Milk production increases following treatment of subclinical parasitisms in Wisconsin dairy cattle

Over the past 20 years a series of surveys based on worm egg counts has been conducted on the prevalence of worm parasitisms in Wisconsin dairy cattle. In full acceptance of the many uses, limitations and interpretations of egg counts, these nevertheless have led us to conclude that, when eggs are found, live worms are prey sent within the cattle, that is, that active and important parasitisms are present. Our first state-wide surveys of Wisconsin dairy herds, conducted in the early 1950s, established universal prevalence of active worm parasitisms in the herds, and the latest state-wide surveys in the 1970s established the same continuous prevalence (Cox and Todd, 1962; Meyers, 1970; Todd et al 1972; Bliss, 1973; Bliss and Todd, 1973). In the past 20 years the parasitisms have not been controlled, have scarcely ever been treated until recent years, and have not declined. In three recent field studies conducted in commercial herds the worm eggs found in 5 g faeces averaged 36 in 1028 cows, 16.3 in 1003 cows and 10.2 in 488 cows…