A comparison of the diet composition of guanacos (Lama guanicoe) and sheep when grazing swards with different clover : grass ratios

An experiment was conducted to compare the diet composition of guanacos and sheep when grazing grass/clover swards containing different amounts of clover. Experimental plots were prepared with clover:grass ratios of 40:60 (Low), 60:40 (Medium) and 80:20 (High). Two separate grazing trials were then conducted with these plots at two different swards heights, 20 cm (Tall) and 10 cm (Short). Sward composition and herbage biomass were determined for each plot using quadrat cuts, and the sward surface of each plot was characterised using a vertical point quadrat. Diet samples were collected using five animals of each species fistulated at the oesophagus. The sheep diet contained significantly more clover than the guanaco diet when the animals grazed the Medium plot of the Tall trial (31% versus 10%, P < 0.05) and the Low plot of the Short trial (56% versus 25%, P < 0.05). Statistically significant differences in the amounts of green grass leaf, dead grass leaf, grass vegetative stem, dead clover leaf and clover petiole in diets consumed by the two animal species were also recorded during the experiment. The sward composition and diet composition results obtained were used to calculate selectivity indices for individual dietary components. Both species strongly selected green grass leaf. In contrast, there was no consistent pattern to the selectivity indices for green clover leaf, although the response of the guanacos to this component was generally more negative than that of the sheep. The results of this study suggest that grazing by guanacos has the potential to improve the nutritive value of grass/clover swards for sheep, particularly if the sward being grazed initially contains more grass than clover.