Animal Production Science
Volume 55 Number 3 2015
The Meal Dynamics of Grazing Herbivores
AN14481Feeding behaviour in ruminants: a consequence of interactions between a reward system and the regulation of metabolic homeostasis
Feeding behaviours have a direct impact on livestock production, health and welfare. In this paper, we discuss how the integration of signals arising from a reward system and from metabolic regulation influence food selection and intake. Understanding these processes, which include how animals can learn about foods and their consequences, will help managers to influence feeding behaviours for positive outcomes.
AN14449Understanding and manipulating diet choice in grazing animals
Selection of a single plant by a herbivore is typically studied by analysing the plant’s abundance and chemical composition. However, selection of such plant is also influenced by the herbivore’s previous experiences with the abundance and chemical composition of neighbouring plants. A better understanding on how these experiences are manifested in herbivores grazing diverse plant communities will help managers enhance the health, nutrition and welfare of their animals while maintaining the health and integrity of grazing landscapes.
AN14487Translating physiological signals to changes in feeding behaviour in mammals and the future effects of global climate change
Herbivorous mammals cannot entirely avoid ingesting potentially toxic plant secondary metabolites and therefore must regulate their intake carefully. We review how animals use conditioned aversions mediated by nausea, non-conditioned aversions and recognition of detoxification limits to achieve this. We also discuss how ambient temperature can affect mammals’ tolerance of toxins and highlight how this may impact herbivores under global climate change.
AN14641Spatial and temporal domains of scale of grazing cattle
The spatio-temporal distribution of grazing by ruminants is a dominant process in vast areas of the world, and it determines the productivity and environmental impact of grazing animals. We found that distribution patterns result from a highly flexible interaction among meal patterns, forage nutritional quality and availability of areas for thermal comfort. Regrazing of areas grazed less than a week earlier was more prevalent when cows were restricted by high temperatures and low forage quality.
AN14462Effect of terrain heterogeneity on feeding site selection and livestock movement patterns
Livestock movements associated with feeding site selection play a major role in grazing distribution and they can affect the forage available for diet selection. This study evaluated day-to-day movement patterns of cattle in pastures with gentle topography and in pastures with rugged and diverse terrain. Cows regularly alternated among sites in homogeneous pastures with gentle topography and stayed longer in sites within diverse pastures with rough terrain, which likely helped cattle mix their diets.
AN14415How French shepherds create meal sequences to stimulate intake and optimise use of forage diversity on rangeland
Sheep and goat herders in France use understanding of foraging behaviour to design grazing circuits that expose animals to a sequence of complimentary forage patches to stimulate appetite. In so doing, they encourage animals to use a range of forages, some highly palatable and others that would be neglected if the animals were grazing in fenced pastures. These practices enable herders to increase appetite and intake while managing grazing impacts and targeting grazing to prevent wildfires, restore habitat, and encourage biodiversity.
AN14546Can animal performance be predicted from short-term grazing processes?
We investigated whether longer-term animal performance can be explained by changes in short-term grazing processes in a heterogeneous native grassland. Although bite mass and its interactions accounted for 10.8% of the variation in average daily gain, stocking treatments and season had significant effects not incorporated in bite mass. We conclude that a large portion of the variation in performance may be related to temporally variable grazing of tussocks and changes in diet quality not contemplated in the model.
AN14484Behavioural adaptation of grazing dairy cows to changes in feeding management: do they follow a predictable pattern?
The results of studies examining interactions between sward state, grazing behaviour and intake are reviewed, and their validity and application in commercial dairy herds to improve feeding management are discussed. The shortcomings of such research are examined with a view to identifying future research strategies required for future grassland-based dairy enterprises.
AN14540Continuous bite monitoring: a method to assess the foraging dynamics of herbivores in natural grazing conditions
In heterogeneous feeding environments, herbivores constantly modify their foraging behaviour to cope with variations in the external environment and to account for changes of their internal milieu. Assessing the variation of these behaviours, particularly the intake rate of food, has long been considered challenging. We present a methodology based on continuous bite monitoring through direct observation that help address this difficulty and facilitates the study of the foraging strategies of herbivores under natural grazing conditions.
The behaviour of grazing ruminants is characterised by periods of eating interspersed with periods of not eating and the influences on this behaviour are poorly understood. Catastrophe theory concerns the generation of sudden changes in the state of one dependent variable from one or more influencing continuous variables, and we apply it to the on or off characteristic of feeding behaviour as influenced by such variables as hunger–satiety, ease of prehension and metabolic demand. This approach may offer a new perspective on grazing behaviour and range management.
AN14472Modelling preference and diet selection patterns by grazing ruminants: a development in a mechanistic model of a grazing dairy cow, MINDY
In this paper, we describe a new development of MINDY, a model of the diurnal grazing pattern of a dairy cow. This development integrates a theory of dietary choice, based on post-ingestive feedbacks and total discomfort. The new MINDY simulates daily and diurnal patterns of selective grazing behaviour of ruminants from several studies. The ability to model preference and selective behaviour is useful for mechanistic research on foraging behaviour, intake and design of feeding managements for grazing ruminants.
AN14428Temporal dynamics in the foraging decisions of large herbivores
Determining how foraging decisions vary over space and time is fundamental to understanding resource–consumer interactions. We use examples from research on free-ranging bison to demonstrate how changing an animal’s currencies, options and constraints in optimal foraging models can reveal key factors controlling the foraging process. We conclude that optimal foraging theory can provide an effective framework to study temporal changes in dietary choice within a foraging patch or during the course of a day.
AN14424Optimising the interrelationship between intake per cow and intake per hectare
Grazed systems remain inherently constrained by the fundamental trade-off between maximising individual herbage intake and pasture utilisation. We investigated such trade-off from the perspective of economic optimisation, for an intensive pasture-based dairy farm in New Zealand. Optimisation modelling indicated that the goal to maximise both individual intake and herbage utilisation in grazing systems is misinformed; it is the latter that is principally important. Seeking to maximise both simultaneously is not possible, and trying to maximise individual intake can impose enormous cost.
AN14602Managing the herbage utilisation and intake by cattle grazing rangelands
Producing livestock by grazing rangelands is a difficult endeavour that requires constant management to balance the economic sustainability of the ranch with the need to sustain other ecological services from the rangeland that often competes with resources needed for production. This difficulty arises from the diversity of the rangeland forage resource being managed at large spatial–temporal scales. Monitoring of this resource from the ground in near-real time is impossible, so scientists need to explore the use of satellite imagery to monitor its change. Systems modelling would allow the estimation of herbage intake to predict cattle performance and estimation of residual herbage mass to maintain other ecological services.
AN14679Synthesis: foraging decisions link plants, herbivores and human beings
Herbivores make decisions about where to forage, what combinations of foods to eat, and in which sequences to eat them. Their choices integrate influences that span generations; they begin in utero and become manifest within the lifetime of each individual from interactions that arise daily among needs and contexts unique to biophysical and social environments. Understanding behavioural mechanisms that influence meal dynamics and distribution patterns can help humans manage foraging behaviours better for ecological, economic and social benefits.