Two experiments were conducted to determine if type of stocking system influenced the intake and live-weight gain (LWG) of cattle co-grazed with sheep on sown ryegrass/white clover pasture.
In experiment 1 (134 days), yearling heifers (no. = 9) plus ewe hoggets (no. = 27) were co-grazed (1: 1 M0·75) using continuous (C-CS) or rotational (R-CS) stocking. In experiment 2 (126 days), a cattle alone (no. = 9) treatment was included under each stocking system (C-C and R-C). Initial live weight of heifers was 266 (s.e. 4·5) and 232 (s.e. 4·4) kg and that of hoggets was 54 (s.e. 0·9) and 47 (s.e. 0·7) kg in experiments 1 and 2, respectively. In both experiments, the area offered daily to R-CS group was manipulated to promote a weekly live-weight change in sheep similar to that on the C-CS treatment. C-C cattle in experiment 2 were grazed at similar sward surface height (SSH) to C-CS, and R-C cattle at similar pre- and post-grazing SSH to R-CS. SSH was measured daily on all treatments and regulated on the continuously stocked treatments by addition and removal of non-experimental animals. Organic matter intake (OMI) was determined from the ratio of n-alkanes in faeces and herbage. Animals were weighed weekly.
Mean SSH on continuously stocked pastures was 5·10 (s.e. 0·03) and 4·26 (s.e. 0·02) cm for C-CS in experiments 1 and 2, respectively, and 4·27 (s.e. 0·02) cm for C-C in experiment 2. The mean pre- and post-grazing SSH for R-CS was 15·9 (s.e. 0·12) and 5·60 (s.e. 0·07) cm, respectively in experiment 1, and 15·2 (s.e. 0·08) and 4·82 (s.e. 0·03) cm, respectively in experiment 2. On R-C swards pre- and post-grazing SSH was 14·9 (s.e. 0·08) and 4·87 (s.e. 0·03) cm, respectively.
In experiment 1, cattle continuously co-grazed with sheep grew significantly more slowly than those rotationally co-grazed with sheep (804 (s.e. 41·6) v. 1039 (s.e. 47·7) g/day, P < 0·01). Sheep LWG did not differ between stocking treatments (150 v. 138 g, P > 0·05 for C-CS and R-CS respectively). These findings were confirmed in the second experiment in which C-CS cattle only grew at 0·69 of the daily LWG achieved by R-CS cattle (706 v. 1028, (s.e. 72) g/day; P < 0·05) at similar sheep LWG (155 v. 147, (s.e. 6·5) g/day respectively). LWG of C-C and R-C cattle was similar (916 v. 1022, (s.e. 72) g/day; P > 0·05). LWG per ha in both experiments was higher on R-CS than on C-CS treatments, and on cattle alone than on CS treatments. Treatment effects on OMI and final fasted live weight were similar in pattern to LWG.
It is suggested that the observed disadvantage to cattle when co-grazed with sheep under continuous stocking and the lack of effect when rotationally co-grazed reflected a difference in the two stocking systems in providing opportunities for complementary/competitive use of pasture resources.