The suckling stimulus from the calf has a negative effect on cyclic activity during the postpartum period, however, animals on a positive energy balance and in adequate body condition generally overcome this negative stimulus prior to the breeding season. Another factor that influences cyclicity is uterine involution , which is the time needed for repair of the reproductive tract so another pregnancy can be established. Uterine involution does not generally limit cyclicity unless disease conditions occur which delays normal involution. Table 1 . Body condition, level of nutrition, age of cows, milk production, weather, disease, parasites, and other factors will affect the ability to shorten the postpartum interval.
Nutrition is probably the easiest way to shorten the postpartum period.
As mentioned previously, pre calving is equally important. Nutritional demands increase greatly in late gestation and even more in early lactation. There is promising research at Ft. Keogh and other institutions indicating that supplemental fat may have such an effect. Caution should be used with feeding great excesses of other nutrients at this time, protein is a good example, several scientists have shown that excess protein may be detrimental to reproductive performance in cattle because of increased urea content in the reproductive tract which appears to be detrimental to embryonic development.