Heat stress and ACTH administration on cortisol and insulin-like growth factor I (IGF-I) levels in lactating Holstein cows

Abstract

Physiological and productive responses were studied in five Holstein cows in thermal comfort (T1), stress by exogenous adrenocorticotropic hormone (ACTH) administration (T2) and heat stress (T3) to compare acute and punctual stress (ACTH) and prolonged stress (heat stress). During T1 and T2, cows were housed in a climatic-free stall barn. In T3, the animals were kept in a climatic room (air temperature of 37°C from 08:00 to 13:00 h, and of 26°C from 14:00 to 07:00 h) for 7 days. Milk yield, rectal temperature (RT), respiratory rate (RR) and blood samples were obtained before, during and after all treatments. In T1 at 08:00 h, RT and RR were below the upper critical limit. Simultaneously, cortisol and insulin growth-factor I (IGF-I) were within the normal limits. After ACTH administration (T2), cortisol significantly increased, reaching maximum levels at 60 min and returning to basal levels at 300 min. However, IGF-I was not affected. During T3, Holstein cows did not effectively dissipate their body temperature and RT, RR and cortisol significantly increased. There was a 26.6% reduction in milk production after heat stress (P < .05). Prolonged heat stress was more stressful and cows had higher levels of CORT in T3 than in T2 even before the increase in body temperature. Although the total amount of cortisol and IGF-I presented a negative and significant Pearson correlation (r = −0.79), IGF-I was not significantly influenced by heat stress or ACTH administration, and the relationship between IGF-I and heat stress remains controversial. ARTICLE HISTORY

Productivity and physiological response of lactating Holstein cows to sugarcane supplementation and evaporative cooling under heat-stress

“…Hence, the environmental conditions of the freestall-type feedlot system were sufficient to induce high-intensity physiological responses of the mild-moderate stage of heat stress in cows during the afternoon period. A similar observation was reported by Titto et al (2017) in lactating cows at thermal comfort in a freestalltype feedlot system with fans and nebulizers. When the ET exceeds the maximum comfort for the animal, the RH assumes critical importance in the elimination of heat (Sota, 1996).…”

“…The results of RR, BS and RT were higher with Wo conditions than with W, and higher in the afternoon (14.00 h) compared with the morning (09.40 h). Similar results were obtained by Chaiyabutr et al (2008) and Titto et al (2017). However, in the afternoon period, RT, BS and RR did not exceed the levels considered normal for the thermal comfort of the cows, as shown by Renaudeau et al (2012) and Igono et al (1992) with an RT of 38.5°C.…”

“…A similar observation was reported by Titto et al . (2017) in lactating cows at thermal comfort in a freestall-type feedlot system with fans and nebulizers. When the ET exceeds the maximum comfort for the animal, the RH assumes critical importance in the elimination of heat (Sota, 1996).…”

“…However, in the afternoon period, RT, BS and RR did not exceed the levels considered normal for the thermal comfort of the cows, as shown by Renaudeau et al (2012) and Igono et al (1992) with an RT of 38.5°C. Titto et al (2017) evaluated the physiological responses of high-production cows in indoor climatic rooms with meteorological monitoring, with a THI range 75.5-96.6, air temperature of 26.0-38.0°C and relative air humidity of 71-84%, from 08.00 to 13.00 h for 7 consecutive days. These authors had to reduce the temperature and relative air humidity rapidly after 6 h of experimentation because RT and RR had reached critical and damaging values for the cows (39°C and 70 breaths/min, respectively, which are characteristic of heat stress).…”

Changes in climate conditions and their effects on production and reproduction of medium yielding cows in temperate continental climate

“…As the dairy industry in Romania is strongly depending on planted pasture (including the local grain production), the climate change is likely to have a negative impact on livestock production. In addition, economic losses could be caused directly by heat stress since it impairs milk production, reproductive rates and immune function (Titto et al, 2017;Spiers et al, 2018). Recently, Dobrinescu et al, (2015) have studied the long term changes and physical mechanisms controlling the variability of Temperature Humidity Index, which is directly implied in human heat and animal stress, for the period 1961-2010.…”