Bovine Clinical Nutrition Flashcards
What are the main aims of feeding cows?
Efficient production, good rumen health and good cow health
Name some forages and their role in bovine diet.
Grass, silage, straw. Fibrous part and biggest volume so its quality is important, as this will have a big impact on the total nutrient intake of the animal
Name some supplementary feeds and their role in bovine diet.
Wheat, soya, maize grain/gluten. To balance out nutrients in the forage
What are NDFs?
Neutral detergent fibre content, forages around 50%, supplementary feeds less so – cell wall content, including cellulose, hemicellulose and lignin
Distinguish the characteristics of straw and wheat.
Straw will cause rumination, rumen fill, salivation, energy density is low, fermentation of straw in the rumen will cause acetate production, and straw is relatively cheap.
Wheat contains lots of starch, doesn’t stimulate rumination, rumen full or salivation, higher energy density and decreased acetate (which will increase milk fat), and is more expensive.
What are 2 ways of conserving forages?
Ensiling (fermentation using the sugars in the grass) – grass, maize silage
Drying, wilting – hay, straw
What does the amount and quality of grass in the diet depend on?
- Soil type and rainfall
- Variety with/without clover
- Fertilizers
- Sward quality
What happens to grass ages through the year?
It becomes more fibrous, less nutrient and so less fibrous
What are the objectives of grazing strategies?
Maximising DMI and minimising damage to pasture. Cattle can withstand temperatures, we house cattle to protect the fields and crops more than the cattle.
Name the possible grazing strategies.
Continuous
Rotational (“paddock”)
Strip
Zero
Extended
Why is grass conserved?
- Increased maturity, increased dry matter, increased NDF
- Decreased energy and decreased protein
- Decreased moisture
What are the characteristics of maize silage?
- Increased energy and decreased protein
- Increased yield and milk quality
What is primary fermentation of stored silage?
- Anaerobic
- Lactobacilli produce lactic Acid
- pH < 4.5
- Rapid pH drop produces a stable silage
- Increased water soluble carbohydrate minimum 30g/kg fwt – early season/May, wilting, afternoon cropping
- Increased dry matter – dry, windy weather, wilting, appropriate maturity
- Remains a stable product as longas you exclude oxygen, so are wrapped in plastic
What is secondary fermentation of stored silage and why do we not want this to take place?
- Butyric acid/protein degradation
- Decreased palatability and so decreased dry matter intake
- Decreased nutritional content
What are the possible silage additives and their effects?
- Acids or acid salts – decreased pH
- Sugars – increased soluble CHO and increased palatability
- Inoculants – which contains other bacteria to start and speed up fermentation or viruses to kill the bacteria you don’t want
- Enzymes – release CHO
What is the first limiting step to feeding cows?
Voluntary feed intake – they can only get energy and protein from the food they eat/based on her appetite
What are the cow factors affecting voluntary feed intake?
- Size – increased size increases VFI
- Yield – increased yield increases VFI
- BCS – increased BCS decreased VFI
- Stage of pregnancy – pre-calving = foetal size, post-calving = rumen size, adjust to new diet
- Presence of other animals
- Familiarity – on a gut microbe level, them being adapted to digest this
What are the feed factors of voluntary feed intake?
- Quality – increased NDF = increased time to digest = increased rumen fill = decreased VFI
- Moisture content – VFI can decrease is too wet or too dry
- Taste – select for sweet, avoid sour or bitter
- Chop length – VFI increases if short chop length
- Complete diet/mixed forages – increase VFI. Improved rumen function, taste and balanced nutrient intake
- Little and often – stimulus to eat and variety
What are the external factors affecting voluntary feed intake?
- Access - truly ad lib, bullying, space (min 70cm trough per animal)
- Light
- Water – constant free access
- Ambient temperature
How can voluntary feed intake be calculated from DMI?
VFI is measured on a dry matter basis – convert wet weight intake in Kg into dry matter by multiplying by dry matter content.
What is the rule of thumb for predicting DMI?
2.5% body weight + 10% of yield. 3% body weight at BCS 2.5, mid lactation and not in calf
After VFI, what is the next limiting step in feeding cows?
Energy
Define FME.
Fermentable metabolisable energy (FME) – available for use by rumen flora as energy sources
How do we feed the rumen?
- Some are used by the microbes and some are absorbed by the cow and then some rumen microbes feed the cow
- Rumenal microbes require energy to make protein and nucleic acid
- Unable to use fats and fermentation acids
- Fermentable metabolisable energy
What does slow fermentation produce?
- Volatile Fatty Acids (VFAs) > absorbed into the blood stream
- Acetic acid (2C)
- Propionic acid (3C) > oxaloacetate (glucogenic – ruminants produce glucose by proprionate, glucose often used by the microbes)
- Butyric acid (4C)
- Carbon dioxide and methane
Describe fats in the bovine diet.
- Coat fibre affecting digestion
- Most decreased milk butterfat
- Restrict to <6% of total diet
- Protected fats – won’t degrade in the rumen, pass through, but may pass through to the abomasum to be digested there
Describe the metabilisable energy system.
- Gross energy = energy trapped in food if burnt
- Goes through digested tract, some is not digested, so faecal energy is removed to get digestible energy
- Some of this is lost as methane, in urine = metabolizable energy is the energy the animal can utilise
- Utilised for lactation, maintenance, pregnancy and growth
- At each step, heat is liberated and so it is metabolisable energy for each function minus the heat produced
What are the ME requirements of cattle?
Beef 65MJ metabolisable energy/day
Dairy 5MJ metabolisable energy/L
What is the conversion efficiency, k, and what is it dependent on?
- The efficiency with which ME is converted to net energy
- Dependent on – use of energy, quality of feed, animal production level
How does quality of diet affect conversion efficiency?
Fibrous feeds are more difficult to digest – more energy is used to make the energy available
How is APL calculated? What happens in APL is increased?
Animal production level/APL = total energy requirement / energy for maintenance
Increased APL = increased DMI = decreased gut transit time = decreased k
How does weight affect ME?
Weight loss/gain during lactation is more efficient than during the dry period
How is the protein content in crude protein calculated?
- Nitrogen x 6.25 = Protein content
- Does not tell you what type of protein it is, very crude measure
How is protein metabolised in cattle?
- RDP is degraded in the protein
- UDP travels through rumen and is digested in the small intestine
- Proportion of proteins that degrade is determined by time in protein which is determined by DMI
- Degrade into peptides and amino acids.
- Ammonia and proteins are built back up.
- Rumen microbes will utilise FME and amino acids and proteins to produce microbial proteins, which passes out of the rumen and is absorbed by the cow.
- Nitrogenous waste is recycled in the rumen, excreted in saliva and excreted by the kidneys.
- Excess ammonia is converted to urea in the liver and excreted by the kidney in the rumen.
What is rumen outflow rate?
- Slow outflow = increased digestion = increased RDP
- Outflow ~ VFI ~ APL
- Therefore increased APL = increased UDP
What may elevated urea be due to in cattle?
- Dehydration/hypovolaemia
- Renal disease
- Excessive CP in the diet
- Lack of FME in the diet
What is ERDP?
ERDP/effective rumen degradable protein – the amount of RDP actually available to rumen microbes
How are FME and ERDP linked?
- The ratio of FME:ERDP is critical in achieving efficient protein metabolism
- Can’t utilise ERDP if they don’t have an energy source
What does every 1MJ of FME produce?
10-11g of MCP/microbial crude protein, as long as there is enough FME to utilise this ERDP. Exact amount depends on the APL.
1kg of organic matter yields – 200g of MCP
What are the problems with the MP system?
- Underestimates requirements – 10%
- Individual AAs not considered, such as lysine and methionine
How are calves fed from birth to weaning?
- Consistent preparation of milk replacer
- Consistent timing
- Consistent presentation - cleanliness, concentration, consistency
- Ad lib, clean fresh water
- Roughage - stimulates rumen development
How is compound feed fed to calves?
- Crude protein - for growth and rumen development, which cannot be done on just straw as rumen may impact with straw and won’t be enough microbes
- Constant free access
- Aim for 1Kg/day by weaning
When are beef and dairy cattle weaned?
Weaned from 6-10 months in beef and in dairy weaned 6-8 weeks
Why might beef cattle be fed cereal/barley?
Just grain, will produce a lot of acid and without reasonable fibre will get ruminal acidosis. Need to supplement with proteins. Diet allows calves to be finished at a young age but is not the most efficient
What are the characteristics of cereal beef systems?
Cereal has highest DWG, feeds the most concentrates and finishes earliest
How does nutrition affect profitable management?
- Tight calving pattern – calve and feed as a batch
- Minimising feed costs (max production from grass)
- Body condition score management – low in spring, higher in winter
What are the target condition scores throughout the year of suckler cows?
Spring = 2
Summer = 2.5
Autumn = 3
Winter = 2.5
How does the BCS of dairy and beef cattle differ?
Unlike dairy cows, who are kept at constant BCS to eliminate risk of metabolic disease, beef herds have their ability to change BCS is utilised to minimise the cost of food.
If winter forage is given with silage alone, what happens to calves?
Silage alone with cause chondroplastic dwarfism in calves
What are the advantages of total/complete mixed rations?
- Increased DMI = increased yield
- Improved rumen function and decreases acidosis
- Cheaper – straights not concentrates
What are the disadvantages of total/complete mixed rations?
- Capital investment, storage and time
- Fat cows
- Slow entry to parlour
- Cash flow
What are the advantages of multiple rations in a group?
- Increased precision
- Avoids thin and fat cows
- Decreased standing times helps with lameness
What are the disadvantages of multiple rations in a group?
- Increased bullying
- Increased complexity - multiple groups, diets
- Increased time
What does feeding to yield mean in dairy cattle?
As milk yield increases and decreases, alter rations to follow the same curve
What is flat rate feeding?
Everything gets the same, so is easy, but can end up overfeeding and underfeeding certain cows
What are the advantages of feeding to yield?
- Simple
- Avoids overfeeding and underfeeding
What are the disadvantages of feeding to yield?
- Increased acidosis
- Increased metabolic stress
- Streep decline after after
What are the advantages of flat rate feeding?
- Simple
- Decreased metabolic stress
- Decreased acidosis
What are the disadvantages of flat rate feeding?
- Risk of underfeeding and overfeeding
- Increased BCS loss around peak
What is stepped feeding?
Compromise between feeding to yield and flat rate
How much dry matter intake should dry cows get?
2% bodyweight or less
10-15kg/day
What are the physiological factors that decrease dry matter intake?
Increase calf size
Increased BCS as this causes decreased appetite
What are the management factors that decrease dry matter intake?
Decreased feed access and palatability
What is the BCS aim at drying off and calving?
2.5-3
What is the effect of BCS being above 3 at calving?
- Increased calving difficulties
- Decreased DMI and decreased yield and so increased risk of negative energy balance
What does BCS loss in the dry period cause?
Causes decreased fertility as follicles develop through the dry period, takes 60 days, so is being influenced by cow’s nutrition way before oestrous or service
What is energy requirements of dairy cows at drying off and near calving?
At drying off ~(65 + 15) = 80MJ/day
Near calving ~(65 + 45) = 110MJ/day
What are the protein requirements of dairy cattle at drying off and near calving?
At drying off (300 + 100) = 400g metabolisable protein/day
Near calving ~(300 + 190) = 490g MP/day
What does digested undegraded protein in the dry period cause?
- Foetal growth
- Increased milk yield + quality (due to increased protein content)
- Increased fertility
What does excessive rumen digestible protein/crude protein cause?
Increased down cows
What are the aims of drying off?
- Recovery from lactation
- Maintain condition
- Restrict energy density
- Rumen recovery
- Stabilise mineral/vitamin status
- Calf growth
What are the aims at transition?
- Fitness for lactation
- Maximising DMI
- Metabolic health
- Prevention of hypocalcaemia
- Rumen acclimatisation
- Maintain condition
- Calf growth
What are single ration diets and what is the problem with these?
Very high in fibre with/without shorter dry periods to offset cost, not very good at acclimatising the rumen
What are the advantages of single rations?
- Avoids sudden change in diet during early dry period
- Maintain DMI better
- Allow improved energy balance
- Reduced risk of LDAs
What is the effect of DMI on calcium requirements?
Increased DMI cause increased Ca requirement as some is lost and not absorbed with increased gut movement with eating more
10kg DMI = 15g/day
25Kg DMI = 30g/day
What is the maintenance calcium requirement in lactation?
2g per litre of milk
Explain how calcium deficiency causes calving complications and LDAs.
- Most of the calcium in a cow is in the bones so cows are not calcium deficient in the same way you would you copper deficient.
- There is a sudden demand surge that must be resorbed from bone.
- If this cannot be done, you get relaxation of smooth and skeletal muscle – effects of gut, uterus, skeletal muscle.
- If uterine tone is affected, there is calving complications, more likely to be infected.
- Increased incidence of LDAs and cows won’t be able to eat as much so DMI decreases which exacerbates the problem.
How is milk fever prevented in dairy cattle?
- Calcium restriction to kickstart normal calcium homeostatic mechanisms, so this why we do not feed lots of grass in the dry period as it contains a lot of calcium.
- Magnesium supplementation
- DCAD/DCAB manipulation
What are the feeding strategies used to restrict calcium to prevent milk fever?
- Grass/grass silage high in calcium concentration
- Dilute calcium concentration by increasing straw in ration
- Tightly stock transition cows if at grass
How does magnesium affect calcium in dairy cattle?
Mg is a cofactor in mobilising calcium from bone, so cows low in Mg will be less able to mobilise calcium
What are the feeding strategies to supplement magnesium to prevent milk fever?
- MgCl2 in TMR or drinking water
- Can affect ration palatability
- Will influence DCAD
What is the consequence of diets with low DACD/
Diets with low DCAD include mild metabolic acidosis due to difference in charge (not amount of each)
What are the consequences of metabolic acidosis?
- Increased vitamin D3 is activated per unit PTH
- Target tissues (especially bone) are more sensitive to PTH and 1,25(OH)2D3
- More rapid mobilisation Ca from body reserves around calving
What are the disadvantages of fill DCAD diets?
- Expensive
- Unpalatable
- Very soluble - wash out in rain
- Relative pH instability in the face of variable DMI