A heifer or cow will generally have two or three groups of ovarian follicles-called waves-develop during a single estrous cycle (the range is one to four waves). During this phase, there is rapid growth of a dominant ovarian follicle and increased estrogen production.Ī follicle is a structure containing an egg, also called an ovum, and other cells that can produce estrogen. The follicular phase of the estrous cycle refers to the narrow period of time right before estrus (heat) and ovulation (release of the egg for possible fertilization). The Follicular Phase: Waves of Ovarian Follicles 1 Image cannot be reprinted in any other publication in hard copy or electronic form without written permission from Current Conceptions, Inc.) from Pathways to Pregnancy and Parturition, 3rd ed. (Figure used with permission from Current Conceptions, Inc. Note: E 2 = estrogen and P 4 = progesterone. The estrous cycle in cattle is complex and regulated by several hormones and organs (see Figure 1).įigure 1 -Phases of the bovine estrous cycle.
The age at puberty for some cattle breeds, such as Brahman, can be as late as 24 months.Īfter puberty, a heifer continues to have regular estrous cycles every 21 days (the normal range is every 18 to 24 days). Dairy heifers tend to reach puberty earlier, at 9 to 12 months, whereas beef heifers tend to reach it a bit later, at 13 to 15 months. Heifers fed an appropriate diet will generally reach puberty between 9 and 15 months of age. The age at puberty is influenced by genetics, nutrition, and body weight. This understanding is also critical when using a drug regimen to control and synchronize estrous cycles in cattle.Ī heifer has her first estrus, or heat, at puberty. Normal Estrous Cycle in CattleĪ good understanding of the normal estrous cycle in cattle can help producers address reproductive challenges in both heifers (young female dairy or beef animals that have not yet had their first calf) and cows (female dairy or beef animals that have had at least one calf). Estrus is commonly called “heat.” Estrous is an adjective used to describe things related to estrus, such as the behaviors associated with estrus (estrous behaviors) or the period from one estrus to the next (estrous cycle). Estrus is a noun and refers to the short period in which a cow is sexually receptive and will stand to be bred. With only a one letter difference, the words “estrous” and “estrus” look and sound similar, but there’s an important difference.
Table 1-Available FDA-Approved Drugs to Control and Synchronize Estrous Cycles in Cattle.Estrous Control and Synchrony in Cattle.
0 kommentar(er)
