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A comparative study of grazing behaviour, herbage intake and milk production of three strains of Holstein-Friesian dairy cow was conducted using three grass-based feeding systems over two years. The three strains of Holstein-Friesian cows were: high production North American (HP), high durability North American (HD) and New Zealand (NZ). The three grass-based feeding systems were: high grass allowance (MP), high concentrate (HC) and high stocking rate (HS). In each year seventy-two pluriparous cows, divided equally between strains of Holstein-Friesian and feeding systems were used. Strain of Holstein-Friesian cow and feeding system had significant effects on grazing behaviour, dry matter (DM) intake and milk production. The NZ strain had the longest grazing time while the HD strain had the shortest. The grazing time of cows in the HC system was shorter than those in both the HS and MP systems. There was a significant strain of Holstein-Friesian cow by feeding system interaction for DM intake of grass herbage and milk production. The NZ strain had the highest substitution rate with the HP strain having the lowest. Hence, response in milk production to concentrate was much greater with the HP than the NZ strain. Reduction in milk yield as a consequence of a higher stocking rate (MP vs. HS system) was, however, greater for the HP and HD strains compared with the NZ strain. The results suggest that differences in grazing behaviour are important in influencing DM intake and milk production. [ABSTRACT FROM AUTHOR]

The effect of the structure of a tropical pasture, based on Dichanthium spp., on the ingestive behaviour, in vivo digestibility of the diet and herbage intake by eight Creole tethered heifers was studied. Two levels of nitrogen fertilizer (0 and 50 kg ha−1) were applied to plots after each grazing cycle and there were 28 d between each of the three grazing cycles. Four heifers grazed individual subplots daily on each plot for 14 d in each of the successive grazing cycles. Simultaneous measurements of bite depth, bite mass, biting rate, short-term intake rate and daily grazing time were made in two 4-d periods at the end of each 14-d period. The in vivo organic matter digestibility (OMD) and daily herbage organic matter intake (OMI, expressed on a kg LW0·75 basis) were also measured at the same times. Relationships among pasture characteristics and ingestive behaviour were similar to those reported in other short-term studies: pasture height was highly correlated with bite depth, bite mass and biting rate ( r = 0·91, r =0·79 and r = −0·68, respectively, P < 0·001). Pasture variables had lower correlations with grazing time and short-term intake rate than with bite depth, bite mass and biting rate. Pasture structure was more highly correlated with OMD than OMI: leaf mass and length and also the extended tiller length were highly correlated with OMD ( r = 0·77, r = 0·76 and r = 0·72, respectively, P < 0·001) whereas the crude protein concentration of the herbage was correlated with OMI and digestible OMI ( r = 0·50 and r = 0·69, respectively, P < 0·001). Ingestive behaviour variables, as well as OMD, were correlated more with pasture characteristics than was OMI. [ABSTRACT FROM AUTHOR]

The study examined whether high-yielding cows grazing pasture respond differently from low-yielding cows in milk production and feeding behaviour, to increasing the time made available for eating a maize silage and soyabean meal (TAMS) diet indoors and reducing the time available for grazing (TAG). Two experiments, each lasting 42 d, were carried out in spring (Experiment 1) and autumn (Experiment 2) using Holstein-Friesian cows at two different levels of milk yield (MYL). Milk production and feeding behaviour were examined for TAG + TAMS systems of 19 h, TAG plus 1 h TAMS (19 + 1), and 5 h TAG plus 15 h TAMS (5 + 15). There were two levels of concentrate (0 and 6 kg d−1), and in the spring experiment two sward heights (4–6 and 8–10 cm) were also studied. Milk yield, persistency of milk yield, liveweight change and estimated total DM intake were significantly higher on the 5 + 15 than on the 19 + 1 grazing system in Experiment 1 but not in Experiment 2. There were no significant interactions of TAG + TAMS treatment with MYL for any production or behavioural measurements except for maize silage feeding time, where high MYL cows spent a significantly greater time eating maize silage than low MYL cows on the 5 + 15 treatment but not on the 19 + 1 treatment. It can be concluded that high- and low-yielding cows respond similarly in milk production and feeding behaviour to different combinations of TAG and TAMS. In autumn, estimated daily intakes of herbage were lower on both grazing treatments relative to spring, resulting from lower rates of herbage intake with no compensatory increase in grazing time. In contrast, rates of intake of maize silage were higher in autumn especially on the 19 + 1 system. These results may imply a change of preference from herbage to maize silage between spring and autumn. [ABSTRACT FROM AUTHOR]

The grazing behaviour of cows from two mixed herds grazing semi-natural mountain grasslands was studied for two weeks each summer during three years. The two breeds included in the study were the high yielding, modern dairy cattle breed Norwegian Red (NR) and the moderate yielding, old dairy cattle breed Blacksided Trønder and Nordland Cattle (STN). Grazing behaviour included general activities such as walking, standing, lying and playing, and grazing activities such as grazing, drinking and ruminating. During the daily grazing period the cows’ grazing behaviour were recorded at fixed intervals of 10 or 15 min. Breed differences were found in three of the recorded traits. The NR cows showed a higher frequency of ‘standing’ than the STN cows (p<0.01), and the STN cows showed higher frequencies of ‘walking’ (p<0.05) and ‘playing’ (p<0.01) than the NR cows. The time spent on grazing showed no difference between the breeds. The number of observations in the present study was somewhat limited as these types of studies are very resource demanding. Longer recording periods, more animals and farms would have been preferable. However, the breed differences expressed are in line with the expectations with regard to playing, standing and walking, while grazing activity did not follow the hypothesis made. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to assess grazing behaviour, intake, rumen function, milk production and composition of dairy cows grazing perennial ryegrass varieties that were morphologically and chemically similar, but differed in their water-soluble carbohydrate (WSC) concentration. Eight multiparous rumen cannulated dairy cows were offered four varieties of perennial ryegrass under a 1-day strip-grazing system using a 4×4 Latin square design in two consecutive years. Two of the varieties were characterised by a high WSC content (HSV) and the other two varieties had a lower concentration of WSC (LSV). Grazing behaviour was recorded using a solid-state behaviour recorder. Daily intake was estimated using the n-alkane technique. Rumen function was measured using rumen evacuation. As expected the HSV had a higher WSC content (P <0.05) than the LSV with an average difference of approximately 32 g/kg dry matter. The other chemical constituents did not differ significantly between HSV and LSV. The sward surface height, herbage allowance and tensile strength were not significantly different between HSV and LSV. None of the grazing behaviour parameters (eating time, rumination time, bite rate, chewing rate and bite mass) were significantly different between HSV and LSV. Daily dry matter intake (DMI), fibre clearance rate, milk production and milk composition (fat, protein and lactose) were not different between cows grazing the HSV and LSV. At the level of difference in WSC content between the grass varieties reported in this study (32 g/kg), offering dairy cows a high sugar pasture did not influence grazing behaviour and rumen function and was not beneficial in improving DMI, milk yield or in altering the composition of milk. [Copyright &y& Elsevier]

Abstract: Grazing itineraries of herded and free grazing cattle (n =194), goats (n =148), and sheep (n =129) were monitored in a village territory over a 1-year cycle by direct observation of grazing and excretion behaviour and by parallel animal tracking using a Global Positioning System. During the study period, standing and litter biomass of spontaneous vegetation and crop residues was measured repeatedly on sample plots of fields (n =16), fallows (n =15) and rangeland (n =8). Based on a land use map, a Geographic Information System on forage availability was produced for the territory and overlaid with the livestock grazing itineraries. The animals’ behaviour at pasture was related to the forage mass encountered along their daily itineraries in order to analyse the spatial variation in behaviour as influenced by season, livestock species and herd management mode. Maximum daily itinerary lengths were 25km in cattle, 20km in goats and 21km in sheep; itinerary length varied significantly between species, herd management modes and season. Animals spent between 456 and 625min per day on pasture, the grazing day of cattle being longer than that of sheep and goats. Across seasons, all three species spent on average about 60% of the daily grazing time feeding, 20–26% walking and 12–20% resting. The forage mass encountered along the animals’ itineraries was higher than the average amount of forage available in the area. Particularly during the late dry and the rainy season, herding increased the amount of forage on offer to grazing livestock. Throughout the year, 39% of the observed excretions occurred on cropland, 31% on rangeland, 20% on fallows and 10% in and around settlements; the spatial repartition of excreta deposits differed between herded and free grazing animals, with free grazing animals depositing a higher share of excretions on barren land. The obtained information on the variation of grazing and excretion behaviour with respect to ruminant species, land use type, forage supply, season and herd management can be coupled with quantitative data on feed intake and excreta deposition, in order to compute livestock-mediated nutrient budgets for Sahelian agro-pastoral land use systems. [Copyright &y& Elsevier]

Abstract: On grasslands, herbivores make a trade-off between the quality and the quantity of their intake. They improve their searching efficiency by modulating their foraging velocity and/or their path sinuosity through the perception of their feeding environment. The aim of this study was to test the pertinence of fractal analyses of foraging paths in order to improve the understanding of spatial utilisation at grazing. By the analysis of grazing paths of herbivores grazing a continuously distributed and spatially limited resource, we aimed to identify the spatial scales at which the animals perceive heterogeneity of the sward, and to characterise how sheep modulate their foraging paths through resource abundance and heterogeneity. Two groups of five dry ewes, grazing two plots of contrasting areas from April to the end of September 2000, were studied. On the smaller plot (1500m2), the application of a high stocking rate (HSR) produced a resource of good quality but low quantity, and on the larger plot (3000m2) a low stocking rate (LSR) created a sward of low quality but good quantity. We show that on initially homogeneous swards, sheep exhibited correlated random walks, reducing movement quantities to achieve their intake. After a few weeks of grazing, vegetation structure become more complex and sheep modulated their foraging paths through resource abundance and/or sward structure. We identified a breakpoint at 5m for which fractal dimension is always low. At lower scales (below 5m), the modulation of sinuosity was not linked to sward abundance and structure, and sheep adapted grazing behaviour at bite and feeding station scales. At higher scales (above 5m), modulation of grazing activity was achieved through path sinuosity in relation to perception of the environment. Grazing paths were tortuous on tall swards in summer, and straighter on heterogeneous, well-structured swards showing visual cues in autumn. Fractal dimension of grazing paths proved to be a synthetic measurement, which allowed identification of a hierarchical threshold in the spatial adaptation of foraging behaviour in domestic herbivores at grazing. [Copyright &y& Elsevier]

Abstract: Wooded rangelands are a vast grazing land resource globally, including shrublands, savannas and forested ranges. They generally provide forage year-round for small ruminants and they are vitally important for livestock production, especially goats. While the productivity of wooded rangelands is low to moderate, their importance to small ruminant production is considerable. In this paper, we begin by discussing some anti-quality characteristics (mechanical and chemical defences) of woody vegetation that reduce their forage value, deter foraging, and reduce performance and productivity of small ruminants. We then present examples of grazing studies that illustrate how small ruminants select their diets on wooded rangelands. We conclude by discussing why small ruminants select the diets they do within the evolutionary processes of plant–herbivore interactions. Finally, we discuss how this knowledge can be integrated into approaches for sustainable management of wooded rangelands for small ruminant production. Plant defences are abundant in wooded rangelands but they are not a complete barrier to small ruminants as they often use woody plants as part of their diets. Indeed plants with such defences may represent a significant forage resource enabling small ruminants to survive on wooded rangelands with a prolonged dry period when more preferred defenceless species are absent. Future research in plant–herbivore interactions should include investigating how plant biochemical diversity influences herbivore preference for various plant communities, and integrating this information to develop recommendations for managing wooded rangelands. [Copyright &y& Elsevier]

Abstract: A small herd of donkeys was introduced in a coastal dune reserve ‘Houtsaegerduinen’ (ca. 80ha) in Belgium, in order to slow down expansion of dominant grass and shrub species. The Houtsaegerduinen is a nutrient poor scrub-dominated dune system with a spatially heterogeneous vegetation pattern. Different aspects of the grazing behaviour (grazing time, bite rate, habitat use, diet composition) of the free-ranging donkeys are described and analysed. Behavioural data (of maximum six adult mares) were collected through continuous focal animal observation in three consecutive years (1998–2001). Temporal variation in grazing time, habitat use and diet composition was determined. During daylight, donkeys spent most of their time on grazing (56%). In all 3 years, grazing time was significantly shorter in summer (45% of their time), longest grazing times were achieved in spring (64%). In spring, the donkeys also achieved the highest bite rate (21.5bites/min). The grassy habitat was preferred for foraging in all seasons, while the use of scrub and woodland was variable over time. Averaged over the four seasons, the general diet consisted for 80% of graminoids, 10% of forbs and 10% of woody plants. However, diet composition varied not only among seasons and years, but depended also on the foraged habitat type. We discuss the possible role of the donkeys in nature management. [Copyright &y& Elsevier]

Abstract: Foraging herbivores are often faced with spatial and temporal heterogeneity within the vegetation they have available to graze and therefore have to make decisions where and when to graze. The study reported in this paper investigated the influence of sward height on diet selection by horses grazing perennial rye-grass swards. The study comprised two experiments. In Experiment 1, perennial rye-grass paddocks were mown to four sward heights (heights: 3.5, 4.5, 7.5 and 15cm) to create a patchy environment. Within each paddock one horse grazed for a period of 1h during which residence time, number of bites and frequency of visits per patch were recorded. This was replicated with all seven horses used in the experiment. The same experiment was repeated in Experiment 2, but without mowing the field and allowing 1 week of re-growth for each paddock. During both experiments horses entered equally often but resided significantly longer on patches with long grass (15cm) than on those with short grass (below 4.5cm; P &#60; 0.05). Grazing time and number of bites on a patch were highly correlated. The number of bites on patches with the highest sward height was greater than that on short patches (P &#60; 0.05). Horses behaved as selective grazers, feeding mainly on grass taller than 7cm. In Experiment 2, re-growth of the sward reduced the difference in sward height between the patches. Time spent per patch and total numbers of bites taken were less affected by sward height than in Experiment 1. It is suggested that horses behaved as energy maximisers (residing longer periods on patches and increasing number of bites taken). These data complement previous findings that bite dimension and bite mass increase with increasing sward height. When grazing, a horse rarely resided on a preferred patch for a long duration of time (maximum 305s, median 79s), but moved on after a few minutes. They sampled their environment continuously, but almost exclusively returned to long patches for feeding. [Copyright &y& Elsevier]

Forty spring-calving cows and heifers (20 of each) were allowed to acquire infection with gastrointestinal (GI) nematodes naturally during grazing. The control group (10 cows and 10 heifers) were compared with 20 similar animals treated with eprinomectin in order to evaluate the effect of GI nematodes on grazing behaviour, milk production, body condition score and live weight. The animals were paired according to parity and milk yield during the week prior to treatment, then within replicate pair randomly allocated to a different treatment group. The grazing area was sub-divided into 20 replicated paddocks of equivalent size and topography. Grazing pairs of either control or treated animals were randomly assigned to each paddock over the duration of the study (one pair per paddock).Grazing behaviour was recorded for both groups over a 10-day period commencing 4 days after treatment with eprinomectin. Milk yield was recorded daily and milk quality was recorded weekly. Live weight and body condition score were recorded on the day of allocation, the day of initial treatment and thereafter at weekly intervals until the end of the 4-week trial.Faecal samples were collected from each animal prior to, and after, allocation and submitted for counts of nematode eggs. Additional faecal samples were taken at the end of the study for culture and nematode identification. Individual faecal samples were also analysed for residual digestibility. Pasture samples for nematode larval counts were taken at the same time as faecal sampling. The parasitological results showed low levels of faecal nematode egg output throughout the study, with the heifers having higher counts than the cows. Faecal culture yielded species of Ostertagia, Cooperia, and Trichostrongylus. Pasture larval levels were very low throughout with no value exceeding 68larvae/kg dry matter (DM) of herbage.There were significant (P < 0.05) effects of treatment on grazing time, eating time, total bites, total grazing jaw movements (TGJM), idling time and mean meal duration. Treated cows and heifers grazed for 47 and 50min longer per day, respectively, than controls (P = 0.016). Mean meal duration was extended as a result of anthelmintic treatment by 11 and 38min, in cows and heifers, respectively (P = 0.012). There were no significant (P > 0.05) treatment effects on ruminating time or residual faecal digestibility, but idling time was significantly reduced in both treated cows and heifers, by 50 and 110min, respectively (P = 0.010).In the treated cattle, there was an increase in solids-corrected milk yield compared with the control cattle, which was significant (P < 0.05) in weeks 2 and 3 after treatment. The response was particularly marked in heifers, where the difference in yield between treated and controls was up to 2.35kg/day. The differences in live weight gain and condition score over 28 days post-treatment were significant (P < 0.05) in both cows and heifers, in favour of the treated animals. [Copyright &y& Elsevier]

Forage selection by buffalo and the contribution of grass species to buffalo diet were investigated by comparing two herds occupying granite and basalt landscapes in the Kruger National Park. Observations spanned the late dry season, from July to October 2002. Grass remained greener in bottomlands than in midslopes or uplands within each landscape, but greenness was not significantly different between the basalt and granite landscapes. The favoured grass species remaining highly acceptable to buffalo throughout the late dry season included Panicum maximum, Panicum coloratum, Cenchrus ciliarisand Heteropogon contortus. However, the dietary contribution by these species declined with the progress of the dry season owing to a reduction in the available forage that they retained. The acceptance frequency as well as the dietary contribution of Urochloa mosambicensis, Digitaria eriantha and Eragrostis superba increased over time, while Bothriochloa spp. became moderately acceptable at the end of the dry season in October. Themeda triandra, a species highly rated as forage for cattle, appeared intermediate in its acceptability to buffalo and made a relatively small dietary contribution in both landscapes. In accordance with foraging theory, buffalo expanded the range of grass species accepted, changed the proportions of grass species in their diet and shifted their grazing locations within the landscape. [ABSTRACT FROM AUTHOR]

Pairs of ewes or heifers were allowed to graze for short periods from previously prepared ‘homogeneous’ areas of ryegrass, in order to study their bite dimensions and movement patterns and to investigate the role of different species in initiating spatial heterogeneity. Apparent bite area was calculated from number of bites and total bitten area when ewes or heifers took 10–15 bites from an 80 cm×80 cm area in a homogeneous Lolium perenne sward. Apparent bite depth was calculated from sward surface height (SSH) within and adjacent to bitten areas. Apparent bite mass was calculated from grazed stratum bulk density. Incisor arcade breadth was measured. Animals also grazed 20 m×40 m plots for 45 min. Position and activity were recorded and distance travelled calculated. Number of bites and steps, number and duration of grazing bouts, feeding station dimensions and horizontal head sweep were recorded. Bites per bout, per feeding station and per m forward movement, bite rate, inter-bout interval, and distance travelled, speed of movement, number of steps, step length and step rate within and between bouts were calculated. Distribution of grazing bout and inter-bout durations and the animals’ foraging paths were tested for randomness.Apparent bite area for heifers was 2.2 times that for ewes and incisor arcade breadth 1.8 times that for ewes. Apparent bite depths were similar at 0.35 of SSH. SSH distribution within bitten areas was non-normal and differed between animal species. Heifers’ bite mass was 2.1 times that for ewes. Heifers had longer grazing bouts, more feeding stations per bout, moved farther per bout but had similar movement speed while grazing. Distance between feeding stations was similar between species but heifers’ feeding station residence time was twice as long. Heifers’ biting rate was lower but they took more bites per bout, per feeding station and per metre of forward movement. Mean head sweep distance was greater for heifers. Both species moved a similar distance between grazing bouts but ewes moved more slowly with more, shorter steps. For both species, grazing bout and inter-bout durations were not randomly distributed. At a 1 m2 scale for both species and a 5 m2 scale for heifers, movement was non-random with a strong propensity to walk in a straight line but at a 5 m2 scale sheep movement was uniformly distributed on the circle. [Copyright &y& Elsevier]

Using heterogeneous vegetation through grazing is a necessary component of de-intensification of livestock systems and conservation of natural environments. Better understanding of the dynamics of animal feeding behaviour is therefore needed, in particular in response to feed diversity and variability. On the basis of three on-farm experiments with ewes and goats, we improved a direct observation method that links intake behavioural response with variations in plant structure. This method makes it possible to continuously and closely monitor an individual animal’s ingestive behaviour during the daily meals, by recording the mass and nutritive quality of its ingestive bites in situ and within its group. “Language” stemming from a coding grid for “bite categories” is proposed for real-time recording of all the bites taken from the full range of available plant parts. Bite categories are defined in order to be applicable to diverse and numerous plant species which allowed real-time recording in very diversified environments, while the impact of grazing alters the plant structure. The continuous presence of an observer does not appear to disturb the animals being monitored, since the variations of their total daily intake time and their diet quality are close to the ones of the groups. The dynamics of ingestive behaviour is explored at different time scales: daily intakes, meal kinetics and biting process. Daily intakes were similar for dry ewes grazing swards invaded by shrubs (77.9±10.2 and 75.1±16.9 g DM/kg LW0.75). They were much higher for lactating goats browsing within a shrub encroached oak coppice (125.8±7.5 g DM/kg LW0.75). Cumulative meal kinetics were quite regular and their slopes are of descending form. Our method allowed characterising the huge diversity of bite types that compose such a regular meal. Bite mass ranged between 0.01 and 1.72 g DM. Instantaneous DM intake rate and instantaneous quality of intake were highly variable (i.e. about 20% of variation in OM digestibility during a single meal). At the scale of biting, our method allows to explore the effect of plant structure alteration on the ingestive response and the resulting intake rate. We confirm that intake rate is more influenced by the mass than by the frequency of bites. The main advantage of this method lies in its capacity to characterise bite intake dynamics in very diversified vegetation, from the very short term, i.e. the meal components, to the long term, i.e. several days in a paddock. [Copyright &y& Elsevier]

In contrast to horses in pastures, it is thought that free-ranging horses do not perform latrine behaviour, i.e. a behavioural pattern whereby the animals graze and defecate in separate areas. However, few studies deal with this particular subject, reporting contrasting conclusions. We hypothesize that horses free-ranging in large heterogeneous areas do not perform latrine behaviour. Thus, we believe that grazing and elimination behaviour are spatially related: where horses graze, they will also defecate. Behavioural data were collected from Konik horses, Haflinger horses, Shetland ponies and donkeys, grazing in different nature reserves (54–80 ha). Data for the different equids were analyzed separately, as well as data for mares and stallions (Konik and donkey stallions only). We investigated the proportion of the number of defecations/urinations while grazing on the total number of defecations/urinations; furthermore, we searched for the sequence of behaviours representing latrine behaviour in the strict sense. Additionally, we analyzed the correlation between grazing behaviour and eliminative behaviour on both vegetation type level and patch level. All the female equids often continued grazing while defecating. During urination, grazing ceases in the majority of instances. Cases where a mare terminated grazing in a certain vegetation type and sward height to eliminate in another vegetation type or in another sward height within the same vegetation type were rarely observed. On the vegetation type level as well as on the patch level, there was a highly significant (P<0.001) positive correlation between grazing time and number of eliminations (or eliminating time). The high values of the correlation coefficients (in case of the defecation variables r ranges between 0.553 and 0.955; in case of the urination variables r ranges between 0.370 and 0.839) illustrate that the spatial distribution of the eliminative behaviour can be explained to a high degree by the spatial distribution of the grazing behaviour. Results in the case of the stallions are preliminary, but indicate the same pattern. Horses, free-ranging in large heterogeneous areas, do not perform latrine behaviour, but defecate where they graze. Possibly, animal density is of major importance to explain this behavioural difference with horses in pastures. We suggest that also spatial vegetation heterogeneity and plant productivity of the grazed area, as well as parasite status of the grazing animals could play a role. [Copyright &y& Elsevier]

The grazing process determines not only the nutrient intake of ruminants at pasture but also the intensity of their impact on vegetation. Grazing dynamics are the result of complex interactions between animal and sward characteristics. While sward is being depleted, a decline in intake rate is partly offset by longer grazing time. This behaviour may be controlled by nutritional feedback from digestion and nutrient absorption as the quality of the ingested herbage decreases. To simulate the dynamics of feeding behaviour and intake during sward exploitation, we developed a mechanistic model of intake rate that combines sward architecture and foraging decisions, and we linked this model with another focusing on control of intake. The sward was divided into horizons characterised by bulk density and nutritive value (NDF content and digestibility), enabling prediction of bite mass and potential intake rate for each grazed horizon. Animal decisions were simulated at two levels: (i) animal activity (eating, ruminating or resting) was self-regulated every minute by comparing a motivation-to-eat function with a satiation function based on a digestion and metabolic sub-model; (ii) while eating, the horizon to be grazed was decided through a choice function taking into account the relative availabilities and potential intake rates of the two upper horizons. The model simulates the animal–sward interactions from elementary parameters (bite mass, intake rate, etc.) to integrated outputs (sward height, daily intake, etc.). Hence, the interplay between characteristics of the vegetation and the internal state of the animal is dynamic taken from the level of a few bites to several successive days. Satisfactory validations were obtained on experimental data sets obtained in both rotational grazing with dry ewes and continuous grazing with lactating ewes. The sensitivity analysis highlights the balance between factors that control bite mass and intake rate and factors that control grazing time. Combining both series of factors in the same model represents significant progress in predicting intake at grazing in a mechanistic way. The model makes it possible to explore the balance between intake regulation by nutritional variables (animal needs and sward quality) and by the availability and structure of the sward. Finally, it is a promising tool to explore the sensitivity of the grazing process to characteristics of both sward (height, bulk density, nutritive value) and animals (weight, nutritional requirements, behavioural traits), and to management practices (stocking rate, rotational versus continuous grazing). [Copyright &y& Elsevier]

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 x 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 x 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... [ABSTRACT FROM AUTHOR]

Abstract Patch selection by grazing dairy cows in response to simultaneous variation in combinations of sward structural characteristics was examined in three experiments in which four mature dairy cows were offered a choice of patches (typically 0.9 m × 0.9 m) of perennial ryegrass (Lolium perenne) presented in a linear arrangement. Treatments involved combinations of variations in sward height, stubble height and/or depth of regrowth, prepared by preliminary cutting treatments. They were arranged in balanced sets of four to nine treatments, which were arranged in linear sequences of eighteen to twenty-seven patches. Within experiments, sequences were balanced across replicate sets of patches, which were grazed separately by individual cows. The number of bites removed and the residence time for each patch were highly correlated in all three experiments, and the results are reported using number of bites per patch as an estimator of foraging behaviour. In the first experiment, with vegetative swards, cows preferentially selected the tallest swards. When swards comprising reproductive stem were offered in Experiment 2, cows selectively grazed short-stubble swards rather than tall-stubble swards, although both offered a similar depth of regrowth. Cows did not exhibit preference for swards comprising the greatest quantity of leaf mass, indicating that the spatial distribution of plant components assumed greater importance. In the third experiment, the number of bites removed increased with increasing depth of regrowth, and was negatively correlated with sward height. The three patch-appraisal cues investigated were broadly ranked in order of importance as (i) depth of regrowth, (ii) sward maturity and (iii) sward height. There was no evidence, at least at a short temporal scale, that patch behaviour was influenced by conditions in adjacent patches, suggesting that the cows assessed grazing opportunities on a patch-by-patch basis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

Studies of the grazing behaviour of ruminants show that there is a recurrent daily pattern of grazing behaviour. Various researchers have hypothesised that this pattern is controlled by daylight, but this theory is difficult to test with grazing animals under field conditions. The total solar eclipse that occurred across parts of Europe on the 11 August 1999 gave a rare opportunity to test this hypothesis.Twelve lactating Holstein–Freisian dairy cows were divided into four groups of three cows, and each group grazed a 0.96 ha grass paddock. The grazing and ruminating behaviour of all 12 cows was recorded automatically for two 24 h periods before and four 24 h periods after the total solar eclipse. The cows were milked twice daily, at approximately 07:00 and 16:30 h.The period of totality of the eclipse started at 10:11 GMT and lasted for 2′02″, during which time light intensity fell to less than 10 lx, i.e. similar to night-time levels. The total time spent grazing in the 24 h period after the eclipse was significantly lower than four of the five other 24 h periods. However, a downward trend in grazing time in the 24 h period before the eclipse makes it difficult to attribute this affect to the eclipse alone. The eclipse had little, if any, effect on ruminating behaviour.The total solar eclipse did not have a major affect on the grazing or ruminating behaviour of the cattle in this study. This suggests that light intensity alone does not play a major role in the control of circadian patterns of grazing behaviour. Other factors (e.g. the integration of light intensity over time, or the quality of light) cannot, however, be excluded. A total solar eclipse provides a useful tool for the investigation of the control of circadian grazing patterns, and further studies are encouraged. [Copyright &y& Elsevier]

Social grouping tendencies are known to influence the grazing behaviour of domestic herbivores. Here, we investigate how the strength of social bonds in a flock influences the choice of grazing location in sheep. Eight experimental ewes of INRA 401 breed grazed in plots in which a preferred feeding site, i.e. a patch of taller grass, was located 35 m away from a socially attractive site, i.e. five sheep confined in a pen, at one end of the plot. These penned sheep were either all familiar or all unfamiliar to the experimental ewes. Each experimental ewe was tested with one or four companions, which were either familiar or unfamiliar to her. The two group sizes, two degrees of familiarity with the penned sheep and two degrees of familiarity with the companions were incorporated into a Latin square design. In a series of 20 min tests, we recorded the behaviour of the experimental ewes by focal sampling and the location of each animal in the plots by scan sampling. As in a previous experiment, ewes in a larger group were more likely to move away from the penned sheep and to graze the preferred feeding site, and were also less vigilant. There was an additive effect of the degree of familiarity: the ewes with familiar companions grazed the preferred feeding site for longer, vocalised less and were less vigilant than those with unfamiliar companions. Inter-individual distances were also reduced when ewes grazed with familiar companions. Conversely, the degree of familiarity with the penned sheep had no effect on the ewes’ behaviour. Differences in the strength of social bonds within a flock are thus likely to affect the formation of subgroups and influence the way herbivores forage in patchy grasslands. [Copyright &y& Elsevier]

This experiment investigated how season-long, free-choice grazing affected weekly cattle grazing behavior and resource use. Our objectives were to determine if known forage preferences change through the season, if feedbacks from previous grazing intensity affect current use, and if resources such as water and salt in combination with a shorter forage base increase grazing time compared to previously rested pasture. Two replicate 24.4-ha grazing enclosures contained four forage types: smooth bromegrass (Bromus inermis), crested wheatgrass (Agropyron desertorum), western wheatgrass (Pascopyrum smithii) and native range. Each forage type was divided into three sub-areas containing either: a water source, a salt block, or forage deferred from use before the experiment (rested). Resource use was tracked with analysis of aerial photos of the pastures before and after the 3-year study and with weekly direct observation of animal use of each area of the pastures. As each season progressed, use of smooth bromegrass declined and use of crested wheatgrass and western wheatgrass increased. Use of native range remained relatively constant and low throughout the study. The previously rested sub-areas of the replicate pastures had significantly and substantially more grazing than those with salt or water. Significant auto-correlation in the data was well described by an auto-regressive parameter comprised of the sum of the previous 2 weeks grazing time, which showed gradual shifts in forage preference from 1 week to the next. Aerial photo analysis supported the findings of the behavioral data; preference between forage types changed over time, and grazing use within pastures was uneven and negatively correlated with salt and water sites. Cattle can rotate themselves among various pasture types if given free-choice; and season-long grazing may be an effective system if a variety of forage types are available. [Copyright &y& Elsevier]

Grazing by cattle on the scale of a single feeding station was studied to determine the patterns of defoliation and bite dimensions in short bite sequences. The sward was a continuous and homogeneous expanse of alfalfa without any imposed patchiness of structure. Treatments were bite sequences of 3, 6, 9 and 12 bites, with the forelegs of the observed animal stationary. Four 18-month-old heifers were used and the treatments were conducted over two grazing cycles. The bite scale defoliation imprints (non-contiguous grazed areas separated by undefoliated vegetation) were marked with white spray paint and photographed for shape and area measurements.The mean pre-grazing plant heights for all lengths of bite sequence were 24.8±0.6 cm (cycle 1) and 20.9±0.7 cm (cycle 2), and the mean grazed (residual) plant heights within the defoliation imprints were 14.4±0.6 cm (cycle 1) and 12.9±0.7 cm (cycle 2). One or more separate defoliation imprints was/were obtained for each length of bite sequence. Each imprint was created by one bite or a number of bites in touching or overlapping locations, and contained few undefoliated plant elements. The bite sequences created a variety of defoliation imprints with irregular, often lobed or fingered shapes, which were clearly related to the number of bites removed. The maximum dimension of the grazed imprint tended to be perpendicular to the orientation of the animal, and increased from 46 and 40 cm in cycles 1 and 2, respectively, after three bites to 76 and 85 cm in cycles 1 and 2, respectively, after 12 bites. The overall mean effective bite areas were 101±6.2 and 115±7.5 cm2 per bite in cycles 1 and 2, respectively. The mean effective bite area tended to decline with bite number in cycle 1 only, but the effect was not significant in the overall model. In the absence of a discrete, imposed feeding station structure, bite placement may result in depletion without depression. Care should be taken in applying patch depletion curves to continuous swards when these are derived from discrete-patch studies in which patch dimensions constrain bite placement. [Copyright &y& Elsevier]

[Display omitted] • Dairy cows divergent for MUNBV express different diurnal ingestive patterns. • Low MUNBV cows consistently have more mastications per bite than high MUNBV cows. • Low MUNBV cows have more chews per boli during different periods of the day. • MUNBV divergent cows grazing strategies differ at the same herbage allowance. The objective of this study was to describe the diurnal pattern of grazing behaviour of multi-parous dairy cows divergent for milk urea N breeding values (MUNBV) and the consistency of these differences across different sward compositions (perennial ryegrass [RG; Lolium perenne L.] or ryegrass with plantain [ Plantago lanceolata L.; RGPL]) and stages of lactation (early and late lactation). Jaw movement recorders were fitted to 24 animals in early lactation and 16 cows in late lactation, in early lactation 12 cows were assigned to the ryegrass diet and 12 cows assigned to the plantain diet, in late lactation 8 cows were assigned to ryegrass with the remaining 8 cows assigned to the plantain diet. For each diet half of the animals during both stages of lactation were classified as high for MUNBV and the other half as low for MUNBV. Low MUNBV animals had more mastications per bite over the day (P < 0.01) with a one-unit decrease in MUNBV resulting in 0.07 more bites per mastication during the first two grazing bouts, as well as differences in the temporal distribution of grazing bouts compared with high MUNBV cows. A one-unit decrease in MUNBV resulted in a 0.11 ± 0.02 increase in mastications per bite during the first grazing bout across both stages of lactation and sward composition. Ingestive behaviour has a large impact on the physical features of ingesta and thereby rumen function. The results of this study indicate that dairy cows divergent for MUNBV grazing the same forage apply different grazing strategies in terms of oral processing of ingesta and diurnal meal pattern. These results present potential explanatory variables for phenotypical differences observed in dairy cows divergent for MUNBV. [ABSTRACT FROM AUTHOR]

• Jaw movement data can be reliably recorded in an extensive semiarid rangeland. • Hourly grazing time measurements show high accuracy in vertically heterogeneous swards. • Grazing bite measurements exhibit moderate to high accuracy in heterogenous swards. • Cattle ingestion patterns shift with forage limitation within and across seasons. • Automated noseband sensor provides ingestion metrics underlying animal performance. Advances in on-animal sensor technologies to monitor location and activity have enhanced the ability to study foraging decisions of free-ranging herbivores. Sensors monitoring jaw movements that quantify ingestive behaviours, such as the RumiWatch (RW) noseband sensor system, have primarily been used in indoor animal housing systems or structurally homogeneous, small pasture (paddock) environments. Continuously monitoring these ingestive behaviours in extensive and heterogeneous rangelands has not been previously conducted. We evaluated the accuracy of the RW noseband sensor system for two grazing seasons in 130-ha pastures (paddocks) composed of native, mixed-species plant communities in a semiarid environment. The noseband sensor was used to compare ingestive behavior at different sites and seasons characterized by varying sward complexity, stocking rate, and levels of forage limitation. We evaluated the noseband sensor against direct visual observations of yearling steers grazing with two different validation studies. First, the time duration of grazing recorded by the sensor was compared to direct visual observation data (Validation Study 1). A high correlation (r s = 0.95) for hourly grazing time resulted between the RW system and visual observations. Second, we examined the ability of the RW system to measure prehension bite rates in distinct plant communities varying in height and leaf angle (Validation Study 2). The accordance between direct observation and measurement by the RW system for bite rate improved from 2019 (Concordance Correlation Coefficient (CCC) = 0.71) to 2020 (CCC = 0.80) after modifications to improve the fit of the halter supporting the noseband sensor. Correlations between the sensor and visual observations increased by ∼17 % with this modification for grazing bouts in mixed-species and midgrass-dominated swards; correlations remained ∼10 % lower in shortgrass-dominated swards. Our results show that the RW system is an effective tool for monitoring free-ranging cattle grazing activity and quantifying bite rates in a heterogeneous rangeland ecosystem. Bite rate measurements are more accurate in swards with vertically oriented stems and leaves compared to lawn-like prostrate swards. Grazing bout length and rumination chew rate may represent behavioral indicators employed in managing animal performance in semiarid rangelands. Our validation study and experimental investigation indicate that the RW noseband sensor is a useful animal-borne sensor technology for research demanding sustained ingestion measurements across mixed-species forage communities. [ABSTRACT FROM AUTHOR]

Simple Summary: Grazing behaviour measures herbage intake and varies according to herbage type, climate conditions, and social status of the animal within the herd. Rumination behaviour indicates the digestive efficiency and health status of the animal and varies according to herbage quality, type, and maturity. Both intake and digestive efficiency substantially affect the animal's performance. Knowledge about grazing and rumination behaviours could improve the health and welfare of animals, pasture management, and overall production efficiency in a grazing-based system. Dairy farming in New Zealand is characterised by pasture-based grazing systems. In this system, monitoring the individual animal behaviour, especially grazing and rumination, has been less explored, primarily because visual observation is labour intensive and subject to human error. Advancements in precision livestock farming (PLF) have introduced behaviour monitoring tools that can record grazing and rumination behaviours. However, the adoption of PLF is still a challenge in the farming community due to the lack of research-based knowledge to address the accuracy of PLF tools in a grazing-based system. The objective of this study was to evaluate the accuracy of a grazing and rumination behaviour monitoring device (AfiCollar) for grazing dairy cows. This study evaluated the accuracy of a sensor-based device (AfiCollar) to automatically monitor and record grazing and rumination behaviours of grazing dairy cows on a real-time basis. Multiparous spring-calved dairy cows (n = 48) wearing the AfiCollar were selected for the visual observation of their grazing and rumination behaviours. The total observation period was 36 days, divided into four recording periods performed at different times of the year, using 12 cows in each period. Each recording period consisted of nine daily observation sessions (three days a week for three consecutive weeks). A continuous behaviour monitoring protocol was followed to visually observe four cows at a time for each daily observation session, from 9:00 a.m. to 5:00 p.m. Overall, 144 observations were collected and the data were presented as behaviour activity per daily observation session. The behaviours visually observed were also recorded through an automated AfiCollar device on a real-time basis over the observation period. Automatic recordings and visual observations were compared with each other using Pearson's correlation coefficient (r), Concordance correlation coefficient (CCC), and linear regression. Compared to visual observation (VO), AfiCollar (AC) showed slightly higher (10%) grazing time and lower (4%) rumination time. AC results and VO results had strong associations with each other for grazing time (r = 0.91, CCC = 0.71) and rumination time (r = 0.89, CCC = 0.80). Regression analysis showed a significant linear relationship between AC and VO for grazing time (R2 = 0.83, p < 0.05) and rumination time (R2 = 0.78, p < 0.05). The relative prediction error (RPE) values for grazing time and rumination time were 0.17 and 0.40, respectively. Overall, the results indicated that AfiCollar is a reliable device to accurately monitor and record grazing and rumination behaviours of grazing dairy cows, although, some minor improvements can be made in algorithm calibrations to further improve its accuracy. [ABSTRACT FROM AUTHOR]

Simple Summary: Grass-fed beef is becoming popular; however, there is little research information on optimising beef cattle performance in such production systems. In grass-forage-only beef systems, the removal of dietary concentrates increases the difficulty in achieving target live-weight performance and carcass fatness. Post-grazing sward height can potentially influence animal live-weight gain at pasture, whilst sire breed maturity (genotype) can potentially influence carcass fatness and, therefore, the duration required to achieve a commercially acceptable carcass fat score. Therefore, contrasting post-grazing sward heights and beef steer genotypes were evaluated within a grass-forage-only and grass-forage + concentrate production system. The high post-grazing sward height (6 cm) increased intake and live-weight gain at pasture and resulted in a heavier carcass after an indoor finishing period compared to the low post-grazing sward height (4 cm). The early-maturing genotype had a greater intake, live-weight gain and carcass fatness, but similar carcass weight and lower conformation score compared to the late-maturing genotype. Although concentrate supplementation indoors increased carcass weight and fatness, grass-forage-only steers still achieved a commercially-acceptable fat score when slaughtered at 24 months of age. In conclusion, grazing higher sward residuals and utilising early-maturing animal genotypes can increase live-weight pasture gain and carcass fatness, respectively, in grass-forage beef production systems. This study evaluated the effects of post-grazing sward height (PGSH, 4 or 6 cm) on herbage production, its nutritive value, dry matter (DM) intake, grazing behaviour and growth of early- (EM) and late-maturing (LM) breed suckler steers (n = 72), and the subsequent effect of indoor finishing diet (grass silage + 3.8 kg concentrate DM/head daily (SC), or grass silage only (SO)) on performance and carcass traits. Animals rotationally grazed pasture for 196 days, followed by indoor finishing for 119 days. At pasture, daily live-weight gain (LWG) was 0.10 kg greater for PGSH-6 than PGSH-4, resulting in a tendency for carcass weight to be 11 kg heavier. Although EM had a 0.10 kg greater daily LWG at pasture than LM, carcass weight did not differ between the genotypes. There was a genotype × PGSH interaction for carcass fat score, whereby there was no difference between EM-4 (8.83, 15-point scale) and EM-6 (8.17), but LM-6 (7.28) was greater than LM-4 (6.33). Although concentrate supplementation during indoor finishing increased carcass weight (+37 kg) and fat score (1.75 units), the majority of steers (83% of EM and 78% of LM) achieved a commercially-acceptable carcass fat score (6.78) at slaughter in the grass-forage-only system. [ABSTRACT FROM AUTHOR]

Sex differences in habitat use (termed `habitat segregation') are widespread in sexually dimorphic ungulate species. They are a puzzling phenomenon, particularly when females use better foraging habitats than males. It has been suggested that males, owing to their larger body size and higher forage requirements, are inferior in indirect competition to females and are forced by female grazing pressure into marginal habitats (`indirect-competition hypothesis'). This hypothesis has been widely cited and has important theoretical and practical implications. However, evidence for it is inconclusive. The present paper presents the results of the first experimental test of the indirect-competition hypothesis. We manipulated female and male numbers of red deer ( Cervus elaphus L.) on a large scale on the Isle of Rum, Scotland, and tested the influence of this manipulation on deer habitat use. We predicted that where female numbers were reduced, male use of preferred habitat should increase and sex differences in habitat use should decrease, while a reduction in male numbers should not have such effects. In contrast, we found that the manipulation of female and male numbers did not affect habitat use, and conclude that the indirect-competition hypothesis does not explain habitat segregation on Rum. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]