There is a certain set of production standards that should be required of cows within a herd to maximize profitability of a cow/calf operation. At the top of this list is that cows must have a marketable calf every 365 days. Seems as though this should be easily accomplished by the cow, but when you begin to add up the days in the production cycle and then look at the obstacles that must be overcome, it becomes much more complex. Therefore gaining an understanding of the annual production cycle will allow producers to manage their cow herd in a way to help them accomplish this production standard. The beef production cycle will be based on a 365 day model with a 283 gestation period. The cycle will be broken down into four phases (Figure 1).
Figure 1. The annual production cycle of beef cows.
Day zero of the production cycle is parturition (calving), with phase 1 continuing through the postpartum interval, and concluding with at the time of conception. This phase is the most critical in terms of setting the stage for the remaining four phases. With a 365 day production cycle, and 283 average gestation, the maximum length of time that this phase can continue is 82 days to allow the production of a calf yearly. Therefore cattle must be managed to successfully overcome their postpartum interval (the time from calving to conception). See: Management of Postpartum Anestrus in Beef Cows by University of Florida IFAS Extension. In addition, these females are lactating, which not only puts a nutritional stress on them, but they also are experiencing the suckling effect which causes an inhibition of reproductive hormones from the physical stimulation of suckling.
This phase begins with the maternal recognition of pregnancy, which takes place approximately 18 days following conception. During this phase the cow is responsible for maintaining three lives: her own, her calves, and the fetus. Through this phase lactation will continue, carrying over the increased nutritional requirements of the cow from phase 1.
Weaning initiates this phase and typically takes place at around day 200 of the production cycle. Thus a tremendous drop in nutritional requirements is seen during this phase. The removal of lactation reduces the required protein and energy needed to maintain the cow and mid gestation does not cause a sizable draw in requirements. This is the best phase both physiologically and economically to increase the body condition of cows. See: Basics of Body Condition Scoring (BCS) by SDSU Extension.
This is the final phase before parturition. Nearly 75% of total fetal grow takes place during this phase; Therefor, the nutritional requirements of the cow will increase from phase 3 to 4. In addition, with the growing calf, the physical room within the cow will be reduced resulting in a reduction in feed intake in the latter portion of phase 4.
As one evaluates the four phases of the production cycle, it becomes clear that the cow must be managed to successfully complete each phase in order to ensure the production of a calf every 365 days.
Source: Kalyn Waters