Cattle Nutrition Flashcards
What is the ratio of Primary: Secondary rumen contraction?
What is each one followed by?
2 Primary: 1 secondary
Followed by regurgitation
How much DMI in % does a lactating cow need to eat per day?
4% (30-50 litres per day)
What does microbial fermentation of carbohydrates produce?
Volatile Fatty Acids (VFAs)
Carbon dioxide
Methane
How are VFAs produced and used?
What happens to proprionate?
Produced by microbial fermentation of carbohydrates
Absorbed across rumen wall
Enter Krebbs cycle to produce energy
Proprionate goes into glucose synthesis to produce milk
What is the target BCS loss for early lactation?
0.5-1 BCS
1 BCS = 50kg
How much energy is required (MJ) for maintenance?
How much energy is required per litre of milk?
65-70 MJ
5 MJ/litre milk
How is protein degraded in the rumen?
It is fermented in the rumen
Broken down into ammonia
Turned into microbial protein (by microbes)
Digested in abomasum and SI
What happens if rumen microbes don’t receive enough energy for protein synthesis?
Ammonia is absorbed across the rumen wall
High urea in the blood
What is the DMI (kg) in the dry period?
What is the danger level?
12-14kg
< 11kg/cow
Which type of silage has the highest ME?
What about protein, starch and fibre content?
Maize silage
Low protein, high starch (FME), poor long fibre source (short + pulverised)
Describe these feeding systems for lactating cows: Traditional TMR "Hybrid" Buffer feeding
Traditional: - Silage at barrier and cake in parlour - Grazing in summer and cake in parlour Total Mixed Ration: - All food at barrier, 24 hours a day, ad lib "Hybrid": - Partial mixed ration at barrier - And cake in parlour Buffer feeding: - TMR supplement to grazing in the summer
What is the disadvantage of a “Hybrid” feeding system for lactating cows?
Risk of SUBSTITUTION
Cow eats more concentrate in parlour, will eat less forage in barrier
Reduced long fibre intake
Risk of SARA (reduces DMI)
What is BHB (Beta-hydroxybutyrate) an indicator of?
Negative energy balance
Subclinical ketosis
How many days is the calving index?
How many days is the dry period and the lactation period?
370-400 days
60 days dry period
305-340 days lactation period
What is the transition period?
3 weeks before to 3 weeks after calving
What is the periparturient period?
Period immediately before and immediately after calving
What are the 3 requirements for cows towards the end of the dry period and the start of lactation?
What is the main problem with this?
- Foetal growth
- Mammary development
- Milk production
DMI is reduced! Cows are entering a period of NEB
What is the main energy source at the start of lactation?
How is this produced?
Glucose Ruminal fermentation Produces VFAs: Propionic acid (form of proprionate) Absorbed across rumen wall Enters Krebs cycle for gluconeogenesis
What is the main energy reserve used in NEB?
Adipose tissue (NEFAs released)
What is “Fatty liver”
Reduced hepatic function
Due to excess NEFAs converted into triglycerides and stored as fat droplets
What are 3 problems with obesity in dairy cows?
- Accumulation of fat in the liver reducing hepatic function, “fatty liver”
- Type 2 diabetes, decreased response to insulin
- Proinflammatory cytokines from adipose tissue cause inflammation in liver
Which type of fat distribution do Holsteins tend to have?
Visceral fat “hidden”
When should you check the BCS in dry cows?
At drying off
Halfway through dry period
At calving
Early lactation
What are the risks of overfeeding during the dry period?
- Major increase in visceral fat (little increase in CS)
- Decreased immune function
- Risk factor for metabolic syndrome
What is the traditional feeding regime for the dry period?
Far-off group (5 weeks)
- Low energy/high fibre
Close-to group (last 3 weeks)
- Transition diet
What is a typical early dry period ration?
Grass (densely stocked)
Straw (4-5kg per day)
What are two types of transition diet?
- High yield TMR diluted with straw
2. Silage, straw + dry cow concentrate
What is the “Keenan diet”
What is the advantage of it?
What are two essential components for it to work?
One diet for whole dry period
Reduces social stresses, no moves
1. Adequate feed space (as cows must eat a lot)
2. Chopped straw
What BCS do you want cows to be calving at?
2.5-3.0
How long does it take for the ecosystem of microbes in the rumen to adapt?
3 weeks
How does rumen acidosis cause liver abscesses?
What type of cattle is this common in?
Increased acid production causes rumenitis, allowing bacteria into the hepatic portal system and they enter the liver
Barley beef and Feedlot cattle
What is normal rumen pH
What is rumen pH in SARA?
What is rumen pH in acute ruminal acidosis
6-7
Below or equal to 5.7 (5.5 in USA)
< 5
How does low rumen pH affect digestion?
What clinical signs will be evident and why?
Reduces efficiency of digestion
Osmotic diarrhoea: Due to undigested particles
Fibrin casts in faeces: Due to colonic acidosis
What are the three main effects of SARA?
- Reduced DMI
- Reduced digestibility (reduced energy intake from diet, NEB)
- Immunosuppression (disease susceptibility)
How can SARA cause endocarditis?
Causes rumenitis, damaging rumen wall and allowing bacteria into bloodstream
What would you see in faecal sieving in SARA?
- Undigested grain
- Long fibre (>1/2”)
- Mucus casts (indicate colon inflammation from secondary digestion - hindgut fermentation)
Which cows do you select for pH sampling for SARA?
What is a positive herd diagnosis?
Cows calved 14-21 days (assess transition + early lactation management)
Cows calved 60-80 days (assess overall diet quality)
Diagnosis: 2 cows from EITHER group are below threshold pH
What length should fibre be in a TMR?
What is the maximum concentrate: fodder ratio?
1” - 4”
60: 40 (max, ideally more fodder)
Name two causes of Acute Ruminal Acidosis
- Barley poisoning (e.g. barley beef, sudden introduction of lots of grain)
- Pet sheep pre-lambing (increased concentrate +/- restricted fodder intake)
What is the treatment for subacute ruminal acidosis?
What is the treatment for peracute?
Subacute: oral antacids (Mg hydroxide or carbonate) + hay
Peracute: Rumenotomy, sodium bicarbonate i/v + fluids
