Late-gestation ear-surface temperatures and subsequent postpartum health, activity, milk yield, and reproductive...

A retrospective study was conducted to determine if postpartum health, milk yield, and reproductive traits in addition to peripartum daily physical activities (resting, eating, active time, and rumination) differ in dairy cows having greater or lesser ear-surface temperatures during late gestation (Days 230-239) compared with contemporary herd mates within season. Herd records collected from Holstein heifers (n = 348) and dry cows (n = 503; second through seventh lactations) were fitted with SensOor ear tags to collect hourly ear-surface temperatures. Mean temperatures were calculated from 240 hourly measures during Days 230-239 of gestation and cows within season were grouped into two median temperature groups. On Days 230-239 of gestation during May through September (hotter months) cows with high (H, range of 33.67-38.89 °C, mean ± SEM = 32.9 ± 0.2 °C) or medium high (MH, 25.06-31.66 °C, 29.4 ± 0.2 °C) temperatures were grouped together (n = 209 per group). For comparable gestational days during October through April (colder months), cows with medium low (ML, 17.82-25.00 °C, 21.1 ± 0.2 °C) and low (L, -0.70 to 17.80 °C, 13.4 ± 0.2 °C) temperatures were grouped together (n = 216 per group). Prepartum traits including mean ear temperature, gestation length, days in milk at dry-off, days in close-up pen, previous 305-d milk yield, proportion of heifer calves born, and cow PTA for milk differed (P < 0.05) between seasons, but not between temperature groups within season, except predicted transmitting ability for milk was greater (P = 0.02) for ML than L cows. Postpartum treatment with antimicrobials occurred more (P = 0.02) often in H than MH cows, whereas more (P = 0.04) lameness and greater (P = 0.05) projected 305-d mature equivalent milk yield was observed in ML vs. L cows. No other health or reproductive traits were associated with temperature group, but many seasonal effects were observed across temperature groups. Less (P = 0.04) prepartum eating time during the last 10 d before calving was detected in L than in ML cows, less (P = 0.06) rumination time in ML than L cows, and more (P = 0.03) activity time was observed in H than MH cows. After calving, H cows were more (P = 0.03) active than MH cows and ML cows tended (P = 0.07) to be more active than L cows. In conclusion, late gestational ear-surface temperatures were associated with some postpartum health disorders and modifications in daily eating, ruminating, and active times during the transition period of gravid heifers and dry cows.