Infection with gastrointestinal nematode parasites, particularly Haemonchus contortus is an important constraint to profitable small ruminant production in the southeastern US and worldwide. Anthelmintic drugs (dewormers) have been over-used in attempts to control this problem. Over use has resulted in high levels of resistance to dewormers where H. contortus is a problem. A more sustainable approach to parasite control involves integrating targeted, limited use of anthelmintics with non-chemical alternative control methods that reduce nematode numbers in the host animal and lower pasture contamination with eggs and larvae. The 2 studies here evaluated the use of allowing ewes and lambs to have a choice of grazing Auburn Grazer sericea lespedeza (AUGSL), a condensed tannin containing forage, or bermudagrass (BG) for a deworming affect on mature ewes and lambs. Results showed that it took about 4 weeks for the ewes and lambs to acclimate to consuming enough AUGSL to have a reduction in FEC compared to the control ewes and lambs. This indicated if ewes and lambs are give a choice, they grazed enough AUGSL to be beneficial and this might be a potential alternative for nematode control.
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Gastrointestinal nematodes are a serious constraint affecting ruminant production world-wide. Economic losses are caused by decreased production, cost of prophylaxis, cost of treatment, and the death of infected animals. Problems with nematode parasitism are often classified as production disease (i.e. chronic subclinical condition affecting productivity). These losses are compounded in the southeastern region because climatic conditions are generally more conducive to the growth and establishment of large nematode parasite populations. The most recent surveys by USDA APHIS Veterinary Services revealed that 62% and 75% of sheep producers surveyed in the US and the southeast, respectively, identified stomach/intestinal nematodes as a major concern (USDA, 1996ab). The nematode of particular concern is H. contortus that feeds on blood. Severe blood loss can occur, resulting in anemia, anorexia, depression, loss of condition, and eventual death.
The control of nematode parasites over the past several decades has relied on anthelmintic treatment. The evolution of anthelmintic resistance in nematode populations now threatens the success of these drug treatment programs (Flemming et al., 2006). There is a need for alternative non-chemical control strategies that minimize drug use.
A number of new control methods are being developed which include nematode-trapping fungi, copper oxide wire particles, hidden-gut vaccines and condensed tannin containing forages. The later was the focus of this proposal. An initial report, using goats grazing common sericea lespedeza (SL) showed a reduction of fecal egg count (FEC) (Min et al., 2004). Since establishing SL pastures may not be feasible for many producers, dried SL produces were evaluated. Feeding the AU Grazier cultivar of SL (AUGSL) as hay showed reduced FEC in goats (Shaik et al., 2006) and sheep (Lange et al., 2006). Fecal cultures of AUGSL hay-fed goats also showed reduced egg and larval viability (Shaik et al., 2006). Feeding sheep and goats ground AUGSL hay and pellets also resulted in reduced FEC and some reduction in worm numbers (Chafton, 2006; Terrill et al., 2007; Miller, unpublished data). It should be noted that the Chafton (2006) work was supported by a previous SARE Graduate Student Grant. It has been shown that to achieve the desired effect, dried forms of SL have to be fed at 50-75% of the total intake (Dykes et al, 2006). Thus, using a dried product as a supplement to grazing animals may not be practical. Preliminary work showed that providing AUGSL hay, ground hay and pellets as a supplement (approximately 10-15% of total intake) to grazing lambs did not affect FEC (Miller, unpublished data). The concept of rotating animals through a deworming paddock of SL at scheduled intervals to ensure total intake for a specified period has not been done.
This project is part of an overall approach to develop and test small ruminant control methods that will eventually be integrated for routine use on-farm. This research effort is being directed by scientists and extension personnel who formed the Southern Consortium for Small Ruminant Parasite Control (SCSRPC) in 2000. Producer education is a major objective of the Consortium and a critical component to changing paradigms and increasing adoption of new technologies. The validity of this approach of testing and validating new technology and then emphasizing producer education to increase adoption of the technology was demonstrated by previous work using FAMACHA which was successfully tested on sheep and goat farms throughout the southeastern US (Kaplan et al., 2004). Producer training workshops on proper use of FAMACHA in integrated control programs have now been conducted across most of the eastern US and the number of requests for workshops continues to increase each year.
The overall strategy for controlling nematode parasites will be to build on the successes of the Consortium which has already impacted sheep and goat production by changing the thought process of control from eradication of nematodes by the next anthelmintic “silver bullet”, to managing them with what works and is available, thus, keeping producers in business. Information has been and will continue to be disseminated through scientific and popular publications, through the Consortium web site (SCSRPC.org), and through producer workshops. Producer interest in these methodologies continues to growing rapidly, and feedback from producers that have implemented the FAMACHA system has been very positive. Developing integrated control programs that incorporate smart use of anthelmintics and alternative, non-chemical strategies along with producer education has the potential to redirect parasite control paradigms in small ruminant production systems, increasing viability and profitability.
The focus of the Consortium is to help sustain the small ruminant industry across the southeastern US and other regions that have similar problems by developing and testing environment-friendly, non-chemical methods for controlling infection that can be used in integrated on-farm programs. Educating producers to the dangers of over-use of anthelmintics is paramount to success. It is anticipated that recommended practices will be applicable to a wide geographic area. The main emphasis is on simple, effective, inexpensive techniques which will be expected to lead to producer-friendly implementation that will be both affordable and sustainable by reducing dependence upon anthelmintics while improving animal health. Use of natural deworming agents will also reduce potential chemical residues in the animal and the environment.
The concept of a deworming paddock where animals rotate through a paddock of SL at scheduled intervals has not been evaluated. Since supplement feeding of SL to grazing lambs did not efficiently reduce FEC/infection, this grazing scheme will ensure total intake of SL for a specified period which should result in a reduction of FEC/infection before returning to graze their normal pasture. This is a compromise for those producers that want to maintain their base pasture forage system, but yet can allocate a smaller paddock to SL for the purpose of deworming.
The original objective was to determine the effect of grazing sericea lespedeza, as a treatment (deworming) paddock, on gastrointestinal nematode infection in lambs. However, since some limited AUGSL forage was available for summer 2008 grazing, a group of ewes was used for an initial evaluation of this concept. Also, more recent experience indicated that sheep may take an extended period of time to acclimate to eating AUGSL, so rotating through such a pasture for short periods may not achieve the consumption necessary for adequate control. Therefore, the study design was changed to give free choice access to both bermudagrass and AUGSL pastures to see if animals would prefer grazing one over the other.
Pastures. The AUGSL pasture (1.5 acres) for this trial was planted in summer, 2007. The other 2 adjacent pastures were bermudagrass (BG, 1.5 acres each). AUGSL is a perennial forage that takes at least one year to establish for grazing purposes, therefore, the initial study was done in summer, 2008.
Study 1. The experimental conditions tested the effect of allowing mature ewes (not lambs as originally planned as not enough lambs were available) free choice access to either the AUGSL pasture or BG pasture as a means to help control nematode infection over a summer grazing season. Twenty-seven naturally infected mature ewes were randomly allocated to 2 groups based on FEC. Group 1 (control) continuously grazed one of the 1.5 acre BG pastures (n=9). Group 2 had free access to the AUGSL pasture and the other 1.5 acre BG pasture (n=18). The study period was 8 weeks. FEC and PCV were determined weekly to monitor infection level. Processing of samples was conducted in accordance with established procedures. If necessary, individuals were dewormed with a combination of levamisole and albendazole based on PCV less than 15.
Study 2. The experimental conditions tested the effect of allowing lambs free choice access to either the AUGSL pasture or BG pasture as a means to help control nematode infection over a summer grazing season. Forty-five naturally infected lambs were randomly allocated to 2 groups based on FEC. Group 1 (control) continuously grazed one of the 1.5 acre BG pastures (n=15). Group 2 had free access to the AUGSL pasture and the other 1.5 acre BG pasture (n=30). The study period was 15 weeks. FEC and PCV were determined weekly to monitor infection level. Processing of samples was conducted in accordance with established procedures. If necessary, individuals were dewormed with a combination of levamisole and albendazole based on PCV less than 15.
Study 1. FEC was equivalent (about 700 epg) at the start of the study and both groups decreased through 4 weeks when the FEC of control and AUGSL ewes was 144 and 482 epg, respectively (Figure 1). Subsequent to week 4, the control group increased and the AUGSL group decreased and at the end of the study the FECs were 580 and 94 epg, respectively. PCV remained similar through week 4 and subsequently, the control group remained relatively the same and the AUGSL group increased slightly (about 1.5%) (Figure 2). No individual dewormings were necessary during the study.
This study indicated that it took about 4 weeks for the ewes to acclimate to consuming AUGSL as that was the time of the FEC switch over. It was observed that the ewes spent most of their time in the AUGSL pasture, but they did move to and graze the BG pasture at times. It was also observed that the ewes ate more of the AUGSL over time.
Study 2. FEC was equivalent (about 6200 epg) at the start of the study and both groups decreased through 4 weeks when the FEC of control and AUGSL ewes was 2901 and 1818 epg, respectively (Figure 3). Subsequent to week 4, the control group increased and the AUGSL group remained reduced. This difference was maintained through week 11 at which time the control group decreased to the level of the AUGSL group and both groups remained similar to the end of the study. PCV remained relatively similar and decreased slightly for both groups throughout the study (Figure 4). Because initial infections were quite high, 50% of the animals in each group were dewormed in the first 2 weeks. Between week 3 and 10, 8% and 7% of the control and AUGSL groups were dewormed. On week 11, 40% of the control group was dewormed and only 7% of the AUGSL group was dewormed. Up to this point an equivalent number of dewormings was administered. The additional dewormings in the control group accounted for the decrease in FEC to the AUGSL group level. Subsequently, 4% of each group was dewormed. The initial weights of the control and AUGSL groups was 52.8 lbs and 50.4 lbs, respectively. At the end of the study the weights were 71.4 lbs and 71.8 lbs, respectively. The AUGSL group gained 2.8 lbs more than the control group.
This study indicated that it took about 4 weeks for the lambs to acclimate to consuming AUGSL as that was the time the control group FEC increased and the AUGSL group remained reduced. This was similar to the time it took the ewes in Study 1 to show a difference. Similar to Study 1, it was observed that the lambs spent most of their time in the AUGSL pasture, but they did move to and graze the BG pasture at times, and the lambs ate more of the AUGSL over time.
Educational & Outreach Activities
Results were reported at the annual meeting of the USDA SCC-81 held in Atlanta, GA in February, 2009, at the annual meeting of the Southern Consortium for Small Ruminant Parasite Control held in Athens, GA in May, 2009 and at the annual meeting of the USDA NCERA-190 held in Baton Rouge, LA in June, 2009. Results are also being presented at various producer meetings.
A manuscript is in preparation which will be submitted to Veterinary Parasitology for publication.
Results indicated that the benefit of grazing AUGSL was not achieved until about 4 weeks, so it appears that a 4 week time period is necessary for ewes and lambs to acclimate to consuming AUGSL. Thus, grazing AUGSL appears to be a viable alternative for nematode control for ewes and lambs which should help to conserve and extend the useful life of available anthelmintics.
Lambs that had free choice grazing of AUGSL and BG gained a little more than lambs that grazed BG alone.
Although this study was not intended to evaluate farmer adoption, it is apparent that producers who have the capability of planting AUGSL (seed is available) should be able to adopt this method of parasite control quite readily. And, there appears to be the added benefit of it’s nutritional value.
Areas needing additional study
The next step in this line of investigation is to test various methods of integrating AUGSL grazing and/or other AUGSL dry produces as producers capabilities dictate under on-farm evaluation conditions.