Antinutritional Factors in

Forages

Dr. A T Adesogan

Department of Animal Sciences,

University of Florida

Antinutrients

Definition

Substances which either by themselves or

through their metabolic products, interfere with

food utilisation and affect the health and

production of animals

General characteristics

Products of secondary metabolism

Found in virtually all plants to some degree

Common in tropical forages

Defensive role:

Bitter, colors, poisonous, odor, antinutritive /

immunosuppresive

GlycosidesGenerally bitter

Structure

Contain CHO and non-CHO moiety (aglycone)

Mode of action

Toxicity results from aglycone release during enzymic degradation

Sources

Linseed, cassava, sorghum, soya, clover etc

Sub-Groups

Cyanogenic

Goitrogenic

Coumarin

Nitropropanol

Carcinogenic

Isoflavons (phytoestrogens)

Steroidal (Saponins )

Glycosides - effects

Phytoestrogens

E.g. Formononetin in Red & Subterranean clover

• Female sterility

E.g. Genistein in soya

• Estrogenic activity & male sterility

Saponins

Have distinctive foaming characteristics

E.g. in White clover, alfalfa, Brachiaria decumbens &

Panicum spp.

Cause bloat, hemolysis, GIT erosion, inhibit enzyme

action

Saponins

Alkaloids

Usually basic, bitter & toxic (v. potent)

eg. Cocaine, nicotine & caffeine

Animal feed sources

Lupins, potatoes contain solanine-based alkaloids

Effects

Kidney, pulmonary & liver damage, diarrhea, vomiting

Ergot Alkaloids & Fescue Toxicosis

Most pre 80s tall fescue in US infected with endophyte

fungi (Neotyphodium coenophialum) that produced

ergot alkaloids e.g. clavine alkaloids, lysergic acid

amides, and ergopeptines

Symptoms

Vasoconstriction

Foot problems

Retained winter coat

High body temp

& respiration

Fat Necrosis

Reproductive

& birthing problems

Images from Roberts & Andrae (2004) http://www.plantmanagementnetwork.org/pub/cm/management/2004/toxicosis/

Solutions

Dilute pasture with clover or other spp.

Graze closely

Plant endophyte-free fescue cultivars

No animal health issues and great performance

More susceptible to drought, pests, & overgrazing

Novel / introduced endophyte cultivars

Have endophytes but they don’t produce ergot alkaloids

Overcome problems with endophyte-free cultivars

Non-protein amino acidsMimosine

Found in Leucaena leucocephala (20-30% CP)

Metabolic derivative 3,4-DHP (3-hydroxy-4(1H)-pyridone) causes goiter, alopecia, anorexia, gastroenteritis, hepatotoxicity

R. Jones discovered that Leucaena toxins are inactivated by a rumen microbe (Synergistis jonesii) in Hawaii sheep and has introduced cultures

Florida Senopol (origininated from St Croix) cattle are also resistant to DHP

Alopecia

http://images.google.com/imgres?imgurl=http://www.tropicalforages.info/key/Forages/Media/Html/images/Leucaena_leucocephala/Leucaena_leucocephala_02.jpg&imgrefurl=http://www.tropicalforages.info/key/Forages/Media/Html/Leucaena_leucocephala.htm&h=654&w=461&sz=99&hl=en&start=1&um=1&tbnid=iD1ZAsHyzQLczM:&tbnh=138&tbnw=97&prev=/images%3Fq%3Dleucaena%26um%3D1%26hl%3Den%26sa%3DN

Glucosinolates

Thioglucose group bound to an amino acid

Source

Linseed

Brassica forage crops e.g. kale, rape

Effect

Milk taint, thyrotoxic & goitrogenic

Glucose

removal

aglycone

residue

toxic

derivatives

e.g nitriles

isothiocyanates

Mycotoxins

Name Produced by:

DON Fusarium moniliforme and F. graminearum

(vomitoxin)

T-2 F. sporotrichioides

Zearalenone F. graminearum

Fumonisin F. moniliforme

Aflatoxin A. fumigatus

Sources – moldy feed, e.g. soybean, barley, spoiled silage

Hemorrhagic bowel syndrome

>2% of deaths of adult cows -increasing/

under-diagnosed (Forsberg, 2004)

Tannins

Compounds that tan leather

Polyphenolic plant defense compounds that can form

stable complexes with:

Proteins

Carbohydrates

Minerals

Have beneficial /deleterious effects

Ubiquitous

Grapes/wine, tea, fruit juices, apples/cider, trees

Selected Forage Plants with Tannins

Lotus species

Sainfoin

Faba beans

Peas

Sorghum

Calliandra calothyrsus

Leucaena leucocephala

Sesbania sesban

Gliricidia sepium

Acacia species

Content varies

- 0 % in temperate grasses

-Low (0-5 %) in most temperate legumes

-Up to 50 % in tropical browses but less than

5% in some tropical legumes

Least complex

Least known

Brown algae

Phlorotannins

Susceptible to

enzymic & non-

enzymic hydrolysis

V. Water soluble

Can be toxic

Hydrolyzable

tannins/

Anthocyanidins

Most

widespread

Typical

plant

tannins

Less toxic

Condensed tannins /

Proanthocyanidins

(PAs)

Types

PAs affect forage utilization by:

Forming strong H bonds with with nutrients

Inhibition of digestive enzymes

Inhibition of rumen microbial activity

Concentrations of 2-4% of DM increase N

utilization due to increased bypass

Concentrations >7% usually reduce nutrient

utilization

R

OH O C

CH R

HN

ProteinH - bond

Effect of PAs depends on:

Proanthocyanidins

Concentration

Properties

• Molecular weight

• Degree of

polymerisation

Proteins

Concentration

Properties

• Size of polymers

• Chemical structure

• Richness in proline

Animal spp

Proline-rich proteins abundance

/tannin tolerance :

deer> goat> sheep> cattle

pH

Tannin-binding agents

E.g PVP, PEG, proline rich

proteins

Effect of tannins on rumen digestibility of cellulose

and hemicellulose

450

500

550

600

650

700

750

Cellulose Hemicellulose

Lotus

Lotus+PEG

Negative

Reduction in VFI

• Astringent

Reduction in

digestibility

Erosion of GIT lining

Toxicity – HT

Positive

Increased efficiency of protein utilisation

Reduction of parasite burden

Reduction of proteolysis during ensilage

Bloat prevention

Increase quality of animal products

Reduction of N emission into the environment

Defaunate rumen

Effect of PAs on forage quality

DM intake of sheep fed straw & increasing

levels of Calliandra (22% CP; 10% tannins)

500

550

600

650

700

750

800

DM

in

tak

e (

g/d

ay

)

Straw+0% Straw+20% Straw+30% Straw+40% Straw+50%

(Salawu, 1996)

OM digestibility of sheep fed Straw

+ increasing levels of Calliandra

350

400

450

500

550

600

OM

dig

. (g

/kg

DM

)

Straw+0% Straw+20% Straw+30% Straw+40% Straw+50%

Lotus

Sainfoin

N-balance in sheep fed different

legume forages

-5

-2.5

0

2.5

5

7.5

10

12.5

15

Lotus (6.5% tannin) Sainfoin (11% tannin)

Tannins as silage inoculants: Protein

protection during ensilage

36 %

29 %

32 %

25

27

29

31

33

35

37

% r

ed

ucti

on

Formaldehyde

Mimosa tannin

Quebracho tannin

Effect of PAs and anthelmintics

on infective larvae of H.contorus

0

10

20

30

40

50

60

70

80

90

Mo

rta

lity

(%

)

0 20 40 Piperazine

(50mg/ml)Proanthocyanidin (mg/ml)

References

D’Mello, JPF 2000. Farm animal metabolism and

nutrition. (Ed.). CAB, Wallingford. P319. Chapter 18

Caygill, J C and Mueller-Harvey 1999. Secondary plant

products. Nottingham University press.

Cheeke, P R and Shull L R 1998. Natural toxicants in

feeds and poisonous plants. AVI Publ. Co.

Garland T and Barr, C. 1998. Toxic plants and natural

toxicants. CAB International