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Gastrointestinal Parasites in Australian pastoral lactating dairy cows
Loughnan, T.; Beggs, D.; Mansell, P...
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Objectives: In Australian pastoral dairy systems, a variety of ‘routine’ anthelmintic programs are used in lactating cows. These programs vary from no use of anthelmintics to administration of two doses to cattle annually. This suggests that there may be either some overuse potentiating the development of anthelmintic resistance, or underuse with consequential production inefficiencies. We aimed to identify the predominant gastrointestinal parasites in recently calved dairy cows in south-west Victoria, Australia. We also assessed the different anthelmintic management practices used on commercial, pasture-based dairy farms and their effect on measurable worm burdens.
Materials and Methods: The study included 18 commercial, pasture-based dairy farms in south-west Victoria, Australia. Faecal egg counts (FEC) were measured in recently calved cows (<30 days in milk). Fifteen primiparous and 15 multiparous animals were selected based on age (multipa- rous; 3-4 animals from each age up to 6 years of age) and calving date. Parasitism of individual animals was assessed through ultra-sensitive FEC, sensitive to 2.5 eggs per gram of faeces, in recently calved cows. These animals were sampled for individual FEC and pooled larval cultures (per group of 15 animals). Farm data such as recent anthelmintic use, management and cow body condition score (BCS) at sampling was recorded. Data analysis was undertaken using the Jamovi statistical package.
Results: Thirty-six per cent of all animals and 46% of primiparous cows had FEC of greater than 2.5 eggs per gram (epg). Ostertagi ostertagi was the most commonly identified gastrointestinal nematode in all age groups and on all farms. Cooperia oncophora were found to be the most frequent Cooperia spp, however C. pectinate or C. punctata were also present on some farms.
Multiparous cows in low BCS post calving are more likely to have a FEC of greater than 5 epg. Herds utilising anthelmintic routinely during lactation or at drying off did not have significantly different mean FEC or proportion of cows with individual FEC > 0 compared to those which did not utilise anthelmintics in lactating cows. Primiparous animals were more likely to have a reduced FEC post calving if the most recent anthelmintic was administered less than 50 days prior to calving.
Conclusion: Measuring the FEC at a sensitivity of 2.5 epg is an effective indicator that parasites are present in primiparous dairy cattle and may still be useful in assessing the presence of infection in multiparous animals if BCS is low. Whilst O. ostertagi is the most pathogenic and important gastrointestinal nematode in south-west Victoria, Cooperia punctata or C. pectinata are more prevalent than previously reported. In some herds these parasite species are still abundant in multiparous animals in moderate levels.
Anthelmintic use in Australian pasture-based systems during lactation or dry off is not likely to be effective at reducing the worm burden of cows in early lactation. Further investigation of timing and value of anthelmintic use in multiparous cattle is warranted.
Keywords: Dairy, roundworms, FEC, Australia, gastrointestinal parasites.
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About
Affiliation of the authors at the time of publication
Colac Vet Clinic, Colac, Australia;
The University of Melbourne, Melbourne, Australia;
Dawbuts, Camden, Australia.
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