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Diet selection and grazing behaviour (Factors influencing grazing…
Diet selection and grazing behaviour
Factors influencing grazing behaviour
Pasture: Nutrient concentration, horizontal and vertical distribution, Biomass, Plant defences and dung deposition
Animal: Body size, energy requirements, mouth size, gut type, physiological status, metabolic status and environmental conditions.
Spatial grazing systems- animals grazing together but using different vegetation- mixed grazing system
Temporal grazing systems - animals grazing same pasture at different times - Rotational system
Effects of mixed grazing
sheep with steers - mixed grazing can improve performance (Lwg)
Sheep with suckler cows - Mixed grazing increased weight gain of lambs particularly post weaning
Why: Increased availability of clover due to cattle being less selective grazers, Removal of stemmy material, lower parasite burdens, less avoidance of grass around dung patches increasing sward use efficiency
Cattle
Less selective grazers- greater ability to remove low digestibility biomass. Trampling helps to create bare ground and open up dense swards
Role of breed type
Previously thought breed type might have an effect but study has shown that there is no effect of breed (Cattle) type on utilisation of molinia
when fed ryegrass there was no difference in LWG or methane emissions. when on the hill sward the liveweight gain remained similar but the lim X steers produced significantly more methane than the WB steers
Sheep
Role of breed type
Evidence from europe that there is differences in breed type, diets of scottish blakcface and welsh mountain sheep grazing moorland differs
Types of pasture
Permanent pasture:
lower nutritive value compared to new lays, may have invasion by non-sown species. Legume component still important. Management can have a substantial impact on the composition of the sward
Application of fertiliser will affect composition. No fertiliser = Increased percentage of moss and dead material
Application of fertiliser will also increase the sward carrying capacity - application of calcium, phosphorus, potassium and nitrogen can double the number of sheep per ha
Forage legumes
Source of home grown protein, higher rate of particle breakdown, can reduce need for nitrogen fertiliser
Presence of plant compounds: PPO and condensed tannins- increased compounds = decreased protein degradation
Finishing lamb grazing experiments: legumes gave higher growth rates, reduction in time to finish while maintaining similar live weights and carcass composition at finish
Semi-natural rough grazing:
Lower nutritional value than improved pasture- high fibre, low protein. Management and seasonal effects on sward
Reduced production potential- liveweight gain for SNRG less than
Effect on fatty acid composition - SNRG = less overall fat and slightly better PUFA content. Higher vitamin E in meat from SNRG.
Integrated systems
Frees up better quality grassland for productive stock and forage convervation. Can select stock type to suit and target timing of grazing to maximise nutritional value.