Intensive grazing and seasonal dairying provide some unique opportunities as well as challenges in the area of heifer rearing. Intensive grazing allows a very economical method of rearing replacement heifers by reducing feed costs, housing requirements, and labor required to spread manure. It also reduces exposure to internal parasites compared with traditionally pastured heifers. Another major advantage is that, contrary to the practice of housing heifers at another location away from the cows, breeding age heifers integrated into the cow's grazing scheme can be on the home farm and in view of farm workers. This allows for better heat detection and the use of A.I., especially with seasonal dairying where the heifers are all the same age. One disadvantage of heifers grazing behind the cows is exposure to contagious diseases, such as Johne's.
Seasonal dairying requires an aggressive heifer rearing program because heifers must calve at 24 months of age. Such heifers must be well fed because it has long been known that small first-lactation cows give less milk than well-grown cows. The incentive to calve heifers at 24 months, rather than the Ohio average of 28 months, can earn greater returns for enhanced management.
The heifer rearing program at the Mahoning County Farm started new-born calves on colostrum and whole milk for 60 days. Calves were housed in a converted grain storage building which had good natural ventilation. Individual calf stalls were constructed to prevent nose-to-nose contact. To enhance colostrum value, an oral E. coli preparation was given at birth for the first two years of the project. During the last three years, cows were vaccinated for E. coli. This program and the skill of the herdsman resulted in a 100% heifer calf survival for the five-year project among all born alive.
After weaning at 60 days, calves were moved to an exercise pasture where they were fed free choice a complete calf pellet. During this time, they received vaccinations for brucellosis, BVD and IBR. During late fall and winter, they received a ration of hay and concentrate with an ionophore. During their yearling year, they grazed for 24 hours behind the milking herd and received no concentrate. During dry years when pasture was short, heifers were rotationally grazed on their own pasture or were traditionally grazed and received supplemental feed, depending on what was available. Calves were dewormed once their first year and twice their yearling year. Using this program, Holstein heifers gained an average of 1.45 lb (.66 kg) per day and Jersey heifers gained 1.1 lb (.5 kg) per day.
Before first calving, Holstein heifers averaged 1,138 lb (517.3 kg) in weight and Jersey heifers were 829 lb (376.8 kg). This is slightly less than desirable and can be overcome by feeding supplemental concentrate with an ionophore during the grazing season. The amount of concentrate will vary with pasture quality, but less than 5 lb (2.3 kg) per day is usually sufficient.
Before heifers are grazed behind the milking herd, the herd
veterinarian should determine the status of Johne's Disease in the
herd. This disease is spread from cows to younger animals through
fecal contamination. Only after it is determined that the herd is
Johne's free should heifers be allowed to graze behind the cows.