behaviour of equids – a comparative approachffffffff-f77d... · Digestive physiology and feeding...

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Digestive physiology and feeding behaviour of equids – a comparative approach Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Switzerland Gent 2013

Transcript of behaviour of equids – a comparative approachffffffff-f77d... · Digestive physiology and feeding...

Page 1: behaviour of equids – a comparative approachffffffff-f77d... · Digestive physiology and feeding behaviour of equids – a comparative approach Marcus Clauss Clinic for Zoo Animals,

Digestive physiology and feeding

behaviour of equids – a comparative approach

Marcus Clauss Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of

Zurich, Switzerland Gent 2013

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Large herbivore diversity: Equids

≈ 8 species

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from Stevens und Hume (1995), Clauss et al. (2008)

Digestive tract: Equids

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Large herbivore diversity: Perissodactyls

≈ 16 species

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from Stevens und Hume (1995), Clauss et al. (2008), Müller et al. (in prep.)

Digestive tract: Perissodactyls

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Large herbivore diversity: hoofed mammals

≈ 16 species > 300 species

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Stevens und Hume (1995), Clauss et al. (2008), Schwarm et al. (2010), Müller et al. (in prep.)

Digestive tract: Perissodactyls vs. Artiodactyls

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Large herbivore diversity: hoofed mammals

≈ 16 species > 300 species

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Large herbivore diversity: Europe

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Large herbivore diversity: Europe

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Large herbivore diversity in deep time: Perissodactyls

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Large herbivore diversity in deep time: Perissodactyls

Chalicotheres

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Large herbivore diversity in deep time: Perissodactyls

Brontotheres Chalicotheres

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Large herbivore diversity in deep time: Perissodactyls

Brontotheres Chalicotheres

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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from Janis et al. (1994)

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Large herbivore diversity: hoofed mammals

≈ 16 species > 300 species

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Large herbivore diversity: hoofed mammals

≈ 16 species > 300 species

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times).

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times). Days of gestation period (to apparently similar level of precociality)

Cattle: app. 280 days Horse: app. 340 days Dromedary: app. 390 days Okapi: app. 440 days

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times). Days of gestation period (to apparently similar level of precociality)

Cattle: app. 280 days Horse: app. 340 days Dromedary: app. 390 days Okapi: app. 440 days

The difference cannot be due to body size!

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times). Days of gestation period (to apparently similar level of precociality)

Cattle: app. 280 days Horse: app. 340 days Dromedary: app. 390 days Okapi: app. 440 days

nearly extinct in a very limited geographical range

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times). Days of gestation period (to apparently similar level of precociality)

Cattle: app. 280 days Horse: app. 340 days Dromedary: app. 390 days Okapi: app. 440 days

only in extreme, resource-poor habitats

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times). Days of gestation period (to apparently similar level of precociality)

Cattle: app. 280 days Horse: app. 340 days Dromedary: app. 390 days Okapi: app. 440 days

rule the world !!

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Mammal gestation period

For any mammal, achieving the same degree of neonatal development in a shorter gestation period – if not associated with higher costs – should be advantageous (higher fecundity due to shorter generation times). Days of gestation period (to apparently similar level of precociality)

Cattle: app. 280 days Horse: app. 340 days Dromedary: app. 390 days Okapi: app. 440 days

We would predict that animals with a shorter gestation period should be particularly ‘successful’ (e.g. in terms of species diversity).

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(Precocial) Mammal gestation period

from Clauss et al. (2013)

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Mammal chewing efficiency

For any herbivore, increasing chewing efficiency – if not associated with higher costs – should be advantageous (higher feeding efficiency due to higher digestibility) because there is …

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Mammal chewing efficiency

For any herbivore, increasing chewing efficiency – if not associated with higher costs – should be advantageous (higher feeding efficiency due to higher digestibility) because there is …

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Mammal chewing efficiency

For any herbivore, increasing chewing efficiency – if not associated with higher costs – should be advantageous (higher feeding efficiency due to higher digestibility) because there is …

and therefore …

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Mammal chewing efficiency

For any herbivore, increasing chewing efficiency – if not associated with higher costs – should be advantageous (higher feeding efficiency due to higher digestibility) because there is …

and therefore …

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Simple-stomached Nonruminant ff

Mammal chewing efficiency

from Fritz et al. (2009)

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from Fritz et al. (2009)

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Mammal chewing efficiency

from Fritz et al. (2009)

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from Jernvall et al. (1996)

Large mammal molar surfaces

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from Jernvall et al. (1996)

Large mammal molar surfaces

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from Jernvall et al. (1996)

Large mammal molar surfaces

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from Jernvall et al. (1996), Schwarm et al. (2008)

Large mammal molar surfaces

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from Jernvall et al. (1996), Schwarm et al. (2008)

Ruminant sorting mechanism

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Parallel evolution?

Perissodactyls Artiodactyls

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among

Parallel evolution?

Perissodactyls Artiodactyls

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among

Parallel evolution?

Perissodactyls Artiodactyls

Equids Ruminants

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among

Parallel evolution?

Perissodactyls Artiodactyls

achieve comparatively high chewing efficiencies

and food intakes

Equids Ruminants

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among

Parallel evolution?

Perissodactyls Artiodactyls

achieve comparatively high chewing efficiencies

and food intakes

Equids Ruminants

but …

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Due to their superior chewing efficiency, ruminants achieve higher digestibilities ...

Advantage ruminants?

from Clauss et al. (2009; data from Foose 1982)

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Due to their superior chewing efficiency, ruminants achieve higher digestibilities ...

Advantage ruminants?

from Clauss et al. (2009; data from Foose 1982)

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Due to their superior chewing efficiency, ruminants achieve higher digestibilities ... and therefore do not require as high a food intake.

Advantage ruminants?

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Due to their superior chewing efficiency, ruminants achieve higher digestibilities ... and therefore do not require as high a food intake.

Advantage ruminants?

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Because they need to feed more (and do not have ‘rumination breaks’), equids nearly feed continuously.

Advantage ruminants?

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Because they need to feed more (and do not have ‘rumination breaks’), equids nearly feed continuously.

Advantage ruminants?

Grazing

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Because they need to feed more (and do not have ‘rumination breaks’), equids nearly feed continuously.

Advantage ruminants?

Grazing

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Because do not have ‘rumination breaks’, equids have higher ingestive mastication activity.

Advantage ruminants?

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Are horses more susceptible to low food intake than ruminants?

Advantage ruminants?

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Advantage ruminants?

Horses cannot achieve the difference between particle and fluid retention (SF selectivity factor) as observed in ruminants.

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Advantage ruminants?

In spite of theoretical concept …

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In spite of theoretical concept … no net empirical indication for differentiated passage in horses.

Advantage ruminants?

from Lechner et al. (2010), Clauss et al. (pers. obs.)

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Other differences: Calcium digestibility

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from Stevens & Hume (1995)

Phosphorus is supplied directly to microbes via saliva

P

Other differences: Calcium digestibility

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from Stevens & Hume (1995) hypothesis by Clauss & Hummel (2008)

Phosphorus is supplied directly to microbes via saliva

PIn order to guarantee phosphorus availability in the hindgut, calcium is actively absorbed from ingesta and excreted via urine

Ca

Other differences: Calcium digestibility

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Why equids?

Other perissodactyls survive in body size ranges beyond the ruminant range (rhinos) or in absence of ruminant competition (tapirs). Why / how do equids survive (only in the upper ruminant body size range, and only in the grazing niche)?

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Camelid

Equids

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Wallaby

Hyrax

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Guinea pig

from Franz et al. (2010)

Other differences: Methane production?

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from Franz et al. (2010)

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Other differences: Methane production?

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from Franz et al. (2010)

Other differences: Methane production?

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from Franz et al. (2010)

Other differences: Methane production?

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Equid-ruminant facilitation?

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Digestive advantage for equids?

When resources are scarce on African game farms, the ruminants lose condition first … … but it is when the zebras lose condition that you need to start to worry.

(Adrian Shrader, pers. comm.)

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The traditional view of foregut vs. hindgut fermentation

Janis (1976)

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Do you believe it?

“if diet quality gets lower, a horse simply eats more”

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Data in sheep

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The traditional view of foregut vs. hindgut fermentation

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I (g

kg

-0.7

5 d

-1)

SheepCattleBisonBanteng/GaurYakWater buffaloS. cafferMuskox

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140

160

10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

Donkey

Meyer et al. (2010)

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

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-0.7

5 d

-1)

Sheep

Cattle

Donkey

Meyer et al. (2010)

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

Horses

Meyer et al. (2010)

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

Horses

Meyer et al. (2010)

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

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-0.7

5 d

-1)

Sheep

Cattle

Horses

Wild equids

Meyer et al. (2010)

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

Horses

Wild equids

0

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80

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120

140

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

White rhino

Indian rhino

Black rhino

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

Horses

Wild equids

0

20

40

60

80

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120

140

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

White rhino

Indian rhino

Black rhino

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0

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60

80

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120

140

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10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

-1)

Sheep

Cattle

Horses

Wild equids

0

20

40

60

80

100

120

140

160

10 30 50 70 90

Forage NDF (%DM)

DM

I (g

kg

-0.7

5 d

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Sheep

Cattle

White rhino

Indian rhino

Black rhino

Misinterpretation of anatomical features?

from Stevens und Hume (1995), Clauss et al. (2008)

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The traditional view of foregut vs. hindgut fermentation

Janis (1976)

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Extant horses are grazers

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Diet and mesowear

Kaiser and Fortelius (2003)

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Diet and mesowear

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Diet and mesowear

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Adapted to abrasive diets

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-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

Diffe

rence in s

core

Less abrasion than in the wild

More abrasion than in the wild

from Kaiser et al. (2009)

Diet and mesowear: zoo vs. wild

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-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

Diffe

rence in s

core

Less abrasion than in the wild

More abrasion than in the wild

from Kaiser et al. (2009), Taylor et al. (in prep.)

Diet and mesowear: zoo vs. wild

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Wild equids in captivity

Similar as in grazing ruminants, few health problems related to nutrition in captive wild equids (because zoo diets are typically more forage dominated?)

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Wild equids in captivity

Similar as in grazing ruminants, few health problems related to nutrition in captive wild equids (because zoo diets are typically more forage dominated?) -  Incidents of dental abnormalities

(a)  Free-ranging (b) Captive

from Taylor et al. (in prep.)

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Wild equids in captivity

Similar as in grazing ruminants, few health problems related to nutrition in captive wild equids (because zoo diets are typically more forage dominated?) -  Incidents of dental abnormalities

Hoyer et al. (2012)

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Wild equids in captivity

Similar as in grazing ruminants, few health problems related to nutrition in captive wild equids (because zoo diets are typically more forage dominated?) -  Incidents of dental abnormalities

-  Hoof overgrowth/laminitis

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Equid seasonality

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Wild equids in captivity

Similar as in grazing ruminants, few health problems related to nutrition in captive wild equids (because zoo diets are typically more forage dominated?) -  Incidents of dental abnormalities

-  Hoof overgrowth/laminitis

-  Obesity

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Equid seasonality

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Equid seasonality

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Equid seasonality

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Wild equids in captivity

Similar as in grazing ruminants, few health problems related to nutrition in captive wild equids (because zoo diets are typically more forage dominated?) -  Incidents of dental abnormalities

-  Hoof overgrowth/laminitis

-  Obesity

-  Colic

-  Vitamin E deficiency

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Conclusion

From a nutritional point of view, wild equids appear well understood: (grass) forage diets available at all times, ideally with mimicking seasonal patterns in the wild. How the digestive physiology of equids differs from that of ruminants, especially in terms of minimum intake tolerable and differential digesta movements, remain to be investigated. The sequence, and the mechanisms, of the equid-ruminant diversification and competition in evolution remain to be explained in a way that matches empirical data.

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thank you for your attention

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