Effect of sericea lespedeza leaf meal pellet supplementation on Haemonchus contortus infection in grazing ewes

Effect of sericea lespedeza leaf meal pellet supplementation on Haemonchus contortus infection in grazing ewes

Summary

Infection with gastrointestinal nematode (GIN) parasites, particularly Haemonchus contortus, a blood-feeder, is the most important constraint to profitable small ruminant production in the southeastern US and worldwide. Weanlings are especially susceptible to infection during their first grazing season. Infection with H. contortus can rapidly lead to lost production and even death. Over use of anthelmintics (dewormers) has resulted in high levels of dewormer resistance in GIN throughout the southeast and other regions where H. contortus is a problem. The problem has become so severe that it is threatening viability of small-scale and limited-resource small ruminant farm operations in this region despite continued high demand for sheep and goat products. A more sustainable approach to parasite control involves integrating targeted, limited use of anthelmintics with non-chemical alternative control methods that reduce GIN numbers in the host animal and lower pasture contamination with eggs and larvae. Grazing sericea lespedeza [a condensed tannin containing forage] and feeding whole plant (AUGrazier cultivar) hay and pellets in confinement has been shown to effectively reduce GIN infection in sheep and goats. In this study, AUGrazier sericea lespedeza (AUGSL) leaf meal pellets which have a higher concentration of condensed tannin, was evaluated, as a supplement feed, for affect on naturally acquired H. contortus infection in grazing ewes. The study had 2 phases, one during parturition/lactation and another during summer grazing. Results indicated that suplementation did not affect fecal egg count (FEC), blood packed cell volume (PCV), FAMACHA score or percent survival/developement of larvae in feces. However, there was a reduction in survival and development of Haemonchus larvae in AUGSL leaf meal supplemented parturition/lactation ewes. Results will be disseminated to scientific and producer groups via producer workshops, the Southern Consortium for Small Ruminant Parasite Control web page (SCSRPC.org), and various scientific and extension publications.

Objectives/Performance Targets

Determine the effect of AUGSL leaf meal pellets, fed as a supplement, on Haemonchus contortus infection in grazing ewes.

Accomplishments/Milestones

For Phase I of the study, 25 naturally infected pregnant crossbred (Suffolk x Gulf Coast Native) ewes were randomly allocated to 2 groups based on FEC and PCV. Group 1 (control, n = 13) and Group 2 (treatment, n = 12) were supplement fed with alfalfa pellets and AUGSL leaf meal pellets (2 pounds per head per day), respectively. Diets were fed starting 2 weeks before the start of lambing and continued through weaning. Each week, feces (for FEC) and blood (for PCV) were collected and FAMACHA scores were recorded to monitor infection level. Residual feces from each group were cultured for recovery, enumeration and identification of infective larvae. There was no difference (p > 0.05) in FEC between groups through week 6, at which time the FEC of both groups exceeded 2000 epg and it was decided to give Group 2 a strategic treatment of COWP. The efficacy of that treatment was 72.9% (p < 0.05). Subsequently, the FEC of Group 1 decreased to the level of Group 2 and there was no difference (p > 0.05) between groups for the remainder of Phase I. There was no difference (p > 0.05) between groups for PCV or FAMACHA score. Fecal cultures showed that there was no difference in percent development and survival of larvae between groups. Percent Haemonchus was similar between groups on week 0, but there was a 57% reduction for Group 2 at week 2 and remained consistently reduced by 9-43% throughout Phase I. Overall reduction of Haemonchus larvae was 29%.

For Phase II of the study, 23 of the same ewes (now open) were re-allocated to 2 groups based on FEC and PCV. Group 1 (control, n = 11) and Group 2 (treatment, n = 12) were supplement fed with alfalfa pellets and AUGSL leaf meal pellets, respectively. Diets were fed starting 4 weeks after their lambs were weaned and continued through the summer grazing season. Each week, feces (for FEC) and blood (for PCV) were collected and FAMACHA scores were recorded to monitor infection level. Residual feces from each group were cultured for recovery, enumeration and identification of infective larvae. There was no difference (p > 0.05) between groups for FEC, PCV or FAMACHA score throughout Phase II. No additional dewormings were necessary. Fecal culture data is pending.

Impacts and Contributions/Outcomes

It was expected that Group 2 supplemented ewes would have reduced FEC (specifically the peri-parturient rise in FEC during Phase I) and worm burden, which in turn would be beneficial in reducing pasture contamination for subsequent reinfection or for grazing lambs that may be put on that pasture. It was also expected that Group 2 supplemented ewe feces would have fewer infective larvae to migrate onto pasture forage, thus helping to further reduce pasture infectivity. Unfortunately, results did not indicate that supplementing (at the level provided) grazing ewes with AUGSL leaf meal pellets was effective in reducing FEC or the total number of larvae that survived and developed in feces. However, there was a consistent reduction in Haemonchus larvae surviving and developing in feces, which in itself may help to reduce some issues with Haemonchus. Overall, under the conditions of this study, the level of AUGSL leaf meal pellet supplementation that was used did reduce Haemonchus survival and development in feces, but was not adequate (by itself) for control of GIN in grazing ewes.

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