American Holstein Dairy Cattle and Their Erythrocytes

The Holstein dairy cow is a remarkable animal. It is singular in its milk production and its erythropoietic system is dissimilar from other mammals. The latter is viewed, at least in part, as special biology that promotes its unusual lactation.

The Holstein dairy cow is recognized as the single predominant most efficient, high volume producer of milk. It comprises 90% of America's 9 million dairy cows. The United States maintains more dairy cows than any geographic region with the exception of the European Union. An average Holstein cow produces 23,000 pounds of milk (roughly 2,800 gallons) each lactation or milking cycle (the total milk production associated with the delivery of one calf). This yield is the result of generating 75 pounds (9 gallons) of milk per day. American Holsteins are distributed in ∼40,000 dairy herds with an average size of 240 cows. The family Holstein dairy farm has evolved from herds of 40 to 100 cows to milk-producing institutions that have 10,000 or more bovines.

Holstein cattle are ruminants and are therefore herbivorous, divided-hoofed, even-toed mammals that typically have a complex four-chambered stomach which allows the animal to gather a large amount of plant food at one interval and then chew and digest it later. The sequential stomach compartments are the rumen, reticulum, omasum, and abomasum. This digestive system is adapted to digest otherwise non-nutritive fibrous grasses and is the basis for some of the capability of the cow to generate the energy for extended lactation. Cud-chewing is discussed in the text.

Several readily identifiable features characterize the Holstein's erythropoietic picture. The erythrocyte count of the blood is high. It is consistently above five million Rbc per microliter and is typically between six and eight million/𝜇L. The cow's erythrocellular blood picture demonstrates quantifiable correlative alterations during specific periods of lactation. The size of the individual red cells of the Holstein breed is definitely small (∼40 fL). Unlike other mammalians the final maturation of the reticulocytes occurs in the bone marrow leading to an absence or an almost absence of reticulocytes in the blood. A notable cytologic feature of the Holstein is that its Myeloid/Erythroid ratio is predominantly normoblastic (an unusual condition in comparison with non-ruminant mammals such as the dog). The erythrocytes of Holsteins (and other bovines) maintain very low levels of 2,3-diphosphoglycerate.

The Holstein cattle of contemporary USA can be conceptually viewed as a circumscribed subgroup of the Holstein breed that may have evolved its own genetic imprint. The erythrocellular blood picture of American Holstein cattle has changed in the past 50 years. This is attributed to modifications in the genetic makeup of the breed, the environment in which the cattle are maintained, diet, and disease prevalence. According to the US Department of Agriculture, a typical Holstein cow in 2000 produced approximately threefold the mean quantity of milk that it generated in 1950.

The text includes breed history, veal, age-related matters, pregnancy, phylogeny, somatotropin, porphyria, Rbc life span and many Holstein species illustrations.