Whether buffalo and cows can breed depends entirely on the specific species involved. This question often leads to misunderstandings due to the common use of the term “buffalo.” The ability for two distinct species within the Bovid family to hybridize successfully is dictated by how closely related their genetics are. Some interspecies crosses produce viable offspring, while others are biologically impossible due to significant genetic divergence.
Clarifying the Term “Buffalo”
The term “buffalo” is commonly used to refer to three distinct groups of animals, only one of which is closely related to domestic cattle (Bos taurus or Bos indicus). The African Cape Buffalo (Syncerus caffer) and the Water Buffalo (Bubalus bubalis) are true buffaloes, but they belong to different genera than domestic cattle. The American Bison (Bison bison) is often incorrectly called the American Buffalo. The American Bison is the only one closely related enough to cattle to produce viable offspring. Bison and cattle are both classified within the tribe Bovini and share a relatively recent common ancestor.
The Successful Cross: Cattle and Bison (Beefalo)
The hybridization between domestic cattle and the American Bison has been successfully achieved, resulting in an animal known as a “Beefalo” or “Cattalo.” This cross began as early as the 1700s, driven by the desire to combine the desirable traits of both species. Ranchers sought the hardiness, disease resistance, and foraging ability of the bison with the meat quality and docility of cattle. The Beefalo breed is officially recognized by the American Beefalo Association as having 3/8ths bison ancestry and 5/8ths cattle ancestry. Backcrossing to domestic cattle is done repeatedly to stabilize the line and ensure commercially desirable characteristics.
Genetic Barriers and Chromosomal Differences
The success of the cattle-bison hybrid stands in contrast to the impossibility of breeding cattle with true buffalo species like the Water Buffalo or Cape Buffalo. The primary biological barrier lies in the difference in chromosome numbers, which must be similar for successful meiosis and development of a viable zygote. Domestic cattle and American Bison both possess 60 chromosomes, making their cross-species pairing highly probable. Water Buffalo have a diploid number of either 48 or 50 chromosomes, depending on whether they are the swamp or river type, respectively. This difference in chromosome number prevents the chromosomes from pairing correctly during fertilization, causing reproductive isolation. Attempts to hybridize domestic cattle and Water Buffalo show that resulting embryos fail to develop past the eight-cell stage, indicating a fundamental genetic incompatibility.
Hybrids and Fertility
Even in the successful cross between cattle and bison, the resulting first-generation hybrids, known as F1 crosses, experience reproductive constraints. This phenomenon is an example of Haldane’s rule, which states that in a hybrid cross, if one sex is sterile, it is almost always the heterogametic sex—in mammals, the male. First-generation female hybrids are generally fertile and can be bred back to either a bison or a cattle bull. However, the first-generation male hybrids are consistently sterile or sub-fertile due to the inability of the different parental chromosomes to pair properly during sperm production. Subsequent backcrossing of the fertile female hybrids to domestic cattle is necessary to dilute the bison genetics to a point where male fertility is restored.