Effects of grazing by sheep or cattle on sward structure and subsequent performance of weaned lambs

The study was designed to test the hypothesis that grazing management in early season could alter sward structure to facilitate greater animal performance during critical periods. The effects of grazing a mixed perennial ryegrass/white clover sward at different sward surface heights, by cattle or sheep, in early season on sward composition and structure, and on the performance of weaned lambs when they subsequently grazed these swards in late season were determined. In two consecutive years, from mid‐May until mid‐July, replicate plots (three plots per treatment) were grazed by either suckler cows and calves or ewes and lambs at 4 or 8 cm sward surface heights (Phase 1). From mid‐August (Year 1) or early August (Year 2), weaned lambs continuously grazed, for a period of 36 d (Year 1) or 43 d (Year 2) (Phase 2), the same swards maintained at 4 cm (treatment 4–4), 8 cm (treatment 8–8) or swards which had been allowed to increase from 4 to 8 cm (treatment 4–8). Grazing by both cattle and sheep at a sward surface height of 4 cm compared with 8 cm in Phase 1 resulted in a higher (P < 0·001) number of vegetative grass tillers per m² in Phase 2, although the effect was more pronounced after grazing by sheep. Sheep grazing at 8 cm in Phase 1 produced a higher number of reproductive tillers per m² and a greater mass of reproductive stem (P < 0·001) than the other treatment combinations. The mass of white clover lamina was higher under cattle grazing (P < 0·05), especially on the 8‐cm treatment, and white clover accounted for a greater proportion of the herbage mass. These effects had mainly disappeared by the end of Phase 2. On the 4–4 and 8–8 sward height treatments the liveweight gain of the weaned lambs was higher (P < 0·05) on the swards previously grazed by cattle than those grazed by sheep. The proportion of white clover in the diet and the herbage intake also tended to be higher when the weaned lambs followed cattle. However, there was no difference in liveweight gain, proportion of white clover in the diet or herbage intake between swards previously grazed by cattle or sheep on the 4–8 sward height treatment. It is concluded that grazing grass/white clover swards by cattle compared with sheep for the first half of the grazing season resulted in less reproductive grass stem and a slightly higher white clover content in the sward, but these effects are transient and disappear from the sward by the end of the grazing season. They can also be eliminated by a short period of rest from grazing in mid‐season. Nevertheless these changes in sward structure can increase the performance of weaned lambs when they graze these swards in late season.     

THE USE OF CATTLE AND SHEEP FOR EVALUATING GRASS AND LEGUME SWARDS, A COMPARISON OF METHODS

A comparison was made of the effects of grazing with cattie and sheep separateiy hy two methods, continuous and rotationai on two forage mixtures. The two mixtures were timothy (Phleum pratense L.) with iadino white ciover (Trifolium repens L.); and brome grass (Bromus inermis Leyss) witii aifalfa (Medicago sativa L.). The rotationai system of grazing created different effects on sward composition from those caused hy the continuous grazing system. The legumes survived hetter under rotational than continuous grazing. Sheep, under both grazing systems, grazed more severeiy than cattie; they defoliated the ieaf portion of the plants and ieft more stem standing than did the cattle. Protein of the sward increased with the leaf portion, but in vitro digestibility was not altered as leaf to stem ratios changed. Although the gross effects of sheep and cattle were similar, there were differences in detail in the effect on these swards.     

Comparative studies of the influence of sward conditions on the ingestive behaviour of cows and sheep

Separate groups of non-lactating cows and wether sheep grazed at similar herbage allowances for two successive 5-d periods on swards that had previously been grazed frequently or infrequently with the intention of creating differences in canopy structure. Measurements were made of sward structure and composition, ingestive behaviour and diet composition. The preliminary treatments had little effect upon either sward conditions or animal behaviour.
Herbage mass was reduced from 4020 kg dry matter (DM) ha⁻¹ to 3290 kg DM ha⁻¹ on average over a 5-d grazing period as a consequence of the relatively low grazing pressure imposed. This resulted in a mean decline in intake per bite of 28%, and the changes for cattle and sheep did not differ significantly. However, there was a marked difference in the other behavioural responses of the two species; in the sheep biting rate fell and grazing time increased with declining herbage mass, particularly in the sward previously grazed infrequently, whereas the changes in the cattle were small.
Differences in the botanical composition of the herbage eaten by cattle and sheep were minor, but there was a small but consistent advantage to the sheep in the digestibility of the herbage eaten.
In the first of the two periods the variation in surface height after grazing was substantially greater for sheep-grazed than for cattle-grazed swards, indicating more patchy grazing by the sheep.
Estimates of daily herbage organic matter (OM) intake calculated from ingestive behaviour variables were high (means 38 and 32 g (kg LW) ⁻¹ for cattle and sheep respectively) and usually declined substantially over a grazing period.     

The effect of grazing versus cutting on dry matter production of multispecies and perennial ryegrass‐only swards

Dry matter (DM) production of multispecies swards compared to perennial ryegrass (Lolium perenne; PRG) swards under intensive grazing warrants investigation as it is relatively unknown. A 5 × 2 factorial experiment, with five sward types and two defoliation methods, was used to investigate the effect of grazing versus cutting on dry matter (DM) production of multispecies and PRG‐only swards. Five sward types were established namely: a PRG‐only sward, receiving 250 kg N ha^?1 year^?1 (PRG250), and a PRG‐only sward (PRG90), a two‐species sward with PRG and white clover (Trifolium repens; PRGWC), a six‐species sward (6S) and a nine‐species sward (9S), each receiving 90 kg N ha^?1 year^?1. Cutting plots measured 1.95 × 10 m and grazing plots measured 10 × 10 m. All plots were harvested concurrently every 21–30 days from April‐November for two years (2015 and 2016). A strip from the grazing plots was cut for DM yield determination prior to turning in cattle for grazing. There was an interaction between sward type and defoliation method (p < .01), whereby there was no effect of defoliation method on the PRG‐only swards, however, the annual DM production of PRGWC, 6S and 9S swards reduced under grazing compared to cutting (p < .001; on average 1,929 kg DM/ha lower). Multispecies swards had lower DM production under grazing compared to cutting, while the DM yield of PRG‐only swards was unaffected by defoliation method.     

Evaluation of tall fescue (Festuca arundinacea) as a forage for sheep in the temperate high‐rainfall zone of south‐eastern Australia

Tall fescue (Festuca arundinacea Schreb.) is currently seldom used in the high‐rainfall (>600 mm) zone of south‐eastern Australia. To determine its potential to improve forage availability during the summer‐autumn feed‐deficit period, a field plot‐scale experiment with sheep evaluated a Continental cultivar of tall fescue (cv. Quantum) at Hamilton, Victoria, between September 2006 and January 2009. Four grazing treatments represented set stocking or rotational grazing at the two‐, three‐ or four‐leaf stage, in a completely randomized design with three replications. Grazing treatment effects on tall fescue tiller population dynamics, forage accumulation rates and consumption, sward nutritive value and botanical composition were measured. Results showed tall fescue can persist and support year‐round grazing by sheep, subject to water availability for summer growth from summer rain or on moisture retentive heavy soils. During the summer‐autumn (December–April) vegetative phase, grazing at the three‐leaf stage optimized forage consumption, with no difference in feed value or botanical composition between the grazing treatments during these months. During the reproductive phase (September–November), feed value was highest under set stocking and declined with the production of each successive leaf. Grazing at the three‐ or four‐leaf stage prevented winter weed invasion, but winter forage consumption was low in these treatments. Set stocking or grazing at the two‐leaf stage improved winter forage consumption rates, but these swards were invaded by winter growing weeds.     

Performance and quality of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) and mixtures of both species grown with or without white clover (Trifolium repens L.) under cutting management

There is increasing interest in tall fescue (Festuca arundinacea Schreb.) in Western Europe and elsewhere, mainly because of its better drought resistance and yield potential compared with perennial ryegrass (Lolium perenne L.). Important drawbacks of tall fescue, compared with perennial ryegrass, are its lower digestibility and voluntary intake. Mixtures of both species might combine the advantages of each, and species interactions may eventually lead to transgressive overyielding. We compared the agronomic performance of tall fescue, perennial ryegrass and tall fescue–perennial ryegrass mixtures, as pure‐grass swards or in association with white clover (Trifolium repens L.). Tall fescue–perennial ryegrass mixtures differed in the proportion and ploidy of the perennial ryegrass component. Yield, feed quality and botanical composition were measured in the 3 years after the sowing year. We found significant effects of ploidy of the ryegrass variety and of the proportion of ryegrass in the initial seed mixture on the botanical composition of the swards. Nevertheless, all swards were dominated by tall fescue at the end of the experiment. No overyielding of the mixtures compared with that of single‐species swards was found, but feed quality was intermediate between that of the single‐species swards. Mixed swards had better drought resistance than L. perenne and higher feeding quality than F. arundinacea swards.     

Performance of cultivated perennial grass mixtures under different grazing intensities in the alpine region of the Qinghai-Tibetan Plateau

In 1998, seeds of four cultivated native perennial grasses, Bromus inermis (B), Clinelymus nutans (C), Elymus nutans (E) and Agropyron cristatum (A), were sown as mixtures with different seed rates in three combinations (B + C, B + E + A and B + E + C + A) in a field study in the north‐eastern part of the Qinghai‐Tibetan Plateau, China. A grazing experiment was conducted in 2000 to investigate the performance of these grass mixtures at leaf, plant and sward scales under different grazing intensities (GI). Four GIs, expressed as the proportion of herbage consumed by Tibetan lambs in relation to the available biomass (IP), were applied in the summer: no grazing, and 0·30, 0·50 and 0·70 of IP. Tiller numbers of the grasses increased and leaf photosynthetic rate, sward leaf area index (LAI) and herbage mass declined with increase in GI. No effect of GI on specific leaf area was observed. Interactions between GI and grass mixtures on the dynamics of species composition, swards’ LAI and herbage mass were found. Large fluctuations in species composition with different GIs showed the poor species compatibility and sward persistence of these grass mixtures under high GI by sheep.     

SOME EFFECTS OF MECHANICAL TREATMENTS AND SURFACE SOWING ON ROUGH HILL GRAZINGS

An experiment involving two adjacent, but contrasting, sites was conducted to examine the effect of using the rotary cultivator and the forage harvester as instruments in the improvement of indigenous hill swards at 1600 ft alt. by surfaee sowing. On a dry sward dominated by Nardus/ Festuca, both an autumn and a spring rotary cultivation were necessary to give the highest number of established seedlings. This also resulted in the greatest improvement in hotanieal composition. On a wetter Molinia-dominant sward, two separate rotary cultivations did not increase seedling establishment, compared with a single rotary cultivation. On the dry site, an autumn and a spring topping with a forage harvester established fewer seedlings, but on the wetter site the difference as compared with rotary-cultivation treatments was not significant. On this wetter site, topping by forage harvester gave an improved botanical composition by effecting a reduction in Festuca species to give a sward dominated by Agrostis and timothy.     

Defoliation and productivity of a phalaris-subterranean clover sward, and the influence of grazing experience on sheep intake

Swards of Phalaris aquatica-Trifolium subterraneum were subjected to four defoliation treatments—zero, low (11 sheep ha⁻¹) and high (22 sheep ha⁻¹) stocking rates, and weekly cutting. At high stocking rate the annual grass Hordeum leporinum dominated while clover was dominant at low and zero stocking rates. Weekly cutting suppressed species other than clover and so failed to simulate grazing.
There were similarities in net herbage production between zero and lightly grazed swards and between heavily grazed and repeatedly cut swards. Net herbage production decreased in the order undisturbed sward < lightly grazed sward < heavily grazed sward < repeatedly cut sward.
When sheep grazed swards where herbage mass was low their daily consumption of herbage, and therefore liveweight change, depended on their recent grazing experience. Sheep accustomed to swards where herbage mass was low ate more because they grazed for much longer each day than unaccustomed sheep, although they selected a diet of similar digestibility.     

Intake characteristics of perennial ryegrass varieties when grazed by yearling beef cattle under rotational grazing management

Four intermediate‐heading perennial ryegrass (Lolium perenne L.) varieties, which in previous studies had been associated with high‐ or low‐intake characteristics when swards containing them had been continuously stocked with sheep, were sown as monocultures. They were rotationally grazed, using 1‐d paddocks, with core groups of four yearling Simmental × Holstein beef heifers in 2002 and 2003 and ingestive and ruminative behaviour, and sward factors, were measured. There were two diploid (Belramo and Glen) and one tetraploid (Rosalin) perennial ryegrass varieties and one tetraploid hybrid (Lolium × boucheanum Kunth) (AberExcel) variety. Intake rate (IR) was significantly higher in August 2003 for heifers grazing Glen than those grazing Belramo [27·5 vs. 20·6 g dry matter (DM) min^?1; P = 0·019], but there were no significant differences between varieties in two other measurement periods. This is in contrast to previous results with sheep when IR were significantly higher for Glen than Belramo and for AberExcel than Rosalin. Total jaw movement rates during grazing were significantly higher for heifers on the tetraploid swards than those on the diploid swards (87·7 vs. 83·6 jaw movements min^?1; P = 0·023) in September 2002. Ruminating time was significantly lower for heifers on the tetraploid swards than those on the diploid swards (453 vs. 519 min 24 h^?1; P = 0·012) in July 2002. Digestibility of grass snips was significantly higher on the tetraploid than the diploid swards [697 vs. 680 g digestible organic matter (DOM) kg^?1 DM; P = 0·042] in September 2003 and, within diploids, was significantly higher for Glen than Belramo (696 vs. 663 g DOM kg^?1 DM; P = 0·014). There were significant differences in sheath tube and leaf lengths and in the population density of tillers between and within ploidies, which might have been expected to have influenced intake characteristics, but this was not generally found under rotational grazing with cattle. In order to separate the effects of defoliation interval from those of grazing style of the different ruminant species, it is suggested that grass variety evaluations using continuously stocked cattle swards are required.     

Grazing preference of Merino sheep for naturalized annual clover species relative to commonly sown clover species

Selective grazing of white clover (Trifolium repens) over grass species in temperate pastures results in reduced clover abundance and availability over time. Within sheep‐ and cattle‐grazed dryland (<800 mm annual rainfall) hill and high country areas of New Zealand, naturalized unsown annual clover species show greater persistence and abundance over sown clovers. With a view to understanding legume abundance in these areas, Merino sheep grazing preference was investigated for pure swards of naturalized species Trifolium dubium, T. glomeratum, T. arvense and T. striatum and commonly sown species T. repens and T. subterraneum. The Chesson–Manly preference index was used to explore the hypothesis that grazing preference differs between these species and changes as plants mature. Herbage offtake was quantified at vegetative (mid–late spring; November) and reproductive (early summer; December) stages of plant maturity. Significant preference distinctions between species (P < 0·05) occurred in December, with relative preference ranging from 0·248 for T. repens to 0·065 for T. dubium. Reduced relative preference for naturalized species was related to decreasing nutritive value from spring to summer, reflecting increased stem and flower sward content. Relative preference was negatively related to increasing acid detergent fibre and neutral detergent fibre and positively related to greater crude protein and dry‐matter digestibility. Naturalized annual clover species of lower grazing preference at reproductive maturity will benefit pasture sustainability via herbage and seed production and associated nitrogen‐fixation inputs.     

Production performance and meat quality of grazing lambs finished on red clover, lucerne or perennial ryegrass swards

The combined benefits of a high crude protein concentration, and possible protein protection and growth‐promoting properties, make forage legumes potentially attractive as a natural means of increasing liveweight gain and time to slaughter of lambs in lamb finishing systems. An experiment was conducted to compare the production performance and meat quality of grazing lambs finished on red clover (Trifolium pratense), lucerne (Medicago sativa) or perennial ryegrass (Lolium perenne) swards. Replicate (n = 2) swards of red clover, lucerne and perennial ryegrass were rotationally grazed by ten ram lambs and ten ewe lambs from weaning until selection for slaughter at UK fat class 3L. Lambs grazing the red clover sward had a significantly higher liveweight gain and required significantly fewer days to slaughter than lambs grazing the lucerne sward (305 g d^?1 vs. 243 g d^?1; 38 d vs. 50 d), which in turn had a higher liveweight gain and required fewer days to slaughter than lambs grazing the perennial ryegrass sward (184 g d^?1; 66 d). Lambs grazing the red clover and lucerne swards had significantly higher herbage intakes than those grazing the perennial ryegrass sward (2·06, 1·72 and 1·16 kg DM d^?1 respectively), but in vivo digestibility of herbage was similar. Lambs grazing the red clover and lucerne swards also had significantly higher serum urea concentrations than those grazing ryegrass (12·5, 11·1 and 6·2 mmol L^?1 respectively). Killing‐out percentage was significantly higher for lambs grazing the red clover sward than for lambs grazing the perennial ryegrass sward (48% vs. 46%). There were no significant effects of finishing system on meat flavour, but meat from lambs finished on the lucerne sward was oxidatively less stable than that from lambs finished on the perennial ryegrass sward. Grazing the forage legume swards significantly increased the proportion of linoleic and linolenic acid in muscle tissue, and therefore the proportion of unsaturated to saturated fatty acids (0·19, 0·16 and 0·12 for the red clover, lucerne and perennial ryegrass swards respectively). However, the n?6/n?3 ratio was significantly lower for the muscle of lambs grazing the perennial ryegrass sward compared with those grazing the forage legume swards (1·13, 1·08 and 0·98 for the red clover, lucerne and perennial ryegrass swards respectively). The results indicate that by grazing lambs on forage legume swards it is possible to increase individual lamb performance without compromising meat quality.     

Seasonal changes in herbage mass and nutritive value of a range of grazed legume swards under Mediterranean and cool temperate conditions

Seasonal changes in herbage mass and herbage quality of legume‐based swards under grazing by sheep or cattle were investigated at four locations in climatically different zones of Europe: Sardinia (Italy), southern France, northern Germany and south‐west England (UK). At each location standard treatments were applied to legumes typical of species widely used in each locality: Medicago polymorpha in Italy, Medicago sativa in France, and Trifolium repens in Germany and in UK. At each site comparisons were made of two other legumes: Trifolium subterraneum and Hedysarum coronarium in Italy, Onobrychis sativa and Trifolium incarnatum in France, Trifolium pratense and Lotus corniculatus in Germany, and Trifolium ambiguum and L. corniculatus in UK. Legumes were sown in mixture with locally appropriate companion grasses, and measurements were made over two or three grazing periods. In Italy M. polymorpha swards gave the greatest herbage mass in grazing period 1 but H. coronarium was more persistent. At the French site all legumes established poorly with no significant herbage mass differences between treatments. At both the UK and German sites L. corniculatus maintained a high proportion of legume in the sward; T. repens showed poor persistence under continuous sheep grazing in UK but persisted under cattle grazing in Germany, while T. ambiguum was slow to establish in the UK, and T. pratense proved to be of comparable herbage mass to the standard T. repens‐based sward in the last year of the experiment. The concentration of crude protein and in vitro digestibility of organic matter in the dry matter of herbage showed greater within‐season variation than between treatments at each site. It is concluded that, in addition to currently used species, legume‐based swards containing H. coronarium, O. sativa and L. corniculatus all have potential to contribute to forage production for low‐input grazing and their use merits further consideration in systems of livestock production in Europe.     

Livestock‐type effects on biomass and nitrogen partitioning in temperate pastures with different functional‐group abundance

Livestock grazing can be a means to maintain biodiversity in grasslands, but the outcome for vegetation structure and species composition depends on livestock type and grazing regime. This study aims at disentangling the effects of plant functional‐group abundance and livestock type on the above‐ and below‐ground biomass and N allocation in temperate pastures. We investigated the effects of cattle, sheep and mixed stocking on above‐ground biomass (AGB) and belowground biomass (BGB) and plant N pools in a replicated grazing experiment in two pasture community types with different plant functional‐group abundance (diverse vs. grass‐dominated swards). In the six treatments, AGB was reduced up to 80% compared with an ungrazed control. Cattle reduced AGB to a larger extent than sheep in diverse pastures (80 vs 44% reduction) while sheep grazing tended to do so in grass‐dominated pastures (57 vs 46% reduction); mixed stocking led to intermediate values. Grazing reduced AGB more than the N pool in AGB, thus lowering the biomass C/N ratio relative to the ungrazed control. Neither BGB nor the N pool in BGB differed between the grazing treatments and the control plots. We conclude that livestock type and functional‐group abundance are interacting factors that influence plant biomass and N pools in swards of managed temperate pastures. The contrasting biomass removal rates of cattle and sheep could be used to increase the structural heterogeneity and total plant species pool of pastures by keeping different livestock species in neighbouring patches.     

Diet selection by sheep and goats and sward composition changes in a ryegrass/white clover sward previously grazed by cattle, sheep or goats

An experiment was conducted to examine how variation in the composition and structure of mixed grass/white clover swards affected diet selection by sheep and goats. Sward composition in a mixed perennial ryegrass/white clover sward was manipulated by continuous grazing from 28 May to 28 July (pre-experimental phase) with cattle, sheep or goats, and then from 29 July to 2 September (experimental phase) with sheep or goats in a factorial design replicated twice. Sward surface height was maintained at 6 cm by regular adjustment of stocking density. Grazing by different sequences of animal species resulted in significant differences in the proportions of white clover in the sward, and especially in the proportion of clover lamina and petiole. Grazing by goats in the pre-experimental phase led to greater proportions of clover lamina and petiole in the whole sward and the sward surface. The proportion of white clover in the diet selected by sheep in the experimental phase was consistently higher than that in the sward as a whole, but was closely related to that near to the sward surface (approximately the top 2 cm). For goats there was no significant relationship between the proportion of clover in the diet and in the whole sward, and they generally selected a diet with a lower proportion of white clover than was present in approximately the top 2 cm of the sward. It is concluded that on mixed grass/white clover swards goats do not graze as deeply into the sward as sheep and that this results in a lower proportion of white clover in their diet and therefore allows higher proportions of white clover to develop under grazing by goats than by sheep.     

Controlled grazing studies on Nardus grassland: effects of between-tussock sward height and species of grazer on diet selection and intake

Groups of mature, non-lactating sheep and cattle grazed a Nardus stricta community during the growing season for six consecutive years from 1984 to 1989. Three unreplicated treatments were applied by continuous variable stocking to maintain between-tussock sward height at (a) 4·5 cm by cattle grazing and (b) 4·5 cm or (c) 3·5 cm by sheep grazing. Diet composition and herbage intake were measured from 1984 to 1987 on three occasions in the growing season, and live weight and stock density were recorded from 1984 to 1988. The diet of cattle usually contained more dead herbage, Nardus, sedges and rushes but less forbs and other fine-leaved grasses than the diet of sheep. Principal coordinate analysis showed different trends across years in diet composition, especially between the sheep and cattle treatments at 4·5 cm. Diet digestibility was usually higher for sheep treatments than for the cattle treatment. Diet digestibility and herbage intake increased between 1984 and 1985, and 1986; they also declined from spring to late summer. Regression of diet digestibility on independent principal components — which were derived from diet composition measurements — showed that the two most important principal components accounted for 72% of the variation in digestibility. Stock-carrying capacity (kg LW × d ha^?1, calculated from live weight, grazing days and stock density) was greater on the cattle treatment than on either sheep treatment. Stock-carrying capacity also increased more in successive years on the cattle than on either sheep treatment, and it was greater on the sward maintained at 3·5 cm than at 4·5 cm by sheep. These increases in stock-carrying capacity were generally positively associated with the increase in the percentage specific frequency both of live material and of the more productive grasses in the swards. These data indicate that sheep-only stocking tends to Nardus dominance and suggest that further study using productive cattle — either alone or mixed with sheep — is needed, preferably in association with measurements of floristic change both within and between tussocks.     

Frequency distributions of sward height under sheep grazing

Cattle and sheep can create and maintain a mixture of relatively tall and short patches in grass swards through selective grazing. In swards that are grazed by cattle this heterogeneous structure can result in the frequencies of height measurements having a skewed distribution that has variously been better described by the double‐normal distribution the gamma distribution and the Weibull distribution than by the more common normal distribution. The fit of these statistical distributions, and the adequacy of the potentially useful log‐normal distribution, to sward height frequencies were tested in sown temperate swards grazed by sheep and compared within a single sward. It was concluded that the single‐normal and Weibull distributions were inadequate and that overall the log‐normal and gamma distributions had the best fit to the measurements.     

How do severity and frequency of grazing affect sward characteristics and the choices of sheep during the grazing season?

The effect of grazing frequency and severity on sward characteristics and preferences by sheep was investigated from April to September. Two levels of grazing severity were imposed by varying the numbers of ewes grazing 200 m² plots for 24 h: four (S, severe) or two (L, lax) ewes. Grazing frequency was either 1 d week^?1 (F, frequent) or 1 d every 2 weeks (I, infrequent). By combining frequency and severity, four treatments were obtained: SF, LF, SI and LI. The six binary combinations (SF/LF, SF/SI, SF/LI, LF/SI, LF/LI and SI/LI) were studied in preference tests. Treatments LF, SI and LI were characterized by a high sward surface height, biomass and amount of reproductive green tissues relative to treatment SF. Herbage quality was not different between the grazing treatments between April and July. In September, after a 6‐week period of regrowth, herbage quality was significantly higher for the SF treatment than the other treatments. The sheep preferred the swards grazed at a low frequency between April and July, and then changed their preference in favour of the sward with higher quality herbage (treatment SF). The relative abundance of green laminae and the relative digestibility of the swards helped to explain the preferences observed. For a low grazing pressure at the spatio‐temporal scale studied, sheep should graze swards at a relatively low frequency but at a high severity of grazing rather than the reverse.     

The effect of different legume‐based swards on intake and performance of grazing ruminants under Mediterranean and cool temperate conditions

Intake and performance of sheep or cattle grazing legume‐based swards were assessed over 2 years at four locations in Europe with different climatic conditions: Sardinia (Italy), southern France, northern Germany and south‐west England (UK). Legume species were sown in mixtures with locally appropriate companion grass species. Standard legume species commonly used at the location (Medicago polymorpha in Italy, Medicago sativa in France, and Trifolium repens in Germany and UK) were compared with two alternative legume species characterized by different agronomic or nutritional characteristics. They were: Trifolium subterraneum and Hedysarum coronarium in Italy; Trifolium incarnatum and Onobrychis sativa in France; Trifolium pratense and Lotus corniculatus in Germany; and Trifolium ambiguum and L. corniculatus in the UK. Lactating milk sheep in Italy, non‐lactating ewes in southern France, growing cattle in Germany, and ewes and lambs in the UK were used in three replicates per treatment. Intake and performance of sheep and cattle in various treatments varied with location, year and period within year. In Germany, intake and performance by cattle were not affected by treatment. In contrast, at the other locations, sheep grazing standard or alternative legume species known to contain condensed tannins (sulla, sainfoin and birdsfoot trefoil) had higher proportions of legume and crude protein (CP) concentrations in the diet and higher CP intakes than those grazing the other alternative legume species. Sheep performance paralleled these results. It is concluded that there is potential for a greater use of alternative legume species, at least for sheep‐grazing systems, in both the Mediterranean and cool temperate zones of Europe.     

Effects of grazing by sheep or goats on sward composition in ryegrass/white clover pasture and on subsequent performance of weaned lambs

An experiment was conducted to assess the effects of grazing a perennial ryegrass (Lolium perenne) / white clover (Trifolium repens) sward by sheep or goats on sward composition and structure and on subsequent diet selection, herbage intake and liveweight gain by weaned lambs. From mid-May to late July (phase 1), ewes with twin lambs or yearling Scottish Cashmere goats grazed continuously swards maintained at 4- or 8-cm sward surface height. From mid-August to the end of September (phase 2), weaned lambs continuously grazed the same swards maintained at 4 cm (treatment 4–4) or at 8 cm (treatment 8–8) or which had been allowed to increase from 4 cm to 8 cm (treatment 4–8). By the end of phase 1, swards grazed by goats had higher proportions of white clover in the whole sward (0.377 vs. 0.181; s.e.d 0.0382; P < 0.001) than those grazed by sheep, irrespective of sward height treatment. This resulted in phase 2 in a higher proportion of white clover selected ( P <0.001), higher herbage intakes ( P < 0.001) and higher liveweight gains ( P < 0.001) by weaned lambs grazing swards previously grazed by goats compared with those previously grazed by sheep. There were higher proportions of clover present in the swards from treatment 4–8 at the beginning of phase 2 compared with the other sward height treatments and consequently weaned lambs had, on this treatment, a higher proportion of clover in their diet ( P <0.001), higher herbage intakes ( P <0001) and higher liveweight gains ( P <0.001). It is concluded that goats can be integrated into sequential grazing systems with sheep on grass/clover swards and this can result in an increase in the proportion of clover in swards and increased sheep performance.