GASTROINTESTINAL NEMATODE INFECTIONS OF FIRST-GRAZING SEASON CALVES IN WESTERN-EUROPE - ASSOCIATIONS BETWEEN PARASITOLOGICAL, PHYSIOLOGICALAND PHYSICAL FACTORS

Analysis of 85 studies on gastrointestinal nematode infections in firs t-grazing season (FGS) calves is presented. The studies cover a 26-yea r period and were carried out in 13 countries in Western Europe. Both control and chemoprophylactic-treated (early in the season) FGS calf g roups were included. In 53 of the 85 studies, clinical outbreaks of pa rasitic gastroenteritis (PGE) were observed during the FGS in the cont rol groups. The mean initial age (and weight) of the control calf grou p was significantly associated with PGE outbreaks: 82% of control calf groups less than or equal to 6 months of age had outbreaks of PGE, co mpared to only 33% of control calf groups >6 months of age. In 92% Of trials where the geometric mean faecal egg count (MFEC) was greater th an or equal to 200 EPG on Day 56, PGE outbreaks were observed, but whe re it was <200 EPG, only 29% had PGE. The use of these two factors in assessing the likelihood of PGE outbreaks in untreated calf groups in the future FGS is therefore, proposed. No chemoprophylactic-treated gr oups had PGE, but there was a highly significant negative relationship between maximum faecal egg counts in the chemoprophylactic-treated ca lves and the proportion of the trial covered by the different chemopro phylactic systems. Higher stocking densities were significantly associ ated with higher pasture contamination in both control and chemoprophy lactic-treated calves. A highly significant positive relationship betw een the weight gained in the chemoprophylactic-treated groups and the estimated duration of the various chemoprophylactic systems was found, but there were large variations in weight gains (60-160 kg) between g roups even with the same chemoprophylactic. Despite this and other hig hly significant associations, it was not possible to indicate what wei ght gains were obtained by the end of the FGS, from factors measured e arly in the FGS. (C) 1998 Elsevier Science B.V.