ANSC 322 - Exam 3 - Udder Health article

Who is the author of the article “Udder health is an animal breeding success story”?

Chad Dechow

What is Chad Dechow’s professional role?

He is an associate professor of dairy cattle genetics at Penn State University.

According to Dechow, what two trends stand out in the annual DHI (Dairy Herd Improvement) statistics?

A steady increase in milk, fat, and protein yields and a decline in somatic cell counts.

Why is the combination of increasing yield and lower somatic cell counts particularly impressive, according to the article?

Because there is an antagonistic genetic correlation between high milk yield and mastitis risk, so one would expect more mastitis as yield goes up.

What udder trait is most strongly genetically correlated with mastitis resistance, Dechow argues?

Udder depth — udders held close to the body (shallower) are less susceptible to mastitis

Besides udder depth, what other udder conformation trait is mentioned as favorable for udder health?

A strong fore udder attachment

What historical evidence does Dechow cite to support that good udder conformation has helped limit mastitis?

He references a 1994 Swedish study: when Sweden imported North American Holstein semen, milk yield rose but mastitis rates did not — attributed to the superior udder conformation of those Holsteins.

When was “udder composite” first included in the Net Merit index, according to Dechow?

In 2000

What newer genetic evaluations does Dechow mention that help assess udder health more directly?

Somatic Cell Score (SCS) evaluations and “productive life” (PL) evaluation

Does Dechow suggest that udder health breeding progress is “done,” or are there further improvements possible?

He argues further improvements are possible, especially via direct mastitis PTA (Predicted Transmitting Ability) using health data.

According to Dechow, what is lacking in the U.S. that prevents the widespread use of direct mastitis breeding values?

A nationalized cow-health database (like the ones in Nordic countries) to reliably estimate mastitis-resistance PTA

Besides genetics, what other factors does Dechow credit for improved udder health?

Management improvements, milking routines, housing strategies, and economic incentives (like quality bonuses).

How have the average test-day somatic cell counts changed from 1995 to the time of Dechow’s writing?

They declined from over 300,000 (cells/mL) in 1995 to just over 200,000

Despite selection pressure for higher milk yields, what risk did Dechow mention regarding udder conformation?

That udders might become deeper or more loosely attached, which would increase the risk of mastitis and injury.

In Dechow’s view, whose efforts deserve credit for the improvements in udder health?

It’s a team effort: breeders (for udder conformation), geneticists (developing SCS and health traits), farmers (management), and industry incentive systems.