Effects of prepartum stocking density and a blind on physiological biomarkers, health, and hygiene of transition Holstein dairy cows.

Many dairy cows succumb to disease after calving. Disease risk may be affected by the cows' social environment and ability to perform maternal behaviors. In nature, cattle isolate from others and find seclusion to give birth; these behaviors may be limited in indoor group pens and could potentially affect the cows' ability to cope. The aim was to determine whether stocking density and a physical blind in prepartum bedded-pack group pens affected physiological biomarkers, disease risk, and hygiene of peripartum dairy cows. A randomized complete block designed with a 2 × 2 factorial arrangement of treatments was used. Approximately 3 wk before calving, 374 cows (primiparous = 127; multiparous = 247) were assigned randomly to 1 of 4 treatment pens with the following 2 factors: (1) high versus low stocking density (7.7 to 12.9 m2 vs. 15.4 to 25.8 m2 lying space per cow), and (2) presence or absence of a blind. The blind was created using plastic road barriers and plywood, a steel gate, and shade cloth. After calving, cows were moved into a freestall pen and milked 3 times per day. Blood was sampled on the day of enrollment (baseline; -24 d) and approximately -14, -7, 3, 7, 10, and 14 d relative to calving, to measure inflammatory (haptoglobin) and metabolic (nonesterified fatty acids and ß-hydroxybutyrate) biomarkers. ß-Hydroxybutyrate (≥1.2 mmol/L) was used to diagnose subclinical ketosis. Vaginal discharge was scored 3, 7, 10, and 14 d after calving, to diagnose metritis (none, mild, or severe). Hygiene was scored on -24, -14, and -7 d before calving. Before calving, haptoglobin was lower in pens with a blind. After calving, cows in pens with low stocking density before calving tended to be at greater odds of being diagnosed with metritis. Cows were more likely to have poorer hygiene scores in high stocking density pens. No treatment effects were detected for pre- and postpartum nonesterified fatty acids, ß-hydroxybutyrate, postpartum haptoglobin, or subclinical ketosis. Results suggest that the provision of a blind and lower stocking density may be beneficial for reducing inflammation before calving. However, low prepartum stocking density might increase the odds of metritis after calving. Although the reason for this paradox is unclear, the effects of prepartum stocking density may require further exploration.