Interpretive Summary: Effects of grazing birdsfoot trefoil–enriched pasture on managing Haemonchus contortus infection in Suffolk crossbred lambs
By: Dr. Caitlin Vonderohe
Gastrointestinal nematodes, particularly Haemonchus Contortus, represent one of the most significant challenges to international sheep and goat production. Historically, gastrointestinal parasites have been controlled with anthelmintics, which has led to widespread anthelmintic resistance. This has resulted in producers and scientists exploring alternative, innovative methods to control gastrointestinal nematodes to preserve livestock health and productivity.
One of these approaches is to include condensed tannin-rich legumes in the small ruminant diet. Condensed tannin-rich legumes may directly affect gastrointestinal nematodes, influence the host by improving host nutrition or influence the host’s immune response to nematode infection. Previous studies have shown that condensed tannin-rich forages, such as birdsfoot trefoil, may be highly beneficial additions to a comprehensive parasite control strategy. A recent study published in the Journal of Animal Science, entitled “Effects of grazing birdsfoot trefoil-enriched pasture on Haemonchus contortus infection in Suffolk crossbred lambs” by Mata-Padrino et al., sought to determine if birdsfoot trefoil-enriched pasture could prevent or reduce Haemonchus contortus infection in grazing lambs.
Thirty-six Suffolk/Hampshire crossbred lambs, naïve to gastrointestinal nematodes, were assigned to one of three treatments: lambs adapted to grazing birdsfoot trefoil before being experimentally infected with Haemonchus contortus larvae, lambs infected with Haemonchus larvae prior to grazing birdsfoot trefoil, and a control where lambs were allowed to graze birdsfoot trefoil pasture without exposure to Haemonchus. Bodyweight, blood packed-cell volume and fecal egg count were measured weekly on each lamb.
Lambs grazed on birdsfoot trefoil after experimental exposure to Haemonchus larvae had the highest fecal egg counts and lowest blood packed cell volumes across all time points. In these animals, the fecal egg count peaked one week after grazing then fell 88% 4 weeks after starting grazing. Packed cell volume started to increase 4 weeks after grazing, coinciding with the 88% drop in parasite load. Lambs grazed on birdsfoot trefoil prior to experimental Haemonchus infection had the greatest fecal egg counts 4 weeks after infection. The control lambs (never experimentally exposed to Haemonchus) had the greatest body weights, highest packed cell volumes and lowest fecal egg counts of the three treatments.
Overall, these results indicate that grazing birdsfoot trefoil may be somewhat effective in treating Haemonchus contortus infection. However, all of the lambs grazed on birdsfoot trefoil had modest weight gains, which indicates that lambs may need additional protein and energy supplementation to maximize the benefits of grazing birdsfoot trefoil, particularly late in the summer. Overall, nutrition, management, and forage-type are all significant aspects of a holistic parasite management system which is necessary for success in small ruminant production.
To view the full article, visit the Journal of Animal Science.