Effect of cooling heat-stressed dairy cows during the dry period on insulin response

Abstract

Heat stress (HT) during the dry period affects hepatic gene expression and adipose tissue mobilization during the transition period. In addition, it is postulated that HT may alter insulin action on peripheral tissues. Our objective was to evaluate the effect of cooling heat-stressed cows during the dry period on insulin effects on peripheral tissues during the transition period. Cows were dried off 46 d before expected calving and assigned to 1 of 2 treatments: HT (n = 16) or cooling (CL, n = 16). During the dry period, the average temperature-humidity index was 78, but CL cows were cooled with sprinklers and fans, whereas HT cows were not. After calving, all cows were housed and managed under the same conditions. Rectal temperatures were measured twice daily (0730 and 1430 h) and respiration rate recorded 3 times weekly during the dry period. Dry matter intake was recorded daily from dry-off to 42 d relative to calving (DRC). Body weight and body condition score were measured weekly from dry-off to 42 DRC. Milk yield and composition were recorded daily to 42 wk postpartum. Glucose tolerance tests (GTT) and insulin challenges (IC) were performed at dry-off, -14, 7, and 28 DRC in a subset of cows (HT, n = 8; CL, n = 8). Relative to HT, CL cows had lower rectal temperatures (39.3 vs. 39.0°C) in the afternoon and respiration rate (69 vs. 48 breath/min). Cows from the cooling treatment tended to consume more feed than HT cows prepartum and postpartum. Compared with HT, CL cows gained more weight before calving but lost more weight and body condition in early lactation. Cows from the cooling treatment produced more milk than HT cows (34.0 vs. 27.7 kg/d), but treatments did not affect milk composition. Treatments did not affect circulating insulin and metabolites prepartum, but CL cows had decreased glucose, increased nonesterified fatty acid, and tended to have lower insulin concentrations in plasma postpartum compared with HT cows. Cooling prepartum HT cows did not affect the insulin responses to GTT and IC during the transition period and glucose responses to GTT and IC at -14 and 28 DRC were not affected by treatments. At 7 DRC, CL cows tended to have slower glucose clearance to GTT and weaker glucose response to IC relative to HT cows. Cows from the cooling treatment had stronger nonesterified fatty acid responses to IC postpartum but not prepartum compared with HT. In conclusion, cooling heat-stressed dairy cows in the dry period reduced insulin effects on peripheral tissues in early lactation but not in the dry period.

Effects of stocking density on oxidative stress status and mammary gland permeability in early lactating dairy cows

“…It is known that heat stress plays an important role in depressing plasma insulin concentration of dairy cows (Itoh, Obara, Rose, & Fuse, ; Tao et al., ), which is in agreement with the current study, that high SD‐stressed animals had lower plasma insulin content. In the current study, plasma glucagon contents did not differ between 75SD‐ and 100SD‐cows.…”

“…In mid-lactating dairy cows, higher plasma cortisol was found when they were in a greater SD than that of lower SD condition (Pence et al, 2005). However, in the current study, plasma cortisol concentrations did not differ between the cows of the two treat- It is known that heat stress plays an important role in depressing plasma insulin concentration of dairy cows (Itoh, Obara, Rose, & Fuse, 1998;Tao et al, 2012), which is in agreement with the current study, that high SD-stressed animals had lower plasma insulin content. In the current study, plasma glucagon contents did not differ between 75SD-and 100SD-cows.…”

Food intake dependent and independent effects of heat stress on lactation and mammary gland development

“…Late gestation heat stress has been reported to either shorten or not affect gestation length in human and farm animals (Collier et al, 1982; Porter et al, 1999; Tao et al, 2012; Williams et al, 2013). We found no effect of gestational heat stress on gestation length in mice.…”

Field Trial on Glucose-Induced Insulin Response in High-Yielding Dairy Cows under Different Environmental Temperatures

“…As far as we know, there is no literature data related to fi eld studies on insulin response to glucose challenge in cows continuously exposed to heat stress during the early lactation and midlactation periods. Recently, Tao et al, (2012) [11] presented results of insulin response to glucose challenge in dry cows exposed to heat stress and concluded that insulin response to IVGTT varies according to the phase of productive-reproductive cycle. Therefore, the results related to IVGTT in heat-stressed cows at days 30 and 60 of lactation can not be directly comparable with others.…”

“…It is still an open question if the realignment of metabolism in conditions of heat stress is any different during the early stages of lactation when cows usually are in a stage of negative energy balance. Recently, Tao et al (2012) [11] emphasized the importance of studying the insulin response of heat-stressed cows in all phases of productive-reproductive cycle including the dry period, too.…”