM were highly correlated (F = 1.02, M = .84). The existence of these correlations, which are less than unity, indicate that selection for BW alone will lead to increasing levels of fat in commercial turkeys, and to disproportionate increases in breast vs. leg muscles.

Antibody response to Newcastle disease virus and Pasteurella multocida of two strains of turkeys

The primary and secondary response to Newcastle disease virus (NCDV) and Pasteurella multocida (PM) of two turkey lines were studied following vaccinations with either NCDV or PM alone, or in combination. The two turkey strains were 1) a randombred control line (RBC1) and 2) a subline (E) of Line RBC1 selected 27 generations for increased egg production. This study consisted of five trials. Each trial represented a separate hatch. In Trial 1, poults of each line were subcutaneously vaccinated with a 1-mL dilution of B1 type LaSota strain NCDV vaccine. In Trial 2, poults of each line were wing-web vaccinated with the M-9 strain of PM Heddleston Type 3 x 4 cross at 6 and 10 wk of age. In Trial 3, poults of each line were subcutaneously vaccinated on the back of the neck with 1 mL of inactivated NCDV at 6 and 10 wk of age. In Trial 4, .5 mL of a PM bacterin containing Types 1, 3, and 4 in an oil emulsion was used to subcutaneously vaccinate poults of each line at 6 and 10 wk of age. In Trial 5, poults of each line were simultaneously vaccinated with inactivated NCDV (subcutaneously) and a PM bacterin (intramuscularly) at 6 and 10 wk of age. Line RBC1 had significantly (P less than .01) higher maternal antibodies to Newcastle disease at 3 wk of age than those of Line E. The RBC1 line generally had significantly higher levels of antibodies than Line E in response to vaccination for both NCDV and PM when administered singularly or in combination.

Estimates of genetic parameters in turkeys. 1. Body weight and skeletal characteristics

Heritabilities (h2) of and genetic (rG) correlations among body weight and a number of skeletal characteristics were estimated from data on 1,088 pedigree turkeys (504 females and 584 males) of a randombred control line. All measurements were made at 16 wk of age. The h2 estimates (sire component) obtained from females (F) and males (M), respectively, were: BW .23, .60; shank width (SW) .54, .47; shank length (SL) .43, .54; drum length .66, .60; rough-cleaned weights of the thigh (nonestimable, .60), drum .09, .57, and shank .28, .69; cleaned weights of the drum .37, .71, and shank .30, .40; fat-free weights of the drum .44, .93, and shank, .45, .82; bone density measured at 40 and 60% of the length from the proximal end of the drum .68, .80 and .34, .92, respectively, and shank .28, .69 and .31, .55. Genetic correlations (rG) among the various bone weights were all above .66, with most above .85. The rG between BW and SW were .33 from M and .47 from F. These correlations suggest there is a relatively weak relationship, indicating that selection for BW alone might not cause a large enough increase in SW to support the increase brought about in BW. Shank width also had relatively low correlations with bone weight measurements, ranging from .27 to .53 from M and .17 to .56 from F. The h2 of walking ability score (WA) was .06 and the rG of WA with BW was -.73, which indicated that the low body weight families tended to have poor WA (i.e., higher scores). This may be a spurious rG, because poor walking ability scores tended to be grouped in families. Birds with poor walking ability would have difficulty eating, and would, therefore, tend to have low BW. The rG between SW:WA (-.09) and SL:WA (.03) indicated little relationship between those traits. The WA and the bone density readings had high negative rG (range -.75 to -1.47), indicating that families with poor WA ratings also had low bone density scores.

Comparison of pedigreed and nonpedigreed randombred control systems for use with artificial selection in the Japanese quail

The performance characteristics of six replicate sublines of a randombred control, three pedigreed (P) and three nonpedigreed (NP), were studied to see if the NP mating system could be used as a method for maintaining a randombred control for selection experiments. Each subline was maintained with 32 single-pair matings, with 64 offspring placed each generation for each line. Brother X sister matings were avoided in the P but not in the NP system. The NP chicks were pedigreed in order to determine the exact numbers of brother X sister matings selected in that system, but pedigrees were not considered during selection. Records were collected on the numbers of matings producing offspring, the expected rate of inbreeding based on the effective population size, hatchability, egg production, egg weight, and the body weights of the males and females. Replicate lines in the P system had more matings that produced viable offspring, which resulted in larger effective population sizes, lower rates of inbreeding, and smaller average family sizes than those in the NP system. A number of significant differences were found between means of the replicate lines within system and between regressions of the traits measured in the individual lines on generation number. Most of these differences disappeared when the data from the three replicates within mating system were pooled and compared, suggesting that differences found between lines within system were due to random genetic drift due to restrictions in population size. It is suggested that the NP system can be used as an effective control procedure for Japanese quail breeding experiments, but that more than 32 mating pairs should be used for its maintenance in order to reduce the amount of genetic drift within the control population.

Association of the slow feathering (K) and an endogenous viral (ev21) gene on the Z chromosome of chickens

A dominant sex-linked gene, K, regulates slow feathering (SF), whereas a recessive allele, k+, determines rapid feathering (RF) in chickens. This trait provides a convenient and inexpensive approach to gender identification of White Leghorn (WL) chicks at hatch, i.e., in a sex-linked mating using k+/k+ males mated with K/- females, the K/k+ male chicks are SF, and the k+/- females are RF. However, in many WL strains, female progeny of SF dams produce fewer eggs and have higher mortality than progeny of RF dams. This loss in productivity has been attributed to higher infection and shedding rates for leukosis viruses (ALV) in SF than in RF dam lines. Because infectious endogenous viruses (EV) can induce immunological tolerance to ALV, we examined the expression and distribution of ev genes in SF and RF siblings from heterozygous K/k+ sires and k+/- dams. Infectious ALV and EV were detected by cocultivation of frozen heparinized blood cells on selected chick embryo fibroblasts and culture supernatants were tested for viral antigen by enzyme-linked immunosorbent assay tests. Specific ev genes were identified as restriction fragment length polymorphisms after hybridization with a recombinant plasmid containing the complete genome of a Rous-associated virus. It was concluded that ev21 and K genes are tightly linked because, in different WL crosses, all SF chicks inherited ev21 but RF siblings uniformly lacked ev21. Alternatively, the K gene in WL may be a mutation resulting from the insertion of ev21 in the k+ gene. The SF chicks which harbor ev21 expressed infectious EV21; evidence that EV21 may influence susceptibility to ALV is presented.

Comparison of bone and muscle growth in turkey lines selected for increased body weight and increased shank width

A subline (FL) of a long-term growth-selected line (F) of turkeys was established by mass selecting solely for increased shank width at the narrowest point (dew claw). A comparison was made of bone and muscle growth in Line FL (fourth generation of selection), Line F (17th generation of selection), and a randombred control (RBC2, the base population of F) at 8, 16, and 20 wk of age. Also, a sample of the tibiotarsal and femur bones was studied histologically for evidence of pathological conditions. No significant pathological changes were observed in bones from turkeys of the different lines at the ages examined. Samples for histological study were taken at Day 1, 27, 56, 84, 112, and 140 posthatching. Genetic increases in body weight (F and FL lines) resulted in a significant decline in the relative amount of leg muscles from 16 to 20 wk of age while in Line RBC2 the relative amount of leg muscles increased slightly from 16 to 20 wk of age. This resulted in a significant line x age interaction. No significant differences in the amount of leg muscles were detected between turkeys of Lines F and FL. Amount of breast muscles increased consistently with age in all lines. Amount of breast muscles (absolute and as a percentage of body weight) was larger in Line F than in the FL and RBC2 lines. The actual weight of the breast muscles was larger in Line FL than in the RBC2 line but as a percentage of body weight there was no significant difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Divergent selection for body weight and yolk precursor in Coturnix coturnix japonica. 7. Influence of genetic changes in body weight and yolk precursor on egg production

Japanese quail lines were started from a randombred control by selecting for high (HW) or low (LW) 4-week body weight and high (HP) or low (LP) total plasma phosphorus (P), a measure of yolk precursor. In the 9th generation, 2 sublines were initiated from Line HW based on high (HW-HP) or low (HW-LP) level of P in females while males were continually selected for HW. A subline (LP-HW) was started from Line LP in the 9th generation by selecting the males for HW while continuing to select the females for LP. All lines were maintained with 36 parental pairs. Realized heritability (h2) values for 4-week body weight were .38 +/- .02 in Line HW and .32 +/- -.02 in Line LW for 15 generations. Respective h2 were .32 +/- .01 and .34 +/- .01 for P in Lines HP and LP. Although P increased in Line LW, there was no change in Line HW. Body weight of Lines HP and LP declined slightly, but significantly. Egg production decreased significantly in Lines HW, LW, HP, HW-HP, and LP-HW, but did not change in Lines LP and HW-LP. Decrease in egg production of Line HW-HP was greater than that of Lines HW or HP. These results suggest that if both body weight and P are selected for simultaneously, then egg production will decrease more than if selection pressure is applied on either trait alone, even though the two traits do not appear to be genetically closely correlated.

Clomiphene-citrate does not reduce broodiness of turkey hens

Broody turkey hens were treated by giving them clomiphene-citrate (6 mg/kg body weight), an antiestrogen compound, orally for 5 consecutive days in conjunction with the standard practice of moving them into a different pen and exposing them to continuous high intensity light (greater than 215 lx). This treatment did not reduce broody behavior or have any beneficial effect on egg production.