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vge > Prof Hassen: Grass and forage crops > Flashcards

Prof Hassen: Grass and forage crops Flashcards

1
Q

What is a roughage?

A
  • Feedstuff with >18% CF or >20% ADF >30% NDF
  • High in fibre and low in energy
  • Used by ruminants and nonruminants
  • Nutrient in roughages are made available by microbial digestion
  • examples are pasture grass and other forage crops, silages, hay, straws and chaff.
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2
Q

What is the major enzyme involved in photosynthesis?

A

Ribulose biphosphate carboxylase

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3
Q

Define herbage

A

Plant material, except seeds and roots that can be utilized as food by animals.

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4
Q

Roughage normally include_____

A

herbage or forage, but is not restricted to plants grown for animal consumption(forage plants)

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5
Q

Forage is devided into_____

A

Native and cultivated species

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6
Q

Name the types of pasture:

A

1) Temporary pasture, limited life span (1-4Years), consists of a single sown plant species, ex. italian rye and lucerne
2) Permanent pastures: Life span more than 4 years.

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7
Q

Practically what could be the reasons that there is not sufficient intake of nutrients during the growing season?

A
  • Nutritave value falls
  • soil and climatology may be unsuited
  • grazing management system may fail
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8
Q

Name the advantages of grass as food for grazing animals:

A
  • Most are palatable when immature
  • Very few are toxic
  • Grows in all environments where grazing animals can survive
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9
Q

Describe the pattern of growth for grasses

A
  • temperate grass starts to grow in spring when soil temp. is 4-6 degrees
  • once growth starts, the pattern of growth is the same for all grass species
  • This includes rapid leaf growth, increased stem growth, ultimate emergence of the flowering head, formation of seeds.
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10
Q

What promotes development of vegetative tillers?

A

Removing the seed head

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11
Q

The storage carbohydrates of temperate grasses is ____, while in tropical and sub-tropical grasses it is _____

A

Fructans, starch

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12
Q

When is grass growth very rapid?

A

During the autumn wet season

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13
Q

Growth rates of grasses is dependant on___

A
  • Environment
  • Nutrient availability
  • Amount of leaf within the sward
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14
Q

What does the rate of re-growth in grasses depend on?

A

Maturity of the crop at the time of harvesting

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15
Q

What is the growth range for temperate pastures?

A

40-100 kg DM/ha/day in spring

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16
Q

Name the factors which influence the nutritive value of herbage:

A
  • Stage of growth
  • Species
  • Soils and fertilizer treatments
  • Grazing systems
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17
Q

What is the moisture content of grasses?

A

750-850g/kg in DM

Falls to 650 when the plant matures

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18
Q

What is the CP ranges of grass

A

30 -300 g/kg DM

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19
Q

What is the composition of grass DM dependant on?

A

Relative proportion of cell walls and cell contents

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20
Q

What is the acid detergent fiber ranges of grasses?

A

200-450 g/kg DM

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21
Q

What is included in the cell walls of grasses?

A
  • Water soluble carbs ( fructans, glucose, fructose, raffinose and stachyose) that range from 25-300g/kg DM.
  • Protein
  • Cellulose 200-300g/kg DM
  • Hemicellulose 100-300g/kg DM
  • lignin
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22
Q

True protein accounts for ____% of N

A

80%, but protein content decreases with maturity

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23
Q

_______ constitutes more than 50% of the cellular protein in grasses.

A

Ribulose biphosphate carboxylase

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24
Q

Grasses are rich in the following amino acids?

A

Arginine, glutamic acid and lysine

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25
Q

What are the first 2 limiting amino acids in grasses?

A

Methionine and isoleucine

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26
Q

CP of tropical grass is ___ than the CP of temperate grass.

A

Lower

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27
Q

What does ADIN stand for

A

Acid detergent insoluble nitrogen

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28
Q

What are the main components of NPN

A
  • Amino acids
  • Amides
  • Nitrate
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29
Q

What is the ether extract fraction in grasses ?

A

It is low and does not exceed 60 g/kg DM

30
Q

The ether extract includes:

A
  • triacylglycerols
  • glycolipids
  • waxes
  • phospholipids
    sterols
31
Q

What is the main fatty acid in grasses?

A
  • Linolenic acid, makes up 60-75% of total FA’s

- Linoleic and palmitic acids are the next 2 most abundant FA’s

32
Q

The mineral composition of grasses depends on?

A
  • species
  • stage of growth
  • soil type
  • cultivation condition
  • fertilizer application
33
Q

What is the precursor for vitamin A?

A

Beta-carotene, Grass herbage is rich in this. In green crops= 550mg/kg DM. In green crops the conc. of vit A is 100 times higher than what is needed by a cow.

34
Q

Except for Vit A, what are the other vitamins presents in green forage crops?

A

Vit E, many Vit B’s like riboflavin, Vit D is present more in mature herbage.

35
Q

Why do diets of grazing animals vary?

A
  • There can be a variation in botanical composition
  • Plant growth is diffirent at diffirent times of the year
  • Plant growth rates differ
  • Plant maturities can differ
36
Q

Name the 4 growth stages of grasses:

A

leafy, boot, heading, bloom

37
Q

Name the 4 growth stages of legumes:

A

leafy, prebud, bud, bloom

38
Q

Proteins may be indigestible, why ?

A

Because most of the proteins are bound to fiber.

39
Q

As a plant grows, what happens to its nutritave values?

A
  • The structural carbohydrates increase, these include cellulose, lignin and hemicellulose
  • Conc. of protein and total ash decrease
  • digestibility of organic matter decrease
40
Q

What determines the digestibility of a plant?

A
  • Plant anatomy
  • Age, as plant matures the digestibility will decrease except in spring where digestibility stays the same for a month.
  • Digestibility of grass is also influenced by leaf:stem ratio, in young grass stems are more easily digested that leaves, but over time this changes
41
Q

A low NE value of a mature herbage is due to:

A
  • low organic matter digestibility

- high concentration of cellulose

42
Q

What are the six important tribes of grasses?

A
  • Agrosteae
  • Aveneae
  • Festuceae
  • Eragrosteae
  • Andropogoneae
  • Paniceae
43
Q

Why can it be negative for grasses to grow more quickly ?

A

In arm climates, grasses mature rapidly. This means their protein and phosphorus levels fall to a very low levels quickly and they have a high fiber content.

44
Q

Why do C3 and C4 species have diffirent nutritive values?

A

Due to their differences in photosynthetic pathways

45
Q

C4 plants hav inherently low N content,why?

A

Due to their adaptability to low soil fertility

46
Q

Anatomically, how do temperate and tropical species differ

A
  • There are more there are more vascular and thick wall bundle sheaths and lignin in tropical plants
  • The mesophyl cells are more densely packed in tropical species that temperate species
  • Lower intracellular space in tropcal species than temperate species.
47
Q

The anatomical diffirences between temperate and tropical species mean that_______

A
  • Tropical grasses have a higher tensile strength, which means retarded mechanical and microbial degradation in the rumen.
  • Tropical grasses have lower digestibility and lower voluntary dry matter intake
48
Q

What should the selection of pasture species be based on ?

A
  • Agronomic (persistency and productivity)

- Nutritive value characteristics

49
Q

How do plants react to a mineral deficiency in the soil?

A
  • Limit their growth

- Reduce the conc. of minerals in their tissue

50
Q

Sulpher deficiency leads to

A

reduced digestibility of herbage in sheep

51
Q

What does the application of N fertilisers help with?

A
  • Increase leaf area and photosynthesis rate
  • Increase the CP content and frequently the amide and nitrate contents
  • Depresses the water soluble carb content of temperate grasses.
  • Alters the botanical composition and nutritive value of swards.
52
Q

Name the 3 types of grazing systems:

A
  • Cut and carry, grass is cut and taken to a kraal, this has the best control over an animals diet.
  • Continuous, animals kept on the same pasture through the year
  • Rotational, pastures are grazed for short periods with high stocking rate and grazing pressure
53
Q

What is the connection between the amount of grass eaten by animals and the root growth of that grass?

A
  • With 50% of the plant eaten, roots will not stop growing.
  • If 70% of the plant is eaten, 50% of the roots will stop growing for 17 days
  • If 90% of the plant is eaten, 100% of the roots will stop growing for 17days.
54
Q

What are the nutritional disorders associated with grasses?

A
  • nitrate poisoning
  • mycotoxicosis
  • grass sickness
  • grass tetany
55
Q

What causes the toxic effect of nitrogen in ruminants?

A

Reduction of nitrate to nitrite, nitrate oxidises the ferrous iron of haemoglobin to the ferric state producing the brown pigment methaemoglobin which cannot transport oxygen to the body.

56
Q

What are the toxic signs of nitrate poisoning?

A
  • Trembling
  • Staggering
  • Rapid respiration
  • Death
57
Q

What is the lethal dose of nitrate in herbage?

A

2.2 g/kg DM

58
Q

What is mycotoxicoses?

A

A disorder of grazing animals caused by the invasion of grasses by fungi ( fungi produces mycotoxins)

59
Q

Which fungi causes rye grass staggers?

A

Acremonium loliae, which produces the neurotoxin alkaloid lolitrem B.

60
Q

Which fungi causes Paspalum staggers?

A

Claviceps paspali, which is relted to the ergot fungus

61
Q

Tall fescu is infected by the fungi ______

A

Acremonium coenophalium, which produces an ergot alkaloid ergovaline. Ergovaline causes the condition fescue foot.

62
Q

Which micotoxin is produces by Pithomyces chartarum?

A

Sporidesmin, which causes liver damage in grazing animals. This causes the release into the circulation of bile and the chrolophyll breakdown product phylloerythrin, which causes the disorder called facial exzema.

63
Q

The control of mycotoxicoses is based on ______

A
  • Use of fungicides on pasture
  • selection of resistant plants and animals
  • modification of grazing practices to avoid consumption of infected herbage.
64
Q

What is the scientific name of grass sickness and what is grass sickness?

A
  • Equine dysautonomia
  • Happens when horses graze on pasture after a dry period and involves the toxin botulinum. Damage occurs to the autonomic nervous system.
65
Q

Grass sickness (equine dysautonomia) is characterised by _______.

A
  • Muscular tremors
  • Loss of weight
  • Abnormal stance
  • difficulty to swallow
  • impaction of the colon
  • regurgitation of stomach contents
66
Q

The main sugar in clover is ____

A

sucrose

67
Q

What is the conc. of starch in clovers?

A

50g/kg DM

68
Q

Give 3 examples of efforts to introduce legumes in the pasture system:

A

1) Centrosema pubescens into pasture of the wet tropical
2) Macroptilium atropurpurium into drier areas
3) Medicago staiva into warm temperate areas and in many tropical and sub-tropical areas.

69
Q

What are egyptian clovers valued for?

A

Rapid growth in the winter season in sub-tropics and for its good recovery after cutting or grazing.

70
Q

What is the protein in foliage of leguminous trees

A

200-300g/kg DM

vge (9 decks)

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