Dairy farmers and veterinarians are noticing the effects of heat stress in the dry cow herd. While dry cows can stand a bit more heat than the milking herd, their comfort is important for optimizing future production.
Research has shown that dry, pregnant cows or nulliparous pregnant heifers exposed to heat stress will make less milk in their next lactation, and their gestated calves will be born earlier and smaller with reduced milk yields at maturity across multiple lactations.” – Bethany Dado-Senn
Source: Progressive Dairy, July 20, 2022. Link. Vital responses in dry cows begin to sharply increase when the environmental temperature-humidity index (THI) reaches 75 to 77 or when ambient temperature reaches around 75ºF to 80ºF (depending on the level of relative humidity). These dry cow thresholds are markedly higher than the benchmarks for lactating cows (THI between 68 to 72) due to the difference in milk outputs.