This is a draft schedule. Presentation dates, times and locations may be subject to change.
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Effects of High Heat Load Conditions on Rectal Temperature, Panting Score, and Respiration Rate of Hair Sheep Breeds from Different Regions of the USA
Effects of High Heat Load Conditions on Rectal Temperature, Panting Score, and Respiration Rate of Hair Sheep Breeds from Different Regions of the USA
Tuesday, July 11, 2017
Exhibit Hall (Baltimore Convention Center)
Thirty-seven Dorper (DOR), 35 Katahdin (KAT), and 31 St. Croix (STC) ewes (57, 58, and 44 kg; SEM=2.2) from 45 commercial farms in the Midwest (MW), Northwest (NW), Southeast (SE), and central Texas (TX), between 2.2 and 3.4 yr of age, were used to evaluate responses to high heat load index (HLI) conditions. There were four sequential 2-wk periods (8 wk total) with target HLI during day/nighttime of 70/70, 85/70, 90/77, and 95/81, with weekly measures at 0700 (before increased daytime HLI), 1300, and 1700h (preceding lower nighttime HLI). Rectal temperature (RT; ºC) was affected (P=0.003) by breed×time (38.58, 38.92, and 39.07 for DOR, 38.67, 38.92, and 39.05 for KAT, and 38.45, 38.69, and 38.85 for STC at 0700, 1300, and 1700h, respectively; SEM=0.034). There were interactions between week and time (P<0.001) in respiration rate (RR; breaths/min; 52, 72, 66, and 85 at 0700h, 120, 130, 151, and 144 at 1300h, and 116, 123, 141, and 142 at 1700h; SEM=3.1) and panting score (0-4; 0.05, 0.03, 0.11, and 0.28 at 0700h, 0.48, 0.86, 1.61, and 1.47 at 1300h, and 0.76, 0.91, 1.54, and 1.51 at 1700h in wk 5, 6, 7, and 8, respectively; SEM=0.042). Breed×time RR (P=0.008) means were 57, 107, and 103 for DOR, 55, 101, and 96 for KAT, and 47, 88, and 90 for STC at 0700, 1300, and 1700h, respectively (SEM=3.1); however, there was an interaction (P=0.007) among breed, region, and time (MW DOR 57, 110, and 101, KAT 59, 110, and 108, and STC 43, 89, and 88; NW DOR 65, 113, and 111, KAT 54, 104, and 96, and STC 56, 92, and 94; SE DOR 49, 93, and 96, KAT 52, 105, and 96, and STC 45, 79, and 87; TX DOR 57, 110, and 104, KAT 54, 83, and 84, and STC 46, 91, and 89 at 0700, 1300, and 1700h, respectively; SEM=6.1). In conclusion, RT of STC was low at all times compared with DOR and KAT even with lower RR. There appeared to be considerable adaptation from wk 1 to 2 during the two highest HLI periods via evening respiration. Region effects varied with breed, such as relatively high RR by STC from the NW to maintain low RT, lower RR of DOR from the SE than other regions, and a smaller difference among times in RR of KAT from TX.