Bite Mass Research Articles

Short-term grazing and urination behaviour of dairy cows differing in their genetic merit

ABSTRACTBreeding cows for improved production and production efficiency may have led to indirect selection for behavioural traits including grazing and urination behavioural patterns. This study investigated the relationship between genetic merit (breeding worth; BW) and grazing and urination behaviour in Holstein-Friesian × Jersey lactating dairy cows. Two groups of 12 cows were assigned into high BW (HBW; NZ$146 ± 12.8) or low BW (LBW; NZ$40 ± 11.8) groups. Cows were observed for grazing (grazing, ruminating, idling and bite rate) and urinating (frequency and duration of urination events) behaviour during the first grazing session of the day (5 h; between milking 0900–1400 h). Based on the whole grazing and urination behaviour data matrix, MANOVA and PCA procedures suggested no difference in the grazing and urination behaviour of HBW and LBW cows. Further work measuring additional traits (e.g. intake rate, bite mass, diurnal urination patterns) may be required to differentiate cows of divergent BW based on behavioural patterns.

Milk performance and grazing behaviour of dairy cows in response to pasture allowance

This study aimed to evaluate the effects of pasture allowances on forage production, milk yield and composition, and grazing behaviour of Holstein cows during autumn. Thirty-six Holstein cows calving in the autumn were allocated to blocks considering: calving date, bodyweight, and body score. Treatments consisted of three pasture allowances as follows: high (HA; 38.4 kg DM/cow.day), medium (MA; 30.3 kg DM/cow.day), and low (LA; 26.8 kg DM/cow.day) pasture allowances. Forage mass and forage height pre-grazing were similar (P > 0.05) for all grazing targets. Pasture-use efficiency was affected (P < 0.05) by the pasture allowance. The highest and lowest efficiency was obtained with treatments LA and HA, respectively. The neutral detergent fibre content of forage harvesting was affected (P < 0.05) by the pasture allowance, with average of 44.8, 47.0, and 49.4 to HA, MA, and LA, respectively. There was an effect of pasture allowances (P < 0.05) on the milk yield per hectare and milk yield per cow. The highest production was observed in LA (438 L/ha.day) and the lowest in HA (314 L/ha.day). The percentage of milk fat, milk protein, and milk fat (g/cow.day) did not differ (P > 0.05) among pasture allowances. There was effect (P < 0.05) of pasture allowance with higher grazing time (369 min) and lower rumination time (23.3 min) observed to HA. Pasture allowances affected (P < 0.05) the total number of bites/day and bites/min, but did not affect (P > 0.05) bite mass. The pasture managements with low (26.8 kg DM/cow.day) pasture allowances provided better conditions for milk yield per area, likely due to the better grazing efficiency. However, pasture allowance provide little measurable changes on grazing behaviour.

Sward structure and herbage intake of Brachiaria brizantha cv. Piatã in a crop-livestock-forestry integration area

Forage species tolerate varying degrees of shading. In agrosilvopastoral systems, forage plants are able to adjust and partially compensate growth reduction under light stress. These adjustments change morphological proportions and composition along the vertical profile of the sward. Sward morphological composition is directly related to animal intake behavior and performance. One objective of this study was to evaluate the effects of different tree shading levels on sward vertical structure of Piatã palisadegrass cultivated in a crop-livestock-forestry integration area. Another objective was to identify the relationship between sward vertical structure and herbage intake by cattle (Boss pp.). Three experiments were conducted simultaneously to evaluate three shading levels: 1. Full sunlight (FS); 2. Moderate shade (MS; 338 trees.ha−1); and Intense shade (IS; 714 trees.ha−1). Evaluation was performed during three periods in which total rainfall during the experimental period corresponded to 86, 12 and 2% (periods 1, 2 and 3, respectively). Pastures were rotationally stocked and grazed at 95% canopy light interception (LI) during regrowth (95% LI). Two strategies for taking the reference readings of LI were tested in IS paddocks: LI reading inside (under the tree canopy) and outside (under full natural light) the experimental area. The IS had greatest forage height and proportion of stems, both pre- grazing and post-grazing. Consequently, animals under IS had decreased bite mass and intake rate, pre- and post-grazing except for period 3. There was an effect of shading level on herbage crude protein (CP) concentration. Greatest CP concentrations were observed on IS areas. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) did not vary with shading levels. Herbage dry matter digestibility varied with evaluation period, and lowest values were recorded during period 3. Greater herbage intake was observed on FS and MS relative to IS, due to greater leaf proportion in sward herbage mass. Moderate shading is not so detrimental to system's productivity, highlighting the importance of adequate choice of tree species, plant density and arrangement.

Sward structure and short-term herbage intake in Arachis pintoi cv. Belmonte subjected to varying intensities of grazing

AbstractThe use of forage legumes has been proposed as a means of generating sustainable grazing environments. Their limited use, particularly in tropical pastures, is partially due to the limited knowledge regarding the efficiency of utilization by animals. The present study characterized the sward structure, nutritive value and ingestive behaviour of dairy heifers in pastures of peanut cv. Belmonte under continuous stocking management. Treatments corresponded to sward heights of 5, 10, 15 and 20 cm, according to a randomized complete block design, with four replications. The following response variables were evaluated: vertical distribution of the morphological components within the sward, forage mass, nutritive value (simulated grazing), bite rate (BR), bite mass (BM) and short-term herbage intake rate (STIR). The top half of the sward height was mainly composed of leaves and the bottom half mainly of stolon and dead material regardless of management height. Greater values of neutral detergent fibre and acid detergent fibre were recorded during autumn, while higher values of in-vitro dry matter (DM) digestibility (0·85) occurred during spring regardless of management height for the grazed stratum. In relation to treatments, greater values of crude protein were recorded on swards managed at 5 cm (0·27) and 10 cm (0·26). Bite rate, BM and STIR varied with sward height, but not with a season of the year. The STIR followed a broken line response to sward height, with increasing values up to 13·1 cm (106 g DM/kg body weight). Sward structure played an important role in determining the STIR. To maximize the STIR of dairy heifers under continuous stocking management, swards should be managed at heights of not <13·1 cm.

Effect of supplementation frequency in feeding behavior, displacement patterns and forage intake of beef heifers

Our work was carried out to evaluate forage intake, feeding behavior and displacement patterns of beef heifers fed exclusively on pasture or receiving oat grain, either daily (“frequent”) or from Monday to Friday (“infrequent”), in two phenological stages of Alexandergrass (Urochloa plantaginea Link.): “Vegetative” and “Reproductive”. The grazing method was continuous, with a variable number of animals. The experimental design was completely randomized with measures repeated in time with three feeding frequencies and two phenological stages. Forage intake was estimated using the chromic oxide technique as an indicator of fecal output. Heifers on exclusive Alexandergrass pasture and frequently supplemented had higher forage intake of dry matter (DM, 2.91 kg DM 100 kg BW-1) than those that were infrequently supplemented (2.00 kg DM 100 kg BW-1). Forage intake was greater in the “Vegetative” stage. The use of feeding stations is modified in response to supplementation frequency and phenological stages of Alexandergrass. Bite mass was higher for daily supplemented heifers, and these animals spent less time grazing. Also, bite mass was the item that best explained DM total ingestion. Bite mass and grazing time were similar throughout the phenological stages, whereas bite rate decreased in the reproductive stage. Feeding behavior and forage intake responses of beef heifers were influenced by supplementation frequency and phenological stages of Alexandergrass.

Changes in the short‐term intake rate of herbage by heifers grazing annual grasses throughout the growing season

AbstractAnnual temperate grasses go through abrupt changes in morphological composition during the growing season, which can affect ingestive behavior of grazing cattle. However, few studies have examined the effects of gradual structural changes in annual temperate pastures on the herbage intake rate during the growing season. We hypothesized that lenient grazing (removal of 40% of the initial pre‐grazing height) maintains short‐term intake rate (STIR) of grazing cattle over the entire growing season, even with decreased leaf/stem ratios. The studied pastures contained Avena strigosa, Lolium multiflorum and a mixture of the two species. Short‐term intake rate was measured using the double weighing technique, evaluating both bite rate and bite mass. The percentage of stem + pseudostem and leaf lamina lengths in the herbage mass were measured. Relationships between sward structure and animal ingestive behavior were also examined. As the pasture growing season progressed, the STIR of heifers grazing annual temperate grass swards was affected more by the time required to take a bite than by bite mass. Moreover, the sward structure also changed after each grazing cycle, reducing the pre‐grazing leaf/stem ratio. However, reductions in the pre‐grazing leaf lamina mass (up to 37% of the sward herbage mass) and/or in the leaf lamina length (up to 52% of the extended tiller height) did not affect the STIR of grazing heifers, since the animals maintained their bite mass and time per bite. In summary, with a grazing down target of 40% of the pre‐grazing height, reductions in STIR of heifers grazing annual temperate grasses occurred when the pre‐grazing leaf lamina percentage was <37% of the sward herbage mass and/or <52% of the extended tiller height. These results suggested that to avoid STIR reductions during the last grazing cycles, managements to stimulate tillering and delay stem + pseudostem elongation are necessary and should be investigated.

Mechanisms and implications of a type IV functional response for short-term intake rate of dry matter in large mammalian herbivores.

The functional response (i.e. the relationship between consumers' intake rate and resource density) is central in plant-herbivore interactions. Its shape and the biological processes leading to it have significant implications for both foraging theory and ecology of grazing systems. A type IV functional response (i.e. dome-shaped relationship) of short-term intake rate of dry matter (intake while grazing) has rarely been reported for large herbivores and the conditions that can lead to it are poorly understood. We report a type IV functional response observed in heifers grazing monocultures of Cynodon sp. and Avena strigosa. The mechanisms and consequences of this type of functional response for grazed system dynamics are discussed. Intake rate was higher at intermediate than at short or tall sward heights in both grass species. The type IV functional response resulted from changes in bite mass instead of a longer time needed to encounter and process bites. Thus, the decrease of intake rate of dry matter in tall swards is not explained by a shift from process 3 (potential bites are concentrated and apparent) to process 2 (potential bites are apparent but dispersed, Spalinger & Hobbs 1992). Bite mass was smaller in tall than in intermediate swards due to a reduction of bite volume possibly caused by the greater proportion of stem and sheath acting as a physical barrier to bite formation. It is generally accepted that potential bites are abundant and apparent in most grassland and meadow systems, as they were in the present experiments. Therefore, a type IV response of intake rate not directly related to digestive constraints may determine the dynamics of intake and defoliation under a much larger set of conditions than previously thought. These results have implications for foraging theory and stability of grazing systems. For example, if animals prefer patches of intermediate stature that yield the highest intake rate, grazing should lead to the widely observed bimodal distribution of plant mass per unit area, even when tall patches are not of significantly lower digestive quality than the pasture average.

Profile of Mass Casualties of Animal Bite Cases Reported to a Tertiary Care Institution from April 2014 to March 2015 in North Kerala : India

International Journal of Medicine and Public Health,2017,7,1,33-37.DOI:10.5530/ijmedph.2017.1.5Published:March 2017Type:Original ArticleProfile of Mass Casualties of Animal Bite Cases Reported to a Tertiary Care Institution from April 2014 to March 2015 in North Kerala : IndiaLathika Velichapatt Ramakrishnan, Lilabi Shakir, Priya Chandran, and Jayakrishnan Thavody Lathika Velichapatt Ramakrishnan1, Lilabi Shakir2, Priya Chandran2, Jayakrishnan Thavody2 1Department of Community Medicine, Government Medical college, Kozhikode, INDIA. 2Department of Community Medicine, Government Medical College, Kozhikode, INDIA.Abstract:Background: Animal bite is an emerging Public health problem causing injuries and even death. Increase incidences of dog bite have been reported from the Indian state of Kerala from last two years and there have been several instances of a single animal biting several victims at the same area. The preventive clinic of Calicut Medical College is a referral centre for the management of animal bite cases in North Kerala. Incidents of mass casualties are a source of panic and alarm among public. The present study analyses these incidents of mass casualties of animal bites studying the epidemiological profile of animals involved. Considering the paucity of studies in this area the information obtained from the present study may help in mapping risk areas and to take necessary control measures. Objectives: To find out the epidemiological and clinical profile of mass casualty due to animal bites reported to the institution. Methodology: Record based cross sectional study design. Review of the mass casualty register maintained at the Preventive Clinic. Details of animal bite cases treated in the clinic from 2014 April to 2015 March were collected. Sociodemographic characteristics, clinical profile and management details were analyzed. Results: A total of 7072 animal bite cases reported to the preventive clinic during the study period. Of this, there were 54 incidents of mass casualty involving 236 patients were registered to receive treatment in the clinic. Majority were males (53%). Adults (79.2%) were commonly effected than children (20.8%).Median age was found to be 36yrs . Exposure to dogs constituted 77.1% of cases, followed by fox (11.9%). All were category 3 wounds and were given anti rabies vaccine, anti rabies immunoglobulin and antibiotics. Conclusion: There were 54 incidents of animal bite mass causalities involving 236 people. Dogs were the commonest animal causing mass casualty. Control of stray dog population by animal birth control needed. Keywords:Animal bite, Clinical profile, Epidemiological, Mapping, Mass casualty, Risk areasView:PDF (136.06 KB)

Forage intake processes by goats on a massai grass pasture with different sward heights

The objective of this study was to evaluate the forage-intake process of goats feeding on Massai grass pastures with different heights (40, 50, 60, and 70 cm). The experimental design was completely randomized, with treatments corresponding to four sward heights with two replicates over time and space. Collected data were related to the forage-intake process and the chemical and morphological composition of the pasture. Grazing trials (45 min) were performed with four Anglo-Nubian crossbred goats. Total forage mass intake, bite mass, and intake rate were expressed in relation to animal weight. Pasture density, forage mass, and leaf blade increased as forage height increased. The chemical composition of forage at the evaluated heights was similar, except for reduced crude protein content at 70-cm height. Bite rate, intake rate, and time per bite had a quadratic relationship with increasing sward height. The greatest intake rate was observed at 54.7 cm of height, with 0.136 g DM min-1 kg-1 LW. Bite rate exhibited a linear and positive correlation with increase in intake. At the 50-cm height, goats harvested a mass of 3.65 g DM bite-1 kg-1 LW, when they performed 34.5 bites per minute. Adult goats had a greater forage intake on 50-cm high Massai grass pastures because they could obtain a greater bite mass in a shorter time per bite.

Nutritional ecology of elk during summer and autumn in the Pacific Northwest

Nutritional ecology of elk during summer and autumn in the Pacific Northwest

Giraffe browsing in response to plant traits

Intake rates by large herbivores are governed by among other things plant traits. We used Masai giraffe (Giraffa camelopardalis tippelskirchi Matschie) as study animals, testing whether they as very large browsers would follow the Jarman–Bell principle and maximize intake rate while tolerating low forage quality. We worked in Arusha National Park, Tanzania. We investigated how intake rate was determined by bite mass and bite rate, and show that bite mass and bite rate were determined by plant characteristics, governed by inherent plant traits, plant traits acquired from previous years’ browsing, and season. We predicted that; (1) bite mass would be larger in trees without spines than with (2) bite mass would be larger in the wet season than in the dry, (3) bite rate would be higher in spinescent trees than in non-spinescent, (4) bite rate and/or bite mass would increase with previous years’ browsing, (5) bite mass, bite rate or browsing time per tree would be highest for high trees with large, although still available canopies. Visual observations were used to collect data on tree attributes, number of bites taken and time of browsing. Sample size was 132 observed giraffe. We found that bite mass was larger in spineless than in spinescent trees and was larger in the wet season than in the dry. Bite rate, but not bite mass, increased with increasing browsing in previous years and was highest on two to three meter high trees and in spinescent trees. Intake rate followed bite mass more than bite rate and was higher in spineless than in spinescent trees, higher in the wet season than in the dry, and tended to increase with tree height. Giraffe did not prioritize the highest intake rate, but browsed much on Acacias giving a high quality diet but a low intake rate.

Canopy structure, ingestive behavior and displacement patterns of beef heifers grazing warm-season pastures

Analyses in a data set of six experiments (n=436) was performed with the aim of characterizing canopy structure and forage intake patterns of beef heifers grazing on Pearl millet (Pennisetum americanum), Alexandergrass (Urochloa plantaginea) and Coastcross (Cynodon dactylon). Forage and leaf lamina mass were similar among species, 3001.4 and 668.1kg of DM/ha, respectively, while leaf:stem ratio of canopy vertical strata was different. Intake rate (12g DM/minute), bite mass (0.343g DM/bite) and bite rate (36.6bites per minute) were similar in Pearl millet and Alexandergrass. In Pearl millet, neutral detergent fiber content (56.1%) in forage as grazed, grazing time (518.9 minutes/day) and displacement rate (8.8 steps/minute) were lower. Increased grazing time (639 minutes/day) represented the main compensatory mechanism for smaller bite masses (0.234g DM/bite) and reduced intake rates (8.8 grams of DM/minutes) in Coastcross. Bite rate variations happened as a response to constraints imposed by canopy structure. Surface utilization on Alexandergrass and Coastcross was increased by greater number of feeding stations visited and displacement rate. Ingestive behavior components of beef heifers are affected by differences in the canopy structure of Pearl millet, Alexandergrass and Coastcross.

Circadian Ingestion Behaviors: Animal Models Outlooks

Submit Manuscript | http://medcraveonline.com Grazing occurs mainly around sunrise and sunset. In grazing sheep, the maximum jaw movement occurs in the late afternoon before sunset. Dairy cows exhibit three main grazing bouts of dawn, afternoon, and dusk. However, the diurnal patterns in grazing appear to vary across seasons. In Western Australia with hot summers and mild winters, the main summer grazing activity occurs during early morning and late afternoon with a smaller activity around midnight. Sheep and cattle likely have comparable grazing patterns in summer. In winter, however, the cattle show intensive grazing activities not only in the morning and afternoon but also during the period from 2000-0100 h. Unlike in summer, in winter, sheep has a progressive grazing activity from 0600 through 1700 with low activity in the evening. Under intensive feeding systems, dairy cows and finishing bulls fed only once daily in the morning exhibit two peaks in eating activity. The greatest one is right after feeding and another around dusk. The eating/ grazing pattern has circadian patterns [1]. Cows seem to stop the morning eating before reaching the maximum rumen capacity. The observation that rumen capacity peaks at dusk but not during the morning and afternoon grazing has implications. It is found that time spent eating during the dusk grazing bout is longer than that during the dawn and afternoon bouts. Moreover, during dawn and afternoon bouts, the cows finish eating before reaching a rumen capacity which was reached during the dusk bout. Therefore, the rumen fill has probably a more significant role in regulating the dusk feed intake compared to dawn and afternoon feed intakes [2,3]. Despite feeding adequate coarse corn silage as 45% of diet dry matter (DM), finishing bulls select the coarse particles for as long as 16-h post-feeding. Such a late selection of the more structured total mixed ration particles is an effort to optimize the intake of long roughage particles. In beef cattle, the herbage allocation time (e.g., 0700 h vs. 1500 h) alters daily patterns in eating, ruminating, and idling behaviors in heifers. The heifers turned unto the ungrazed strip at 0700 h have more intense evening grazing with faster bite rates compared with the heifers allotted the herbage at 1500 h. The morning grazing is 36-39% of total daily grazing time in the latter group but only 25-28% in the former group. The nutritional status of the animal before feeding can affect the postfeeding eating intensity. Fasting, for instance, hastens eating by increasing the bite rate and enlarging the bite mass. However, the data on the effects of feeding strategies on diurnal patterns in feed intake of non-grazing ruminants is scarce [3-5]. The large evening meals in grazing cows are partly linked to an optimal foraging strategy. The plant content of DM and water soluble carbohydrates rises and NDF decreases as day progresses. The accumulation of highly-digestible nutrients in the evening is due to the daylight photosynthesis in plant leaves. This may partly explain why cattle, sheep, and goats prefer the fresh forage grass and legumes harvested at sunset compared to that harvested at sunrise. A higher in vitro true DM digestibility for PM-cut than for AM-cut alfalfa hay is known. Ruminants may have greater feed intake and greater total tract DM digestibility when they are offered the sunset-cut alfalfa hay instead of the sunrise-cut alfalfa hay. The grazing ruminants appear to learn the time of maximum plant nutrient quality, leading to a more intensive eating in the evening than in the morning [4-6].

Ingestive behavior and short-term intake rate of cattle grazing on tall grasses

Tall grasses (>1m tall) are an important forage resource for grazing ruminants. Understanding the ingestive behavior and short-term intake rate of cattle grazing on tall grasses will help facilitate grazing management of tall grass pastures. The aim of this study was to determine the allocation of jaw movements in grazing cattle in relation to tall grasses and to assess whether such allocations of jaw movements are effective for maintaining a short-term intake rate. Four plants were used as test plants: bahiagrass (Paspalum notatum Flügge; a short grass), Sudangrass (Sorghum×drummondii; a typical tall grass) and two growth forms of a dwarf bamboo (Sasa senanensis; a semi-woody form of tall grass): a naturally growing form (NGDB, approximately 2m tall) and a form that is under grazing (DBUG,<0.8m). Four Japanese Black cows were allowed to graze each plant in random order. The grazing jaw movements and intake rate were measured using an integrated method with a microsward technique and acoustic monitoring. The cows performed the highest number of total bites (simple bites+chew-bites) for bahiagrass, an intermediate number of total bites for Sudangrass and DBUG and the lowest number of total bites for NGDB (P<0.05). The total number of chews (simple chews+chew-bites) was similar among NGDB, DBUG, and Sudangrass, whereas the total number of chews for bahiagrass was less than that for dwarf bamboos. The number of observed chew-bites exhibited an order similar to that observed for the number of total bites. As a result of each jaw movement, cows ingesting the DBUG moved their jaws more frequently among the plants, and cows ingesting the bahiagrass performed the fewest grazing jaw movements. Bite mass was considerably greater in the cows ingesting NGDB than in the cows ingesting other plants. Conversely, the chew mass for bahiagrass was clearly greater than that for the two taller plants. Cows ingesting Sudangrass processed the least amount of forage with each chew (P<0.05). The intake rate did not significantly differ among the plants (P>0.05), except for Sudangrass. Cows ingested Sudangrass at a lower intake rate than observed for the other plants (P<0.05). The results suggest that cattle were able to control their ingestive jaw movements depending on plant characteristics such as height, the spatial arrangement of the leaves and leaf morphology. However, the lower short-term intake rate for tall grasses implies that there is a limit to the adaptability of grazing jaw movements.

Bison foraging responds to fire frequency in nutritionally heterogeneous grassland

Foraging decisions by native grazers in fire‐dependent landscapes modulate the fire–grazing interaction. Uncovering the behavioral mechanisms associated with the attraction of grazers to recently burned areas requires understanding at multiple spatial scales in the ecological foraging hierarchy. This study focused on feeding in the area between steps in a foraging bout, the feeding station, as forage chemistry and vegetation architecture play central roles in these fine‐scale, feeding‐station decisions. The forage maturation hypothesis (FMH) uses the temporal dynamics of forage quality and quantity in grasslands to explain the distribution of large herbivores, but does not address herbivore responses to inter‐patch variation caused by fire‐induced nutrient increases of forage quality. Using an experimental setting with contrasting fire treatments we describe the effects of variable burn history on foraging kinetics by bison at Konza Prairie Biological Station (KPBS). We assessed the potential to link the FMH in a complementary fashion to the transient maxima hypothesis (TMH) to explain temporal variation in bison responses to grassland forage quality and quantity in response to burning at different temporal frequencies. Forage attributes met predictions of the TMH that allowed us to investigate how forage maturation affects feeding station foraging behavior across watersheds with varying burn frequency. At sites burned in the spring after several years without burning, both bite mass and intake rate increased with increasing biomass at a greater rate during the growing season than during the transitional midsummer seasonal period. In these infrequently burned watersheds, early growing season bite mass (0.6 ± 0.05 g; mean ± SE), bite rate (38 ± 1.5 bites/min), and intake rate (21 ± 2.3 g/min) was reduced by ~15%, 13%, and 29% during the midsummer transitional period. A behavioral response in foraging kinetics at the feeding station occurred where a nonequilibrial pulse of high‐quality resource was made available and then retained by repeated grazing over the growing season. Our results provide the first experimental evidence for demonstrating the fine‐scale behavioral response of a large grazer to fire‐induced changes in forage attributes, while linking two prominent hypotheses proposed to explain spatial variation in forage quality and quantity at local and landscape scales.

Why elephant have trunks and giraffe long tongues: how plants shape large herbivore mouth morphology

AbstractWe investigated whether mass and morphological spatial patterns in plants possibly induced the development of enlarged soft mouth parts in especially megaherbivores. We used power functions and geometric principles to explore allometric relationships of both morphological and foraging characteristics of mammalian herbivores in the South African savannah, covering a body size range of more than three orders magnitude. Our results show that, although intradental mouth volume scaled to a power slightly less than one to body mass, actual bite volume, as measured in the field, scaled to body mass with a factor closer to 1.75. However, when including the volume added to intradental mouth volume by soft mouth parts, such as tongue and lips (or trunks in elephant), mouth volume scaled linearly with actual bite volume and in a similar fashion as actual bite volume to body size. Bite mass and bite leaf mass scaled linearly with body size. We conclude that these scaling relationships indicate that large herbivores use their enlarged soft mouth parts to not only increase bite volume and thereby bite mass, but also select soft plant parts and thereby increase the leaf mass fraction per bite.

Can animal performance be predicted from short-term grazing processes?

Despite all the biotic and abiotic factors affecting foraging by ruminants, there is a common and fundamental process, which is bite gathering. We hypothesised that because the mechanics of bite formation dominate the foraging process, changes in short-term bite mass are reflected in longer-term animal performance across a wide range of sward conditions. We focus at the meal level of foraging, using experiments in which the effect of abiotic factors and digestive constrains are minimised, making intake rate the main currency. We estimated bite mass across a wide range of structural challenges to large-herbivore foraging in a long-term experiment with heterogeneous native grasslands. A conceptual model was developed for average daily gain, where energy gain and energy costs were proximate causal variables. Energy gain was a function of diet quality and components of daily intake rate, where bite mass was the main component estimated. In turn, components of intake rate were determined by sward structure and bodyweight. Energy costs were a function of bodyweight and abiotic conditions. Finally, sward structure, bodyweight and abiotic conditions were determined by experimental treatments, seasons and years. Then, the conceptual model was translated into statistical models that included variables measured or estimated, and coefficients representing all links in the conceptual model. Weight gain was a function of bite mass, forage characteristics, and animal and abiotic conditions. Models were set up to test whether forage and stocking conditions affected monthly gain beyond the effects through bite mass, after correcting for abiotic factors. Forage mass, height and disappearance did help predict monthly gain after bite mass was included in the model, which supported our hypothesis. However, stocking treatments and season had significant effects not incorporated in bite mass. Although the model explained 77.9% of liveweight gain variation, only 35.2% was due to fixed effects, with 10.8% accounted by bite mass and its interactions. Concomitant experiments showed that sward structure (first with sward height and the second with tussock cover) does determine bite mass and short-term intake rate in the complex native grasslands we studied. Yet, other temporal varying components of monthly gain not correlated with bite mass, temperature or wind, added most of the observed variation in monthly animal performance. Part of the model failure to account for variation in performance may be related to a significant and temporally variable grazing of tussocks. We used a bite mass model that assumed no tussock grazing. In light of these results and a parallel experiment, we conclude that tussock grazing must be incorporated in future versions of the model.

Continuous bite monitoring: a method to assess the foraging dynamics of herbivores in natural grazing conditions

Accurate estimates of bite mass and variations in the short-term intake rate of grazing herbivores has been historically considered as a fundamental methodological difficulty, a difficulty that increases with the complexity of the feeding environment. Improving these methodologies will help understand foraging behaviours in natural grazing conditions, where habitat structure and interactions among different forages influence feeding decisions and patterns. During the past 30 years, we have been developing the ‘continuous bite-monitoring’ method, an observational method that allows continuous assessment of foraging behaviours, including bite mass, instantaneous intake rate and food selection, in simple to complex feeding environments. The centrepiece of the method is a ‘bite-coding grid’ where bites are categorised by structural attributes of the forage to reflect differences in bite masses. Over the years, we have been using this method with goats, sheep, llamas and cattle across a range of different habitats. After reviewing the development of the method, we detail its planning and execution in the field. We illustrate the method with a study from southern Brazilian native Pampa grassland, showing how changes in the forages consumed by heifers strongly affect short-term intake rate during meals. Finally, we emphasise the importance of studying animals grazing in their natural environments to first identify the relevant processes that can later be tested in controlled experiments.

Behavioural adaptation of grazing dairy cows to changes in feeding management: do they follow a predictable pattern?

Research conducted over recent decades to improve understanding of the functional responses among sward characteristics, intake rate and grazing behaviour has been reviewed. The opportunities to modify grazing pattern by changes in feeding management are discussed and the implications for dairy-farm feeding strategies are highlighted. Progress in the understanding of the functional responses between sward characteristics and intake rate and their main components (bite mass, bite area, bite depth and bite rates) has been substantial. However, progress in understanding the factors that mediate the initiation and the end of individual meals has been poorer and requires further study. Much of the research has been conducted using short-term experiments with a limited number of experimental animals and mostly conducted on mono-specific uniform swards. The physiological state of the animal as well as the maintenance energy associated with grazing strategies have received very little, if any, attention. More integrated (sward, animal, management) and long-term basic research is required to improve feeding practices at the farm level and the design of farms for the new generation of grassland-based dairy-production systems.

Nutritional implications of increased shrub cover for caribou (Rangifer tarandus) in the Arctic

Shrubs are increasing in the annual range of arctic caribou (Rangifer tarandus (L., 1758)), but it is unknown how much summer browse caribou could consume. We measured instantaneous intakes of resin birch (Betula glandulosa Michx.) and feltleaf willow (Salix alaxensis (Andersson) Coville) by caribou during summer. Daily intake of a formulated diet without toxins was measured during the same period to monitor appetite. Caribou appetite increased from 64.1 to 86.7 g DM·kg–0.75·day−1 as animals gained body mass from 96.8 to 113.5 kg. We estimated that caribou required 645 kJ·kg–0.75·day−1 of digestible energy to maintain body mass and 1113 kJ·kg–0.75·day−1 to gain body mass for autumn reproduction. Caribou had the same bite mass (9.7 mg·bite−1·kg–0.75) and instantaneous intake rate (0.17 g DM·min−1·kg–0.75) on both forages; however, birch contained more phenols (3.3% vs. 1.5%) and less available protein (6.2% vs. 10.2%) than willow. A 100 kg female caribou would need to consume 2.4–8.7 kg of fresh browse, requiring 3.1–8.5 h·day−1 of eating time to meet daily energy requirements. Birch is unlikely to provide enough nitrogen for maintenance of body protein. Therefore, caribou may depend on abundance and diversity of plants to offset toxin loads and low protein intake from shrubs during summer.