PRL-release inhibition could be used as a tool to reduce milk production at drying-off and to stimulate involution. Quinagolide caused a transient depression of feed intake as a side effect. The BW at the end of the experiment was not affected by treatment and was similar to that at the start of the experiment for both groups In the current experiment, Researchers did not find no effects or indicators on mastitis

1. Effect of prolactin-release inhibition on milk production
and mammary gland involution at drying-off in cows
Ollier S, Zhao X, Lacasse P.
By: Faisal A. Alshmairy
Advisor: Dr.Moez Ayadi
Journal of Dairy Science-
Jan 2013

2. A dopamine agonist used to treat elevated levels of prolactin
Somatic cell count
Bovine Serum Albumin
Is the main constituent playing a buffer role in the udder
Is a component of the natural protection systems of animals, with bactericidal
& iron-binding properties
Is a Enzyme: Matrix metalloproteinase
Intra mammary Infection
Prolactin
Concepts
&
Abbreviations
Quinagolide
SCC
BSA
Citrate
Lactoferrin
MMP
IMI
(PRL)

3. • The lactation cycle of the dairy cow requires a dry period for optimal milk
production in the following lactation.
• Period is critical for mammary gland remodeling, the cow is highly
susceptible to new (Intra mammary Infection) IMI during the early dry period.
• After drying-off, although milk is not being removed, the mammary gland
temporarily continues to synthesize milk, which accumulates in the udder.
• The resulting increase in mammary pressure may cause leakage of milk via the
teats, allowing microorganisms to gain entry into the mammary gland.
INTRODUCTION

4. Beginning of Involution
low concentrations of natural protective factors: Immunoglobulins Lactoferrin
Mammary Gland Secretions Contain
Beginning of Involution
High Concentrations Of: Fat Casein Lactose Citrate
Mammary Gland Secretions Contain
-
+
Which can interfere
with the defense
capacity of the
gland & provide an
excellent medium
for bacterial growth
INTRODUCTION

5. • Once involution is completed, within 30 d after cessation of milking, the
mammary gland becomes much more resistant to new IMI because of a low
fluid volume in the udder and a medium unfavorable for bacterial growth.
• With increasing milk production, drying-off has become a challenging
period for the dairy cow.
• That the risk of IMI at calving increases by 77% for every 5 kg of milk
produced above 12.5 kg when milking is stopped.
• Common to dry off cows that are still producing 30 kg/d, it is important to
develop strategies that reduce milk production before drying-off & to hasten
mammary gland involution.
INTRODUCTION

6. Metabolic
Stress
Drastic reduction in feed
supply
in the days that precede
drying-off.
IMI
???
Intermittent Milking,
but its association with a
reduction in IMI at calving has
not been clearly proven
Method commonly used to reduce milk production is:
New
Decreasing the lactogenic
signals driving milk
production.
@agrfaisal

7. • Prolactin (PRL) is a hormone known to be mammogenic & lactogenic in
both monogastric & ruminant mammals.
• Inhibition of PRL secretion by quinagolide gradually decreases milk
production of cows in early lactation → suggesting also a galactopoietic
role of PRL in cows.
• This approach has never been investigated in late-lactation cows.
INTRODUCTION
1

8. OBJECTIVE OF THIS STUDY:
Assess the effect of inhibition of PRL release by quinagolide on milk
production just before drying-off & on concentrations of involution
markers in mammary secretions after the last milking

9. According to:
Milk yield, SCC, & Parity.
From 4 d before drying-off to 3 d
after (Quin)
Design of experiment

10. Fed ad libitum a late-lactation diet containing After drying-off, the cows were fed
a dry-period diet containing: DM:-
The feeding

11. Feed intake was recorded daily throughout the experiment, Cow’s BW was determined at the start & end of the experiment.
Before drying-off, the cows were milked twice daily, at 08:00 & 20:30 h, & milk yield was recorded at each milking
during the last 2 week.
Milk samples were collected at the A.M. milking on the last 5 days before drying-off (d −5 to d −1).
After the last milking, each quarter was treated with dry-cow therapy containing cloxacillin benzathine.
Mammary
secretions
60 mL - manually
1 quarter at 08:00
1d 3d 5d 7d 10d 14d
To measure SCC & determination of BSA, Lactoferrin, citrate, Na+, & K+ concentrations, and gelatinase activity.
Taken just before collection of milk and mammary secretions on
-5d -2d -1d 1d 3d 5d 7d 10d 14d

12. min. relative to the start of milking
All blood tubes (without additive) were left for approximately 2 h at room temperature
for clotting before centrifugation (1,900 × g, 4°C, 15 min).
Then, the serum was stored at −20°C until determination of PRL concentration.
-4 -3 -2 -1 0 1 2 3
4 day preceding drying-off 3 day after drying-off
start of drying-off

13. PRL concentration
@agrfaisal
Somatic cell count
(SCC) @agrfaisal
Concentration of BSA
in Milk. @agrfaisal
Concentrations of
Lactoferrin & Citrate
in Milk
Na+ & K+
Concentrations in Milk
@agrfaisal
Statistical Analysis
Data were analyzed by ANOVA using the MIXED procedure of SAS
Milk Samples
Concentrations of
Lactoferrin & Citrate Na+&K+ BSA SCC Gelatinase
Activity

14. RESULTS

15. Figure 1. Basal concentration of prolactin in the blood of cows injected twice daily with water (control,—▄—; n=8) or quinagolide
(2 mg per injection, - - □ - -; n = 8) from 4 d before drying-off (symbolized by an arrow) to 3 d after. On d −4, blood samples were taken before the first injection.
Data are presented as least squares means ± SEM, and significant differences between the treatments are indicated as follows: *P< 0.05, **P< 0.01, ***P< 0.001.
Injections
Basal concentration of prolactin in the blood
Figure 1.
Control
Treatment

16. Figure 2. Milk production during the last 10 d of lactation in cows injected twice daily with water (control, - ▄ -; n = 8) or quinagolide
(2 mg per injection, -- □ --; n = 8) for the last 4 d preceding drying-off.
Data are presented as least squares means ± SEM, & significant differences between the treatments are indicated as follows:*P < 0.05, ***P < 0.001.
Injections
Milk production during the last 10 d of lactation
Figure 2.
Control
Treatment

17. Figure 3. Somatic cell count in milk and mammary secretions of cows injected twice daily with water (control, - ▄ - n = 8)
or quinagolide (2 mg per injection,--□--; n=8) from 4d before drying-off (symbolized by an arrow) to 3d after.
On d −4, milk samples were collected before the first injection.
Data are presented as least squares means ± SEM of log10-transformed values.
Significant differences between the treatments are indicated as follows: ***P < 0.001.
Injections
Somatic cell count in milk & mammary secretions
Figure 3.
Control
Treatment

18. Figure 4. Concentration of BSA in milk and mammary secretions of cows injected twice daily with water (control, -▄-; n = 8) or quinagolide
(2 mg per injection, --□--; n =8) from 4 d before drying-off (symbolized by an arrow) to3 d after.
On d −4, milk samples were collected before the first injection. Data are presented as least squares means ± SEM, and significant differences
between the treatments are indicated as follows: **P < 0.01.
Injections
Concentration of BSA in milk&mammary secretions
Figure 4.
Control
Treatment

19. Figure 5. Citrate: Lactoferrin molar ratio in milk and mammary secretions of cows injected twice daily with water (Con. -▀- ; n = 8)
or quinagolide (2 mg per injection, --□--; n = 8) from 4 d before drying-off (symbolized by an arrow) to 3 d after.
On d −4, milk samples were collected before the first injection.
Data are presented as least squares means ± SEM of log10-transformed values.
Injections
Citrate: Lactoferrin molar ratio in milk & mammary secretions
Figure 5.
Control
Treatment

20. Figure 6. Matrix metalloproteinase-2 (MMP-2) level in the milk and mammary secretions of cows injected twice daily with water
(control,-▀-, solid line; n=8)or quinagolide(2mg per injection,--□--;n=8) from 4d before drying-off(symbolized by an arrow)to3d after.
On d −4, milk samples were collected before the first injection.
Data are presented as least squares means ± SEM of log10-transformed values.
Injections
Control
Treatment
Matrix metalloproteinase-2
Figure 6.

21. • PRL-release inhibition could be used as a tool to reduce milk production
at drying-off and to stimulate involution.
• Quinagolide caused a transient depression of feed intake as a side effect.
• The BW at the end of the experiment was not affected by treatment and
was similar to that at the start of the experiment for both groups
• In the current experiment, Researchers did not find no effects or
indicators on mastitis…
CONCLUSION

22. Quinagolide
@agrfaisal
Thank you
for the care & attention