Characterization of four endogenous viral genes in semi-congenic lines of meat chickens.

Restriction fragment length polymorphism analyses were used to examine endogenous viral genes (ev genes or ALVE genes) of the avian leukosis viral (ALV) family in semi-congenic lines of meat chickens. The Generation 6 lines examined in this study were semi-congenic in that each contained birds with either zero or with one ALVE gene in hemizygous state plus some solitary long terminal repeat (LTR) elements. Using four restriction enzymes on chicken genomic DNA and two probes, one representing the entire ALV retroviral genome and one with only a small part plus the LTR, four ALVE genes were characterized. Each seemed to be complete with no detectable deletions. None appeared to be similar to known ALVE genes of White Leghorns, whereas two of the four may be the same as ALVE genes reported by others in White Plymouth Rock chickens.

Characterization of eight endogenous viral (ev) genes of meat chickens in semi-congenic lines.

Restriction fragment length polymorphism analysis was conducted for a set of eight different meat chicken-derived endogenous viral genes (ev genes) of the avian leukosis viral (ALV) family. Each viral element was first isolated into a separate single-element line by selective breeding. Genomic DNA from the founder male for each semi-congenic, single-element line was digested with each of four restriction enzymes, and the resulting Southern blots were each hybridized with up to four probes representing different portions of the ALV retroviral genome. Among the eight elements, there was one that represents the broiler equivalent of locus ev3 of White Leghorn chickens. A second broiler element showed a SacI-specific junction fragment similar to that of ev8. The remainder appeared to be different from any of the 21 ev genes previously described for White Leghorn chickens. Four of the eight elements examined were essentially complete, but the rest have sustained internal deletions.

Research note: avian leukosis retroviral genes are not detected in geese.

Genomic DNA from four strains of geese was analyzed for the presence of endogenous viral elements using a probe that can detect over 20 Rous-associated endogenous viral genes (ev genes) in chickens, as well as a probe and protocol that detects endogenous avian viruses (EAV). Southern blot analysis of genomic DNA did not reveal any ev genes in DNA of 15 geese from Chinese, Synthetic, or two Embden goose strains. Even under low stringency conditions, using a probe that covered most of the polymerase (pol) gene of the Rous-associated virus (RAV) and that revealed EAV elements in a chicken without ev genes, no viral loci were evident in goose DNA.

Endogenous viral gene distribution in populations of meat-type chickens.

The present study was designed to document the complexity of endogenous viral (ev) genes and seek evidence for their association with production traits in selected and control strains of meat-type chickens. Three populations were studied, each consisting of a control strain and one to three strains selected for various production traits. The ev genes were revealed by digesting genomic DNA with restriction enzymes and detecting DNA fragments on Southern blots using radioactive probes from nucleotide sequences of the avian leukosis virus genome. A total of 31 polymorphic ev loci were identified in these populations from a SacI digest, with an average of 7.3 ev genes per bird. There were no significant differences in ev genes per bird between strains within populations or between selected and control strains overall. Thirty of 62 comparisons in the three populations indicated ev gene frequency differences (P less than .05). Within populations, 13 of 93 comparisons of ev gene frequencies between control and selected strains and 8 of 62 between three selected strains of a sire population showed such differences (P less than .05). Selection for body weight and feed efficiency had been observed to reduce gene frequencies of the slow-feathering gene, which usually contains the ev21 locus; however, these effects were not detected (.05 less than P less than .06) between strains of the dam population in the current study. Such differences suggested possible associations between ev genes and production traits in meat-type chickens.

Effects of vitamin D3 metabolites on physiological traits of White Leghorn hens.

This study was conducted to determine the effect of feeding vitamin D3(D3) metabolites on BW of hen, weight of uterus, plasma Ca, jejunal and uterine adenosine triphosphatase (ATPase), and carbonic anhydrase. At 416 days of age each of 7 groups of laying hens was fed the basal ration supplemented with one of 7 concentrations (micrograms per kg) of D3 or its metabolites as treatments: 0 micrograms of D3; 27.5 micrograms of D3; 3, 5, or 7 micrograms of 1,25(OH)2D3; 5 micrograms of 24,25(OH)2D3; and 5 micrograms of 24,25(OH)2D3 plus 5 micrograms of 1,25(OH)2D3. Treatment effects were compared at various periods after the start of the study. Hens fed the unsupplemented ration had lower (P less than .05) values for all traits than hens fed the D3-supplemented ration by 162 days after the start of treatment. In a comparison of all dietary treatments except the one involving 0 micrograms D3, from 154 to 161 days after the start of the experiment, treatment effects were significant (P less than or equal to .05) for BW, uterine ATPase, and carbonic anhydrase; hens fed 5 micrograms of 24,25(OH)2D3 per kg of ration ranked the lowest of all treatment groups for these traits. Hens fed 27.5 micrograms of D3 and those fed 5 micrograms of 1,25(OH)2D3 per kg of ration did not differ (P greater than .05) for any traits studied. The results suggest that 5 micrograms of 1,25(OH)2D3 per kg of ration can replace 27.5 micrograms of D3 per kg of ration but that 5 micrograms of 24,25(OH)2D3 per kg of ration tends to have a negative effect on physiological systems of the hen.

Effects of cholecalciferol or calcium deficiency on oestrogen metabolism in the laying hen.

1. Seventeen 32-week-old White Leghorn laying hens were induced to become deficient in calciferol or in calcium (laying thin or soft shelled eggs) by withdrawing either cholecalciferol (27.5 micrograms/kg diet) or calcium (31 g/kg diet) supplements from the control diet. 2. The metabolic fate and metabolic clearance rate (MCR) of intravenously injected 3H-oestradiol-17 beta were then monitored for 40 min. 3. In both the calciferol and calcium-deficient groups a major oestrogen sulphate pathway was particularly affected, resulting in a decreased conversion of oestradiol-17 beta-3-sulphate to oestradiol-17 alpha-3-sulphate, with a concomitant reduced MCR of oestradiol-17 beta from plasma. 4. The metabolic defect was corrected by feeding the control diet. 5. Because the metabolic defect observed in calciferol deficiency occurred in Ca deficiency in a more severe form, we conclude that the more immediate cause was calcium rather than calciferol deficiency. To our knowledge, this is the first observation of a calcium-deficient effect on oestrogen sulphate metabolism in vivo.

Effects of vitamin D3 deficiency on estradiol-17 beta metabolism in the laying hen.

Evidence is presented that in vitamin D deficiency there are aberrations of estrogen metabolism in the laying hen. Five White Leghorn hens, 35 weeks of age, all laying soft shelled eggs as a result of complete withdrawal of supplemental vitamin D3 (D3) from the diet, were found to have a 3-fold higher molar ratio of plasma estradiol-17 beta-3-sulfate (E2 beta-3S) to estradiol-17 beta (E2 beta) compared to five control laying hens fed a D3-supplemented diet. A time course tracer study with [3H]E2 beta administered iv revealed an abnormally high accumulation of [3H]E2 beta-3S in plasma, and concomitantly, a markedly reduced formation of [3H]estradiol-17 alpha-3-sulfate [( 3H]E2 alpha-3S) compared with the control hens. This observation suggests a defect in the conversion of [3H]E2 beta-3S to [3H]E1S, previously shown to be a major pathway for E2 beta metabolism (E2 beta E2 beta-3S in equilibrium E1S E2 alpha-3S). As a result, the MCR of [3H]E2 beta from plasma of the D3-deficient hens was about 15% below normal. The calculated production rate of E2 beta was reduced even more, by 60%. However, the reduced production rate could have been related to the lengthening of the ovulatory cycle due to vitamin D deficiency. It is concluded that vitamin D deficiency affects the biosynthesis and catabolism of E2 beta in the laying hen.

Effects of vitamin D3 deficiency on adenosine triphosphatase activity of jejunums from white Leghorn hens.

Supplemental vitamin D3 (D3) was removed from the diet given to an experimental group of White Leghorn hens, at 227 days of age, while a control group continued to receive a supplemental diet. By 14 days after D3 withdrawal, egg weight, egg specific gravity, shell weight, percent shell, shell thickness, and plasma calcium were lower (P less than .05) in the experimental compared to the control group. At 30 to 37 days after D3 withdrawal, experimental hens had less (P less than .05) jejunal adenosine triphosphatase (ATPase) activity than the control hens. The study indicated that lack of D3 supplementation in laying diets reduced jejunal ATPase activity as well as egg shell quality.

Production, clearance rates and metabolic fate of estradiol-17 beta in the plasma of the laying hen.

A single dose of tritiated estradiol-17 beta (3H-E2 beta) was injected i.v. into 5 high egg producing White Leghorn hens, 31 weeks of age, at 19.2 +/- 2.1 (mean +/- S.D.) hr before oviposition. Blood (2 ml) was sampled at approximately 5 min intervals over 40 min. Whenever possible, metabolites were monitored and identified by the double isotope technique with the addition of the corresponding 14C-labelled standards to plasma prior to analysis. The metabolic half-life and clearance rate of 3H-E2 beta in plasma were 10.9 +/- 1.9 min and 118 +/- 18 ml/min/kg body weight, respectively. The calculated production rate of E2 beta at 19.2 hr before oviposition was 19.5 +/- 5.7 ng/min based on the plasma level (93 +/- 22 pg/ml) measured at that time. The relative concentrations (% of plasma radioactivity) of the major metabolites isolated at 5.7 +/- 0.6 min post injection were, in descending order: estradiol-17 beta-3-sulfate (E2 beta-3S: 14.9 +/- 2.7), estradiol-17 alpha-3-sulfate (E2 alpha-3S; 5.7 +/- 0.3), estrone (E1; 4.6 +/- 0.5), estrone sulfate (E1S; 2.2 +/- 0.5), and estradiol-17 alpha (E2 alpha; 1.2 +/- 0.4). As time proceeded, the relative concentration of E2 alpha-3S gradually increased so that by 43.2 +/- 1.0 min it became the most abundant identifiable metabolite (12.3 +/- 1.1) followed by E2 beta-3S (9.1 +/- 1.7), E1S (1.2 +/- 0.6), E1 (0.7 +/- 0.4) and E2 alpha (0.3 +/- 0.2). These findings are consistent with the view that one of the major pathways of E2 beta metabolism in the circulation of the hen is via E2 beta in equilibrium E2 beta-3S in equilibrium E1S in equilibrium E2 alpha-3S.

Effect of estradiol on calcium and calcium binding in serum of thick and then-shell lines of chickens.

Estradiol (10 mg/bird) was injected intramuscularly into hens of a thick-shell line and a thin-shell line as well as into roosters of both lines on day 0. Serum levels of calcium (Ca), phosphorus (P), and Ca binding involving the proteins vitellogenin (a phosphoprotein) and albumin were measured on day 0 and day 6 or 7. Serum levels of all measured Ca and P parameters and vitellogenin binding of both sexes were significantly greater, while levels of albumin binding were significantly less on day 6 or 7 than on day 0. Serum levels of non-diffusible Ca in hens and vitellogenin binding in both sexes were significantly greater in the thick-shell than in the thin-shell line. There were no significant differences between lines for total serum P of either sex. A study of the hens only revealed that the change in nondiffusible Ca and vitellogenin binding from day 0 to day 6 or 7 was significantly different between lines. The correlations between vitellogenin binding and total P, expressed as either change or percent change, were greater than .8.

Inheritance of adenosine deaminase variants in chickens and turkeys.

Blood cell lysates of chickens and turkeys were subjected to starch gel electrophoresis and the gels were stained for adenosine deaminase. Two zones were observed singly or together in the electrophoretic patterns of each lysate. Zones of chicken lysates were analogous in electrophoretic mobility to those of turkeys. An extra zone which appeared in patterns of a sample stored over one month was not detected in patterns of a second aliquot of stored sample treated with a reducing agent prior to electrophoresis. Family data involving 110 chicken progeny and 221 turkey progeny supported the hypothesis that these zones were controlled by two codominant alleles designated ADAA and ADAB. In the two Leghorn strains studied ADAB was much more frequent than ADAA, but the frequency distribution was reversed in the Small White turkey strain examined.

Studies on genetic and vaccination-induced resistance of chickens to lymphoid tumor transplants. 1. Marek's disease tumor transplant (JMV).

Six strains and 4 inbred lines of chickens that differed in susceptibility to Marek's disease (MD) were inoculated in the wing web with JMV when 5 weeks old. Wing web tumors (WWT) developed in all strains and lines inoculated with low-passage JMV (JMV-L) but were largest in Cornell Strain S (highly susceptible to MD). Of 3 strains inoculated with high-passage JMV (JMV-H), only Strain S had appreciable WWT development. Seventy-five percent of the unvaccinated S strain chickens challenged with JMV-L or JMV-H died during the experiments, and approximately half of this mortality occurred during the second week postinoculation. Inbred Line GC ranked next in susceptibility to Strain S and was more susceptible than other lines and strains, including the strain from which it originated. Vaccination with turkey herpesvirus one week before challenge protected against mortality and suppressed WWT development. The effect on WWT development was less, however, in Strains S and NH than in other strains. The transplantability of the tumor was investigated with the use of sex chromosomes as cell markers. Five to 7 days postinoculation of male Strain S chicks with JMV-L or JMV-H, most cells in metaphase from wing web or visceral tumors were of female origin. By 56 days, only male cells were found in visceral tumors. The interpretation was that early lesions were due to tumor transplantation and later lesions were induced by virus.

Studies on genetic and vaccination-induced resistance of chickens to lymphoid tumor transplants 2. Transmissible lymphoid tumor of Olson.

Transmissible lymphoid tumor (TLT) was inoculated in wing webs of five-week-old chickens of 6 strains. About half of the chickens of each strain had been vaccinated with turkey herpesvirus (HVT) one week before challenge in the wing web with TLT. Tumors which developed at the site of inoculation usually reached maximum size within 2 weeks and then regressed. In some chickens, however, tumors developed in visceral organs and caused death in the 2nd through 5th weeks postinoculation. Comparisons among strains of chickens in Expt. 1 revealed no differences in mortality. Vaccination with HVT reduced mortality and also the incidence of wing-web tumors (WWT) in all strains of chickens. A lymphoid leukosis virus and a Marek's disease (MD) virus of low virulence were detected in preparations of TLT, and it is suggested that the immunity induced by vaccination may have been directed against tumor antigens associated with MD virus.

Effects of strain of chickens and vaccination with turkey herpesvirus on Marek's disease and lymphoid leukosis in breeding stocks.

1. A total of 3236 females from eight meat-type strains, half of which were vaccinated for Marek's disease (MD), and 11,193 Leghorn females from ten strains, all vaccinated for MD, were adventitiously exposed to MD and lymphoid leukosis (LL) viruses and observed to 392 and 497 d of age, respectively. 2. In the meat-type birds, vaccination reduced total mortality from 43-4% to 27-1% and mortality due to MD from 16-4% to 5-4% but did not affect mortality and LL (2-9% and 3-4%). 3. In the vaccinated Leghorns total mortality was 11%, including 2-1% from MD and 1-2% from LL. 4. Significant differences between strains of chickens were found in total mortality, as well as in MD and LL mortality. 5. Strain by vaccination interaction was observed in total rearing and adult mortality, as well as in the MD mortality of adult meat-type females. 6. Leghorn strains with higher rate of egg production and meat-type strains with lower growth rate to have better viability.