Effects of clinical and subclinical gastrointestinal helminthiasis on digestion and energy metabolism in calves.

Digestion and energy metabolism trials were conducted in 2 groups of 4 steer calves each, experimentally infected with Cooperia and Ostertagia larvae. In group 1 calves given an amount expected to cause clinical parasitism (8,000 larvae/kg 0.75), fed intake and nutrient digestibility were significant (P less than 0.05) depressed at postinfection week (PIW) 3 (the time that infections became patent); nitrogen balance in these calves were also low. The apparent absorbed nitrogen fraction was significant (P less than 0.05) depressed because of a significant (P less than 0.05) decrease in digestion. Protein catabolism was also increased. Although energy balance was significantly depressed at PIW 3, the calves seemed to recover from the effects of parasitism by PIW 5. In group 1 calves, weight gains were significantly (P less than 0.05) depressed, with mean weight gains of 10.68 kg of body weight as compared with gains of 41.44 kg for group 3 calves (noninfected controls). In group 2 calves given an amount expected to cause a subclinical infection (800 larvae/kg 0.75), nitrogen absorption was significantly (P less than 0.05) depressed at PIW 2 and 3 and energy balance was significantly (P less than 0.05) depressed at PIW 3. In group 2 calves, mean weight gains (34.76 kg) were less than were those for group 3 calves (41.44 kg). The degree of parasitism seen in group 2 calves was comparable with that observed in field examinations of naturally infected calves of approximately the same age. Seemingly, under grazing conditions in Maine, these low levels of parasitism could result in appreciable production losses in young animals.