Individualistic herds: Individual variation in herbivore foraging behavior and application to rangeland management

The interaction of genes and environment on percent of juniper in the diet of goats divergently selected for high or low juniper consumption

Diet selection and preference by grazing animals are determined by genetic and environmental factors that interact and affect their efficacy for managing vegetation as targeted grazers and developing animals adapted to local grazing environments. The effect of the rearing environments on the consumption of juniper (Juniperus spp.) by goats that for 15 years were divergently selected for high (J+) or low (J-) percent juniper in their diet was investigated. To test the effect of rearing environment, at the end of the breeding season, pregnant does from both selection lines were grazed on either juniper-infested (JIR) or juniper-free (JFR) rangelands until their kids were weaned at about 75 days of age. Fecal samples were analyzed with fecal near-IR spectroscopy to determine the percent juniper in the diet. Fecal samples were collected from does on JIR when their offspring were 30 days of age and at weaning. Then, does that raised kids in both rearing environments grazed a common JIR pasture for a 28-day adaptation period before collecting fecal samples. After weaning, kids from both rearing environments grazed JIR for 22 days before collecting fecal samples. The J+ does always consumed more (P < 0.001) juniper than J- does, demonstrating different maternal role models for kids reared in the JIR environment. There was no effect of rearing environment (P = 0.488) or rearing environment × selection line interaction (P = 0.096) when J- and J+ does grazed a common JIR pasture. The percentage of juniper in J- kid diets (7%) was the same regardless of the rearing environment. However, the rearing environment did affect the percentage of juniper in the diet of J+ kids, resulting in a gene-environment interaction (P = 0.022). The percentage of juniper in the diet of J+ kids reared in JFR (16%) and JIR (24%) were about two and three times higher than J- kids, respectively, indicating that genetics and the rearing environment contributed about equally to the increase in the percentage of juniper in the J+ kid diets. Regardless of the rearing environment, the J+ kids had a higher percentage of juniper in their diets than J- kids (P < 0.001). Compared to males, female kids had a higher percentage of juniper in their diets (12 vs 17%, respectively; P = 0.002). The ability to select animals with specific dietary preferences holds promise for targeted grazing strategies to restore degraded rangelands, with potential applications in conservation and ecosystem management.

Molecular identification of individual and seasonal variation in incidental ingestion of arthropods by free-ranging goats

The extent of direct interactions between large mammalian herbivores (LMH) and plant-dwelling arthropods (PDA), i.e., the ingestion of PDA by LMH, remains largely unexplored. Grazing LMH may ingest a variety of PDA, yet, it is unknown how different foraging strategies (i.e., browsing, grazing, etc.) influence the ingestion of PDA or whether individual variation within herds affects it. Here we examine how individual variation within a herd of browsing LMH impacts PDA ingestion. This was done using a DNA metabarcoding analysis on feces collected monthly from marked individuals within a herd of free-ranging goats. We found that goats frequently ingest PDA while feeding (all samples contains PDA), including a complex food-chain of herbivores, predators and parasites, which differed over the season and among individual goats. In total, 63 families of insects and 9 families of arachnids from 15 orders were ingested by the goats. Most ingested PDA were herbivores with reduced mobility, such as immature or sessile species. Highly mobile and noxious PDA were rarely detected. We show for the first time that ingestion of PDA by LMH is influenced by seasonal and individual variation within the herd and that it is common among LMH, regardless of feeding strategy or habitat.

Using the natural abundance of nitrogen isotopes to identify cattle with greater efficiency in protein-limiting diets

The difficulty in selecting cattle for higher feed and nitrogen use efficiency (NUE) is an important factor contributing to poor growth and reproductive performance in dry-tropics rangelands. Therefore, the objectives were to examine the cattle variation in retaining nitrogen in a protein-deficient diet and the natural abundance of stable isotopes in body tissues as a practical alternative for the detection of more efficient cattle. In experiment 1, feed efficiency parameters were determined in 89 Brahman steers fed a protein-limiting diet for 70 days, followed by 7 days in metabolism crates for total collection of urine and faeces and calculation of nitrogen retention and NUE. The diet-animal fractionation of nitrogen isotopes (Δ¹⁵N) was quantified in tail hair and plasma proteins using isotope-ratio MS. There was a large variation in growth performance, feed efficiency and nitrogen losses among steers. Quantifying Δ¹⁵N in tail hair (Δ¹⁵N_{tail hair}) resulted in stronger correlations with feed efficiency and nitrogen metabolism parameters than when quantified in plasma proteins. Δ¹⁵N_{tail hair} was positively correlated with nitrogen losses in urine (r = 0.31, P < 0.01) and faeces (r = 0.25, P = 0.04), leading to a negative correlation with NUE (r = -0.40, P < 0.01). The group of steers with lower Δ¹⁵N_{tail hair} had greater feed efficiency, lower nitrogen losses, and greater NUE. In experiment 2, for evaluation of isotope fraction as a predictor of reproductive performance, 630 Brahman-crossed cows were classified for reproductive performance for 2 years. From this group, 25 cows with poor reproductive performance and 25 cows with good reproductive performance were selected. Tail hair representing 7 months of growth were segmented and analysed for carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope enrichment. Reproductive performance was not associated with diet selection, as there was no difference in tail hair δ¹³C between groups. However, more productive cows had lower (P < 0.05) tail hair δ¹⁵N during the dry season, indicating differences in N metabolism and possibly lower N losses. In addition, cows with better reproductive performance and, therefore, greater nutrient demands, had similar body condition scores and a tendency (P = 0.09) for higher live weight at the end of the trial. In conclusion, the findings of the present study confirm that nitrogen isotope fractionation in tail hair can be used as a predictor of nitrogen losses, NUE, and reproductive performance of Brahman cattle on low-protein diets.

Video recording and vegetation classification elucidate sheep foraging ecology in species-rich grassland

Factors influencing grazing behavior in species-rich grasslands have been little studied. Methodologies have mostly had a primary focus on grasslands with lower floristic diversity.We test the hypothesis that grazing behavior is influenced by both animal and plant factors and investigate the relative importance of these factors, using a novel combination of video technology and vegetation classification to analyze bite and step rates.In a semi-natural, partially wooded grassland in northern Estonia, images of the vegetation being grazed and records of steps and bites were obtained from four video cameras, each mounted on the sternum of a sheep, during 41 animal-hours of observation over five days. Plant species lists for the immediate field of view were compiled. Images were partnered by direct observation of the nearest-neighbor relationships of the sheep. TWINSPAN, a standard vegetation classification technique allocating species lists to objectively defined classes by a principal components procedure, was applied to the species lists and 25 vegetation classes (15 open pasture and 10 woodland) were identified from the images.Taking bite and step rates as dependent variables, relative importance of animal factors (sheep identity), relative importance of day, and relative importance of plant factors (vegetation class) were investigated. The strongest effect on bite rates was of vegetation class. Sheep identity was less influential. When the data from woodland were excluded, sheep identity was more important than vegetation class as a source of variability in bite rate on open pasture.The original hypothesis is therefore supported, and we further propose that, at least with sheep in species-rich open pastures, animal factors will be more important in determining grazing behavior than plant factors. We predict quantifiable within-breed and between-breed differences, which could be exploited to optimize conservation grazing practices and contribute to the sustainability of extensive grazing systems.

Fundamental dietary specialisation explains differential use of resources within a koala population

The diets of individual animals within populations can differ, but few studies determine whether this is due to fundamental differences in preferences or capacities to eat specific foods, or to external influences such as dominance hierarchies or spatial variation in food availability. The distinction is important because different drivers of dietary specialisation are likely to have different impacts on the way in which animal populations respond to, for example, habitat modification. We used a captive feeding study to investigate the mechanisms driving individual dietary specialisation in a population of wild koalas (Phascolarctos cinereus) in which individuals predominantly ate either Eucalyptus viminalis or Eucalyptus obliqua foliage. All six koalas that primarily ate E. viminalis in the wild avoided eating E. obliqua for more than 1 month in captivity. In contrast, all seven koalas that primarily ate E. obliqua could be maintained exclusively on this species in captivity, although they ate less from individual trees with higher foliar concentrations of unsubstituted B-ring flavanones (UBFs). Our results show that fundamental differences between individual animals allow some to exploit food resources that are less suitable for others. This could reduce competition for food, increase habitat carrying capacity, and is also likely to buffer the population against extinction in the face of habitat modification. The occurrence of fundamental individual specialisation within animal populations could also affect the perceived conservation value of different habitats, translocation or reintroduction success, and population dynamics. It should therefore be further investigated in other mammalian herbivore species.

Researching Human-Cattle Interaction on Rangelands: Challenges and Potential Solutions

Simple Summary

Research investigating the influence of human-animal interactions on beef cattle production and welfare often occurs during stress-inducing contexts, such as restraint and transport. Given that beef cattle which graze on expansive rangelands do not frequently interact with humans, assessment of animal response to humans may be inaccurate if they are only recorded during such stressful context. Future research aimed at identifying the causes and impacts of individual human–cattle relationships may consider conducting experiments while the cattle are in a low stress context, such as while ruminating, resting, or, grazing. By adapting methods used to research wildlife response to humans, researchers may be able to better understand how animal personality and previous experience can influence cattle production and welfare.

Abstract

Human-animal interaction (HAI) research spans across many scientific fields and animal taxa. For livestock species, HAI research tends to focus on animals that are managed in close proximity with humans such as poultry, dairy cattle, and swine. Given the nature of rangeland cattle production, HAI research with beef cattle often occurs in and around the processing environment. This high arousal context may skew behavioral and physiological responses by the animals due to the potentially negative interaction. The aim of this review is to describe cattle production on rangelands, examine the considerations and limitations of current HAI research used to evaluate interaction quality or traits of rangeland cattle, identify contexts in which rangeland cattle interact with humans, and provide recommendations for improving future HAI research with rangeland cattle. Current research delineating individual differences in response to humans by beef cattle occur during routine husbandry and management on rangelands (pragmatic) and in a research context (experimental). Human-cattle interactions can be distinguished based on the quality and goal of the interaction into four broad categories: human presence, human approach, human contact, and restraint. Limitations of HAI research with rangeland cattle are identified and reconciled by recommendations for HAI research that can take place outside of the processing environment (i.e., while cattle are ruminating, resting or grazing on rangelands).

Biological and environmental factors as sources of variation in nocturnal behavior of giraffe

Upon a drastic decline of the giraffe population in the wild, conservation efforts and therefore the role of zoos have become more important than ever. With their unique opportunities, zoos provide excellent conditions to study animal behavior, expanding the knowledge about the giraffe's behavior repertoire and their ability to adapt. This study therefore examined the nocturnal behavior of 63 giraffe living in 13 different EAZA zoos across Germany and the Netherlands. Giraffe were observed and videos recorded via infrared sensitive cameras during the winter seasons 2015-2018. The observation period spanned nightly from 17:00 to 7:00. Thus, 198 nights, with a total of 2772 h were recorded and analyzed. Linear mixed models were then used to assess potential biological and environmental factors influencing behavior during the dark phase. Results show that individual variables such as age, subspecies and motherhood determined nocturnal activity and sleep behavior most. Among the variables studied, husbandry conditions and environmental factors complying with EAZA standards had no influence on the giraffe's nocturnal behavior. By combining nocturnal activity analyses and an assessment of potential influencing factors, our findings present a holistic approach to a better understanding of captive giraffe behavior and allow for management implications.

Sheep in Species-Rich Temperate Grassland: Combining Behavioral Observations with Vegetation Characterization

Simple Summary

Grasslands cover much of the world, and numerous people depend on the livestock that graze them for their livelihoods. These areas must be properly managed as they are often ecologically fragile. Therefore, how the foraging animal interacts with its environment needs to be understood. These interactions have mostly been studied in highly productive intensively managed and improved grasslands, which typically have only a limited number of commercially developed plant varieties. Little is known about how animals interact with less intensively managed, species-rich grasslands which are often of conservation significance because of their biodiversity. In this preliminary study, we have used video technology to investigate responses of sheep to the vegetation of unimproved grassland in Estonia. We classified the vegetation with a methodology that is standard in plant ecology but which has not been extensively applied in animal behavior. We also demonstrate the use of a novel procedure for quantifying foraging behavior. This combination of methodologies will enable the characterization of individual animal variations in these important behaviors, which could provide a basis for the rational design of sustainable grassland management systems.

Abstract

Foraging behavior of livestock in species-rich, less intensively managed grassland communities will require different methodologies from those appropriate in floristically simple environments. In this pilot study on sheep in species-rich grassland in northern Estonia, foraging behavior and the plant species of the immediate area grazed by the sheep were registered by continually-recording Go-Pro cameras. From three days of observation of five sheep (706 animal-minutes), foraging behavior was documented. Five hundred and thirty-six still images were sampled, and a plant species list was compiled for each. Each plant species was assigned a score indicating its location, in the ecophysiological sense, on the main environmental gradient. The scores of the plant species present were averaged for each image. Thus, the fine structure of foraging behavior could be studied in parallel with the vegetation of the precise area being grazed. As expected, there was considerable individual variation, and we characterized foraging behavior by quantifying the patterns of interspersion of grazing and non-grazing behaviors. This combination of behavior recording and vegetation classification could enable a numerical analysis of the responses of grazing livestock to vegetation conditions.

Innate ability of goats to sense and avoid ingestion of noxious insects while feeding

Large mammalian herbivores regularly encounter noxious insects on their food plants. Recent evidence revealed that goats efficiently avoid insect ingestion while feeding, yet it is unknown whether this ability is innate. We experimentally examined the behavioural responses of naive goat kids to a common insect, the spring-webworm (Ocnogyna loewii). We filmed and analysed the kids' behaviour while feeding and compared it to the behaviour described in adults. Naive kids sorted the webworms apart from the food without ingesting them (all webworms survived). They exhibited behaviours similar to those displayed by adults, demonstrating an innate ability to avoid insect ingestion. The kids detected webworms using tactile stimulation, obtained by repeatedly touching the leaves with their muzzles. This enabled them to pick webworm-free leaves (leaving 93% of webworms behind). While adults frequently shook or discarded leaves with webworms or spat out webworms, these behaviours were rare in kids. The kids' mean feeding rates doubled over the trials, indicating that their feeding efficiency on plants with and without insects improved with experience. As ingesting noxious insects could be fatal, innate avoidance is critical. These findings highlight the importance of direct interactions between mammalian and insect herbivores.

Optimising cattle grazing distribution on rangeland: a systematic review and network analysis

Optimising beef cattle (Bos taurus and Bos indicus) distribution, both spatially and temporally, is one of the most significant challenges associated with managing extensive grazed rangelands. Landscape variability and behavioural patterns of cattle may lead to non-uniform and inefficient forage utilisation, damage to critical habitats, and water quality impairment. In order to overcome these distribution challenges, a large suite of tools have been developed and researched to optimise grazing patterns. The objectives of this synthesis paper are 2-fold: (i) to survey and categorise distribution tools; and (ii) to analyse the connectivity of existing research across academic disciplines to identify and isolate knowledge gaps. A systematic literature review revealed specific types of tools and strategies to improve cattle distribution, which were categorised as either ‘animal’ or ‘environmental manipulations’. Animal manipulations utilise aspects of individual behaviour and herd dynamics to alter grazing patterns, whereas environmental manipulations involve transforming aspects of the animal’s surroundings to overcome challenges associated with inefficient distribution. This review reveals that strategies are overwhelmingly studied in isolation, and that there is potential to increase efficacy by integrating multiple strategies to achieve a desired outcome. Motivated by these findings, an author collaboration network analysis was conducted to investigate connectivity within and among author fields of expertise to understand why more integrated management strategies are not currently studied. Authors were classified into five fields of research: animal behaviour science, animal production science, biophysical rangeland science, economics, and other. The network analysis revealed that communities of authors contributing to papers on enhancing cattle distribution are disjointed. These results suggest that in order to fulfil knowledge gaps about the efficacy and cost of management strategies, there needs to be interdisciplinary engagement with particular attention to strategies that integrate animal and environmental manipulations to enhance cattle grazing distribution on extensively grazed landscapes.

Novel object response in beef cattle grazing a pasture as a group

This study was conducted to investigate how cattle (Bos taurus) respond to objects presented for the first time and repeatedly in a stimulus-rich environment where they can freely graze and interact with conspecifics. Twenty-five Japanese Black cows were subjected to three repeats of a novel object test in which animals stocked on a pasture as a group were exposed to the same and different objects across the test repeats. Responses of cows towards the objects were quantified by both approach (entering within a 0.5-m distance of the object) and contact (physical touch with the object) measures as occurrence (1 or 0) and number of reactions and latency to the first reaction. Cows were consistent in the approach to the first-time objects (repeatability = 0.39-0.62, Kendall's W = 0.58, P <  0.05), but not in the approach to the repeatedly presented objects or in the contact with both types of objects (P > 0.05). Individuals which consistently approached the novel objects could be regarded as highly exploratory and/or bold in personality. Future work should consider novel object response in cattle across a range of contexts.

Use of GPS tracking collars and accelerometers for rangeland livestock production research

Over the last 20 yr, global positioning system (GPS) collars have greatly enhanced livestock grazing behavior research. Practices designed to improve livestock grazing distribution can now be accurately and cost effectively monitored with GPS tracking. For example, cattle use of feed supplement placed in areas far from water and on steep slopes can be measured with GPS tracking and corresponding impacts on distribution patterns estimated. Ongoing research has identified genetic markers that are associated with cattle spatial movement patterns. If the results can be validated, genetic selection for grazing distribution may become feasible. Tracking collars have become easier to develop and construct, making them significantly less expensive, which will likely increase their use in livestock grazing management research. Some research questions can be designed so that dependent variables are measured by spatial movements of livestock, and in such cases, GPS tracking is a practical tool for conducting studies on extensive and rugged rangeland pastures. Similarly, accelerometers are changing our ability to monitor livestock behavior. Today, accelerometers are sensitive and can record movements at fine temporal scales for periods of weeks to months. The combination of GPS tracking and accelerometers appears to be useful tools for identifying changes in livestock behavior that are associated with livestock diseases and other welfare concerns. Recent technological advancements may make real-time or near real-time tracking on rangelands feasible and cost-effective. This would allow development of applications that could remotely monitor livestock well-being on extensive rangeland and notify ranchers when animals require treatment or other management.

Grazing management: setting the table, designing the menu and influencing the diner

Pastoral livestock-production systems are under increasing environmental, social and consumer pressures to reduce environmental impacts and to enhance biodiversity and animal welfare. At the same time, farmers face the challenge of managing grazing, which is intimately linked with profitability. Recent advances in understanding grazing patterns and nutritional ecology may help alleviate such pressures. For instance, by managing grazing to (1) manipulate links between ingestive–digestive decisions and temporal patterns of nutrient excretion, (2) provide phytochemically diverse diets at appropriate temporal (the menu) and spatial (the table) scales and (3) influence the behaviour of animals (the diners) on the basis of their specific ‘personalities’ and needs, to overcome or enhance animal differences, thereby enhancing their and farm productivity and welfare, as well as our health. Under pastoral systems, synergies between animals’ and farmers’ grazing decisions have the potential to offer greater benefits to the animal, the environment and the farm than does simple and parsimonious grazing management based on a single component of the system. In the present review, we look at grazing and its management through an alternate lens, drawing ideas and hypotheses to stimulate thinking, dialogue and discussions that we anticipate will evolve into innovative research programs and grazing strategies. To do so, we combined experimental and observational studies from a wide range of disciplines with simulation-modelling exercises. We envisage a more holistic approach to manage grazing based on recent advances in the understanding of the nutritional ecology of grazing animals, and propose management practices that may enable pastoral livestock-production systems to evolve continually as complex creative systems.

Effects of the presence of grazing-experienced heifers on the development of foraging behavior at the feeding station scale for first-grazing season calves

In this study, effects of grazing-experienced heifer presence on foraging behavior development at the feeding station (FS) scale for first-grazing season calves were determined. A group of four calves grazing alone (C), and another comprising four calves (Wc) and three grazing-experienced heifers (Wh), were alternately stocked every day for 2 h on the same pasture for 26 days. The foraging time budget for Wc was significantly longer than that for C (P < 0.05) on day 7, and was similar to that for Wh on all days. Bite rate per FS was significantly higher for Wc (15.5 bite/min) than for C (13.2 bite/min) from day 1 to 14 (33.4 vs. 29.0 bite/min, respectively; P < 0.01) and significantly lower than that for Wh on all days. The number of steps taken between adjacent FSs by Wc (4.7) was significantly lower than that for C (7.2) on days 1 and 14 (2.1 vs. 2.9 steps, respectively; P < 0.01) and was similar to Wh on all days. This suggests that grazing-experienced heifers have positive effects on the foraging behavior development of new-season grazing calves through 14 days after the start of stocking.

Sympatric speciation in structureless environments

BACKGROUND

Darwin and the architects of the Modern Synthesis found sympatric speciation difficult to explain and suggested it is unlikely to occur. Increasingly, evidence over the past few decades suggest that sympatric speciation can occur under ecological conditions that require at most intraspecific competition for a structured resource. Here we used an individual-based population model with variable foraging strategies to study the evolution of mating behavior among foraging strategy types. Initially, individuals were placed at random on a structureless resource landscape, with subsequent spatial variation induced through foraging activity itself. The fitness of individuals was determined by their biomass at the end of each generational cycle. The model incorporates three diallelic, codominant foraging strategy genes, and one mate-choice or m-trait (i.e. incipient magic trait) gene, where the latter is inactive when random mating is assumed.

RESULTS

Under non-random mating, the m-trait gene promotes increasing levels of either disassortative or assortative mating when the frequency of m respectively increases or decreases from 0.5. Our evolutionary simulations demonstrate that, under initial random mating conditions, an activated m-trait gene evolves to promote assortative mating because the system, in trying to fit a multipeak adaptive landscape, causes heterozygous individuals to be less fit than homozygous individuals.

CONCLUSION

Our results extend our theoretical understanding that sympatric speciation can evolve under nicheless or gradientless resource conditions: i.e. the underlying resource is monomorphic and initially spatially homogeneous. Further the simplicity and generality of our model suggests that sympatric speciation may be more likely than previously thought to occur in mobile, sexually-reproducing organisms.

Modelling preference and diet selection patterns by grazing ruminants: a development in a mechanistic model of a grazing dairy cow, MINDY

The work presented here represents additions to the mechanistic and dynamic model of a grazing dairy cow (MINDY). The additions include a module representing preference and selection, based on two theories, namely, post-ingestive feedback and discomfort. The model was evaluated by assessing its ability to simulate patterns of preference and selection in response to a variety of feeding management. The improvements detailed here enable a realistic simulation of patterns of food selection by grazing ruminants, based on a range of feeding situations from different studies with cattle and sheep. These simulations indicate that the concepts encoded in MINDY capture several of the underlying biological mechanisms that drive preferences and selective behaviour. Thus, simulations using MINDY allow prediction of daily and diurnal patterns of selection based on preference, derived from some post-ingestive feedbacks and total discomfort. Estimates of herbage intake and parallel measurements of ingestive behaviour, rumen function and metabolism in grazing ruminants pose experimental and technical difficulties, and matching these processes to animal preference and selective behaviour is a greater challenge. As a consequence, advances in knowledge of foraging behaviour and dietary choice are slow and costly. On completion of more thorough testing, MINDY can be used as a tool for exploratory mechanistic research, to design and organise experimental programs to address a range of factors that control intake and its ecology, helping advance knowledge faster and at a low cost.

Age and season effects on quality of diets selected by Criollo crossbred goats on rangeland

The objectives of this study were to determine the effects of age of goats (4-week old, 6.2 ± 0.7 kg vs mature, 46.9 ± 5.6 kg) and season (rainy vs dry) on nutrient content of diets selected by Criollo crossbred female goats on an overgrazed Chihuahuan desert rangeland. Two groups of goats, 10 goat kids and 10 non-lactating pluriparous goats from a commercial goat herd were used. Diet quality and dry matter (DM) intake was assessed via repeated collections (3-h periods) of forage from the mouth of goats, which were momentarily restrained using a light short permanent rope tightened to their neck while grazing. Feed intake was assessed by 24-h fecal collection with canvas fecal-collection bags. Mature animals ate more (P  <  0.01, 23 g DM/kg bodyweight ± 7 s.d.) than goat kids (19.5 g DM/kg  bodyweight ± 6 s.d.) across grazing seasons, but DM digestibility of selected diet was greater (P < 0.01) in goat kids than in mature goats (58.5 ± 4.0% vs 55.3 ± 3.5%, respectively) across seasons. Ash (100 ± 16 vs 79 ± 13 g/kg DM), phosphorus (1.36 ± 0.41 vs 1.13 ± 0.36% DM) and crude protein (94.5 ± 4 vs 88.5 ± 5 g/kg DM) contents were greater (P < 0.01) in diets selected by goat kids compared with mature goats. Dietary protein was greater in rainy than in the dry season. Across grazing seasons, herbage selected by goat kids had a lower (P < 0.01) concentration of neutral detergent fibre and acid detergent fibre than did that selected by mature goats. There was an age by grazing season interaction (P < 0.05) for most chemical components of forages selected by goats. In conclusion, both age and season affected diet quality of goats on rangeland, as goat kids ingested a diet richer in nutrients than that of mature goats. This supports the theory that herbage selection is shaped by physiological effort and, consequently, nutrient consumption is driven by higher nutrient requirements for growth, although incomplete development of rumen function and small body mass limited feed intake in preweaning goat kids.

Patterns of livestock activity on heterogeneous subalpine pastures reveal distinct responses to spatial autocorrelation, environment and management

BACKGROUND

In order to understand the impact of grazing livestock on pasture ecosystems, it is essential to quantify pasture use intensity at a fine spatial scale and the factors influencing its distribution. The observation and analysis of animal activity is greatly facilitated by remote tracking technology and new statistical frameworks allowing for rapid inference on spatially correlated data. We used these advances to study activity patterns of GPS-tracked cows in six summer-grazing areas in the Swiss Alps that differed in environmental conditions as well as livestock management.

RESULTS

Recorded GPS positions were assigned to the activities of grazing, resting, and walking, and were discretized on a regular grid. Regression models with spatially structured effects were fitted to the spatial activity patterns using Integrated Nested Laplace Approximation. They indicated that terrain slope, forage quality, and stocking rate were the primary factors determining cow activity in the six study areas. Terrain slope significantly reduced livestock activity in five of the six areas and sparse forage availability significantly reduced grazing in all areas. In three areas, grazing pressure imposed by the pasture rotation was observable in the grazing pattern. Insolation, distance to the shed, and distance to water were less important for cow activity. In addition to the main factors identified across all study areas, we found effects operating only in individual areas, which were partly explained by specific environmental and management characteristics. In study areas with few paddocks, environmental variables exerted a stronger control on livestock activity than in areas with a short stocking period per paddock.

CONCLUSIONS

The data demonstrated that a strict pasture rotation with short stocking periods is necessary to influence livestock activity, and hence potential effects on ecosystem processes. Without grazing management, livestock activity is primarily determined by the environment. Such insight is indispensable for studying relationships between grazing animals and ecosystem characteristics, and for developing management strategies to optimize ecosystem services. The analysis also highlighted the need for an appropriate statistical treatment of bio-logging data, since various estimates were biased if spatial autocorrelation was ignored.