Upload
msd-salud-animal
View
728
Download
6
Tags:
Embed Size (px)
DESCRIPTION
MSD Salud Animal Salud Lechera
Citation preview
The dry period
The basics
The dry period
• What is a dry period?
• Why do we need a dry period?
• The physiology of lactation
• The ideal length of the dry period
• Dry period management
• Udder health
Lactation
What is the dry period?
Dry PeriodHalting of
milk removal
Calving
Non-lactating period
LactationCalving
Lactating periodTo ensure milk production, cows must calve regularly
Lactation
Why do we need a dry period?
To ensure high milk production
Pregnant; No dry period Milk Production
Not Pregnant; No dry period
Dry PeriodHalting of
milk removal
Calving
Non-lactating period
Calving
Lactating period
This is a lactation curveMilk yield declines during lactation
The Udder - Anatomy
Epithelial cells in the udder need renewal
Number of mammary epithelial cells and their secretory activity determine shape of lactation curve
Number or activity of mammary
secretory cells
Milk yieldNumber or activity
of mammary secretory cells
Milk yield
Epithelial cells continuously die and renew
Apoptosis (cell death)
New cellCapuco and Akers, 1999
10 cells 10-2+1 9 cells(1 new)
Decreased milk yield due to:Declining cell numbers
Decreasing secretory capacity
We need a dry period
Capuco et al., 2003
The dry periodThree stages
Colostrum FormationColostrum Formation
Steady StateSteady State
InvolutionInvolution
Apoptosis (cell death)
Cell renewal
Cell renewal
New cells start secreting
Physiological cycle of lactation
Lactation
300-400 days
Involution
Steady state
Colostrum formation
Old cellsNew cells
More milk after a 60 day dry period
Bachman and Schairer, 2003
A 60 day dry period is idealOptimal length to ensure high milk production
Kuhn et al., 2006
Heifers need a 60 day dry period
Pezeshki et al., 2009
* * *
* Significant difference 56d and 35 d (p<0.05)
Short 30 - 40 day dry period
Improved energy balance (Rastani et al., 2005)
Suitable for older over-conditioned cows (Pezeshki et al., 2009)
Less time for dry cows to ‘grow’
Less milk after calving:• Especially in heifers• May be compensated by more milk before calving
Increased complexity• Heifers need a 60 day dry period (Pezeshki et al., 2009)
No margin in case of early calving• Very low milk production after calving, culling
AdvantagesAdvantages
DisadvantagesDisadvantages
Short dry periods are riskyMain reason why few farmers have adopted short dry periods
gestation
280 days220 days
start dry period
Dry period may be shortened unexpectedly
• Exact moment of calving is uncertain
• Cows with twins calve early or abort
• Cow may be pregnant from an earlier insemination
Planning a dry period that is long
enough provides
safety margin
The dry period
Good management is essential success factor for high production in late lactation
Cow comfortHygiene
Feeding
Udder healthThe key for prevention lies in the dry period
0
20
40
60
80
100
120
140
-10 -5 0 5 10 15 20 25 30
Days relative to calving
Cases per 10.000 cow-days at risk
HeifersCows
Recharge of udder healthCure and prevention of blanket antimicrobial DCT vs no DCT
Cure averages 71-85%(Halasa et al., 2009a)
Prevention averages 39%(Halasa et al., 2009b)
The dry period
• What is a dry period?
• Why do we need a dry period?
• The physiology of lactation
• The ideal length of the dry period
• Dry period management
• Udder health
Course Assessment
• 10 questions
• 80% to pass
• More than one answer can be right
• Click Submit button after each question
• If you exit assessment, you will have to restart
• Cumulative score displayed at the end
Question 1Why is milk production declining after peak lactation?
• Because cows eat less• Due to a negative balance of renewal and
apoptosis of epithelial cells• Because the number of alveoli is decreasing• After peak lactation cows are managed
differently
Question 2Why do we need a dry period?
• To give cows a break• To ensure high milk production• To renew epithelial cells• To prevent mastitis
Question 3Name the three physiological stages of the epithelial cells during the dry period
• Stop milking, no milking, calving• Involution , Steady state, Colostrum formation• Apoptosis, Renewal, Secretion• Feeding, Hygiene, Cow comfort
Question 4Why is 60 days the ideal length for the dry period?
• It ensures high milk production after calving• It provides enough time for the three
physiological stages • Gives cows enough time to rest• Provides enough time for the teats to recuperate
from milking• It provides a safety margin for early calving
Question 5What are the advantages of a short dry period?
• Provides a safety margin for early calving• Cows have less time to grow fat• It could help preventing metabolic disease• It is good for heifers• Milk production decreases
Question 6Does age play a role in the ideal dry period length?
• Yes, older cows need a longer dry period• No, age doesn’t matter• Yes, heifers need a longer dry period than older
cows• Yes, heifers need a shorter dry period than older
cows
Question 7Is good management during the dry period important?
• Yes, it helps the cow reach it’s genetic milk production potential
• Yes, otherwise the dry cow treatment does not work
• No, cows get new intramammary infections anyway
• No, in the dry period, the cows do not produce milk anyway
Question 8Why do we need dry cow treatment?
• To cure existing infections• To prevent new infections• To prevent clinical mastitis after calving • To ensure the renewal of epithelial cells
Question 9What are the high risk periods for new infections during the dry period
• During the steady state period• Around calving• Before dry off• Just after dry off
Question 10What can we expect from a dry cow treatment?
• Prevention of 100% of new infections• Cure of all existing infections at dry off• Prevention of around 40% of new infections• A reduction of the incidence of clinical mastitis
after calving