Late-gestation heat stress abatement in dairy heifers promotes thermoregulation and improves productivity

Abstract

Multiparous, nonlactating pregnant cows are negatively affected by heat stress, but the effect of heat stress on more thermotolerant pregnant heifers has received less attention. Our objective was to characterize the effect of late-gestation heat abatement on thermoregulatory responses and subsequent milk production of nulliparous Holstein heifers. Pregnant heifers, blocked by body condition score (BCS) and predicted transmitting ability (PTA) for milk, were enrolled in either heat stress (HT, shade of freestall barn; n = 16) or cooling (CL, shade of freestall barn, water soakers, and fans; n = 15) environments during the last 60 d of pregnancy (~8 weeks). Rectal temperature (RT; thermometer), respiration rate (RR; breaths/min), sweating rate (SR; VapoMeter, Delfin Technologies, Kuopio, Finland), and skin temperature (ST; infrared thermometer) were measured thrice weekly from enrollment to calving. Vaginal temperature (VT; i-button intravaginal device) was measured every 10 min for 7 consecutive days at wk −8, −6, −4, and −2 relative to calving and averaged hourly. Daily thermoregulatory patterns assessed by SR and ST, were measured every 4 h over a 36-h time interval at wk −6, −4, and −2 relative to calving. Upon calving, milk, protein, and fat yields were recorded twice daily for 15 wk. The average temperature-humidity index (Hobo Pro temperature probe, Onset Computer Corporation, Pocasset, MA) in the barn during the precalving period was 77 (minimum of 72, maximum of 82). Only heifers that gave birth to a female calf (CL = 12, HT = 14) were included in the statistical analysis. In the precalving period, CL heifers had lower RR (44.3 vs. 60.0 ± 1.6 breaths/min), RT (38.7 vs. 38.8 ± 0.04°C), unshaved ST (34.7 vs. 35.3 ± 0.17°C), and unshaved SR (19.0 vs. 35.2 ± 1.9 g/m 2 h), relative to HT heifers. Additionally, VT was lower in CL heifers during wk −4, and −2, specifically during early morning and early afternoon hours. When measured over a 36-h time interval, ST and SR were lower in CL heifers, when compared with HT heifers for all weeks. Notably, ST was reduced overnight and SR was reduced during the daytime. Cooled heifers had higher milk yield (35.8 vs. 31.9 ± 1.4 kg/d), when compared with HT heifers. Similar to multiparous cows, our data indicate that actively cooling heifers in late pregnancy is effective in promoting thermoregulation and results in elevated milk production postcalving.

Effect of late-gestation heat stress in nulliparous heifers on postnatal growth, passive transfer of immunoglobulin G, and thermoregulation of their calves

“…Additionally, Tao et al (2012) reported that in utero heatstressed (IUHT) calves had decreased passive immune transfer and cellular immune function as well as reduced plasma total protein and hematocrit (HCT) compared with in utero cooled (IUCL) calves. It was recently established that nulliparous, pregnant heifers are also negatively affected by heat stress, as evidenced by elevated thermoregulatory responses and reduced milk production in their first lactation (Davidson et al, 2021). Notably, the magnitude of differences in the thermoregulatory responses and production variables between cooled and heat-stressed pregnant heifers was not as large as observed differences in multiparous lactating or dry pregnant cows.…”

“…All heifers were housed in the same sand-bedded freestall barn, where the HT pens were provided only with shade of the open-sided barn and the CL pens were provided with shade of the barn, water soakers over the feed line, and fans over the stalls. Details on maternal treatments, thermoregulatory measures, and diets were previously reported by Davidson et al (2021).…”

“…, where T = ambient temperature (°C) and RH = relative humidity (%). Briefly, from Davidson et al (2021), nulliparous pregnant heifers with access to active cooling during the last 8 wk of gestation had lower RR (44.3 vs. 60.0 ± 1.6 breaths/min, P < 0.0001), RT (38.7 vs. 38.8 ± 0.04°C, P = 0.007), ST (34.7 vs. 35.3 ± 0.17°C, P = 0.002), and SR (19.0 vs. 35.2 ± 1.90 g/m 2 per hour, P < 0.0001) relative to the HT heifers. During the precalving period, DMI was not different (7.99 vs. 8.34 ± 1.03 kg/d, CL vs. HT, P = 0.76) between treatments, and postcalving milk production was higher in CL dams (35.8 vs. 31.9 ± 1.4 kg/d, CL vs. HT, P = 0.01) than in HT dams.…”

Evaluation of different cooling management strategies for lactating Holstein × Gir dairy cows

“…Nutritional ( Brandão et al, 2016 ; Leiva et al, 2017 ), genetic, and management ( West, 2003 ) strategies have been reported to improve DMI, milk production and composition, health, metabolism, and reproductive function of dairy cows, or in other words, have demonstrated how heat stress might impair these productive and reproductive parameters in dairy cows ( West, 2003 ; García-Ispierto et al, 2007 ; Roth, 2008 ; Van Os, 2019 ; Bai et al, 2020 ; Pereira et al, 2021 ). Moreover, it is well-known that heat stress occurrence in pregnant dairy cows and heifers impacts gestation length ( Tao et al, 2012 ; Monteiro et al, 2014 ; Davidson et al, 2021a ) and impacts fetal intrauterine development ( Tao et al, 2012 ; Monteiro et al, 2014 ; Dado-Senn et al, 2020 ), early after birth ( Strong et al, 2015 ; Davidson et al, 2021a ), but even more importantly, later in the dairy female’s productive life ( Laporta et al, 2017 ; Tao et al, 2019 ; Davidson et al, 2021b ).…”

A Pilot Study on Across-Generation Impacts of Maternal Heat Stress on Blood Metabolites of Female Holstein Dairy Calves

“…The detrimental effects of heat stress (HS) during late gestation on the mature multiparous cow with severe consequences for several physiological mechanisms and behavioral traits in the following lactation are well known (e.g., [1,2]). Despite their suggested higher heat tolerance when compared to multiparous dry cows, quite similar HS effects during late gestation on production traits were detected for nulliparous heifers [3]. Due to the lower metabolic heat production, dry cows respond less sensitive to HS than lactating dairy cows.…”