Stress-related hormonal alterations, growth and pelleted starter intake in pre-weaning Holstein calves in response to thermal stress

Abstract

This study aimed to investigate the effect of heat stress and month of birth on growth performance, pelleted starter intake, and stress-related hormones in Holstein calves. Birth weight and growth records, representing 4735 Holstein calves from a large commercial dairy herd in northern Mexico (25° N; 22.3 °C mean annual temperature) from 2013 to 2015, were analyzed. Temperature-humidity index (THI) at calving, season of birth, and month of birth were the independent variables, whereas growth traits were the dependent variables. Increased THI at birth from < 65 to > 85 units was associated with a decrease in birth weight from 39.3 to 38.7 kg. Calves subjected to high THI (> 75 units) at calving showed lesser (P < 0.01) pre-weaning gains (405 ± 97 g/calf/day), whereas those calves born with THI < 70 units presented the highest gains (466 ± 112 g/calf/day). Birth during the fall months reduced (P < 0.01) weaning weight by about 5 kg compared with winter months. Also, the pre-weaning average daily gain for calves born in the fall was about 70 g less (P < 0.01) than calves delivered in winter months. Plasma triiodothyronine and tetraiodothyronine levels were lower (1.02 ± 0.21 and 48 ± 7.9 ng/mL, respectively; P < 0.01) in summer and highest in winter (1.64 ± 0.48 and 66 ± 11 ng/mL, respectively). Mean plasma cortisol concentration was higher in heat-stressed calves born in summer (59 ± 40 ng/mL) than calves born in winter (20 ± 28 ng/mL). Pelleted starter intake 1 week before weaning was lowest (P < 0.01) in the fall (0.82 ± 0.26 kg/calf/day; mean ± SD) and highest in spring (1.26 ± 0.43 kg/calf/day). It was concluded that in this particular environment, heat stress affects birth weight and growth rate of Holstein calves. Thus, environmental management of the newborn calf during hot spring and summer months is warranted to optimize pelleted starter intake and calf growth rates.

Exposure to heat-stress environment affects the physiology, circulation levels of cytokines, and microbiome in dairy cows

“…T3 and T4, as modulators, play a major role in the growth and development of the brain and central nervous system 28 , and are known to decrease under HS simultaneously with a decrease in feed intake 29 , 30 . They are both lower in cows under an HS environment than under a none/slight environment, which is similar to the lower values in summer (higher ambient temperature) vs those in winter (lower ambient temperature) 31 . Additionally, oxytocin decreased when dairy cows were exposed to psychological stressors 32 .…”

“…The high-heat-sensitivity cows have a higher RT than low-heat-sensitivity cows under both HS and none/slight-HS environments (H-HS > L-HS; H-nHS > L-nHS), besides increased respiratory rate 45 , and decrease of T3 and T4 31 concentrations to maintain homeostasis and prevent overheating. The increased respiratory rate relates to energy consumption when animals cope with the ambient environment 46 , 47 .…”

Heat stress in dairy calves from birth to weaning

“…Endocrine changes also suggest an increased level of stress due to heat exposure. In a study on preweaned calves exposed to heat load, salivary and plasma cortisol concentrations were elevated indicating an increased level of stress (López et al ., 2018; Kovács et al ., 2019). Plasma concentrations of thyroid hormones T3 and T4 were lower in heat stress (López et al ., 2018).…”

“…The small number of studies seasonal effects of growth in dairy calves all agree on a lower average daily weight gain in seasons with higher ambient temperature (Donovan et al ., 1998; Broucek et al ., 2009; López et al ., 2018). The reduced growth rate is attributed mainly to reduced starter intake in the hottest periods of the year (Bateman et al ., 2012; Holt, 2014), rather than consequences of maternal heat stress.…”

Pre- and postnatal heat stress abatement affects dairy calf thermoregulation and performance

“…High ambient temperature and humidity lead to elevated calf rectal temperatures, skin temperatures, and respiration rates, especially when placed in calf hutch environments without access to supplemental shade (Coleman et al, 1996;Spain and Spiers, 1996;Carter et al, 2014). Calves exposed to heat stress have a reduced ADG and weaning weight compared with calves provided active heat stress abatement or born in winter months (Hill et al, 2011;López et al, 2018). This is in part due to a decline in feed and nutrient intake and an increase in water intake (Beede and Collier, 1986;Broucek et al, 2008).…”