Feeding of dairy cows during lactation (A16) and in the dry period (A18). Compounds having advantageous effect on rumen (A17) Flashcards
Life cycle of dairy cows (365 days)
Cycle - period between calvings. Lactation = 305 days
1. Early lactation ~ 100 days
2. Mid lactation ~ 100 days
3. Late lactation ~ 100 days
4. Dry period ~ 60 days (drying off - 7th month of gestation)
Dry period is the most important part of the cycle for dairy cow. Goal is to abruptly end the milk secretion and close the teat canal. Preparing cow for the ext lactation.
Ideally cow calves every 12 months
Feeding of dairy cows in the 1st phase of lactation
- from calving to 12-13 weeks postpartum
- BCS at the calving (3-3,5 optimum but better 3,5 for 1st time calving cows because its more stressful)
- peak lactation
- energy balance! Mobilisation of body fat —> bw loss
- after calving appetite is only 50-70% of maximum intake because during dry period growing fetus reduces rumen volume as well as density and size of rumen papilla (how ??)
- it takes time for rumen to stretch and papilla to regrow (10-12 weeks PP) then appetite is gonna reach its maximum
- more severe NEB -> more BW is lost -> dairy cows have reduced fertility, reduced conception rate
Body weight loss in dairy cows during first phase of lactation
- bw loss -> reduced fertility, reduced conception
- maximum is ok to lose 1 BCS unit (= 45-50 kg)
- rate of daily weight loss must not exceed 1 kg per day !
- if weight loss > 1 kg/day, then excess amount of ketone bodies is produced —> KETOSIS
Background of UNsuccessful insemination of dairy cow
- successful ovulation of dominant follicle depends on LH secretion
- in NEB LH secretion is inhibited because low blood glucose level inhibits hypothalamic GnRH secretion
- additionally, low blood glucose -> low insulin -> decreased ovarian energy -> proliferation of granulosa cell is inhibited as well as steroid synthesis
- sensitivity of LH receptors sensitivity is decreased because of lack of insulin growth factor (IGF-1)
- growth hormone release is induced (by decreased insulin ???) -> GH stops follicular development
- also GH has lipolytic effect, increasing concentration of non-esterified FAs (NEFAs) -> CCK increases (cholecystokinin) -> appetite decreases -> blood glucose level decreases
When can dairy cows be inseminated?
- NEB and BW loss must be lost ! for formation of dominant follicle
- cows can be inseminated between 60-90 days PP
Key points of feeding of dairy cows in the 1st phase of lactation
- concentrate : forage = 60:40
- DMI ≥3% of BW (concentrates are rich in DM)
- CF requirement is on lower threshold (≤18%) (normal is 18-23%) because less amount of forage is fed
- Protein balance (PB) is +100- +250 (max +300)
Feeding of dairy cows in the 2nd phase of lactation
- week 13-27/28
milk production gradually declines - energy balance is zero
- bw is constant
- concentrate:forage = 50/50
- PB: slightly positive (0-100)
Feeding of dairy cows in 3d phase of lactation
- 28 weeks - 7 months of pregnancy
- milk production declines (drying off)
- energy supply is important so body can build up reserves for next lactation
- energy balance positive
- BW: weight gain, setting up body condition
- concentrates : forages = 40 : 60
- PB is between 0-100
What is special about cows in 1st and 2nd lactation?
- cows in 1st lactation should get +20% of feed during 2 and 3 phases of lactation
- cows in 2nd lactation should get +10% of feed during 2 and 3 phases of lactation
Because they can’t reach adult BW until 3d lactation (5 years age)
Summary of feeding of dairy cows in different lactation phases
Possible improvement of energy status in dairy cows
- maximised DMI -> 3 meals/day
- digestible NDF (neutral detergent fiber) (low lignin content)
- high proportion of cracked grains in corn silage -> starch digestibility upppp
- max concentrate intake + molasses + sugar beet pulp
- rumen-protected glucose
- rumen-protected fat
- drenching
Compounds for drenching with advantageous effects on rumen function and metabolism
- Ca-propionate (will enter GNG, reduces risk of ketosis, reduces risk of hypocalcemia)
- propylene glycol, glycerol (will be converted to propionate -> GNG)
- yeasts (stabilise pH, improve DMI of fresh cow)
- buffers (to reduce probability of acidosis) (sodium carbonate + magnesium oxide)
- hepatoprotective subsctances (methionine, niacin, choline)
- dietary CAB (cation-anion balance) (ammonium chloride)
How long is the dry period? When ? Goal?
- 60 days
- most important period in dairy cow cycle
- cows should be dried off at the 7th month of gestation period
- goal: abruptly end milk secretion and seal teat canal asap
- preparation for next lactation !
Key points of feeding in dry period
- no milk production
- rapid fetal development (70% of development happens in dry period) -> energy requirements increases !
- feeding intensity: 1,2 - 1,3
- goal: maintenance of body condition and avoid obesity
- smaller daily ration (comparing to lactation period): digestibility increases (food stays longer in rumen)
- length of the dry period should never exceed 60 days (to avoid obesity)
- if cow is overweight during calving -> more leptin produced -> inhibited appetite, lower feed intake, lower milk production, impaired fertility
How can we subdivide dry period?
- First 6 weeks - dry period
- Last 2 weeks - transition, close-up
Body condition scoring of dairy cows
5 point scale
