Seasonal pattern in the strongyle egg output of adult dairy cows in the Netherlands.

The strongyle egg output in a herd of dairy cows was studied from January 1980 until January 1981. Egg output was measured as the number of larvae per g of faeces (lpg) and this was accompanied by larval differentiation. The most important findings were an increase in the total strongyle and the ostertagia lpg in June followed by a decrease later in the summer; a marked increase in the incidence and lpg of oesophagostomum from January to May followed by a decrease from July to October and a decrease in the incidence and lpg of trichostrongylus from August onwards. Seasonal trends were not clearly defined for Cooperia oncophora, C punctata and bunostomum. Epidemiologically the ostertagia lpg increase is important. As a periparturient rise of ostertagia lpg was observed in most cows, this increase may be most significant for herds calving in spring and summer.