133 Provision of Artificial Shade During Summer Reduced Vaginal Temperature and Improved Growth Performance of Pregnant Grazing Beef Heifers

Abstract

Abstract This study evaluated the effects of providing artificial shade during the summer in Florida on growth performance and vaginal temperature (VT) of pregnant grazing beef heifers. From July to September 2017 (THI from 61.5 to 92.3), 36 black-hided Angus and Angus crossbred pregnant heifers (418 ± 20 kg BW) were stratified by breed, blocked by body weight (BW) and allocated to 12 bahiagrass pastures (Paspalum notatum Flüggé; 1.3 ha, n = 3 heifers/pasture), with (SHADE; 6 pastures) or without (NO SHADE; 6 pastures) access to artificial shade. The shade structures were comprised of a shade cloth that measured 11 × 7.3 m in length and provided 26.8 m2 of shade per animal. Shrunk and full BW were obtained on d 0 and 47, and on d 14 and 28, respectively, to assess changes in BW and average daily gain (ADG). Vaginal temperature was automatically recorded every 10 min for 5 d during weeks 1, 3, 5, and 7 of the study using an intravaginal digital thermo-loggers attached to a blank CIDR. Herbage mass was measured every 14 d to calculate herbage allowance (HA), and additional heifers were used as needed to maintain the same HA among pastures. No differences were observed for HA (P = 0.78). The ADG from d 0 to 47 (P = 0.08 and SEM = 0.07) tended to be greater for SHADE relative to NO SHADE heifers (0.20 vs. -0.02 kg, respectively), whereas no differences were observed for BW (P > 0.10) throughout the study. Vaginal temperature was reduced for SHADE vs. NO SHADE heifers on weeks 1 and 3 (P < 0.001); however, no differences were observed on weeks 5 and 7 (P > 0.10). Providing artificial shade during summer to pregnant grazing beef heifers reduced vaginal temperature and tended to improve ADG.