Effect of Heat Stress During Late Gestation on Multiparous Holstein Cows and Offspring
Melissa Sacher, Leticia T. Casarotto, Bethany Dado-Senn, Veronique Ouellet, Jimena Laporta, Geoffrey E. Dahl
Professor, Geoffrey Dahl
College of Agricultural and Life Sciences
<p>Dairy cows exposed to heat stress often exhibit decreased milk production and compromised reproductive performance (Dahl, et. al., 2019). Health issues related to heat stress during the dry period may implement an economic burden on dairy producers (Ferriera, et. al., 2016). The objective of the present study was to determine the effects of cooling on late gestation dairy cows and their calves. This trial took place from August until October 2020 on a commercial dairy in Florida. Multiparous Holstein cows were randomly assigned to treatments at ~56 d before expected calving. One group was provided access to shade, fans, and soakers (n=41, CL) while the other group only had access to shade (n=41, HT). Respiratory rates (RR, flank movements per minute) and skin temperatures (ST, infrared thermometer) were measured twice a week. After parturition, the gestation length (GL) of the dams and birth weight (BW) of the heifers were recorded. Also, milk production was observed for both the CL and HT groups using the DairyComp365 software until 120 days in milk (DIM). These data were analyzed using GLIMMIX and MIXED procedure in SAS. The results demonstrated that HT animals had higher respiration rates (77.36 vs. 53.51 ± 0.63 bpm, for HT relative to CL, <em>P < </em>0.001) and skin temperatures (35.95 vs. 34.09 ± 0.05 ˚C, <em>P</em> < 0.001) than CL animals. Also, the HT cows had a GL 3 days shorter than the CL ones (274.97 vs. 278.35 ± 0.68 d, <em>P</em> < 0.001). Furthermore, the heifers born to HT dams weighed an average of 4 kg less than heifers born to CL dams (34.84 vs. 38.95 ± 0.72 kg, <em>P</em> < 0.001). Milk production was not different between treatments (44.1 vs. 43.9 ± 1.0, P = 0.88). Thus, heat stress during late gestation compromises dam thermoregulation and impacts heifer development.</p>
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