Progress 10/01/01 to 09/30/06
Outputs
A high percentage of lambs have consolidation of lung tissue. Consolidated lung tissue was observed to be a seasonally related phenomenon with greater prevalence of the condition occurring in lambs slaughter in the summer months than in lambs slaughtered in the winter. Severely consolidated lung lesions were associated with reduced average daily gain of lambs between weaning to slaughter. A serial slaughter study indicated lung lesion formation was occurring post-weaning, and lung lesions were associated with elevated concentrations of tumor necrosis factor-alpha and alpha1-acid glycoprotein. Lung lesions were also demonstrated to be associated with the presence of Mannheimia (Pasteurella) haemolytica and Pasteurella multocida. Strategies designed to target Pasteurella sp. were tested for ability to reduce lung lesion prevalence. Neither vaccination nor low level feeding of chlorotetracycline was able to reduce the prevalence of lung lesions. Therefore, the ability of
a cattle product designed to combat respiratory disease (NPCoat; Camas, Inc.) to reduce the prevalence of lung lesions in sheep was tested. NPCoat is an intranasal preparation of avian polyclonal antibodies against various respiratory disease pathogens, including Pasteurella sp. The objective of this study was to test the impact of NPCoat administration on the prevalence of lung lesions in lambs. Lambs were assigned to 1 of 4 pens, and all lambs in one pen were treated with 0.5 ml/nostril of NPCoat or carrier. Lambs received the initial intranasal treatment at weaning and a second and third intranasal treatment 7 and 14 days later, respectively. Lambs were weighed every 2 weeks. Lambs were slaughtered at a commercial packing plant, and lungs were collected for lung lesion scoring, histological examination, and bacterial culture. Lambs were determined to have severe lung lesions if over 50% of any lobe was consolidated. Lambs were considered to have moderate lung lesions if greater
than 5% but less than or equal to 50% of a lobe was consolidated. Lambs were considered to have normal lungs if not more than 5% of any lobe was consolidated. Effect of treatment on prevalence and severity of lung lesions were tested by Chi-square. Treatment with NPCoat had no effect on the prevalence or severity of lung lesions (P>0.75). Histopathology indicated bronchopneumonia with mixed mononuclear cells present in lambs with lung lesions. Culture analysis confirmed the presence of Pasteurella sp. in lambs with lung lesions, and revealed the presences of Mycoplasma sp. Mycoplasma sp. was present in a greater percentage of lungs with lesions than in lungs without lesions (51% vs. 15%; P=0.04). Treatment with NPCoat did not affect the presence of Pasteurella sp. or Mycoplasma sp. (P>0.17). These results indicate administration of the current cattle formulation of NPCoat at the time of weaning is not effective at reducing the prevalence of lung lesions in sheep. These results also
suggest strategies to reduce infection of Mycoplasma sp. may reduce the prevalence of lung lesions.
Impacts
Although strategies attempted to reduce the incidence of lung lesions have to date been ineffective, means of preventing the formation or reducing the severity of lung lesions could increase the profitability of sheep production. Knowledge that lung lesions occur post-weaning and may involve Pasteurella sp. and/or Mycoplasma sp. will aid producers in adopting intervention methods.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Lung lesions occur after weaning and are associated with the presence of Mannheimia haemolytica and Pasteurella multocida. Stress associated with weaning may allow bacteria to result in the formation of lung lesions. Feeding low level antibiotics may reduce bacterial challenge at weaning. Diagnostic reports indicated that M. haemolytica and P. multocida at the South Dakota State University Sheep Unit are susceptible to chlorotetracycline (CTC). We tested the effect of feeding low levels of CTC for the 2 week period following weaning on the prevalence of lung lesions. At weaning, lambs were assigned to one of six pens in the same barn and prevented from having nose to nose contact with lambs in other pens. Pens were fed the control diet or control diet plus 50 g/ton CTC for two weeks following weaning. After two weeks, all pens were fed the same diet. Lambs were weighed every 28 days, and were slaughtered when two-thirds of the lambs were 54 kg or greater live weight.
At slaughter, lungs were examined for lesions. Lambs were determined to have severe lung lesions if over 50% of any lobe was consolidated. Lambs were considered to have moderate lung lesions if greater than 5% but less than or equal to 50% of a lobe was consolidated. Lambs were considered to have normal lungs if not more than 5% of any lobe was consolidated. Lungs were also examined for the presence of active abscesses or pleural adhesions. Carcass data (fat thickness at 12th rib, ribeye area, and body wall thickness) were collected approximately 24 hrs after slaughter. Effect of treatment on prevalence and severity of lung lesions were tested by Chi-square. Data were also tested for effect of CTC and lung lesion prevalence and severity on 28 day weights, average daily gain, and hot carcass weight using ANOVA and effect of CTC and lung lesion prevalence and severity on carcass traits using ANOVA with hot carcass weight as a co-variant. Treatment did not alter the prevalence of lung
lesions (79% vs. 84% incidence of lung lesions in CTC fed vs. control diet; P = 0.55) or the prevalence of sever lung lesions (58% vs. 61% incidence of sever lung lesions in CTC fed vs. control diet; P = 0.75). Feeding of CTC did not alter any growth or carcass traits relative to control feed lambs (P > 0.05). The presence of lung lesions or the severity of lung lesion impacted any carcass traits examine (P > 0.05). Lambs with severe lung lesions were heavier than lambs with normal lungs after the first 28 days after weaning (47.0 +/- 1.0 kg vs. 41.2 +/- 2.8 kg, respectively; P = 0.01), but lambs with severe lung lesions had lower average daily gain over the entire feeding period than lambs with normal lungs or moderate lung lesions (0.25 +/- 0.01 kg/day vs. 0.30 +/- 0.01 kg/day or 0.29 +/- 0.01 kg/day, respectively; P > 0.02). These results do not support the hypothesis that feeding antibiotics following weaning would prevent the formation or reduce the severity of lung lesions.
However, these results to confirm that severe lung lesions reduce average daily gain in lambs. These results also suggest that larger or faster growing after weaning may be at greater risk of developing severe lung lesions.
Impacts
Severe lung lesions result in reduced average daily gain in lambs. Although targeted feeding of chlorotetracycline did not reduce the prevalence of lung lesions, reducing the prevalence of severe lung lesions would result in fewer days on feed or increased market weights of lambs.
Publications
- Daniel, J.A., Held, J.E., Brake, D.G., Wulf, D.M. and Epperson, W.B. 2006. Evaluation of the prevalence and onset of lung lesions and their impact on growth of lambs. American Journal of Veterinary Research (in press)
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Progress 01/01/04 to 12/31/04
Outputs
Previous research in cattle and sheep has indicated that lung lesions result in decreased animal growth, but mechanisms by which lung lesions result in decreased growth have not been identified. The objective of this research was to identify possible changes in circulating mediators of inflammation associated with lung lesions. As part of a study to determine timing of the onset of lung lesion development, lambs were slaughtered at three time points after weaning (day 1 n = 21, day 50 n = 20, and day 71 n = 21). Serum was harvested and stored at -80C until analysis. Percentage consolidation of each lobe of the lung was estimated for each lamb. Lambs were classified as having normal (<5 % consolidation of any lobe), moderate lesions (5-50 % consolidation of any lobe) or severe lesions (>50% consolidation of any lobe). Circulating concentrations of tumor necrosis factor-alpha (TNF) were determined by RIA and circulating concentrations of alpha1-acid glycoprotein (AGP)
were determined by radial immunodiffusion. For statistical analysis, sheep with AGP levels below the minimum detectable concentration (50 microg/ml) were assigned an AGP concentration of 50 microg/ml; effect of lesion scores and level of severity on circulating concentrations of TNF and AGP were tested using one-way ANOVA. Lambs with lesions, moderate or severe, had elevated circulating concentrations of TNF and AGP relative to normal lambs (75.9 vs. 68.7 pg TNF /ml and 183.6 vs. 21.3 microg AGP /ml respectively, P < 0.05). Circulating concentrations of TNF and AGP did not differ between lambs with moderate or severe lesions (76.4 vs. 75.3 pg TNF /ml and 139.3 vs 232.3 microg AGP /ml respectively, P > 0.05). These data indicate that circulating concentrations of TNF and AGP are elevated in lambs with lung lesions. Elevations in circulating concentrations of TNF and AGP in lambs with lung lesions are consistent with an inflammatory state that compromises health and growth.
Impacts
Elevated tumor necrosis factor alpha and/or alpha1 acid glycoprotein may potentially be used as markers of animals with lung lesions.
Publications
- Daniel, J.A, Elsasser, T.H. and Epperson, W. 2004. Elevation of tumor necrosis factor-alpha and alpha1-acid glycoprotein in lambs with consolidation of lung tissue. J. Anim. Sci. 82(Suppl. 1):179.
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Progress 01/01/03 to 12/31/03
Outputs
To describe the temporal features of lung lesion development in spring-born lambs, a serial slaughter trial was conducted. Wether lambs (62) born at the South Dakota State University Sheep Research Center in the 32 day lambing period (Feb 4 to March 8, 2003) were allocated to 3 slaughter groups; 1. Weaning (approximately 70 days of age), 2. Mid finish (50 days postweaning), and 3. finish (70 days postweaning). Lambs were slaughtered in a university facility, using standard slaughter technique. Lungs were examined immediately after removal from the thorax, were photographed, and were subjectively scored using established criteria. Affected areas, or the right cranial lung lobe in non-affected lambs, were submitted for bacteriologic culture to the South Dakota Animal Disease Research and Diagnostic Laboratory. Individual identity was retained throughout the study. For analysis, lesions were considered to exist if consolidation affected greater than or equal to 5 percent
of any single lung lobe surface area. Lesion area was estimated for each lobe by observation of the lung surface. For analysis, lesions were considered moderate if they occupied greater than 5 percent and less than 50 percent of the lung, and severe if they affected equal to or greater than 50 percent of any single lung lobe. Lambs in slaughter group 1 (21) had no severe lung lesions, and only 1 lamb had moderate lesions. All others were lesion free. No Pasteurella multocida, Manheimia hemolytica, or mycoplasma was isolated from any of the 21 lungs. Slaughter group 2 had a lung lesion prevalence at slaughter of 12/20 (60 percent). Of these, 7 (58 percent of affected lambs, 35 percent overall) were classified as severe. Of those 7 lambs affected with severe lesions, the median number of lobes affected was 1. Slaughter group 3 had a lung lesion prevalence of 10/21 (48 percent overall), with 8 of the 10 affected lungs (80 percent of affected lambs, 40 percent overall) classified as
severe. Of those 8 lambs affected with severe lesions, the median number of lobes affected was 2.5. Overall prevalence of lesions between slaughter groups 2 and 3 were not different. There was a tendency for increased extent of lung lesions in slaughter group 3, compared to slaughter group 2. This is interpreted to indicate that as time passed, lung lesions progressed in those lambs affected. Therefore, at the time of normal slaughter, lambs were either unaffected or affected with severe lesions, with few lambs in between. Of the 15 lambs affected with severe lesions, 4 yielded Pasteurella multocida only, 3 yeilded Mannheima hemolytica only, 4 yielded both Pasteurella multocida and Manheima hemolytica, and 2 yielded no growth. Mycoplasma was not isolated from any lungs. Data suggest that lung lesions form after weaning but prior to day 50 post weaning. Data suggest that lambs destined to form lung lesions do so after weaning, and that lung lesions may intensify, affecting more lobes
per lamb, over time. Clinical disease was rare in these lambs, so lung lesions apparently are a subclinical manifestation of respiratory tract infection.
Impacts
We have documented that a high proportion of harvested lambs are affected with lung lesions that are associated with a decreased post-weaning average daily gain. The reduced average daily gain will result in either marketing of lighter lambs (2.8 kg) or maintaining lambs on feed for a longer time period. With 100,000 lambs on feed in South Dakota alone, marketing of lambs with lung lesions at a 2.8 kg lighter finished weight reduces income by $120,000 to $240,000 annually without considering reduced feed efficiency. Additionally, any abnormality of the lung will prevent lambs from qualifying for the value-added kosher lamb market. Of the lambs presented for Kosher slaughter at a regional harvest facility, 20-30 percent are rejected due to presence of lung lesions. Carcasses qualifying as kosher have $5-10 per head in added value. Thus, at this single South Dakota plant, a $45,000 loss in carcass revenue is observed. With continued research, it might be possible to
capture 25 percent of the documented loss, resulting in a gain of $41,250 to $71,250 annually for South Dakota producers.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
In 2002, 93 crossbred wethers born at the South Dakota State University Sheep Unit were monitored from birth to slaughter. Ewes were 1/2 Hampshire 1/2 Finn-Dorset-Targhee and crossed onto either Hampshire or Dorper sires. Lambs were born in a 28 day lambing period (February 14 - March 14, 2002) and a blood sample for determination of total protein was obtained at approximately 24 hours of age. Lambs were weaned at 77 days (sem 1.4) of age and group fed a commercial lamb ration. Live weights were collected on lambs at weaning and the day prior to slaughter (designated as finished weight). Lambs were slaughtered at a target weight of 50-54 kg at a commercial facility, where individual identity was maintained. At slaughter, lungs were examined and abnormalities were recorded. A small number of abnormal lungs were returned to the laboratory for bacteriologic culture. Abnormalities defined as lung lesions included extensive pleural adhesions and presence of active
tracheobronchial lymph nodes. In addition, abnormalities included consolidation of lung lobes, nearly exclusively in the right cranial lobe. The percentage of lobe affected was estimated and recorded. For this analysis, lung lesions were defined to exist if the recorded percent of cranial ventral lung lobe consolidation was greater than 50 percent. Data were analyzed for associations between lung lesions and performance variables. Although only 8 percent of lambs required individual treatment for respiratory disease during life, the prevalence of lung lesions, as defined above, at slaughter was 41 of 93, or 44 percent. At slaughter, abnormalities were easily visualized at production chain speed (350 head/hour). Lung abnormalities, of any magnitude, were observed in 65 of the 93 lambs. Of these 65 abnormalities, 60 were consolidation type abnormalities. Consolidated lesions generally appeared as dark purple, firm, depressed areas of the right cranial lung lobe, not unlike observations
made in lambs diagnosed as dying of lower respiratory tract disease. Pleural adhesions were infrequently observed in association with consolidated lesions. Bacteriologic culture of affected lungs yielded Mannheimia hemolytica, M. multocida, and mycoplasma species. Microscopically, affected lungs exhibited a pyogranulomatous inflammatory response. Lambs affected with lung lesions at slaughter were actually heavier (30.11 vs 27.14 kg sem 1.03) at weaning. However, final live weight and average daily gain were both significantly depressed in lambs affected with lung lesions (56.6 vs 54.1 kg sem 0.82; 0.40 vs 0.32 kg sem 0.02, respectively). Though not significant, lambs affected with lung lesions tended to have 0.87 kg lighter hot carcass weight. Serum total protein shortly after birth, a proxy for colostral IgG absorption, was not different between affected and unaffected lambs.
Impacts
Lung lesions were easily observed at slaughter, were prevalent, and were associated with decreased performance of lambs in the feedlot finishing phase. Respiratory pathogens commonly associated with mortality were isolated from affected lungs, and were probably acquired via extension through large airways. It is unclear the timeframe or the risk factor(s) involved in lesion formation, or possible management strategies that could limit lung lesions in lambs.
Publications
- No publications reported this period
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