The four main dairy breeds - Holsteins, Jerseys, Ayrshires and Guernseys - vary in terms of live weight, milk yield and milk composition, but the variations within a specific breed are similarly large.
Holsteins have distinctive markings, typically black and white in colour although red and white also occur. It is a strong and heavy cow ranging from 550 to 750 kg, with high milk yield levels, averaging about 8550 kg in a 305 day lactation period (average 28 liter/day). Average milk fat levels are between 3.0% to 4.2% while protein content varies from 2.5% to 3.8%.
When feed is limited or of poor quality, the large framed Holstein cows will be less suitable. Generally, Holsteins are used in zero-grazing systems such as intensive housing systems or in open camps. They are fed a total mixed ration consisting of forages (hay, grass) and concentrates (bought-in pellets high in energy and protein) mixed according to milk yield or stage of lactation.
Because the Holstein breed is the largest dairy breed in the world, a large number of sires are available for artificial insemination. This means that it would be possible to maintain genetic progress for milk yield while improving traits like fertility.
Jersey cows are smaller, brown and white in colour and weigh 350 to 450 kg. Their milk yield is lower than that of Holsteins, being about 5000 kg per lactation although Jersey milk has higher levels of solids components; fat levels are 4.0% to 5.5% and protein percentages range from 3.5% to 4.5%.
Jersey cows have a mild temperament although Jersey bulls are known to be aggressive. Jerseys are generally used in a pasture-based system because of their good grazing ability while requiring smaller amounts of concentrates because of lower milk yield levels.
Ayrshires, originally from Scotland, are strong robust animals with well-attached udders. Their coat colour varies from light to deep red/brown combined with white. The live weight of Ayrshire cows ranges from 400 to 600 kg.
Milk yield levels and fat and protein percentages are intermediate between Holsteins and Jerseys. Their milk fat particles are well dispersed in their milk, giving the milk a sweet taste and silky texture.
Guernseys are medium-sized yellow to reddish-brown cows ranging in live weight between 400 to 550 kg. Guernseys are efficient converters of feed to product and can produce high-quality milk while consuming 20 to 30% less feed than larger dairy breeds.
Guernseys reach reproductive maturity early and can calve at 22 months - an early return on investment. Guernseys calves are big at birth, which are easy to rear yet with minimum of calving complications. The milk yield and milk composition (fat and protein levels) are intermediate between Jerseys and Ayrshires.