| Abstract: | Three groups of calves, previously grazed on permanent pastures contaminated with bovine trichostrongyle (Ostertagia and Cooperia species) infective larvae, were housed from October to May. During the grazing season one group had received fenbendazole at fortnightly intervals to suppress trichostrongyle infections, one received a morantel sustained release bolus before grazing to limit trichostrongyle contamination of the pasture, and the control group was only medicated when heavy infections caused clinical type 1 ostertagiasis. Digestibility of the whole diet was poorer in the control cattle, particularly for dry matter, crude protein and energy fractions. Balance studies conducted throughout the winter housed period showed that both increased faecal and urinary nitrogen outputs in the control animals contributed to a significantly reduced overall nitrogen retention. The effects were most apparent during clinical type 2 ostertagiasis, which occurred in March in the control group. |
