Ruminant nutrition Flashcards by Alex Pearson

Why does NZ use an extensive pasture production system?

We have suitable/fertile soil.
Enough sunlight and rainfall.
Temperate climate  Animals can stay outside 365 days of the year.
Low input system  less production costs/cheap.

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What are the main types of pastures used in NZ?

NZ uses a mix of forages
•	Mainly perennial ryegrass & white clover. 
Supplement forages
•	Forage herbs – chicory & plantain. 
•	Legumes – Lucerne & red clover.
•	Summer – turnips. 
Winter – Swedes & kale.

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How does seasonality affect pasture growth?

Highest pasture growth is in SPRING , when there is the most rainfall and adequate sunlight.
Lowest pasture growth is in SUMMER and WINTER –
• Winter – too little sunlight + can be dry.
• Summer – too much sunlight, not enough rain.
• Spring – highest pasture growth – adequate rainfall and sunlight.
• Autumn – Waning pasture growth.

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How does land topography and location determine land use?

Flatter areas tend to have more moisture – so yield highly, and enables easier movement of dairy cattle to and from milking.
Hillier/drier areas – Less interaction with Beef and sheep. Don’t have high daily productivity issues – so can survive on less volume of grass.
Alpine/tussock – Merino sheep – prefer dry colder climates.

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What the challenges with the seasonality of pasture?

Pastures yields change month – month, and year – year but generally -
• Deficit in summer
• Surplus in spring
The upper limit of annual pasture growth in NZ is a limiting factor for production yields (meat/wool or milk).

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How does the annual herbage production vary between production systems?

Dairy farms – require the highest level of supplementation + intensively graze the pasture >12 T DM/ha/yr
Lowland/finishing sheep + beef –
• Don’t use as many crops – removed during dry, and graze and use surplus spring growth during lambing/calving - ~9 T DM/ha/yr
• If using farm for finishing – grazing intensively and using more crops - ~14 T DM/ha/yr
Extensive sheep and beef hill country – Grazing is restricted during dry periods – may  SR – less crops grown – 6-10 T DM/ha/yr

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Why is it important to match feed supply and feed demand?

To match high pasture growth with periods of increased animal feed demand so production is not reduced 
• Lactation during spring – high ME demand.
• Growth of offspring through spring + summer
• Adequate energy for cycling (dairy cows).

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How can we ensure optimum feeding levels are maintained despite pasture variation?

Grazing management (rotations etc)
Conserving pasture in silage/balage/hay
Fertiliser application
Crops (maize, cereals, lucerne, brassicas etc)
Concentrates
Change stocking rate.

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How do we ensure efficient utilisation of pasture year-round?

In periods of surplus – High SR so no wastage
Timing events with pasture variation 
1. Calving, lambing when high PGR (helps pasture quality for summer).
2. Weaning when still high PHR for GR – so can sell for summer.
3. Ensuring LW targets are met for sale dates.
4. Drying off or  1xday milking when feed .
5.  SR

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What are some key performance indicators that we can use to assess feeding levels?

Lactation - Total MS yield/cow, daily yield, peak yields, Milk composition & Somatic cell count
Reproduction – Submission rate (% of cows that are inseminated once after a specific period of time e.g. 3 weeks/6 weeks), Conception rate (% of no. of cows/number of services) Empty rate, 6 week in calf rate (% of cows in calf within 1st 6 weeks of mating),% of young born/weaned/docked

Offspring growth – Average daily gain (g/day), no. of days to weaning, weaning %

Meat yield – Carcass weight, Killing out % (carcass weight/LV).

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How can the quality of pasture be maintained?

Sward must be maintained in its young vegetative state in order to regrow
• Rotational grazing – to prevent overgrazing , and ensure pasture eaten is young and leafy.
• Monitoring pre + post grazing residuals dictates SR and rotation lengths.
• Meet residual targets (3-5 cm from ground)
• Conserving surplus pasture in silage – prevents dead matter.
• Topping
• Fertiliser

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Why is the quality of pasture important?

Good quality pasture i.e. leafy and young   DE% and protein.
Old, dead and stem pasture   fibre and  DE.
ENERGY IS 1ST LIMITING INGREDIENT.

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Why is quality of pasture important for animal performance?

The higher the quality, the higher the energy content.
Optimum energy levels needed for maintenance and good performance in different physiological states.
 If quality of pasture declines   DE, and animal cannot consume enough to meet demands.

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Why do extensive dairy systems not yield as much as intensive?

Milk + meat yield  pasture growth + composition.

 15-20% DM,  fibre and have to consume a lot to meet higher yields.

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Why should supplementing feed be carefully considered?

Supplements -  DE, but  cost. 
The profit from feeding crops must exceed the costs of planting
Supplement choice is dependent on 
	Cost per unit of ME
	Production risk
	Availability of paddocks and equipment
	Time/labour/experience.

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What are potential issues when supply does not meet demand?

Animal
 performance.
 health
 reproduction

Welfare
 BCS
 Hunger

Welfare Financial
 BCS
 Hunger  supplementation

Pasture
Overgrazed – slow pasture growth + weeds grow.
Undergrazed -  dead matter.

What production processes would we calculate energy requirements for?

Maintenance
 Lactation
 Reproduction – foetal and placental growth
 Liveweight gain (Either growth or  BCS)
 Activity
 Wool/antler/fibre growth

What factors affect how the energy requirements may differ in production processes?

Maintenance costs
•	Species (cow + deer  > sheep)
•	Age – young > old
•	Grazing environment -  pasture mass  grazing cost
•	Climate -  with cold temperatures
•	Feed quality -  high quality feed

Liveweight gain/loss
• Gain is determined by proportion of fat and protein laid down (fat ME > protein) and rate.
• Loss – Energy is substituted by metabolism of own condition.

Pregnancy costs – Increase exp over time
•	Birthweight – higher means  ME needed. 
•	No. of offspring
•	Growth of foetus and placenta
•	Maintenance of foetus
•	Prep of udder for lactation.

Lactation costs
• Composition
• Volume
• Easy calc for dairy cows when volume + comp known.
• Difficult to calculate lactation requirements for beef cow, deer and ewes.

How to calculate ME requirements for growth?

100kg bull ME requirements/day – eating 11 MJ ME/kg DM
22MJME (maintenance) + 21 x (1) (growth) MJME = 43 MJ ME / 11 MJ ME/kg DM = 3.9kg DM/day

400kg bull ME requirements/day - eating 11 MJ ME/kg DM
66 MJME (maintenance) + (40 x 1.5 – growth)) MJME = 126 MJME / 11 MJME/kg DM = 11.5kg DM/day

How to calculate ME requirements for pregnancy?

60kg ewe eating 10.5 MJ ME/kg DM of pasture 2 week prior to lambing at 3 different live birthweights

3kg (LW) = 10MJME/day (maintenance) + 3 MJME (pregnancy cost) = 13 MJME/day / 10.5 MEMJ/ kg DM = 1.3kg DM/day

How to calculate ME requirements for different stages of lactation?

IN early lactation, a 550kg cow is eating 11 MJME/kg DM/day – and is losing 0.5kg BC/day producing 25L/day milk.
61 MJ ME (maintenance) + 155 MJME (lactation) + 6 MJME (activity) – 18MJME (LW loss) = 204 MJME/day / 11 MJME/kg DM = 18.5 kg DM/day.

In late lactation, a 450kg cow is gaining 0.5kg/day producing 15L/day milk
52 MJME + 24 MJME (LW gain) + 99MJME (lactation) + 5MJME (activity) = 180 MJME/day / 11MJME/kg DM = 16.4 kg DM/day.

What are two ways the efficiency of a dairy cow can be calculated?

Either kg MS/kg LW or
a. 475kg cow producing 380kg MS = 380kg MS/475kg LW = 0.8kg/80g of MS/kg LWT.
Kg MS/kg of feed eaten (feed conversion efficiency).
a. 450kg cow eats 4.5tDM/year to produce 350kg MS = 4.5t x 1000 = 4500kgDM/yr
350kg MS/4500kg DM/yr = 0.078kg MS/kg DM eaten/78g MS/kg DM eaten.

What animal factors limit feed intake?

In late pregnancy – foetus/s take up space in abdomen and limit rumen size – so therefore amount of feed intake is limited/therefore energy requirements difficult to meet.
Early lactation – Such high ME requirements that animal cannot physically consume enough
Non animal factor - If pasture quality low – then cannot intake enough feed to make up ME requirements

Why is adequate body condition important to maintain?

Body condition can be used in times of feed deficit or early lactation/late pregnancy where animals cannot consume required energy.
• A BCS of 6 increases chance of successful mating. Minimum of 4 for mating.
• Loss of BC in lactation and pregnancy, so want to ensure BC is adequate in early pregnancy, as is very hard to gain during these times.
• Want a higher BCS before winter – so BC to lose.

How can the use of body condition influences feed intake?

In periods of high ME requirements (early lactation and late pregnancy) or feed restriction, the animal will use its own fat and muscle reserves for energy in order to ensure they are meeting their energy requirements. It is food they don’t have to physically eat.

Why are protein requirements important for production processes?

Protein is still required for each production phase, including maintenance, wool growth, liveweight gain (muscle deposition), pregnancy and lactation.

When is protein deficiency more likely to occur?

In maize silage and cereal grains have low CP %. IF these are to be used for feed, must be supplemented with higher CP% feed, to level out costs.

How do protein requirements change with age?

The younger animals with higher growth rates will require more CP in DM – this is to ensure high LW gains of muscle. Old animals will require much less protein. Lactating cows animals require higher protein %.

How can we use grazing management to ensure energy and protein requirements are met for production?

When feed is restricted – pasture preference should be given to young growing stock and lactating stock.

How can we use stock grazing strategies to maintain pasture quality?

1. Older animals use to clean up lower quality pastures as ME requirements lower. 2. Beef cattle grazing long pasture for sheep. 3. Using dry cows to graze down pasture after dairy heifers.

What are some animal targets to maximise animal production?

1. Liveweight targets for young when growing 2. Body condition score (because weighing constantly is not always done) – for mating, calving and lactation. 3. Lactation yield (kg MS/cow, fat % yields, protein %) 4. Reproduction – Empty rate + submission rate (no. of cows that receive an AI in a no. of days post calving). 5. Intake (kg DM/day)

What are some pasture targets to meet to maximise pasture mass and intake?

 Pre and post grazing residual |  Average farm cover (kg DM/ha).

Why are liveweight targets important for maximising production?

 30% of MW at 6 months  60% of MW at 15months (1st mating)  90% of MW at 22 months (2 months shy of 2 years) (pre calving) Body weight is the main driver of reaching puberty at 12 months. If they don’t reach these targets, they are potentially less fertile and will not be able to get in calf at 15 months.  If they don’t meet their LW target and are mated, they will potentially lose too much condition and will be less fertile and have less milk yields at lactation and affect next mating.  Growth in first 2 years indicates lifelong performance

What is the target growth rate from weaning – calving?

.66 kg/day – ideal average constant.  Should be high in the first year – 0.4-0.8kg/day  Increase just before puberty at 12 months to ensure good condition.  0.5kg/day in the 90 days before calving ( rumen size)

Why should the averages of the mob be the minimum for LW targets?

Usually the mob average of LW’s are taken. Averages don’t represent accurate LW targets. Need to ensure that you don’t be relaxed at minimum, as it potentially means that some are under LW targets (wasted cows)  Different pastures/seasons will change ADG  These different times of the years they may be above target, under target, or on target.

What is the potential value of a diet

Feeding value = Nutritive value x intake ``` Nutritive value = Digestibility of forage/pasture (i.e. the ability for pasture to meet requirements for MAINTENENCE and PRODUCTION ( EFFICIENCY OF UTILISATION.) Nutritive value is affected by   Intake  Diet composition  Digestibility of feed  Utilisation in tissues Intake = amount eaten is affected by forage quality (due to animal selection)  Selection  Competition between animals – high SR. ```

How does change in forage composition affect production?

HIGH QUALITY PASTURE (spring) –  Generally, has  DM%.  Higher CP%  Higher MJME Due to  concentrations of nutrients, cow can meet needs and has better growth rates and milk yields. MEDIUM QUALTIY PASTURE (autumn)   DM% because has more fibre content.  Lower CP%  Lower MJME/kg.  Due to  digestibility, there are less nutrients to utilise.  Legumes has highly digestible and have higher MJME/kg.

What factors influence selection of feed by livestock?

® Palatability ® Aversion ® Choose based on nutrient needs (young =  high protein,  fibre). Mature not fussed. ® Availability – will eat the easiest part to grab. ® Age – Young stock  new forage. ® Competition – if using break feeding,  SR. ® Species