Grazer Selectivity; benefits for livestock, habitats and people

Dairy cows grazing improved grassland ....

Grazer Selectitivity; is it a good or a bad thing for conservation?

The effects of selectivity are still evident ..........

little chance to express choice

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MONTHS

Grazer selectivity boosts nutritional

quality of feed intake relative to available

forage

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g/kg

. dry

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Herbage

consumed

Herbage available

From: Le DuYLP et al 1981 ‘Herbage intake and milk production by grazing dairy cows’ Grass and Forage Science, 36, 307-318

Increasing nutritional compensation with ongoing seasonal decline

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Conservation grazers have much more variety from which to choose

But how do they make these choices?

Observing where do they go (30 min fixes by GPS collar)

Partial utilization of complex mosaic of plant communities

But not just about grazing Must also meet other needs: eg water, shelter

Late cut hay has better mineral/trace element content

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04/09/2007 Sulber CG9

Ungrazed

04/09/2007 Sulber CG9 grazed

N %

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Observed tendency to select

the most nutritious options?

Short sward Tall sward

30% more

protein

Grazing itself promotes greater species richness

Grazers seem to prefer herbs - often seen grazing species-rich patches with higher cover of herb species e.g. ant-hills

Observed tendency to select for more diverse swards

Cows are very good at demonstrating their preferences by rejecting what they don’t want!

... whilst herb-rich feed keeps their attention

.... unlike the non-herb option

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Herb

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Crude Protein g/kg DM

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Grass component

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P K Mg Ca Na S

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Cu Zn Bo Fe Mn

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Trace Elements mg/kg DM

Minerals g/kg DM

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D Value %

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(energy)

but are they nutritious?

Herb-rich haylage grass haylage

Herbs may be palatable ......

Flowers might look nice but....

Contain chemical defences to protect against grazing impacts

Different species of herb have different defence chemicals

e.g. Terpenes, phenols, flavones, tannins, saponins

What are the implications of a diet rich in toxins?

For livestock?

For people?

Grazers have to eat a mix of species to limit intake of any one compound

Compounds are safely neutralized within healthy livestock. Breakdown products contribute to eating qualities and healthiness of their meat/milk

they are full of toxins

‘Conservation’ carcase @ 5 years old

Commercial carcase @ < 2 years old

Diet affects meat quality

– visible differences in fat-colour

= contrasting meat chemistry

How ‘healthy’ is herb-fed meat vs. grass-only meat?

Significant differences found but implications for human health are not yet clear

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%Saturated % Mono Unsat

Beef Shorthorn Herb-rich sward

Beef Shorthorn Grass-only sward

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% PolyUnsat Long chain n-3

Beef Shorthorn Herb-rich sward

Beef Shorthorn Grass-only sward

Higher proportion of ‘good ‘ fats Lower proportion of ‘less-good ‘ fats

Healthiness and quality of beef produced from traditional and modern breeds reared on species-rich, unimproved grasslands LS 3523

Phytochemicals also thought to make a significant contribution

The role of fats within a healthy diet is still very controversial

Provenza et al 2015

Latest research evidence is beginning to provide some answers

Ourselves

Our livestock Our landscapes

Restoring broken linkages .......... with diets that

nourish and satiate

Providing more choice for grazing animals by enhancing

dietary richness produces food that best meets human needs .

‘You are what you eat’ ‘You are what you eat has been eating ’

https://www.researchgate.net/publication/280774993

http://www.behave.net/

‘Variety is the Spice of Life’

Animals are all individuals too

Grazing behaviour has to be learned.

Browsing forms an important part of their grazing culture, and is learned

from an early age

BEHAVE; a dedicated grazing website providing background and updates

The browsing culture in operation

Plenty of very herb-rich grazing available but these cows still spend time eating blackthorn growing in the hedges

Calves learning by copying their mothers