The current study investigated the effects of pre-grazing herbage mass (PGHM, 1500 or 2500 kg dry matter (DM)/ha) and post-grazing sward height (PGSH, 4 or 6 cm) on herbage production and its nutritive value and DM intake, grazing behaviour and growth of Charolais steers (n = 96; 12 months of age; 396 ± 19.0 kg) during a 222-day grazing season, and the subsequent effect of an indoor finishing diet (grass silage alone or supplemented with concentrates) for 146 days, on performance and carcass traits. Steers were assigned to one of 12 grazing groups and group was assigned to a 2 (PGHM) × 2 (PGSH) factorial arrangement of treatments. At the end of the grazing season, live-weight was 16 kg heavier for PGHM-1500 than PGHM-2500 and 34 kg heavier for PGSH-6 than PGSH-4. After indoor finishing, there was no difference in carcass weight between PGHM treatments, but PGSH-6 had a 19 kg heavier carcass than PGSH-4. Herbage production was 881 and 517 kg DM/ha greater for PGHM-2500 than PGHM-1500 and for PGSH-4 than PGSH-6, respectively. Grazing stocking rate did not differ between PGHM treatments but PGSH-4 carried 1.35 more steers/ha than PGSH-6. Supplementing concentrates during the indoor period increased carcass weight (42 kg) and fat score (2.10 units). In conclusion, grazing to 6 rather than 4 cm, increased individual carcass weight but not carcass weight gain/ha. Compared to PGHM-2500, grazing PGHM-1500 increased steer live-weight gain at pasture, but did not affect carcass weight following indoor finishing.

An understanding of the processes involved in grazing behaviour is a prerequisite for the design of efficient grassland management systems. The purpose of managing the grazing process is to identify sward structures that can maximize animal forage daily intake and optimize grazing time. Our aim was to evaluate the effect of different grazing management strategies on foraging behaviour and herbage intake by sheep grazing Italian ryegrass under rotational stocking. The experiment was carried out in 2015 in southern Brazil. The experimental design was a randomized complete block with two grazing management strategies and four replicates. The grazing management treatments were a traditional rotational stocking (RT), with pre- and post-grazing sward heights of 25 and 5 cm, respectively, and a ‘Rotatinuous’ stocking (RN) with pre- and post-grazing sward heights of 18 and 11 cm, respectively. Male sheep with an average live weight of 32 ± 2.3 kg were used. As intended, the pre- and post-grazing sward heights were according to the treatments. The pre-grazing leaf/stem ratio of the Italian ryegrass pasture did not differ between treatments (P > 0.05) (~2.87), but the post-grazing leaf/stem ratio was greater (P < 0.001) in the RN than in the RT treatment (1.59 and 0.76, respectively). The percentage of the non-grazed area was greater (P < 0.01) in post-grazing for RN compared with RT treatment, with an average of 29.7% and 3.49%, respectively. Herbage nutritive value was greater for the RN than for the RT treatment, with greater CP and lower ADF and NDF contents. The total time spent grazing, ruminating and resting did not differ between treatments (P > 0.05), with averages of 439, 167 and 85 min, respectively. The bite rate, feeding stations per min and steps per min by sheep were greater (P < 0.05) in the RN than in the RT treatment. The grazing time per hour and the bite rate were greater (P < 0.05) in the afternoon than in the morning in both treatments. The daily herbage intake by sheep grazing Italian ryegrass was greater (P < 0.05) in the RN than in the RT treatment (843.7 and 707.8 g organic matter/sheep, respectively). Our study supports the idea that even though the grazing time was not affected by the grazing management strategies when the animal behaviour responses drive management targets, such as in ‘Rotatinuous’ stocking, the sheep herbage intake is maximized, and the grazing time is optimized.

Cultivated pastures in southern China are being used to improve forage productivity and animal performance, but studies on grazing behaviour of goats in these cultivated pastures are still rare. In the current study, the grazing behaviour of Yunling black goats under low (5 goats/ha) and high (15 goats/ha) stocking rates (SRs) was evaluated. Data showed that the proportion of time goats spent on activities was: eating (0.59–0.87), ruminating (0.05–0.35), walking (0.03–0.06) and resting (0.01–0.03). Compared with low SR, goats spent more time eating and walking, and less time ruminating and resting under high SR. Goats had similar diet preferences under both SR and preferred to eat grasses (ryegrass and cocksfoot) more than a legume (white clover). The distribution of eating time on each forage species was more uniform under high v. low SR. Bites/step, bite weight and daily intake were greater under low than high SR. Results suggest that the SR affects grazing behaviour of goats on cultivated pasture, and identifying an optimal SR is critical for increasing bite weight and intake.

The principles of domestic herbivore nutrition are well understood and have been developed through detailed physiological studies, although methods to accurately measure field-based intake still challenge herbivore nutrition research. Nutritional ecology considers an animal's interaction with the environment based on its nutritional demands. Although there are a number of theoretical frameworks that can be used to explore nutritional ecology, optimal foraging provides a suitable starting point. Optimal foraging models have progressed from deterministic techniques to spatially explicit agent-based simulation methods. The development of optimal foraging modelling points towards opportunities for field-based research to explore behavioural preferences within studies that have an array of nutritional choices that vary both spatially and temporally. A number of techniques including weighing animals, weighing herbage, using markers (both natural and artificial) and sampling forage, using oesophageal-fistulated animals, have been used to determine intake in the field. These intake measurement techniques are generally most suited to studies that occur over a few days and with relatively small (often less than 10) groups of animals. Over the last 10 years, there have been a number of advances in automated behavioural monitoring technology (e.g. global positioning systems) to track animal movement. A number of recent studies have integrated detailed spatial assessments of vegetation using on-ground sampling and satellite remote sensing; these data have been linked to behavioural preferences of herbivores. Although the recent studies still do not address nutritional interactions over months or years, they do point to methods that could be used to address landscape scale nutritional interactions. Emerging telemetry techniques used to monitor herbivore behavioural preferences and also to determine detailed landscape vegetation mapping provide the opportunity for future herbivore nutritional ecology studies.

The benefits of using white clover in pastures have been widely recognised for many years. However, clover is perceived as being unreliable because of its typically low content, which is spatially and temporally variable, in mixed pastures. One proposed solution to increase the proportion of clover in the diet of grazing animals and composition in the pasture is to spatially separate clover from grass within the same field. In a field experiment ryegrass and white clover were grown in fine mixtures, and in pure alternating strips of ryegrass and clover of 1.5 m, 3 m or 18 m width within a field. Pastures were grazed for two grazing periods of 9 and 12 weeks, and measurements of sward surface height (SSH), herbage mass and composition and clover morphology were taken. Grazing behaviour was also observed. Results showed that spatial separation in the long term, when compared with a fine mixture, increased clover availability (18% to 30% v. 9%, based on standing dry matter) and was not grazed to extinction. Ewes maintained their preference for clover throughout the experiment (selection coefficient 2 to 5), which resulted in a reduction in the SSH of clover in monocultures to <3 cm and significant changes to the morphology of clover (smaller leaves, shorter petioles and thicker stolon), at the expense of maximising their intake. Spatial separation in the short term may therefore allow grazing animals to select their preferred diet; however, in the long term in continuously grazed pasture, their preference for clover depletes its availability.

One of the main aims of pasture-based systems of dairy production is to increase the proportion of grazed grass in the diet. This is most easily achieved by increasing the number of grazing days. However, periods of inclement weather conditions can reduce the number of days at pasture. The two objectives of this experiment were: (i) to investigate the effect of restricting pasture access time on animal production, grazing behaviour and dry matter intake (DMI) of spring calving dairy cows in early lactation; and (ii) to establish whether silage supplementation is required when cows return indoors after short grazing periods. In all, 52 Holstein–Friesian spring calving dairy cows were assigned to a four-treatment study from 25 February to 26 March 2008. The four treatments were: full-time access to pasture (22H; control); 4.5-h- pasture access after both milkings (2 × 4.5H); 3-h pasture access after both milkings (2 × 3H); 3-h pasture access after both milkings with silage supplementation by night (2 × 3SH). All treatments were offered 14.4 kg DM/cow per day herbage from swards, with a mean pre-grazing yield of 1739 kg DM/ha above 4 cm, – and were supplemented with 3 kg DM/cow per day of concentrate. The 2 × 3SH treatment was offered an additional 4 kg DM/cow of grass silage by night. Restricting pasture access time (2 × 3H, 2 × 3SH and 2 × 4.5H) had no effect on milk (28.3 kg/cow per day) and solids-corrected milk (27.2 kg/cow per day) yield when compared with the treatment grazing full time. Supplementing animals with grass silage did not increase milk production when compared with all other treatments. Milk protein concentration tended to be lower (P = 0.08; 32.2 g/kg) for the 2 × 3SH animals when compared with the 22H animals (33.7 g/kg). The grass DMI of the 2 × 3SH treatment was significantly lower (−2.3 kg DM/cow per day) than all other treatments (11.9 kg DM/cow per day), yet the total DMI of these animals was highest (16.6 kg DM/cow per day). The 22H cows grazed for 481 min/cow per day, which is significantly longer than all other treatments. The 2 × 3H animals grazed for 98% of the time, whereas the 2 × 3SH grazed for 79% of their time at pasture. Restricting pasture access time did not affect end body weight or body condition score. The results of this study indicate that restricting pasture access time of dairy cows in early lactation does not affect milk production performance. Furthermore, supplementing cows with grass silage does not increase milk production but reduces grazing efficiency.

Host-parasite interactions are often seen as an arms race, with parasites attempting to overcome host resistance to infection. Herbivory is a common route of transmission of parasites that represents the most pervasive challenge to mammalian growth and reproduction. The present paper reviews the foraging skills of mammalian herbivores in relation to their ability to exploit plant properties to combat parasites. The starting point is that foraging behaviour may ameliorate the impact of parasitism in three ways; hosts could: (1) avoid foraging in areas contaminated with parasites; (2) select diets which increase their resistance to parasites; (3) select for foods containing anti-parasitic properties (self-medication). Details are given of the pre-requisite skills needed by herbivores if they are to combat parasitism via behaviour, i.e. herbivores are able to: (a) determine their parasitic state and alter their behaviour in relation to that state (behaviours 1, 2 and 3); (b) determine the environmental distribution of parasites (behaviour 1); (c) distinguish plant species or plant parts that increase their resistance to parasites (behaviour 2) or have anti-parasitic properties (behaviour 3). Mammalian herbivores cannot detect the presence of the parasites themselves and must rely on cues such as faeces. Despite the use of these cues contacting parasites may be inevitable and so mechanisms to combat parasitism are necessary. Mammalian herbivores have the foraging skills needed to exploit the heterogeneous distributions of nutrients and parasites in complex foraging environments in order to avoid, and increase their resistance to, parasites. Current evidence for the use of plant secondary metabolites (PSM) by herbivores for self-medication purposes remains equivocal. PSM have both positive (anti-parasitic) and negative (toxic) effects on herbivores. Here details are given of an experimental approach using tri-trophic (plant-herbivore-parasite) interactions that could be used to demonstrate self-medication in animals. There is strong evidence suggesting that herbivore hosts have developed the foraging skills needed to take advantage of plant properties to combat parasites and thus use behaviour as a weapon in the host-parasite arms race.

The introduction of legumes in grass-based swards provides some economic and agronomic advantages, often allowing an increase in the performance of grazing ruminants. The aim of this study was to obtain a better quantification of the nutritional benefits to dairy cows after introducing white clover into swards of perennial ryegrass (PRG), using two ages of regrowth. Four treatments were studied in a 2 ✕ 2 factorial design with two sward types and two ages of regrowth. The swards were either a pure perennial ryegrass sward with nitrogen (N) fertilization, or a perennial ryegrass/white clover mixture (GC) with no N fertilization. The regrowth ages were 19 and 35 days (treatments: PRG19, PRG35, GC19 and GC35). The proportion of clover in the GC swards was on average 420 g/kg dry matter (DM). Twelve late-lactation Holstein cows, fistulated at the rumen and duodenum, were used according to a 4 ✕ 4 Latin-square design with four 11-day periods. The pasture was strip-grazed with 12 kg DM per cow of herbage above 5 cm offered daily in all the treatments.

The effects of sward type and regrowth age were often additive, in particular for herbage intake and milk yield. Herbage organic matter (OM) intake, duodenal non-ammonia N (NAN) flow and milk yields were higher on the GC swards and lower on the older regrowths. Finally, the performance of the cows was similar on the PRG19 and GC35 treatments. The OM digestibility of the selected herbage as well as the duodenal nitrogen flux per kg digestible OM intake was not affected by the sward type. Ruminal fermentations were more intense with mixed swards and the youngest regrowths. The daily grazing time and the daily pattern of grazing activities were modified by the type of sward and by regrowth age. The average OM intake rate was higher on the GC swards than on the PRG swards. In this study, the nutritional advantage of introducing white clover into swards of perennial ryegrass was related to an increase in herbage intake and not to any improvement in the nutritive value of the sward.

Forty single lambs were either artificially reared indoors or were at pasture with their mothers until weaning at 3 months of age, after which one half of each group were joined by five adult, dry ewes, to examine the effects of grazing experience and presence of adult ewes on the response to the introduction of novel grass species. Lamb groups sequentially grazed paddocks with one, two, three and then four grass species in four 1-week periods, and grazing and ruminating times and pasture biting rates were recorded during daylight hours. In the first period the lambs grazed only perennial ryegrass, then timothy, cocksfoot and finally red fescue were introduced in periods 2 to 4 respectively. The total time that lambs spent grazing and ruminating were both increased (P < 0·001) by grazing experience and to a lesser extent by the presence of adult ewes. Pasture biting rate was considerably increased by experience, and to a lesser extent adult presence, with a synergistic effect between these two factors (P < 0·001). Timothy and to a lesser extent perennial ryegrass were the most preferred species, and lambs spent less time grazing cocksfoot than either of these two, and even less time grazing red fescue (P < 0·001). Experience of grazing particularly increased the time spent grazing cocksfoot and red fescue (P < 0·001), but the presence of adult ewes did not increase the time lambs spent grazing novel species (P = 0·59). The pasture biting rate was greater on species that the lambs preferred grazing (P < 0·001), but neither experience nor ewe presence increased the biting rate on novel species in the period of their introduction. It is concluded that although both grazing experience and, to a lesser extent adult presence, increased the total time spent grazing and the pasture biting rate, only grazing experience increased the acceptability of novel species.

Four groups of eight primiparous ewes and their single lambs were grazed for 2 weeks on pasture containing one of four novel grass species – perennial ryegrass, timothy, cocksfoot and red fescue. When subsequently grazed in a field with randomized plots of the four species, both ewes and lambs spent longer grazing the species to which they had been accustomed than was spent by ewes and lambs accustomed to other species. This effect was proportionately greater for the lambs than the ewes, and the lambs responded most to experience of cocksfoot and red fescue. Both ewes and lambs spent most time grazing perennial ryegrass and timothy, and least time grazing red fescue, with cocksfoot intermediate. It is concluded that perennial ryegrass and timothy are grazed by ewes and lambs in preference to cocksfoot and red fescue, but that a two week period of experience will increase the attractiveness of the less-preferred species, particularly to lambs.

The management of pastures used by horses poses various problems: swards are often grazed down rapidly, patches of bare ground and refused areas develop. In order to gain a better understanding of the plant-animal interaction behind this problem the influence of sward height on bite dimensions (bite depth, weight, volume, area) of horses was investigated. Perennial ryegrass (Lolium perenne) microswards were grown on artificial substrate to four different heights (3, 8, 15, 19 cm) but the same plant density. Biomass and bulk density for each sward height was determined. Eight horses (predominantly Thoroughbred ×) were allowed to take six bites of each grass height. Bite depth, weight, volume and bite area were calculated.

Bite depth, weight, volume and area were not fixed, but increased with sward height (P < 005). For all sward heights, the horses removed between 51% and 68% of the initial grass length. The horses adjusted their bite dimensions to sward height but did not maximize food intake per bite. The response to sward height might be explained by a preference for easily digested food or the trade-off between energy intake and the cost for food processing.

This experiment suggests that grass height has a major influence on bite dimensions of horses. However there may be more complex factors influencing ingestive behaviour of horses (e.g. age, dietary experience and social behaviour) that have to be considered when horses are grazing pasture.

The effects of duration of fasting on the short-term feeding behaviour of 12 grazing and 12 silage-fed lactating Holstein-Friesian dairy cows were examined. Four groups of three cows were rotated around fasting treatments of 1, 3, 6 or 13 h following a balanced Latin-square design. Herbage intakes for each treatment group were assessed over al-h period.

As intended there were no significant differences in sward characteristics between the experimental plots grazed by cows from different treatment groups. However, total dry-matter (DM) intake, biting rate and DM intake per bite, measured over the 1-h grazing period, increased significantly when the duration offasting was extended from 1 to 6 or 13 h (P < 0·05). There were only minor differences in grazing behaviour following fasting durations ofl and 3, or 6 and 13 h.

In a parallel study, undertaken to assess the influence offasting duration on appetite independently of grazing, four groups of three cows were housed indoors and offered 30 kg of a high quality grass silage. Silage DM intakes, measured over a 1-h period, increased significantly with extended fasting periods (P < 0·01), though silage DM intake was considerably lower than that of grazing cows for each fasting treatment.

These results suggest that dairy cows grazing on good quality swards may be able to compensate for increased degree of hunger by increasing both biting rate and DM intake per bite to increase DM intake rate. Although the DM intakes of silage and grazed grass followed similar patterns of increasing intake with extended fasting duration, DM intake rates were considerably higher in grazing cows for each fasting treatment.

Mature non-lactating cows, 18-month-old heifersand7-month-oldfemale calves of the Charolais breed (eight animals of each age) were strip-grazedon short (S, sward surface height: 7·5 cm), medium (M,10·2 cm) and tall (T, 21·1 cm) cocksfoot (Dactylis glomerata) swards at a daily herbage allowance of 40 g dry matter per kg live weight over three 15-day experimental periods. The swards were leafy regrowths of 1 (S), 2 (M)and 3·5 (T)weeks of age. Herbage intake was estimated by the n-alkane method, and grazing behaviour was recorded visually.

Intakes per kg live weight of calves and heifers were higher than those of cows on all swards(P < 0·01). Calves tended to maintain intake, whereas cows and heifers reduced their intake as sward height decreased. Bite weight decreased linearly with sward height, this decrease being greater for larger animals (P < 0·001). As sward height decreased, the scaling factor of bite weight to live weight decreased. Biting rates increased as sward height decreased (P < 0·001) and were lower in calves than in older cattle (P < 0·001). Calves had lower intake rates per kg live weight than cows in T swards, and the reverse was true in S swards (P < 0·001). Younger cattle always grazed longer than cows, but differences were reduced as sward height decreased (P < 0·01). Cows and heifers wereunable to increase their grazing time sufficiently to compensate for lower intake rates in S and M swards, resulting in reduced herbage intakes. Faecal markers and grazing behaviour suggested a greater selectivity by calves compared with older cattle.

Mature dry cows, 18-month-old heifers and 7-month-old female calves of the Charolais breed (eight animals of each age) were strip-grazed on moderate (15cm) or tall (52 and 32cm) cocksfoot swards over two 15-day experimental periods. The swards were leafy regrowths of 2 (short) and 8 (tall) weeks of age. Herbage intake was estimated by the alkane method, and grazing behaviour was visually recorded.

Bite weight was lower, grazing time and biting rate greater, and organic matter in take of grass (OMIG) higher on shorter swards, the latter being related to a higher in vitro digestibility and nitrogen concentration. Average OMIG per kg live weight (M) was 15·2, 19·1 and 17·0 (s.e.d. 0·49)g in cows, heifers and calves respectively. The average allometric coefficient between OMIG and M was 0·88 (similar between swards), and close to that obtained with hay after the grazing trial.

Faecal markers suggested a greater selectivity of calves compared with older cattle. Average bite weights (BW) were 310 (s.e. 40), 467 (s.e. 112) and 718 (s.e. 144)mg OM in calves, heifers and cows respectively. The allometric coefficient between BW and M was higher in short swards than in tall ones. Biting rates increased and grazing times tended to decrease with age of cattle.

Two groups of eight Charolais heifers were used to examine the effect of feeding level during the post-weaning winter on the grazing behaviour and herbage intake over three periods during the first 2 months of grazing. The winter diets (L and H) were given to achieve a mean difference of 50 kg between groups at turn-out. The heifers were set-stocked together on a hill pasture where sward height was maintained at 12 cm.

The winter live-weight gains were 0·31 and 0·70 (s.e. 0·032) kg/day for L and H heifers respectively, and spring gains 1·94 and 1·66 (s.e. 0·082) kg/day respectively. Intakes increased throughout the spring grazing for both groups. Absolute intakes were lower for L than for H heifers only during the first period (P < 0·05). Intake per kg live weight was higher in L than in H heifers (23·0 v. 21·1 (s.e. 0·54) g organic matter (OM) per kg live weight). Bite weights of H heifers were constant throughout (434, (s.e. 12·9) mg OM), while bite weights ofL heifers only reached those of H heifers in the last period. Bite weight was linearly related to live weight. Bite rates were not different between groups, but L heifers compensated for lower bite weight by grazing longer and they increased their grazing time after turn-out faster than H heifers. Grazing time was mainly responsible for higher relative intakes in L heifers, and thus, partly, for compensatory gain observed.