Effects of providing artificial shade to pregnant grazing beef heifers on vaginal temperature, growth, activity, and behavior

Abstract

This experiment evaluated the effects of providing artificial shade during summer on activity, behavior, and growth performance of pregnant grazing beef heifers. Thirty-six black-hided Angus and Angus crossbred pregnant heifers [418 ± 9 kg body weight (BW); approximately 90 d of gestation] were stratified by breed, blocked by BW, and allocated to 12 ‘Pensacola’ bahiagrass pastures (Paspalum notatum Flüggé; 1.3 ha, n = 3 heifers/pasture) with or without access to artificial shade (SHADE vs. NO SHADE; 6 pastures each) for 7 wk during summer. The shade structures were composed of shade cloth (11 × 7.3 m length, 2.4 m height: 26.8 m 2 of shade per heifer). Shrunk BW was recorded on enrollment (d 0) and wk 7 (d 47), whereas full BW was obtained on wk 2 (d 14), 4 (d 28), and 6 (d 42) to assess average daily gain (ADG). Vaginal temperature was recorded for five consecutive days during wk 1, 3, 5, and 7 using an intravaginal digital thermo-logger, and individual GPS devices were used to quantify the use of shade for an 8-h period. Activity was monitored using automated monitoring devices (HR-LDn tags SCR Engineers Ltd., Netanya, Israel) through the experimental period. Vaginal temperature was lower (P < 0.01) for heifers in the SHADE compared with heifers in the NO SHADE treatment from 1200 to 1600 h and 1100 to 1900 h for wk 1 and 3, respectively. Heifers in the SHADE treatment spent 70% of the 8-h period evaluated under the shaded structure. Provision of shade increased (P < 0.01) daily lying time (11.4 ± 0.2 vs. 10.3 ± 0.2 h/d) and standing bouts per day (P < 0.01; 12.6 ± 0.4 vs. 10.8 ± 0.4 bouts/d), whereas it reduced (P < 0.01) standing bout duration (61.6 ± 3.0 vs. 82.9 ± 3.0 min/bout) relative to heifers without access to shade. The interaction between treatment and hour affected (P < 0.01) daily rumination time because heifers with access to SHADE had greater rumination between 1000 and 1200 h. Although ADG tended (P = 0.08) to be greater for the heifers in the SHADE treatment (0.20 vs. -0.02 kg, respectively), the access to shade did not (P = 0.79) affect the final BW. In conclusion, providing artificial shade during summer to pregnant grazing beef heifers was effective in reducing vaginal temperatures and exerted changes in heifer behaviors that translated into slight improvements in growth performance.

Artificial shade as a heat abatement strategy to grazing beef cow-calf pairs in a subtropical climate

“…With an impact on BW of Brangus heifers, which were the lightest at weaning and at 14-d post-weaning. In our previous study [ 8 ] we demonstrated that heifers grazing warm-season forages with access to an artificial shade, gained 0.2 kg/d, whereas heifers without shade lost 0.02 kg/d. Enhanced growth performance for grazing beef heifers has been reported by Monn et al [ 22 ], who observed an increase of 0.2 kg/d for beef heifers with access to shade compared to cows with no access to shade.…”

“…When cattle are unable to effectively dissipate heat for the maintenance of homeothermy, body temperature rises [ 18 ]. The provision of shade is associated with reductions in body temperature in beef and dairy cattle [ 8 , 19 – 22 ]. However, in the current study, Brangus and Angus cows with access to shade had similar vaginal temperatures compared to cows without access to shade.…”

“…However, in the current study, Brangus and Angus cows with access to shade had similar vaginal temperatures compared to cows without access to shade. Our previous research showed that artificial shade provided during summer in Florida reduced vaginal temperature of grazing beef heifers in the first 3 wks of the experiment [ 8 ]. The maximum vaginal temperature difference between heifers with or without access to shade was 0.4°C and was achieved in the afternoon, whereas in the current experiment, the magnitude of differences was 0.3°C.…”

“…Adding shade structures in pasture is the most economical means of mitigating HS in grazing animals [ 2 ]. We previously demonstrated that providing artificial shade during summer to grazing beef heifers was effective in reducing vaginal temperatures, increasing rumination and lying time, resulting in an additional 0.20 kg gain per day [ 8 ]. Our results highlighted the positive effects of implementing artificial shaded structures on pasture-based systems during summer in subtropical climates.…”

Influence of climatic conditions on tympanic temperature and milk production in grazing cows

“…Tympanic temperature determination has been performed with good results in dairy cattle (Jara et al 2016;Shu et al 2021). The relationship of physiological responses of animals varies according to the ecological zone and their respective climate conditions (Silva et al 2021). This observation reinforces the need to evaluate the animal's response to particular productive scenarios to analyze adaptive processes and keep contributing to study the associations between climate and milk production under grazing conditions, especially in tropical areas where this activity has been showing a sustained growth and offers an agribusiness opportunity for its population in the coming years.…”