Sustainable control of gastro-intestinal nematodes in organic and grass-fed small ruminant production systems
The purpose of this project is to develop and validate integrated strategies for control of parasitic nematodes in organic small ruminant production in the southern US. Infection with gastrointestinal nematodes (GIN) is one of the leading health problems in sheep and goats, leading to reduced productivity and death losses, particularly of lambs and kids. There is little information available on the accepted parasite control methods for organic production. This project focuses on control of GIN through an integration of non-chemical control, including use of sericea lespedeza, a condensed tannin rich legume, copper oxide wire particles (COWP), use of FAMACHA and selective deworming, and forage systems. As there is no ‘silver bullet’ to solve the problem of GIN infection in small ruminants, combinations of these approaches are being tested at USDA-ARS, Fort Valley State University, Louisiana State University, Auburn University, Texas Agri-Life, Heifer International, and on-farm.
Objective 1A: Establishment of organic forages containing condensed tannins. A 2.5 acre plot of ‘AU Grazer’ sericea lespedeza (SL) has been established and maintained organically at USDA, ARS, Booneville, AR. Approximately 2,400 and 1,600 kg/acre of hay was produced in 2008 and 2009, respectively. Phosphorus and potassium were low in 2007 and poultry litter was incorporated in 2008. Soil will be analyzed again in 2010. Two of four 1-acre plots of ‘AU Grazer’ used for grazing appear to be productive with very few weeds, while the other two are less productive with contaminants of nutsedge, ragweed, and other forbs. Soil and forage quality and forage mass will be measured in 2010. In a study at Auburn University, AL, and Fort Valley State University (FVSU), GA, SL was established alone, with oats, rye, annual ryegrass or wheat in 2006 without or with herbicide application. The SL alone was treated with one application of Post herbicide to eliminate narrow-leaf weeds; the other plots remained untreated. By the end of the growing season, plots were evaluated for SL stand, SL dry matter and weed dry matter. In 2006, results indicated that SL alone had a higher stand and dry weight of SL compared to the other treatments; however, this stand was closely followed by SL established with rye or with wheat and without herbicide application. SL dry matter production was much higher when planted alone/herbicide. The dry weight of weeds was lower in SL alone/herbicide, but was not significantly different from the other treatments. Evaluation in 2007 indicated that SL established with rye or wheat had a forage yield that was 58 and 47%, respectively, of the SL established alone/herbicide. Ground cover in SL established with rye or wheat was 89 and 79%, respectively, whereas SL alone/herbicide had 100% ground cover. This indicated that SL established with rye or wheat had the potential to produce nearly as much as SL alone/herbicide. Establishment over grass stubble in spring of 2007 suffered major plant losses due to drought conditions. SL establishment mixed with grains failed due to heavy rain immediately after planting followed by dry weather. Experiment plots were planted in 2008 but they were lost again due to weather conditions. Objective 1B: SL included as a complete supplement for lambs/kids on pasture. Pellets have been made and feeding and examination of sheep and goats will occur in 2010. At FVSU, feeding hay of SL to small ruminants has been shown to reduce gastrointestinal nematode (GIN) infection, but length of feeding time required to achieve the effect is not known. Intact male goat kids (9-mo-old, n = 17) were fed either SL leaf meal or ground bermudagrass (BG) hay; all were given 5000 larvae of Haemonchus contortus a week after initiation of feeding, and then slaughtered on day 28 post-infection to determine effects on worm establishment. Another group of kids (n = 17) were fed the BG diet and infected with 5000 larvae each. On day 35 post-infection, kids were randomly allocated to two groups, fed either the SL or BG diet, and then groups from each treatment (n = 4) were slaughtered on 7, 14 and 28 days post-feeding. Feeding SL reduced (P < 0.05) establishment of H. contortus and total GIN, had no effect on number of mature (established) worms, but reduced (P <0.05) fecundity (number of eggs per female) of the mature GIN by day 28. The SL diet reduced (P < 0.05) FEC and increased (P < 0.05) PCV on days 7, 14, and 28 post-feeding in kids with a mature GIN infection. Objective 1C: Grazing SL as a deworming paddock. To determine the effectiveness of the condensed tannin containing forage, SL, as a deworming paddock to decrease H. contortus infection in lambs, lambs (n = 42) at Louisiana State University (LSU) grazed SL or a control paddock of mostly BG for 16 weeks. At the start of the study, FEC and PCV for the Control and SL groups were 6367 and 6133 eggs/g and 25.1 and 22.9, respectively. FEC decreased and were similar in both groups through week 4. Subsequently, FEC increased in the Control group and SL group FEC remained consistently and significantly (P < 0.05) lower than the Control group through week 11. On week 11, six Control animals required deworming. Subsequently, the FEC decreased to the level of the SL group FEC and remained similar to the end of the study. The PCV for both groups were similar throughout the study. Individual treatments for the Control and SL groups were 28 (2/lamb) and 39 (1.4/lamb), respectively. Weight gain for Control and SL groups, respectively, were 8.5 and 9.7 kg. Lambs given free choice grazing SL may take up to 4 weeks to reduce H. contortus infection, which then led to fewer required dewormings per animal and increased weight gain. In two studies conducted at USDA, ARS, Booneville, Katahdin lambs (n = 43) grazed BG, SL plus grass pasture (SLG), or continuous SL (SLC) for 56 days. Spanish doe kids (n = 38) were randomly assigned to graze BG, SLG, or SLC. Lambs and kids were supplemented corn/SBM (16% CP) to meet nutritional requirements and supplementation was greater for the BG than SL animals. Initially, H. contortus was the predominant nematode, but the population shifted to other species in the SL groups by the end of the study. The mean number of dewormings/lamb was 0.71, 0.20, and 0.21 ± 0.13 for BG, SLG, and SLC groups, respectively (P < 0.02). FEC were reduced in SLC compared with BG lambs on all days and reduced in SLG compared with BG lambs on day 56 (forage x day, P < 0.001). PCV was greater for SL than BG groups on most days (forage x day, P < 0.03). Body weight was similar among groups. COWP may have been more effective in reducing FEC in SL compared with BG groups (BG, 35.4 ± 11.6; SLG, 53.4 ± 12.3; SLC, 93.1 ± 17.3%; P < 0.05). There were fewer false positive and negative FAMACHA scores in the SL than BG groups (BG, 80.0 ± 3.8; SLG, 90.0 ± 3.8; SLC, 94.7 ± 3.7%; P < 0.02). The mean number of dewormings for doe kids was 2.1, 1.0, and 1.7 ± 0.3 for BG, SLG, and SLC groups, respectively (P < 0.03). FEC were lower in both SL groups compared with does that grazed BG (P < 0.007). PCV tended to be lower in BG does before day 28, but higher after day 42 (forage x day, P < 0.07). The BG does were lighter than both SL groups of does on days 28 and 56, but groups were similar by day 84 (forage x day, P < 0.002). COWP was not effective in reducing FEC in these does. Even though weight gains were similar, more inputs (feed, dewormer) were required for BG than SLG or SLC lambs and does. Because H. contortus was not the predominant nematode, the integrated approaches were only partially effective in controlling GIN in doe kids. Objective 1D: Use of black locust trees/branches to control GIN in goats. Seven month old doeling goats were fed whole black locust branches, chipped branches, or a control diet without condensed tannins in August 2008. There was no reduction in FEC in goats fed the black locust. However, the trees had undergone severe heat stress and the condensed tannins may have become bound and unavailable to the animal. Objective 1E: Use of Desmodium paniculatum to control GIN in goats. Desmodium paniculatum (panicled tickclover) was grown for hay last summer at Texas Agrilife Research, Stephensville. Leaves were separated from stems to make pellets (have done the same with sericea hay, which will be used as a control). Condensed tannin concentration in the leaves is about 10%. A trial will be conducted in 2010 on feeding the two pelleted diets to goats for parasite control. Objective 1F: Continuation of screening for forages high in condensed tannins. We have compiled a list of leguminous and non-leguminous forage and browse species that contain condensed tannins. To date, our list contains herbaceous legumes that have up to 5% N and total CT (TCT) vary from 0 to 16.7% when self-standards were used. Non-legume herbaceous forbs were equally high in N but contained very low TCT concentrations. Browse legumes tended to have lower CT values than herbaceous legumes when a legume was used as a standard. Some non-legume browse species ranged up to 9.3% TCT when a self-standard was used. These results indicate that a wide variability in CT concentrations exists among herbaceous and browse species and these may be useful in improving ruminant nutrition and health. Objective 2A: Identification of annual forages suitable for organic system. Annual forages examined include cowpea, soybean, and pearl millet for growing lambs and kids. Both performed well (parasite control and weight gains) on cowpea and soybean, but not on pearl millet. However, organic practices demand that annual forages not be planted on bare soil. Thus, planting practices must be examined that allow adequate production of these forages by overseeding. Sericea lespedeza and vetch overseeded onto tall fescue perform well in an organic pasture and offer increased protein to growing lambs and kids. Objective 2B: Rotational grazing systems. Growing conditions for annual forages were poor in 2009 and the rotational grazing study on these forages could not be completed. Objective 2C: To develop a forage system for sheep to improve lamb growth throughout summer months, support pregnancy during cooler months and minimize need for deworming. An organic forage system on two 20-acre plots has been managed well year round. However, forage quality continues to suffer in late summer, early fall, and is highly dependent on growing conditions for other seasons of the year. Therefore, a grain supplement is still required to meet nutritional requirements of lactating ewes and early weaned lambs. We will continue to examine other forage species and rotational grazing to minimize grain feeding. Objective 3: Test integrated, forage-based GIN control systems for organic and grass fed small ruminant production on-farm. We had intended to obtain a pelleted sericea lespedeza product from a small farm in Alabama, but implementation of the pelleting process has been slow. Therefore, this has not been tested on farm yet. We have examined the use of chicory grazing on farm, which appeared useful for parasite control in one year, but not the next. Objective 4: Complete impact assessment on non-chemical GIN control techniques on small ruminant producers. This project is still in progress.
We have completed the following objectives 1C, 1D, 1E, and are on target for other objectives except 2B (Rotational grazing) because of the adverse planting conditions in 2008 and 2009.
Impacts and Contributions/Outcomes
Impact of research demonstrated by 1) a news article generated by ARS staff that appeared in ARS News Service and ARS monthly magazine (Forage Plant Wards off Ruminant Gastrointestinal Nematode, Feb. 18, 2010) which generated much interest by producers and the industry, 2) invitation to present research on integrated parasite control at the American Sheep Industry Association Annual Conference in Nashville, TN, January 2010, 3) SBIR grant awarded to company that produces ‘AU Grazer’ sericea lespedeza, 4) invitation to present research on sericea lespedeza to control parasites at the Greater Appalachian Llama and Alpaca Conference in Harrisburg, PA, November 2010, 5) interviewed by Country Today, a farm magazine based in Wisconsin on the use of sericea lespedeza for parasite control in small ruminants; interviewed by Goat Specialist Frank Pinkerton to publish column in the April 2010 Goat Rancher which is distributed to 8,000 goat producers mainly in the Southern US, 6) More than 300 producers that received training or information on parasite control in association with this grant project.