Experimental infections with Hyostrongylus rubidus and the effects on performance of growing pigs.

Pigs infected with Hyostrongylus rubidus at the rate of 550 larvae kg-1 body weight followed 15 days later with 220 larvae kg-1 body weight gained less weight (P less than 0.010) than uninfected control pigs. Feed efficiency (feed/gain) was 8% better (P greater than 0.10) in control than in infected pigs. Peak H. rubidus eggs per gram counts (EPG) occurred 22 days after each infection of pigs. H. rubidus EPG at necropsy were correlated with total number of adults recovered and with female/male ratio. High EPG were associated with H. rubidus populations composed of approximately equal numbers of males and females. Digestion trials consisted of pigs infected with 335 larvae kg-1 body weight compared to uninfected controls. Control pigs had higher (P less than 0.05) crude protein digestion coefficients, excreted less (P less than 0.05) N in feces and had a higher (P less than 0.05) N balance than infected pigs.