Progress 10/01/99 to 09/30/05
Outputs
Participation in this regional project has allowed for the development of close communication and relationships with researchers of common interest and background. Over the course of this project collaborations were established that significantly contributed to my program in genetics. In general, efforts were made to further understand the impact of selection for growth selection on growth and development of the organism. Selected populations of quail were maintained to explore the effect of selection age on selection response. Additional lines were selected to manipulate the shape and form of the growth curve. Relationships between the physiological complications associated with growth selection were also explored. For example, selection for ascites susceptibility was conducted under high hypobaric conditions resulting in populations that have 80% difference in ascites susceptibility when reared to 6 weeks under hypoxic conditions. Line differences in early growth
rate, breast yield and feed conversion were observed for these lines which suggest that current selection practices for increased yield and feed conversion ratio have exacerbate the ascites condition in commercial broilers. The marriage of the results of the quail populations and ascites lines indicate that one could genetically slow early growth without altering processing weights which in turn would reduce ascites incidence.
Impacts
The poultry industry looses millions of dollars a year due to metabolic disorders associated with rapid growth. The understanding of the timing of selection and its concomitant impact on these metabolic disorders is imperative. Research conducted through this project and the development of selected populations has provided insight into phenotypic, genetic and economic relationships impacted by growth.
Publications
- Santos, F., M.B. Farnell, G. Tellez, J.M. Balog, N.B. Anthony, A. Torres-Rodriguex, S. Higgins and A.M. Donoghue, 2005. Effect of prebiotic on gut development and ascites incidence of birds reared in a hypoxic environment. Poultry Sci. 84:1092-1100.
- Santos, F., G. Tellez, M.B. Farnell, J.M. Balog, N.B. Anthony, H.O. Pavlidis, A.M. Donoghue, 2005. Hypobaric hypoxia in ascites resistant and susceptible broiler genetic lines influences gut morphology. Poultry Sci 84:1495-1498.
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Progress 01/01/04 to 12/30/04
Outputs
The development of chicken lines that are resistant (RES) and susceptible (SUS) to ascites syndrome was accomplished by utilizing a hypobaric chamber to induce the disease. Birds were reared in a hypobaric chamber that simulated high altitude by operating under a partial vacuum, which thereby lowered the partial pressure of oxygen. Ascites mortality data from birds reared under hypobaric chamber conditions were used to select siblings to be used for breeding. The response to selection for the susceptible and resistant lines of chickens was very rapid from the base population, which exhibited an incidence of ascites of 75.30%. To date, extremes in incidence of ascites were observed in generation 8, line SUS exhibited an average incidence of ascites of 95.14% and in generation 9 line RES exhibited an average incidence of ascites of 7.14%. The incidence of ascites in the relaxed line has remained relatively stable and currently has a general incidence of ascites of 60%.
The heritabilities for ascites were estimated to be 0.30 and 0.55 for lines SUS and RES respectively. Changes in the incidence of ascites appeared to be associated with livability. By generation 10, selection for ascites in line RES has increased livability by 11.5 days, whereas in line SUS livability has been decreased by 8 days. Although divergent selection for ascites resulted in a reduction in Day 42 BW for both the susceptible and resistant lines, the susceptible line was about 163 grams heavier than the resistant line. Negative genetic correlations between ascites and RV:TV ratio were observed in both the susceptible and resistant lines, however no significant change in RV:TV ratio was observed for birds reared under normal conditions in either line.
Impacts
Ascites is responsible for millions of dollars of production loss per year. Selection for and against ascites has lead to the development of populations that may be studied to provide answers to fundamental questions regarding the etiology of the syndrome. Research has focused on ways to reduce ascites in commercial poultry flocks. The rapid divergence observed for the ascities lines indicates that ascites is a trait controlled by a few major genes. In addition, our data indicate that ascites could potentially be removed from populations without a negative impact on growth performance.
Publications
- Melnychuk, V. L., J. D. Kirby, Y. K. Kirby, D. A. Emmerson, and N. B. Anthony. 2004. Effect of strain, feed allocation program, and age at photostimulation on reproductive development and carcass characteristics of broiler breeder hens. Poult. Sci. 83:1861-1867.
- Cisar, C. R., J. M. Balog, N. B. Anthony, M. Iqbal, W. G. Bottje, and A. M. Donoghue. 2004. Differential expression of mitochondrial electron transport chain proteins in cardiac tissues of broilers from pulmonary hypertension syndrome-resistant and susceptible lines. Poult. Sci. 83:1420-1426.
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Progress 01/01/03 to 12/31/03
Outputs
Divergent selection for the susceptibility of broilers to high altitude simulation was accomplished through a multi-year collaboration with Dr. J. Balog USDA-ARS. Using sire-family selection on a commercial elite line of broilers, lines were derived that exhibit divergent ascites incidence. After eight generations of selection, the ascites resistant line exhibited no more than 22% ascites incidence under hypobaric conditions, the ascites susceptible lines exhibited no less than 95% ascites incidence, and the unselected relaxed line (which served as the control) exhibited 67% ascites incidence. Research focused on whether or not the lines that had been selected under hypobaric conditions would respond in a similar manner to other ascites induction experimental models. Chicks were hatched from the resistant, susceptible and relaxed lines, reared in floor pens, and subjected to a cold stress to induce ascites syndrome. This research showed that the resistant line had a
significantly lower ascites incidence (1.6%) when compared with the susceptible (18.8%) and the relaxed line (12.7%). Similar results were found for the lines when exposed to bronchus clamping and microparticle injection. This work was the first to demonstrate that lines selected under the hypobaric chamber experimental model maintained their divergent ascites susceptibility when exposed to different stressors. The selected lines were also exposed to typical production environments and evaluated to determine the correlated responses to selection for and against ascities. These ascities lines are serving as the basis for the molecular genetic investigation. The identification of genetic markers for ascites is an expected result of our research.
Impacts
Ascites is responsible for millions of dollars of production loss per year. Selection for and against ascites has lead to the development of populations that may be studied to provide answers to fundamental questions regarding the etiology of the syndrome. Research has focused on ways to reduce ascites in commercial poultry flocks. The rapid divergence observed for the ascities lines indicates that ascites is a trait controlled by a few major genes. In addition, our data indicate that ascites could potentially be removed from populations without a negative impact on growth performance.
Publications
- Balog, J.M., B.D. Kidd, N.B., Anthony, G.R. Huff, W.E. Huff, N.C. Rath, 2003. Effect of cold stress on broilers selected for resistance or susceptibility to ascites syndrome. Poultry Sci. 82:1383-1387.
- Anthony, N.B., and J.M. Balog, 2003. Divergent selection for Ascites: Development of susceptible and resistant lines. Pages 39 - 58 Proceedings, National Breeders Roundtable.
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Progress 01/01/02 to 12/31/02
Outputs
Over the past 7 years, our laboratories have used sire-family selection on a commercial elite line base population to produce an ascites resistant (RES) and an ascites susceptible (SUS) line of broilers. After seven generations of selection, the RES line exhibits < 22% ascites mortality while the SUS line has > 86% ascites mortality. To determine the genetic factors involved in ascites susceptibility, reciprocal F1 crosses of the RES and SUS lines were produced. The objective of this trial was to determine the effects of hypobaric exposure on pure-lines RES and SUS, and their reciprocal F1 crosses (RS, SR). Four hundred and eighty vaccinated, pedigreed broiler chickens (40 groups of 12 birds) were randomly assigned to cages in either a hypobaric chamber (simulated 2900 m above sea level) or a matching local altitude chamber (390 m above sea level). Individual bird weights were collected on Day 0, 14, 28 and 42. Daily mortalities were necropsied. On Day 42, birds were
sacrificed, scored for ascites, and BW, liver, spleen, and split heart weights were obtained. Ascites mortality differed between lines, with the SUS line having the highest, the RES line having the least, and the RS and SR lines having intermediate ascites incidence. The number of days to death were highest for the RES (37), with the RS (32) and the SR (32) intermediate and the SUS survived the shortest number of days (19)(P = 0.0001). Significant positive heterosis for BW was observed in the F1 crosses at 14, 28, and 42 days of age, and there were no BW differences between RS and SR. No pure line differences were observed for BW at these same ages. Another objective of this multidisciplinary trial was to determine the effects of hypobaric hypoxia on gut development in the pure-line RES, pure-line SUS, and the reciprocal F1 crosses (RS, SR). Four hundred and eighty vaccinated, pedigreed broiler chickens (40 groups of 12 birds) were randomly assigned to cages in either a hypobaric
chamber (simulated 2900 m above sea level) or a matching local altitude chamber (390 m above sea level). On Day 42, specimens of duodenum and distal ileum were collected from five chickens in each line at each altitude. Each sample of intestine was cut open longitudinally at the antimesenteric attachment. Sections were fixed, cut (5 micrometers) and stained with hematoxylin and eosin. From these stained sections, 10 measurements of villus height were made at random from different parts of each tissue slide using a reticle (100 mm divisions) placed in the eyepiece of the microscope. There were significant effects on gut development due to both altitude and genetic line. Villus height (mm) of the duodenum and ileum were greater across all lines at local altitude compared to the hypobaric chamber (P=0.0001). Similar morphometric increases were observed in pure-line RES and F1 crosses when compared with pure-line SUS at local altitude (P=0.0001). This study suggests that birds selected
for ascites resistance also exhibit improved gut development and this improvement is maintained in their reciprocal crosses. Additionally, hypobaric hypoxia alone results in a reduction in gut development across all lines.
Impacts
Selection for and against ascites has lead to the development of populations that may be studied to provide answers to fundamental questions regarding the etiology of the syndrome. Research will focus on ways to reduce ascites in commercial poultry flocks.
Publications
- R.F. Wideman, Jr., Erf, G.F., Chapman, M.E., Wang, W., Anthony, N.B., Liu, X., 2002. Intravenous Micro-Particle Injections and Pulmonary Hypertension in Broiler Chickens: Acute Post-Injection Mortality and Ascites Susceptibility. Poultry Sci. 81:1203-1217
- Melnychuk, V.L., M.A. Cooper, J.D. Kirby, R.W. Rorie, and N.B. Anthony, 2002. Use of ultrasonography to characterize ovarian status in chickens. Poultry Sci. 81:892-895.
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Progress 01/01/01 to 12/31/01
Outputs
Genetic selection of birds resistant and susceptible to ascites syndrome was accomplished utilizing a hypobaric chamber to induce the disease. Birds were reared in a hypobaric chamber that simulated high altitude by operating under a partial vacuum, which thereby lowered the partial pressure of oxygen. Ascites mortality data from birds reared under hypobaric chamber conditions were used to select siblings to be used for breeding. Subsequent siblings were then reared in floor pens to propagate the lines. The original parent stock came from a commercial pedigree line. A third test line (relaxed line) is representative of the original pedigree line that has been propagated over the generations with no particular selection pressure. As of the 6th generation, the ascites resistant line exhibits an average of 27% ascites mortality, while the ascites susceptible line exhibits an average of 86% ascites mortality, under hypobaric conditions. The relaxed line exhibits an
average of 66% ascites mortality. Heritability of the ascites trait was estimated to be 0.45. In three different experiments, the ascites lines were challenged with a cold stress or a unilateral bronchus clamp treatment, both of which are known ascites-inducing stressors. In all experiments, when the three lines were exposed to a cold stress they responded as they would if placed under hypobaric stress, although not to the same magnitude. Although cold stress did not produce as high an incidence of ascites, the resistant line experienced the least amount of ascites and the susceptible line the most ascites, with the relaxed line being intermediate. When subjected to a unilateral bronchus occlusion, the line distinctions were not as apparent, and all lines experienced heavy post-surgical losses (30 - 50%). Ascites mortality following bronchus clamp was also high, but the relatively small sample size made it difficult to determine if there were differences between lines. Based on the
results of these three experiments, it seems that the lines selected by hypobaric exposure respond in a similar manner to cold stress ascites induction, while bronchus clamping needs to be investigated further to determine the line response.
Impacts
Ascites is responsible for millions of dollars of production loss per year. The rapid line divergence observed for these lines would indicate that ascites is a trait controlled by a few major genes. In addition, our data indicates that ascites could potentially be removed from populations without a negative impact on growth performance.
Publications
- Anthony, N.B., Balog, J.M., Hughes, J. D., Stamps, L., Cooper, M.A., Kidd, B. D., Liu, X., Huff, W.E., Huff, G.R., and Rath N. C., 2001. Genetic selection of broiler lines that differ in their ascites susceptibility 1. Selection under hypobaric conditions. Proc. 13th European Symposium on Poultry Nutrition, Blankenberge, Belgium. Pages 327-328.
- Balog, J.M., Anthony, N.B., Kidd, B.D., Liu, X., Cooper, M.A., Huff, G.R., Huff, W.E., Wideman, R.F. and Rath N. C., 2001. Genetic selection of broiler lines that differ in their ascites susceptibility 2. Response of the ascites lines to cold stress and bronchus occlusion. Proc. 13th European Symposium on Poultry Nutrition, Blankenberge, Belgium. Pages 329-330.
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Progress 01/01/00 to 12/31/00
Outputs
Ascites is a metabolic disease associated with fast growing meat-type chickens. It has been demonstrated that ascites may be induced by high altitude simulation. Using a large hypobaric chamber to simulate high altitude conditions, an ascites resistant and susceptible line of broiler was established. These lines are now in their sixth generation of selection. Significant divergence of the lines was observed where resistant and susceptible lines had approximately 30 and 80 percent mortality respectively when reared under high altitude conditions. Additional ascites research studied the effects of duration of high altitude exposure on ascites incidence. Three replicate trials were conducted in which broilers were exposed to high altitude conditions for 2, 3 and 4 weeks and then returned to local altitudes. In addition birds were reared at local altitude for 2, 3 and 4 weeks and then moved to high altitude. A local altitude and a high altitude controls group was
maintained for the duration of the study. In general, when chickens were moved to high altitude, it took 2 weeks of exposure before a significant increase in ascites mortality was noted. Conversely, when birds were moved from high altitude to low, it took 2 weeks before incidence of ascites mortality significantly declined.
Impacts
Ascites was investigated through the use of a high altitude simulation induction model. Selection was applied for and against the ascites syndrome. Additional research was conducted to investigate the impact of duration of high altitude exposure on growth and incidence of ascites in broiler chickens.
Publications
- Balog, J.M., N.B. Anthony, M.A. Cooper, B.D. Kidd, G.R. Huff, W.E. Huff, and N.C. Rath, 2000. Ascites syndrome and related pathologies in feed restricted broilers raised in a hypobaric chamber. Poultry Sci 70:318-323.
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