Lecture 11- Sheep nutrition Flashcards
What are the systems like with sheep?
- 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
What are the sheep numbers in Australia?
- 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.
What are the nutrients requirements of domesticated animals determined by?
• 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
What is the most important nutrient for sheep?
-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)?
What are the energy requirements for sheep?
- 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
What are other things you need to consider?
-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
What things to consider with milk?
- Milk energy content 6.37
- days of lactation 30
- Milk yield 1.3
- ME requirement for milk 10.3
What to consider for wool?
- 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
How do you have to factor in pastures?
- weather, the maturity of the plants
- as the plants mature then the animal can get less energy from it
What are the protein nutrition requirements in sheep?
• 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.)
What are the main things to consider?
• 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
What is the effect of maturity of the plant on digestibility?
- early- 80% digestible
- mature= 38% digestible
- there are prons and cons as the slower ones will stay in for longer…
What is the impact of metabolic live weight on digesting?
- larger animals can be more efficient
- heavier= better
- due to surface area etc.
Another factor?
- high herbage mass (lot of acceptable grass to eat),
- more high so more eating
How much do sheep eat?
- 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
What are the consequences of underfeeding?
• 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,
What are the consequences of overfeeding?
- Costs more!! (inefficient) • Fat ewes less valuable, too much fat
- Decreases market value • Birthing problems?
What is condition scoring of sheep?
- bit harder than for cows for example
- need to factor in the wool
- feel the bones etc.
- body condition 2 to 4 is optimal
What is the issue with feed aversion in sheep?
- 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
What is the nutrient selective eating?
- ‘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
What is sheep nutrition like?
• 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)
What vitamins are really important?
- sulfur for wool growth
- selenium = can be deficient in pasture system (plants do not need Se) especially in clover and highly fertilised systems
How do you manage lambing?
- 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
What is PRGT (D-perennial ryegrass toxicosis)?
• 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!!!
