Elk (Cervus elaphus spp) are widely used as a terminal sire in the New Zealand deer industry because elk red deer crosses are heavier at 12 months of age than pure-bred red deer (Cervus elaphus) and therefore better fit market demands. However, it is unclear whether nutritional requirements differ between genotypes. A series of experiments compared young (4 - 12 months) red deer and red deer-elk cross (hybrids) in various aspects of their nutrition. Single genotype groups (10-15) of red deer and hybrid weaner stags were offered one of four pasture allowances (2 to 12 kg DM/head/day) on a rotationally grazed mixed ryegrass - white clover pasture system for 9 weeks in winter (June-July), spring (October-December) and summer (February - March). Stags were weighed and given a new allocation of pasture weekly. Pre-grazing pasture mass ranged from 800 kg DM/ha for low pasture allowances to 4500kg DM/ha for higher allowances. Winter live-weight gain was low (40-80 g/day), relatively unaffected by pasture allowance and similar for both genotypes. In spring however, hybrids gained live-weight on average 100 g/day more than red deer across all pasture allowances and the response to additional pasture allowance was large (110 g/day at 2kg DM/head/day to 300 g/day at 9.5 kg DM/head/day). At the highest pasture allowance, hybrids grew faster (350 g/day) than red deer (250 g/day), although red deer were able to achieve this live-weight gain when offered less pasture (4 vs 12 kg DM/head/day, respectively). Summer live-weight gain was lower for both genotypes and responded less to increases in pasture allowance than during spring. A second experiment compared the live-weight gain of both genotypes at ad lib feeding in an indoor environment where intake could be accurately measured. A group of red deer (n =15) and a group of hybrid (n =15) weaner stags were housed indoors during winter (3 June - 27 August) and spring (16 October - 16 December) and fed a pelleted grain based ration ad lib. Mean daily intake for each group (kg DM/head/day) was calculated as the difference between feed offered and feed refused. Hybrids had a significantly higher (P< 0.05) absolute DM intake compared with red deer in both seasons, although when expressed on a metabolic body weight basis, there was no difference between genotypes irrespective of season. Live-weight gain during winter did not differ significantly between genotypes regardless of whether it was expressed on an absolute or metabolic weight basis. Spring live-weight gain, expressed both on an absolute and metabolic live-weight basis, was significantly higher for hybrids compared with red deer (P<0.05). Red deer and hybrids increased their feed intake from winter to spring by 20% and 24% respectively on a metabolic body weight basis. Although the difference between genotypes in their seasonal increase in intake was relatively small there was a large difference in their pattern of live-weight gain. Red deer exhibited a 34% and hybrids a 76% seasonal increase in live-weight gain expressed on a metabolic live-weight basis from winter to spring. These results indicate the greater rate of live-weight gain displayed by hybrids compared with red deer was not associated with a greater ad lib intake (expressed on a metabolic body weight basis) and the seasonal increase in live-weight gain is greater for hybrids than for red deer. A further experiment estimated the energy requirement for maintenance of both genotypes. Five deer of each genotype were housed in separate pens (3.5m²) during winter (3 June - 27 August) and spring (16 October - 16 December) and randomly assigned to one of 5 feeding levels (0.5, 0.6, 0.7, 0.8, or 0.9 times estimated ad lib intake of l.5 and l.7 kg DM/head/day during the winter and 3.0 and 3.3 kg DM/head/day during the spring for red deer and hybrids, respectively. Maintenance requirement was determined by regression analysis of live-weight gain on ME intake. Although there was no seasonal effect on the live weight gain response to intake there was a significant genotype effect. To maintain live weight during either season, hybrids required a higher ME intake (0.52 MJ ME/W0.75/day compared with red deer 0.41 MJ ME/W0.75/day). The rate of increase in live weight gain to increasing intake declined as intake increased and more so for red deer than hybrids. The final experiment in the series involved individually housed deer and aimed to more precisely determine differences in maintenance requirement and examine the difference in composition of gain between genotypes. In addition, in vivo apparent DM digestibility was measured in both genotypes. Red deer (n=7) and hybrid weaner stags (n=7) were housed in individual pens for a period of 8 weeks in both winter (July - August) and spring (November - December) and offered one of 7 feeding levels which ranged from maintenance to ad lib. During each 8 week experimental period, live weight gain, apparent digestibility and feed intake were measured. Immediately prior to, and at the conclusion of each 8 week period body composition was estimated using computer-assisted topography (CT scan). In winter, there was no significant difference in the live weight gain response to intake although red deer tended to have a higher (44 vs 55 MJ/kg) requirement for gain than hybrids. In spring, red deer had a lower requirement for maintenance (0.35 vs 0.47 MJ ME/W0.75/day) but a greater requirement for live weight gain (64 vs 35 MJ/kg) than hybrids. In spring, mean ad lib intake was about 30% higher than in winter and was greater for hybrids than for red deer. Energy retention in whole body (kJ/W0.75/day) did not differ between genotypes in either winter or spring but both the energy requirement for zero energy balance (0.59 vs 0.48 MJ ME/W0.75/day) and the efficiency of utilisation (0.37 vs 0.24) was greater in spring than in winter. The disparity between live weight gain and whole body weight gain may have been due to differences in gut fill. There was no significant difference between genotypes in relative growth coefficients for lean, bone or adipose tissue in whole body. However hybrids tended to have a higher winter and lower spring growth coefficient for fat compared with red deer. Growth coefficients for adipose, lean and bone, respectively were 0.983, 1.063 and 1.026 for winter and 1.02, 0.708 and 1.727 for spring. At the same whole body weight, deer in October had less adipose tissue than in August. It is unclear whether this represents a strategy for rapid spring growth or is an artefact of experimental protocol. Apparent dry matter digestibility (DMD) did not differ between genotypes but was higher by between 7 and 15 percentage units in winter compared with spring. Unexpectedly, digestibility was positively correlated with intake. Digestibility increased by 2.6 percentage units for every 10g DM/W0.75/day increase in either season in one group and 4.1 and 2.1 percentage units for deer in winter and spring respectively in another group. Errors in faecal collection were discounted as causes of the unexpected result.

Two consecutive experiments were conducted to test a hypothesis that mixed grazing outcome is influenced by the type of stocking system applied. The objective of both experiments was to investigate the influence of co-grazing with sheep on cattle liveweight gain (LWG) under continuous (C) and rotational (R) stocking, where sheep weekly liveweight change under the two stocking systems was kept similar. In experiment I nine yearling heifers (266 ± 4.5 kg liveweight) and 27 ewe hoggets (54±0.9 kg liveweight) were continuously stocked for 19 weeks on an irrigated perennial ryegrass-white clover pasture (2.95 ha) maintained at a sward surface height (SSH) of 5cm by adding or removing additional animals in a fixed ratio (1: 1 W⁰.⁷⁵ cattle:sheep). An equal area of pasture was rotationally stocked by a similar group of animals where they received a new area of pasture daily and also had access to the grazed area over the previous 2 days. The size of the new area provided daily was such that the weekly liveweight change of rotationally co-grazed sheep was equal to that of those continuously co-grazed with cattle. Similar groups of animals were used in the second experiment with additional group of 9 heifers grazed alone on C and R pastures. Liveweight of animals was recorded weekly and final fasted weight was determined after 24-hour total feed restriction. SSH on both treatment swards was recorded daily. There were three intake measurement periods spread over the trial period. Organic matter intake (OMI) was predicted from the ratio of N-alkanes in faeces and herbage. Diet composition was determined by dissecting oesophageal extrusa samples. Grazing behaviour (bite rates and grazing time) were also recorded. The mean SSH for C pasture was 5.1±0.09 cm. Overall pre- and post-grazing SSH for R pasture was 15.9 ±0.12 and 5.6 ±0.07 cm, respectively. As determined by the protocol average daily LWG of sheep was similar between C and R (147 (±5.8) vs 138 (±6.7) g day⁻¹; (P>0.05). In contrast, cattle continuously stocked with sheep grew 200 g day⁻¹ slower than those rotationally stocked with sheep (800 (±41.6) vs 1040 (±47.7) g day⁻¹, P<0.0l). R heifers achieved 30 kg higher final fasted liveweight than C heifers (350 vs 381 kg; P<0.01). Overall LWG per ha was also 6 % higher under R than C stocking (674 vs 634 kg ha⁻¹). The OMD of both sheep (73.5 vs 75.8 %) and cattle (75.8 vs 78.0 %) diets was similar under continuous and rotational stocking. There was no significant difference OMI data also concurred with the L WG data (Cattle: 7.94 vs 6.31 (±0.32) kg day⁻¹ (P<0.05); sheep: 1.40 vs 1.44 (±0.04) kg day⁻¹ for Rand C treatments, respectively). There was no difference in clover content of cattle diet under C and R treatments. C heifers had higher number of bites per minute than R heifers (62 vs 56; P<0.05). Proportion of heifers seen grazing (every 15-minute) during four 24-hour observations was greater on C than R pasture (0.44 vs 0.31 (±0.03); P<0.05). The similarity coefficient between sheep and cattle diet was 0.61 and 0.76 under C and R stocking, respectively. The lower daily LWG of C heifers was attributed to (a) the lower SSH under C than R stocking and/or (b) the inability of cattle to compete well with sheep where there is small, continual renewal of resources (C) in contrast to a large periodic renewal under R stocking. This experiment showed that the outcome of mixed gruing can be influenced by the stocking system chosen. But it was not possible to apportion the difference in LWG of cattle between mixed grazing per se and the difference in mean grazed sward height (5.1 for C vs 10.8 cm for R). A second experiment was conducted to determine the relative performance of cattle co-grazed with sheep (CS) and grazed alone (CA) under each stocking system. Hence, there were four treatments. CA- continuous stocking (CA-C), CS- continuous stocking (CS-C), CA- rotational stocking (CAR) and CS- rotational stocking (CS-R). A total area of 4.42 ha was allocated to each stocking system. Under C stocking, 2.95 ha (2/3) was assigned to CS-C and 1.47 ha (1/3) to CA-C, and SSH on both treatments was kept at 4 cm by adding or removing extra animals. Under R stocking, CA-R and CS-R grazed side by side separated by an electric fence. They were given a fresh area daily, the size of which was varied such that the weekly LW change of R sheep was equal to that of the C sheep. CA-R received one-third of the new area though the size was adjusted regularly to achieve the same post-grazing SSH with CS-R. Measurements included: weekly liveweight change, OMI (two periods) and diet composition (using N-alkanes). The mean SSH of CA-C and CS-C swards was 4.27 and 4.26 (±0.02) cm, respectively. CA-R and CS-R swards had mean pre-grazing SSH of 14.9 and 15.2 (±0.08) cm and post-grazing heights of 4.87 and 4.82 cm (±0.03), respectively. The proportion of areas infrequently grazed was higher for CA-C than CS-C swards (0.22 vs 0.17, respectively). C and R sheep daily LWG: 155 (±0.6) and 147 (±0.7) g, and OMI: 1.96 and 2.04 (±0.ll) kg, respectively, were not significantly different. They also had similar diet composition. In comparison, CS-C heifers grew only at 69 % of the daily LWG achieved by CS-R heifers (706 vs 1028 (±72) g; P<0.05). LWG of CA-C and CA-R was 916 and 1022 (±72) g day⁻¹, respectively. The difference in LWG between CS-R and CS-C (D₁) heifers was due to difference in mean sward height, stocking system and mixed grazing, while D₂ (difference in LWG between CA-R and CAC) was due to difference in mean sward height and stocking system. D₁-D₂ (the effect of stocking system on mixed grazing) was 216 g and made up 67 % of the total difference between CS-R and CS-C. There was a significant stocking system-species mixture interaction in the final fasted LW achieved by heifers. Final fasted LW was significantly lower for CS-C than CA-C heifers (283 vs 323 (±9.7) kg), but did not differ between CS-R and CA-R (332 vs 330 (±9.7) kg, respectively). The digestibility of diet OM was similar for both continuously and rotationally stocked sheep (84.4 vs 83.2 %, respectively). Cattle diet OMO was 76.5, 74.7, 79.4 and 77.8 for CA-C, CS-C, CA-R and CS-R respectively (P>0.05). Differences in OMI followed a similar pattern to daily LWG. Mean daily OMI was 8.98, 6.24, 8.80 and 9.45 (±0.40) kg for CA-C, CS-C, CA-R and CS-R, respectively. Clover content of the diet of CA-C heifers was three times higher than that of CS-C heifers (30.7 vs 10.4 % OM; P<0.05); there was no difference in clover content of diets of CS-R and CA-R heifers (21.5 vs 23.9 % OM, respectively). In both stocking systems LWG per ha was higher on CA than CS treatments. These results suggested that the disadvantage of selective clover grazing by sheep outweighed the advantages of sheep grazing around cattle dung patches under continuous stocking. Under rotational stocking, rapid diurnal changes in sward conditions probably limited selective grazing by both sheep and cattle such that there was no disadvantage to CS cattle. The results do not provide a basis for recommending grazing cattle with sheep rather than cattle alone, but do provide some basis for recommending co-grazing of sheep and cattle using rotational rather than continuous stocking.

This study consisted of two sheep grazed dryland pasture experiments. Experiment l compared sheep production from 3-year-old cocksfoot based pastures grown in combination with white, Caucasian, subterranean or balansa clover with a ryegrass-white clover pasture and a pure lucerne forage. Sheep liveweight gain per head from each pasture treatment and the pure lucerne stand was recorded in the 2006/07 and 2007/08 seasons. The cocksfoot-subterranean clover pasture provided equal (381 kg LW/ha in 2006) or higher (476 kg LW/ha in 2007) animal production in spring and gave the highest total animal production (646 kg LW/ha) averaged across years of the five grass based pastures. However, total annual liveweight production from lucerne was higher than any grass based pasture mainly due to superior animal production during summer when lucerne provided 42-85% higher animal production than any of the grass based pastures. In Experiment 2, the effect of stocking rate (8.3 (low) and 13.9 (high) ewes + twin lambs/ha) and time of closing in spring on lamb liveweight gain, pasture production and subterranean clover seedling populations was monitored over 2 years for a dryland cocksfoot-subterranean clover and ryegrass-subterranean clover pasture in Canterbury. In both years, twin lambs grew faster (g/head/d) in spring at low (327; 385) than high (253; 285) stocking rate but total liveweight gain/ha (kg/ha/d) was greater at high (7.26; 7.91) than low (5.43; 6.38) stocking rate. Ewes also gained 0.5 and 1.5 kg/head at the low stocking rate in 2006 and 2007 respectively but lost 0.2 kg/head in 2006 and gained 0.3 kg/head at high stocking rate in 2007. Mean subterranean clover seedling populations (per m²) measured in autumn after grazing treatments in the first spring were similar at both low (2850) and high (2500) stocking rate but declined with later closing dates in spring (3850, 2950, 2100 and 1700 at 2, 4, 6, 8 weeks after first visible flower). Seedling populations measured in autumn after grazing treatments in the second spring were also unaffected by stocking rate (low 1290, high 1190) but declined with later closing dates in spring (1470, 1320 and 940 at 3, 5 and 8 weeks after first flowering, respectively). The effect of stocking rate and closing dates in spring on pasture and clover production in the following autumn was similar to the effects on seedling numbers in both years. However, clover production in the following spring was unaffected by stocking rate or closing date in the previous year at the relatively high seedling populations generated by the treatments. This was presumably due to runner growth compensating for lower plant populations in pastures that were closed later in spring. Subterranean clover runner growth in spring may not compensate in a similar manner if seedling numbers in autumn fall below 500/m². Mean annual dry matter production from cocksfoot and ryegrass pastures grown with and without annual clovers pasture production ranged from 6.4 to 12.4 t DM/ha/y but stocking rate (8.3 vs. 13.9 ewes/ha) during spring did not affect annual pasture production. Pastures overdrilled with annual clovers yielded 23-45% more dry matter production than pastures grown without annual clovers. The study confirms the important role of subterranean clover in improving pasture production and liveweight gains of sheep in dryland cocksfoot and ryegrass pastures. Lowering stocking rate from 13.9 to 8.3 ewes/ha was a less effective method of increasing seed production of subterranean clover in dryland pastures although it did lead to increased liveweight gain per head.