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Table 1 Definitions and values of model parameters

From: Modelling the spread of bovine viral diarrhea virus (BVDV) in a beef cattle herd and its impact on herd productivity

Parameters

Values

Definitions

Sources

ρ sex

0.5

Sex ratio

 

a, b

8.7, 6

Parameters of the gamma distribution used to calculate the next start of pregnancy

 

δ

0.035

Probability of twin birth

 

τ He

0.02

Probability of infertility for heifers

 

τ Co

0.08

Probability of infertility for cows

 

breeding_start

15th of March

Date of start of the breeding period

 

breeding_dur

[16 18 20]

Duration of the breeding period (in weeks)

 

weaning

1st October

Date of weaning

 

pasture_start

1st April

Date of start of the pasture period

 

pasture_dur

[29 32 35]

Duration of the pasture period (in weeks)

 

renewal_rate

[0.286 0.317 0.349]

Ratio heifers/cows

 

sell_period

[autumn winter spring]

Sell period of grassers1

 

size

[42 83 125]

Number of bred females2

 

μ Ca,bi

0.0225

Probability of mortality at birth of calves

 

μ Ca

0.000333

Mortality rate of calves (d-1)

 

intro_week

[(20 25 30) 27 40]

Week of introduction of PI animal(s)3.

 

ε

[0.95 1 1.05]

Level of numerical productivity expected by the farmer

 

μ P,bi

[0.06 0.0667 0.0733]

Probability of mortality at birth of PI calves

 

μ P

[0.0017 0.0019 0.0021]

Mortity of PI animals per day

[20]

ϕ MS

[0.006 0.00667 0.00733]

Trantion rate from state M to state S (d-1)

[21]

ϕ TR

[0.18 0.2 0.22]

Transition rate from state T to state R (d-1)

[22]

β T

[0.027 0.03 0.033]

Daily transmission rate for T animals

[9,23]

β P

[0.45 0.5 0.55]

Daily transmission rate for PI animals

[9,24]

\( {\beta}_b^P \)

[0.09 0.1 0.11]

Daily between-group transmission rate for PI animals

[9,25,26]

α Ra

[0.72 0.8 0.88]

Abortion rate due to infection in early pregnancy

[22,27]

α Rb

[0.18 0.2 0.22]

Abortion rate due to infection in mid-pregnancy

[28,29]

η X

 

Probability of giving birth to a calf in state X if infection in mid-pregnancy and no abortion

[24,28-30]

η P

[0.875 0.9375 1]

  

η M

[0.0625 0.03125 0]

  

η R

[0.0625 0.03125 0]

  

K ext

0

Risk of virus introduction on pasture

 
  1. Nominal values are in bold. Other values are the ones tested in the model sensitivity analysis.
  2. 1In the reference scenario, grassers were sold at the three periods: 45% in autumn, 45% in winter, and 10% in spring.
  3. 2Bred females are heifers and cows, with: 42 = 10 heifers + 32 cows, 83 = 20 heifers + 63 cows, 125 = 30 heifers + 95 cows.
  4. 3In the first case, 3 PI animals were introduced successively in weeks 20, 25, and 30. In the two other cases, a single PI animal was introduced.
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Veterinary Research

ISSN: 1297-9716