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BSC Zoology - Nutrition and Digestion > Lecture 11- Sheep nutrition > Flashcards

Lecture 11- Sheep nutrition Flashcards

1
Q

What are the systems like with sheep?

A
  • Majority of sheep production systems in Australia are based on pasture, so mainly grazing
  • Some intensive feedlot systems are being developed but there are economic and efficiency issues to be considered before a shift in commercial system.
  • Feedlots are used for finishing but profit margins are tight (labour intensive)
  • Useful in times of drought
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2
Q

What are the sheep numbers in Australia?

A
  • Australia has lot of sheep particularly per population
  • the numbers are declining however
  • mostly in coastal areas since they are grazed so need grass and rain
  • most if them in NSW, VIC and WA and SA
  • mostly in Vic and NSW
  • the exports (live) go to UAE and other arab countries
  • wool export is also big, to china etc.
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3
Q

What are the nutrients requirements of domesticated animals determined by?

A

• Standing Committee of Agriculture (1994)
• Agricultural and Food Research Council (1993) and Agricultural
Research Council (1980).
• Development of rationing system for sheep, beef cattle and dairy cows
-this is where we get the info

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4
Q

What is the most important nutrient for sheep?

A

-water!
• Sheep drink 2-4 times the amount of dry matter intake
• 3.5–6L per day
• Lactating females require double!
• Requirements increased with higher temperatures
• Temperature of the water is also important as they use it as heat loss mechanism (through urine)
• Clean
• Free from bacteria
• Copper toxicity?
• Micotoxins (live in water)?

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5
Q

What are the energy requirements for sheep?

A
  • The rationing system is an additive factorial system with energy requirements for maintenance, growth, pregnancy, lactation and wool growth considered.
  • Mean M/D of common feeds: • Wheat 13.7
  • Oats 12.1
  • Barley 13.3
  • Sorghum 13.2 • Maize 13.8
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6
Q

What are other things you need to consider?

A

-Age 4
-Live weight, kg 50
-Fasting Metabolic Rate, MJNE/W 0.75 4.7
-Activity Increment
(additional % of NE for activity=10%) 5.2
-Efficiency of use of ME for -Maintenance of body tissues 0.72
-ME for maintenance of body tissues

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7
Q

What things to consider with milk?

A
  • Milk energy content 6.37
  • days of lactation 30
  • Milk yield 1.3
  • ME requirement for milk 10.3
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8
Q

What to consider for wool?

A
  • Desired rate of wool growth, g/d 15
  • Desired Rate of wool growth, g protein /d 12 NE in Wool, MJNE/d 1.17
  • Efficiency of use of ME for wool growth (assume 0.18) 0.18
  • ME for desired wool growth, MJME/d 6.5
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9
Q

How do you have to factor in pastures?

A
  • weather, the maturity of the plants

- as the plants mature then the animal can get less energy from it

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10
Q

What are the protein nutrition requirements in sheep?

A

• System currently used based on the metabolisable protein system. The system accounts for intake of crude protein, its degradation characteristics and the linkage between protein and energy metabolism in the rumen.
-this requirement changes depending on the life stage (pregnant, lactating etc.)

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11
Q

What are the main things to consider?

A

• The main problem associated with rationing sheep at pasture is the prediction of voluntary intake and measurement of digestibility of herbage.
• Intake of pasture is very difficult to measure in practice and therefore it is difficult to optimise pasture utilisation.
-almost impossible to measure voluntary feed intake
-with grazing it is difficult to ration as will have some below and above average so difficult to optimise

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12
Q

What is the effect of maturity of the plant on digestibility?

A
  • early- 80% digestible
  • mature= 38% digestible
  • there are prons and cons as the slower ones will stay in for longer…
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13
Q

What is the impact of metabolic live weight on digesting?

A
  • larger animals can be more efficient
  • heavier= better
  • due to surface area etc.
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14
Q

Another factor?

A
  • high herbage mass (lot of acceptable grass to eat),

- more high so more eating

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15
Q

How much do sheep eat?

A
  • Ewes – 2-5 % bodyweight
  • Highest for lactating animals
  • Lambs – 3-6 % bodyweight
  • Decreases as lambs get heavier
  • Important stages of production to manage:
  • Late gestation (2nd most important)
  • Singles 2 weeks
  • Twins 3-4 weeks
  • Triplets 4-6 weeks
  • Early lactation (most important)
  • 42 days
  • Late lactation
  • 21 days
  • Weaningration
  • 7 days
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16
Q

What are the consequences of underfeeding?

A

• Weak small lambs with high mortality
• Reduced colostrum quality and quantity (bad immune system for lamb)
• Retarded weight gain pre- and post-weaning (for lamb)
• Reduced peak milk yield and less total production • Decreased re-breeding success
• Reduced wool production for fetus
-compensatory growth,

17
Q

What are the consequences of overfeeding?

A
  • Costs more!! (inefficient) • Fat ewes less valuable, too much fat
  • Decreases market value • Birthing problems?
18
Q

What is condition scoring of sheep?

A
  • bit harder than for cows for example
  • need to factor in the wool
  • feel the bones etc.
  • body condition 2 to 4 is optimal
19
Q

What is the issue with feed aversion in sheep?

A
  • Sheep can learn to avoid feeds with negative post-ingestive consequences • Up to 12 hrs between intake and concequence
  • Length of delay related to severity
  • Strength of aversion related to severity of negative response
  • Aversions learned quickly from mother
  • Older animals ‘trial & error’
  • Aversions can develop if an excess supply of the nutrient is given • Memory can develop
20
Q

What is the nutrient selective eating?

A
  • ‘pica’ – compulsive or persistent ingestion of inedible or non- nutritive substances
  • Selecting feeds that have the best digestibility
  • BUT – intake may not be selected for mineral content
  • Intakes are variable
  • Palatable but poor quality diets are selected over unpalatable nutritious diets
21
Q

What is sheep nutrition like?

A

• Grass-clover systems
• Experiments have examined voluntary intake of sheep using the n-alkane method to determine total intake, intake of clover and grass and therefore selection index.
• Animal production responses with mixed pastures can be +15% in relation to ryegrass only swards.
• The optimal intake seems to be 70% ryegrass 30% clover.
• This reflects the optimal dietary mix to maximise microbial synthesis in the rumen
(in vitro studies)
• Feedback mechanism: complex interrelationship between animal tissue requirements, rumen ecosystem and intake processes.
• Experimental work to investigate diet preferences are advanced especially on pasture based systems
• Diet selective behaviour is the consequence of preference (stay and seek) and aversion (avoid and leave)

22
Q

What vitamins are really important?

A
  • sulfur for wool growth
  • selenium = can be deficient in pasture system (plants do not need Se) especially in clover and highly fertilised systems
23
Q

How do you manage lambing?

A
  • Lambs born when sufficient pasture is available & conditions are ok • Need pasture for lamb growth & lactation for the ewe
  • “creep feeding”
  • The provision of supplements to the lamb but not the ewe
  • Achieved by small openings in fence etc. that only the lamb can access • Important in drought
24
Q

What is PRGT (D-perennial ryegrass toxicosis)?

A

• Otherwise known as Ryegrass Staggers • Cause
- Symbiotic relationship between ryegrass and endophyte (fungi) –
Neotyphodium Lolii
- release of alkaloid mycotoxins, Lolitrem B and Ergovaline
- natural plant defense mechanisms
• Symptoms
- Clinical condition – staggers, uncoordinated,
“flighty” behaviour, stiff gait, heat stress
- Sub-clinical condition – reduced milk production, suppressed appetite, loss of body condition, lower conception rates….its there!!!

25
Q

What is PRGT history?

A

• 6 million Ha PRG in Australia, 4 million Ha in Victoria. Also, SA, Tas, NSW.
• Southern climate experiences lush spring growth under warm, wet conditions predisposing to potentially toxic pastures.
• Toxins release is stress related and concentrated in crown and seed
• Followed by hot, dry summer – increased grazing pressure and toxin
concentration
• Danger months – Dec thru May
• Serious outbreaks 1986, 1993, 2002, 2005..2008??
• 2002 – estimates up to 200 000 sheep mortalities
• 90% of old PRG pasture are infected with wild endophyte
• PRGT is now occurring every year in southern Victoria - like the fires – expect it…just a matter of where, when and how bad!!
• Due to increased fertiliser use, improved pasture productivity and increasing stocking rates
- situation on most dairies

26
Q

What is the impact of PRGT on reproduction?

A
  • Observational study - Pregnancy test results of autumn joined flocks at DPI, Hamilton
  • Potential for Ergovaline to decrease Prolactin concentrations – mediator for mammary tissue differentiation and development prior to lactation.
27
Q

What are some current management practices for PRGT?

A
  • Remove affected stock from infected pastures…(to where??) • Minimise physical stress…conflicting
  • Graze alternative crop/pasture during danger months
  • Establish endophyte free/safe varieties
  • ELITOX- feed additive
  • Endophyte free (or bad endophyte free) grasses?
28
Q

What are forage legumes?

A

Lotus corniculatus
• Condensed-tannin (CT) containing legume • Grows in waterlogged, acidic environments • Responds to summer rainfall
• Reduces CH4 emissions
• Has productivity benefits • Increased fecundity
• Increased liveweight gain (LWG) of lambs
• Increased wool growth of sheep and lambs
-Modelling of wool and prime lamb enterprises
• Wool enterprises
• Average(17.3DSE/ha) • Top (20.2 DSE/ha)
• Prime lamb enterprises • Average(19.8DSE/ha) • Top (24.4 DSE/ha)
• Baseline systems modelled in GrassGro
• Effects of lotus used spreadsheet model
• CH4 from lotus was 5-15g CH4/kg DMI less than perennial ryegrass

29
Q

What are the problems and economics of forage legumes?

A
  • Problems with lotus persistence
  • Initial botanical composition calculated at 40%, 30% and 20% • Declining scale over 10 years
  • Pasture available per annum was 21%, 16% and 10%
  • Economics
  • Median commodity prices 2002-2011 • Pasture establishment cost $350/ha
  • Potential carbon offset income • $6.00/tCO2e
  • $24.15/tCO2e
30
Q

What is Lotus corniculatus

for wool and prime lamb?

A
  • CFI income @$24.15/t CO2e
  • Prime Lamb $9.88 to $11.71/ha
  • Increased wool
  • Prime Lamb $ 8.88 to $12.96/ha
  • Increase LWG and lambs
  • Prime Lamb $54.29 to $68.92
31
Q

What is the effect of underfeeding severely or moderately during pregnancy on birth weight and S:P at birth?

A

A: B: C: D: E: F:
Well fed during pregnancy
Severe underfeeding 112 - 142 days of gestation and then normal.
Severe underfeeding 112 - 131 days of gestation and then well fed 132 -142.
Severe underfeeding 95 - 116 days of gestation and then well fed 117 - 142. Long term underfeeding (moderate) 35 - 142 days of gestation.
Long term underfeeding (moderate) 35 -119 days and then normal 120 - 142

32
Q

How long does it take for nutritional change to be reflected in wool growth?

A
  • quite long
  • 12 weeks or so
  • as the wool has to adjust
33
Q

What are the feeding methods?

A
  • Feeding hay and roughage on the ground can be wasteful • Loss from trampling and soiling
  • Cowra Bale Feeder
  • Purchased commercially or home made • Reduces feed loss from 45% to 3-7%
34
Q

What are the combined effects (Grape Marc)?

A
  • Dietary oils
  • 3.5% less CH4 for 1% oil
  • Tannins
  • Up to 20% less CH4
  • Can we combine these? • Raw Oils + Tannins
  • 0%
  • What about naturally? • E.g. Grape Marc
  • Feeding Grape Marc
  • 18 to 22% less methane
35
Q

What are the diet supplements for sheep?

A
  • Probiotics eg. Yeasts (0-5%)
  • Saccharomycescerevisiae
  • Stimulates acetogenic microbes
  • Consuming H2 to form acetate • Enzymes(9-28%)
  • Cellulases and Hemicellulases
  • Reducing acetate-to-propionate ratio
  • Tannins,Saponins
  • Less methane
  • Less nitrous oxide from urine
  • Dietary nitrate (NO3 -> NH3)
  • Consuming rumen H2 to form ammonia
  • Toxicity issues
36
Q

How can you introduce grain for sheep?

A
  • Need to manage to prevent acidosis • Match with hay
  • Introduce slowly
  • Consider other feeds possible

BSC Zoology - Nutrition and Digestion (24 decks)

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