Effect of heat stress during late gestation on immune function and growth performance of calves: Isolation of altered colostral and calf factors

Abstract

Calves born to cows exposed to heat stress during the dry period and fed their dams' colostrum have compromised passive and cell-mediated immunity compared with calves born to cows cooled during heat stress. However, it is unknown if this compromised immune response is caused by calf or colostrum intrinsic factors. Two studies were designed to elucidate the effects of colostrum from those innate to the calf. The objective of the first study was to evaluate the effect of maternal heat stress during the dry period on calf-specific factors related to immune response and growth performance. Cows were dried off 46 d before expected calving and randomly assigned to 1 of 2 treatments: heat stress (HT; n=18) or cooling (CL; n=18). Cows of the CL group were housed with sprinklers, fans and shade, whereas cows of HT group had only shade. After calving, the cows were milked and their colostrum was frozen for the subsequent study. Colostrum from cows exposed to a thermoneutral environment during the dry period was pooled and stored frozen (-20 °C). Within 4h of birth, 3.8L of the pooled colostrum from thermoneutral cows was fed to calves born to both HT and CL cows. Day of birth was considered study d 0. All calves were exposed to the same management and weaned at d 49. Blood samples were collected before colostrum feeding, 24h after birth and twice weekly up to d 28. Total serum IgG concentrations were determined. Body weight was recorded at birth and at d 15, 30, 45, and 60. Relative to CL calves, HT calves were lighter at birth (38.3 vs. 43.1 kg), but no difference in weight gain was observed at d 60. Additionally, HT calves had lower apparent efficiency of IgG absorption (26.0 vs. 30.2%), but no differences were observed for total IgG concentration. The objective of the second study was to evaluate the isolated effect of the colostrum from HT cows on calf immune response and growth performance. The experimental design was identical to the first study, but all calves were born to cows under thermoneutral conditions during the dry period. At birth, calves were blocked by sex and birth weight and then randomly assigned to 1 of 2 treatments, which meant they received pooled colostrum from HT cows or CL cows. No treatment effect was observed on passive immune transfer or on postnatal growth. Thus, heat stress during the last 6 wk of gestation negatively affects the ability of the calf to acquire passive immunity, regardless of colostrum source.

Acute brief heat stress in late gestation alters neonatal calf innate immune functions

“…In the current study, no difference in the hematocrit was found, but a lower plasma protein concentration was observed in the HS calves compared with the CT calves; however, that concentration is still considered adequate passive transfer. Monteiro et al (2014) demonstrated that it is the calf lack of passive transfer that is responsible for less IgG concentrations rather than the colostrum quality. This suggests that our calves had adequate passive transfer, regardless of the heat stress.…”

“…Adequate colostrum transfer has been recognized to have beneficial effects on the calf's immune response earlier in life (Furman-Fratczak et al, 2011), by the uptake of cytokines (Nguyen et al, 2007;Chase et al, 2008) and the absorption of immunoglobulins during the first 48 h (Sangild, 2003). Recent work has isolated the effects of colostrum from heat-stressed cows and the absorptive ability of the neonate from heat-stressed cows (Monteiro et al, 2014), determining that calves had reduced passive transfer regardless of colostrum source. Previous research of our laboratory (unpublished data), conducted during the summer with a short heat event during the last month of gestation, resulted in calves that were more prone to disease and grew slower even when born after the HS event, prompting the hypothesis of this research.…”

Practices for Alleviating Heat Stress of Dairy Cows in Humid Continental Climates: A Literature Review

“…More specifically, the reduction of dry matter intake for heat-stressed cows is about 10 to 15% relative to cooled cows [5]. Cows under heat stress also have elevated respiration and sweating rates, which results in greater body fluid losses that increase maintenance requirements to control dehydration and blood homeostasis [4].…”

Short communication: Effect of maternal heat stress in late gestation on blood hormones and metabolites of newborn calves

“…Compared with those from cooled (CL) cows, calves born to heat-stressed (HS) dry cows have impaired passive and cell-mediated immune function (Tao et al, 2012;Monteiro et al, 2014) and altered metabolism during the preweaning period Monteiro et al, 2016). Moreover, Monteiro et al (2013) reported that maternal heat stress during the dry period reduced heifer milk production during the first lactation.…”