The transition period, from three weeks before calving to three weeks after, is a highly sensitive time for cows, and a strong predictor of how successfully they will perform in the rest of that lactation. Industry data also shows that about 75% of disease in dairy cows occurs during this critical six-week period.
More than 10 years ago, the dairy group at the University of Wisconsin’s School of Veterinary Medicine developed the Transition Cow Index® (TCI). This measure of transition cow health and performance was developed to normalize data related to transition success between herds. It gave dairy managers an industry-wide benchmark to which they could compare the health and performance of their transition cows.
The factors included in calculating the TCI are:
- days in milk at first test
- previous lactation milk yield
- days in milk in prior lactation
- start of current lactation as calving or abortion
- start of prior lactation as calving or abortion
- month of calving
- somatic cell count (SCC) log score at last test of prior lactation
- days dry
- milking frequency current lactation
- milking frequency prior lactation
- parity number
- recombinant bovine somatotropin (rBST) use at herd level
TCI is expressed in lb. of 305-day projected milk. After calculating the index for millions of cows, and using it to evaluate management practices and systems, we have learned some important lessons about transition cow management from the TCI. Among them are:
- Good milk production does not have to come at the expense of good reproduction. A TCI of 1,000 lb. has been correlated to 1,300 lb. of additional milk per lactation. This level of milk production usually would be associated with a reduced likelihood of pregnancy at 150 days in milk of 1.5%. But if it is achieved through improved transition management, reproductive performance actually improves slightly.
- Bunk space is critical. If cows can’t eat together, the ones that eat later eat less. If they eat less, they are at increased risk of fresh cow disease. Cows normally will fill standard, 24" headlocks to a maximum stocking density of 80%. Feeding space of at least 30" per cow is needed for all animals to eat simultaneously at 100% stocking density. We advise building prefresh pens to provide 30" bunk space, with enough spaces to accommodate every animal, even when cow numbers surge.
- Amply size free stalls with a loosely bedded surface. Heavily pregnant cows find it more difficult to lie down and rise, and a substantial portion of them become slightly tenderfooted. Having wide free stalls, lots of forward lunge room, and a deeply bedded surface of sand, deep straw or other loose bedding is a major factor for improving transition cow feed intake and heath.
- Later transition to calving space is better, and minimize commingling. Movement into calving pens three to 10 days prior to due date was associated with lower TCI than movement at two days or less. Stable social groups also are helpful. If possible, keep cows together in cohort groups from dry-off until immediately before calving.
To view a presentation by Nordlund on the Transition Cow Index®, follow this link.
More transition cow management advice can be found on The Dairyland Initiative’s website.