Dairy Exporter July 2020

Page 73

STOCK BVD

BVD test identifies infective calves

N

ew evidence from a New virus’s transmission across the placenta. Zealand study supports the When fetal infection occurs before the use of Bovine Viral Diarrhoea development of a fully functioning (BVD) calf ear notch testing immune system, persistently infected (PI) to detect persistent infection (PI) cattle are born. A PI calf will always in calves at any age. Identifying carry the BVD virus and will never and culling these animals, who generate antibodies specific to remain carriers of the disease the virus because its immune throughout their lives, system does not recognise minimises the spread of the the virus as “foreign” at the disease and the unnecessary time of infection. PI cattle culling of acutely infected are the leading cause of new animals. acute and fetal infections BVD is a Pestivirus that owing to their shedding of Andrew MacPherson, IDEXX Medical Affairs Veterinarian. spreads rapidly and has been enormous amounts of the found in about 80% of New virus via all body fluids. Zealand’s dairy and beef herds. Its cost to Current estimates place the prevalence NZ dairy farmers is $127 million ($70,000 of PI animals in BVD-infected herds in per average herd). New Zealand at less than two percent, and The disease causes reduced fertility, identifying and appropriately managing abortion, congenital defects, reduced milk PI animals is the primary focus of BVD production and increases susceptibility to control programmes. other infectious diseases due to immune suppression, particularly in young calves, WHY IT IS ESSENTIAL TO TEST which can lead to increased calf deaths. NEWBORN CALVES AND HOW But voluntary control is entirely achievable TO DO IT through a community effort to identify Since the effects of BVD can look similar to and remove infected animals from dairy those of other diseases, knowing the farm herds. BVD status is crucial in the fight to achieve There are three types of infection – control. Comprehensive diagnostic testing acute, fetal, and persistent. plans are fundamental to making informed A first-time exposure to the virus in decisions on controlling and preventing naïve, susceptible animals results in acutely the spread of the BVD virus. infected (known as transiently infected BVD control consists of two critical or TI) animals that recover but shed low mechanisms that, together, break the levels of the virus. within-herd transmission cycle: the early Infected dams will be at risk of identification and removal of PI animals; causing fetal infections due to the and strict herd biosecurity to prevent the

reintroduction of the BVD virus from outside sources. Detecting PI animals is, and should remain, the primary focus for farmers working to remove BVD from their properties. Previous studies have demonstrated that an enzyme-linked immunosorbent assay (ELISA) test using a small bit of ear tissue (ear notch) is an accurate, economical, and feasible way of detecting PI calves in New Zealand. A 2019 research trial by Cognosco Animal Health in New Zealand was designed to assess the sensitivity and specificity of ear notch samples of calves analysed using a specific antigen ELISA test and real-time PCR testing at four time points after birth. The trial results demonstrated an economical breakthrough, said Andrew MacPherson, IDEXX Medical Affairs Veterinarian. “We now have the perfect test to focus our efforts on identifying only PI animals, saving unnecessary culling of acute animals and enabling farmers to maximise their return on the calves born each year. ” Adopting a simple and easily understood test for every calf born is a significant opportunity for the New Zealand dairy industry to control BVD voluntarily. Farmers’ willingness to test all calves to identify PI animals and remove them from their farms, combined with improved biosecurity, will deliver economic benefits for all farmers and lead to significant improvements in New Zealand’s BVD status.

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www.ezicalve.co.nz 73


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Articles inside

Subscribing to monitoring

2min
page 89

Feed additive against subclinical mastitis

2min
page 79

Spotting the Springer

5min
pages 86-87

Solving the Jigsaw of Wellness

5min
pages 82-84

App helps farmers improve in-calf rates

3min
page 88

Drought reduces profit on NARF

2min
page 85

Vet Voice: Mastering mastitis control

5min
pages 77-78

Rolling down cows safely

2min
pages 75-76

BVD test identifies infective calves

3min
pages 73-74

Balanced waterways policies but details to come

5min
pages 68-69

High-tech breeding yields genetic gain

8min
pages 70-72

Dairy farming with pride in Matakana

4min
pages 65-67

Equity partnership gains multiple awards

7min
pages 62-64

Embracing the 4 Rs of fertiliser

2min
page 57

Fertilising with irrigation

8min
pages 58-61

Faster, more accurate soil tests

4min
pages 54-56

Challenging season for organic dairy

4min
pages 52-53

Nitrogen cap a blunt instrument

5min
pages 49-51

Pasture + soils bring success

10min
pages 46-48

Beware selenium sales pitches

4min
page 39

Investment tips shared

9min
pages 32-35

Organic trace minerals improve production

15min
pages 40-45

A new veterinary book for cattle farmers

4min
pages 30-31

Testing key to metabolic problems

8min
pages 36-38

High productivity in a hidden valley

14min
pages 24-29

Global Dairy: Will UK farmers lose in US deal?

3min
pages 20-21

Are higher environmental standards critical to future exports?

12min
pages 14-17

Market View – Dairy holds its ground

2min
pages 22-23

DairyNZ: The view from the chair

6min
pages 18-19

Nialtor McKenzie finds the co-op unco-operative

3min
page 12

Carla Staples sees a good end to a tricky season

3min
page 13

Alex Lond experiences Gypsy Day with a cat

2min
page 10

Anne-Marie Wells tidies her office and goes paperless

3min
page 11
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