Feeding

Feed intake, energy and protein, principles of feeding dairy cattle and farm animal nutrition practical

what are we balancing when creating a suitable diet?

• nutrient supply

• nutrient demand

What is a diary cow’s maintenance energy?

• 10MJ ME/day per 100kg lwt

how do we work out a dairy cows maintenance energy?

• take her weight and divide by 10

how much energy does lactation require?

• 5MJ per L milk

how much energy does pregnancy require in the dry off period?

• 20Mj ME/day

how much energy does pregnancy require at calving?

• 45MJ ME/day

how much energy does it require to gain 1kg of weight in a cow?

• 35MJ ME

how much energy is required to cause 1kg energy loss, during lactation?

• 20MJ ME

what protein ratio do we want to keep in check in our nutrient balance?

• FME: FDP

• fermentable microbial energy: fermentable dietary protein

how do microbes serve as a source of protein in cows?

• they use dietary protein to reproduce, producing some energy in the process (FME)

• some microbes will move into the abomasum and be digested, therefore acting as a protein source

what nutrient requirement is commonly a limiting factor in beef and sheep but not so much iin cows?

• vitamins and mineral

what are 2 types of feedstuffs we give to cows

• homegrown forage

• purchased forage

why may we choose homegrown forage over purchased feed?

• generally cheaper

• can vary a lot

• good fibre supply

• less work if just left to graze

why may we choose purchased feeds?

• more nutrient dense

• more consistent

what is the target dry matter intake daily for a lactating cow?

• 20-25kg per day

how much food does a cow often eat in a day, why is this higher than the amount of dry matter we calculate

• expect 40-50kg of a 50% DM ration

• therfore they get the 20-25+ kg DM intake we expect

• but this also includes other nutrients, minerals, vitamins, concentrates.

how will feed intake compare in a lactating cow vs dry cow?

• dry cow will have a lower intake per day than a lactating cow, due to energy requirements

how do we formulate a ration?

• work out daily required intake (for herd/individual)

• 40-50% should be DM intake

• put other sources of protein, minerals, vitamins etc

  • use a specialist formulation website/code to help

what are 2 feeding systems for cattle

• individual

• group feeding

what are benefits to individual feeding

• more precise/scope to tailor ration to specific cow

• most/all of concentrate is feed is in 2 large meals

what are some advantages of group feeding?

• more cows in the group

• mix concentrate in forage, so each bite is the same

what is a concern with individual feeding, if a cow is then getting two large meals full of concentrates? why

• ruminal acidosis - the rumen is designed for consistent feed intake, not 2 large intakes of concentrate.

what do we call the feed we give to a group of cows

• total mixed ration

what does total mixed ration mean?

• all concentrate feed is mixed with forage and fed with ad lib access

• all cows in same group get exactly the same each day

when do we need to pay close attention to feeding in terms of reducing the risk of hypocalcaemia?

• the last 3 weeks pre-calving

what are 3 hypocalcaemia control strategies?

• DCAB manipulation

• calcium restriction

• targeted supplementation

how do we avoid rumen acidosis (3)

• good feed intake to supply energy - rather than high energy density

• avoid large starch concentrate meals

• sufficient long fibre

how do we calculate digestibility?

• 100 x( intake-faeces/intake)

if we have 100% digestibility vs 0%, how does this affect faeces?

• all digestible = no faeces

• none digestible = all of it is faeces

what are 6 factors that affect digestibility

• food composition

• diet/ration composition

• preparation

• enzyme supplementation

• animal factors

  • level of feeding

what do we call enzyme supplementation?

• probiotics

why may we prepare seeds to make feed more digestible and how?

• to make it easier for the animal to access the starch stored inside

• rolling/crushing/pH

how does the amount of feeding affect digestibility?

• more eaten = faster passage = less digested = more faeces

• less eaten = slower passage = more digested = less faeces

why does grass digestibility decrease over time?

• grass is growing for its own reproduction, wants to grow tall for seed dispersal

• therefore uses more nutrients to create lignins and complex carbs for growth

Lignin

• what is it structurally

• what does it have a high resistance to

• how does this affect digestibility

• how does it affect closely associated structures?

• complex alcohol

• chemical degradation

• reduces it

• reduces their digestibility

what are 3 alternative fibre fractions of crude fibre?

• NDF - neutral detergent fibre

• ADF - acid detergent fibre

• MADF - modified acid detergent fibre

what are the 3 ‘fractions’ we get from forage?

• cell content

• cell wall constituents - hemicellulose, fibre bound protein

• cell wall constituents - cellulose/lignin/silica

how does the solubility of each of these fractions in detergent vary?

1. cell content

2. cell wall - hemicellulose/fibre bound protein

3. cell wall - cellulose/lignin/silica

1. soluble in neutral detergent (NDF)

2. insoluble in neutral detergent but soluble in acid detergent

3. insoluble in neutral detergent, insoluble in acid detergent

how do we control food intake?

• physical limitation

• chemically

• nervous/hormonal input

• physiological

• sensory: palatability, deficiencies, illness, heat, obesity, availability.

give 6 reasons we predict/estimate food intake

1. diet formulation

2. feed availability

3. feed budgeting

4. reducing feed wastage

5. determine stocking density

6. conservation management

what are 3 methods for predicting food intake

1. animals weight

2. rules of thumb

3. using requirement tables/books

what is the rule of thumb food intake for beef cattle

• 22g DM/kg bw

what is the rule of thumb food intake for dairy cattle early lactation

• 28g DM/kg bw

what is the rule of thumb food intake for dairy cow peak lactation

• 32g DM/kg bw

what is the rule of thumb food intake for a regular dairy cow

• 20-25kg/DM/day

what is the rule of thumb food intake for dry cows

• 15kg DM/day

what is the rule of thumb food intake for sheep-lambs

• 0.5-1kg DM/day

what is the rule of thumb food intake for late gestation ewes

• 2.5-3kg DM/day

how does food intake of a ewe change per day in early lactation?

• increases by 0.5-1kg DM/day

what is the rule of thumb food intake for horses

• 2kg DM/100kg bw

how do we ensure we’re meeting nutrient requirements?

• using resources available

8 methods to optimise VFI

• clean troughy, enough space

• feed always present

• adequate clean potable water

• good quality feed

• mixed forage

• short crop length

• increase palatability

• TMR

what are 6 fractions of feedstuffs

1. moisture

2. ash

3. crude protein

4. crude fibre

5. ether extract

6. nitrogen free extractives

what are 2 ways we express food composition

• fresh weight - g/kg

• dry weight matter - g/kg DM

how do we cause moisture loss in dry matter?

• dry at 100 degrees C until no further weight loss

what is essential to measure in food content

• WATER

in dry matter, what constitues towards energy

• carbs

• lipids

• organic acids

• (protein)

what is gross energy

• the total energy food contains

how do they work out gross energy

• bomb calorimetry

what are the typical gross energy values

• MJ/kg DM

what is digestible energy?

• the energy rumen microflora and ruminant can access

what happens to energy not gained via digestion

• expelled as faeces

how do we work out apparent DE content? MJ/Kg DM

(GE of diet - GE of faeces)/DM intake/day

what is metabolisable energy

• energy available for utilisation

  • energy lost in methane

  • and urine

how do we calculate ME?

(Ge of diet - (GE faeces + urine + methane))/DM intake/day

what is net energy?

• the proportion of ME used for maintenance growth, milk, wool or gestation

what form of energy is lost before we finally calculate NE?

• HEAT

what factor do we use for calculating NE?

• k

how is K worked out?

• NE/ME

what does k factor stand for?

• conversion efficiency

what is the heat increment?

• difference b/w metabolisable energy and net energy

what contributes to heat increment? (4)

• digestive motor activity

• secretion and production of digestive juices

• hydrolysis, metabolism and active transport in the GIT

• metabolism of absorbed nutrients and synthesis in the liver

how is k factor affected my increasing feed quality?

• increases - less energy required for digestion, more energy accessed more easily

what is diet quality?

• q

• it’s ME/GE - the proportion of GE that’s metabolisable

how is k affected by decreased production?

• k decreases as well

  • all biological processes are affected by reduced returns

  • more food must be eaten → less transit time

what is APL?

• animal production level

• how hard an animal works above maintenance requirement

what is metabolic rate?

• expenditure of E per given time

what are 5 types of metabolic rates?

1. basal

2. fasting

3. maintenance

4. field

5. mass-specific

what is field metabolic rate?

• energy required to hunt, graze, socially interact etc

what is mass specific metabolic rate?

• metabolic rate/kg body mass

what does crude protein break down into?

• rumen degradable protein

  • undergraded dietary protein

what is crude protein an actual measure of

• nitrogen not protein

what affects undegraded dietary protein

• outflow rate

• protein source

how many fractions of protein are there?

• 5

what’s in protein fraction A, how quickly is it degraded?

• ammonia, nitrate, AA, peptides - instantly

what’s in protein fraction B1 and how is it degraded in the rumen

• globulins, some albumins - slowly

what’s in B2 protein fraction, how quickly is it degraded in the rumen?

• albumins, glutelins

  • somewhat slowly

what is in B3 protein fraction and how quickly is it degraded in the rumen?

• prolamins, cell-wall and denatured proteins

• quickly!

what is in group C of protein fractions and how quickly is it degraded in the rumen?

• maillard products, N bound to lignin, tannin bound protein

• not degraded at all

what are each of the protein fractions soluble in?

1. A

2. B1

3. B2

4. B3

5. C

1. buffer TCA, NDS, ADS

2. buffer, NDS, ADS

3. NDS,ADS

4. n/a

what are most likely to be deficient in pigs and poultry

• lysine or methionine

what should we routinely measure in pigs

• lysine

what are 3 limiting AAs in poultry?

• lysine, methionine, tryptophan