Effects of sheep and cattle alternate grazing on sheep parasitism and production.

Production of sheep (nursing ewes) grazing alternately with cattle (growing weaned heifers) was compared to the production of sheep or cattle grazing alone (controls). Pasture production and sheep parasitism were also monitored. The herbage allowance was higher for the control heifers than for the alternate heifers, but the leaf to green material ratio (LGMR) was lower, and no difference on heifer growth was revealed (443 vs. 431g.d(-1), P = 0.54). The LGMR was higher for the alternate sheep (+3 points) than for the control sheep, except during the dry season, when the herbage density was lower. The effects of parasitism on the packed cell volume of alternate ewes and lambs were lower than those of control ewes and lambs. However, the infection of sheep by Cooperia sp. (better adapted to cattle) was significantly higher for the alternate sheep than for the controls, and some indication of cattle infection by Haemonchus contortus was suggested. The 70-day lamb weight was higher in the alternate grazing system than in the control (+0.76,+1.11 and+0.61kg for the dry, intermediate and rainy seasons, respectively), and the average 70-day lamb production per ewe exposed was 21.42kg in the alternate grazing system vs. 18.59kg in the control (P = 0.003).