Ruminant Nutrition (2) - Lecture 149-150

Ruminant Nutrition - lectures 149-150 

1. Understand how to feed the ruminant to ensure optimum digestion in the rumen

Optimum Digestion:

• Ruminant pH < 5.5 will lead to acidosis
• Fibre digestion decreases with pH < 5.8
• roughage to concentrate ratio is important
• also important is frequency of feeding, feed particle size, whether total mixed ration (TMR) or fed separately.

Components in feeding: 


Soya bean meal is a main source of protein (although high in carbs too) 

• Immediately after feeding concentrates the rumen pH starts to go down
• Feeding concentrates in the milk parlour twice a day can limit the total amount of concentrates that can be offered
• The Total Mixed Ration (TMR) allows to increase the concentrates as the particle sizes are small, so cannot select easily

Lipids in Rumen: 

• Diet should be <100g/kg of lipids otherwise fermentation is affected and feed intake decreases
• Unsaturated fats can convert to saturated fats in ruminants
• Trans fatty acids are generated

Vitamins in rumen: 

• Vitamin A – grass, hay, silage 
• Vitamin D – sun dried hay, out door grazing, supplementation may be necessary 
• Vitamin E – green forages, young grass is better than mature 
• Vitamin K – green leafy feed, lucerne, cabbage and kale 
• Vitamin C – in plant materials 
• Vitamin B complex - all abundant in green leafy materials and seeds - EXCEPT B12
• B12 is special – only synthesised by rumen microorganisms but colostrum is essential for this
• Calves from adequately fed mothers have minimal stores of vitamins at birth. 
• A young calf does not have a fully functional rumen and active microflora, which typically contribute to vitamin synthesis. 
• Colostrum is rich in vitamins, particularly vitamin A, provided that vitamins have been adequately supplied to the dam.

2. Explain how ruminants get energy and other nutrients

rumen ---> reticulum ---> omasum ---> abomasum

Relative volumes of stomach composition

Sheep

                       at birth                    adult

----------------------------------------------------

rumen                 25%                      62%

reticulum             8%                        11%

omasum              8%                         5%

abomasum          60%                       22%

Fully functional rumen: 

calves --> 20 wks

deer --->   16 wks

goats --->  12 wks

lambs -->   8 wks

Many types of bacteria, fungi, protozoa in Rumen:

• Cellulolytic
• Amylolytic
• Hemicellulolytic
• Pectinolytic 
• Proteolytic 
• Deaminative 
• Ureolytic 
• Methanogenic 
• Lipolytic

10¹⁰/ml of bacteria in rumen

Examples of ideal pH for specific microbes:

Ruminococcus flavefaciens pH 6.15

Bacteroides succinogenes pH 6

Megashpaera elsdenii lactate user pH 4.9 

Streptococcus bovis lactate producer pH 4.55

Conditions inside rumen:

• 38-40C
• Anaerobic
• pH 6-7
• movement
• waste removal
• buffered --> If stops ruminating, less saliva, acid builds up
• large holding capacity
• if rumen drops below 5.5, acidosis sets in (streptococcus bovis lactate producer pH 4.55)

Breakdown of carbs in rumen: 

large methane producers

Volatile fatty acids: 

furnish 60-80% of energy needs of typical ruminant

Acetic acid: 

- 50-60% - most important
- predominates on high-roughage diets

Propionic Acid:

- 18-20%

- predominates on a high-concentrate diet (e.g. during pregnancy)

Butyric Acid:

- 12-18%

- provides energy to rumen wall (for motility) 

3. Understand how to maximise use of proteins in ruminant diets

• If you want proteins to bypass the rumen and go straight to the abomasum, coat the proteins with sugar (molasses is usually used) 
• The molasses will provide the initial sugars so microbes use that energy
• Most Dietary Crude Protein is converted to MCP (~70%)
• microbes need energy to grow and therefore convert to MCP

FME - Fermentable Metabolisable Energy

• fraction of feed energy that is available to the rumen microbes
• typical conversion rate is ~ 11g of MCP per MJ of energy available to microbes during rumen fermentation

MCP - Microbial Protein

• Digestibility in abomasum and small intestine is ~80%
• 70% of ruminants requirement can come from MCP

When there is a high concentration of dietary protein but insufficient FME, the liver starts metabolism and urea is recycled to rumen.

4. Explain how energy is partitioned

Energy losses in:

• faeces
• urine
• eructation gasses

Energy available is called Metabolisable Energy (ME) 

ME = energy in diet - (energy in faeces + energy in urine + energy in methane)

ME is used for: 

• maintenance
• protein deposition (growth)
• fat deposition
• milk production (lactation)
• foetal growth (pregnant animals)
• work (draught animals)
• wool growth
• reproductive and other activities
• Efficiency of utilisation of energy for above tasks is different

Energy for maintenance:

• Fasting metabolism = 0.27 MJ/kg BW
• general rule for all species - reality is a slight variation
• related to body surface area
• younger animals have higher/faster metabolism

5. Understand how to balance a diet for ruminants based on their requirements for growth, maintenance, pregnancy and/or lactation

Development of functional rumen
- ingestion of dry feed
- introduction of anaerobic/facultative anaerobes
- interaction of above to speed up development

Calf feeding: 

• Colostrum - antibodies absorbed within first 24 hours
• Milk replacer - good quality milk replacer 100-125 g/l
• Acidified milk substrate - ad-lib milk feeding
• calf starter or calf concentrate - min 20% crude protein
• roughages and water

Weaning Calves: 

• 5 weeks or 0.5 kg conc/d, 1.5 times the birth weight
• This usually happens when calves are 35-40 days old and weigh 65-70 kg (Holstein)
• Components of calf starters - many involved
• acid detergent fibre is most difficult to digest.
• this helps the calf develop the rumen

Adult Cows:

• commercial cows avg ~ 7000 litres of methane a year
• Holstein cow weighs ~ 650 kg
• Eat approximately 2.5-3% their body weight in DM
• 1 calving a year - typical calf ~ 40kg
• typical cow diet
• ME =   10 MJ/kg DM ---> 13 MJ/kg DM
•            low production ---> high production
•       mainly degradable ---> 30% digestible undegraded protein
• Protein content ~ 12% ---> ~ 18%

Feeding pregnant cow in dry period - Example: 

500 kg cow - can consume 1.5% body weight in DM

requirement = 80-82 MJ/d

ME values for 

silo A = 11.0

silo B = 10.0

silo C = 9.0

Amount cow can eat = 500kg (0.015) = 7.5 kg DM

silage A = 11 (7.5) = 82.5 MJ

silage B = 10 (7.5) = 75 MJ

silage C = 9 (7.5) = 67.5 MJ

Silage A is the only one that can meet requirements

Feeding pregnant ewe - Example

Concentrate feed for twin-bearing ewe in late pregnancy

ewe = 65 kg

each ewe needs 22 MJ ME/day

ewe consuming 1.5kg hay (90% DM)  Energy value = 10 MJ ME/day 

Concentrate = 90% DM  Energy value = 12 MJ/ME/kg DM

currently consuming = (1.5)(9) = 1.35
Energy of current = 1.35 (10) = 13.5 MJ/d

still needs = 22 MJ/d - 13.5 MJ/d = 8.5 MJ/d

Concentrate = 8.5/12 = 708g

Want body score ~3 - not over/under weight

Feeding lactating cow - Example

• everything except FME is negative
• FME is only for microbes
• this will decrease pH in rumen
• cow is not getting any nutrients
• cow is going towards acidosis
• pH ~ 5
• body score ~ 2 - no nutrients
• Reduce molasses (less FME), increase roughage - more fibre

6. Describe production and metabolic diseases in relation to nutrition

Nutritional imbalances: 

• milk fever
• ketosis
• bloat
• fat cow syndrome
• displaced abomasum
• rumen acidosis
• laminitis
• vitamin deficiencies

Milk fever: 

• drop in blood calcium
• usually drop in blood phosphorous and increase in K and Mg levels
• animals will collapse ---> give Calcium
• Milk fever starts when calcium is 5 - 7.5 mg/100ml
• normal is 8 mg/100ml

Ketosis: 

• too much fat being used as energy
• usually occurs in first 6 weeks of lactation
• energy output > energy input  - because of lactation
• common in twin pregnancies
• blood levels of ketones and free fatty acids are elevated
• inadequate supply of glucose to maintain glucose levels

Bloat: 

• gas in rumen
• enlarged left abdomen
• feed like fresh spring grass or lucerne can create 'foam'
• extended rumen - no movements
• Treatment
• surfactants
• release of gas - trochanter/cannula
• happens with sudden change in diet

Fat cow syndrome: 

• obese cows in pre-parturient (dry cow) period
• reason - overfeeding during last stage of pregnancy
• symptoms: depression, anorexia, ketonuria, decrease in production, weakness, nervous signs
• fatty liver
• highly susceptible to infectious diseases
• dystocia

Acidosis:

• develops when calves are moved from milk to grass diet
• when rumen pH drops below 5.5
• when ruminants are given large quantities of cereals or changed to a high concentrate diet rapidly