New research from the Ohio State University shows just how important lying time for prepartum cows is for calf survival. In Menichetti el al., (2020) prepartum cows with reduced lying time, or with increased day-to-day variation in the amount of time spent lying the week before calving, had increased serum NEFA concentrations and reduced calf survival.
An observational study was conducted at 3 Ohio dairy herds with 1,044 cows used for analysis. At 14 days before expected calving date, pregnant Holstein cows (multiparous and primiparous) were fitted with electronic data loggers to track behavioral activity. Blood was drawn at 14 and 7 days prepartum to check non-esterified fatty acid levels and a third time within 48 hours of calving for total blood calcium.
Throughout the study 4.8% of all calves were stillborn—either born dead or died within 24 hours of birth. Comparing dams with stillborn calves to those with live calves revealed the following:
- Dams of stillborn calves spent less time lying each day compared to dams of live calves. The difference for primiparous cows was 55 minutes/day, and in multiparous cows the difference was 46 minutes/day less lying time than cows with calves born alive.
- In multiparous cows, dams of stillborn calves had significantly higher NEFA concentrations than dams of live calves, 416 vs 313 μEq/L. There was no difference in NEFA for first-calf heifers.
- Regardless of parity, the proportion of cows with hypocalcemia (≤2.0 mmol/L) within 48 hours of calving was greater in dams of stillborn calves than for those with a live calf.
- A coefficient of variation (CV) for lying time was calculated for each cow within 7 days prior to calving. This measures the change in lying time from day to day. The greater the variation in lying time, the higher the CV ratio. All cows with stillborn calves had higher CV ratios than cows with a live calf.
These findings demonstrate that dams with increased CV ratio of lying time within 7 days prepartum also have increased NEFA concentrations and more stillborn calves. When investigating poor calf survival, the researchers suggest that the consistency of lying time, and the management factors that may impede it, be investigated.