Conditions to evaluate differences in resilience of sheep and goats to high heat load

TitleConditions to evaluate differences in resilience of sheep and goats to high heat load
Publication TypeConference Proceedings
Year of Conference2016
AuthorsMengistu, UL, Puchala, R, Sahlu, T, Gipson, TA, Dawson, LJ, Goetsch, AL
Conference NameInternational Conference on Goats
Pagination216
AbstractThirty-three yearling Katahdin sheep (KAT) and Boer (BOE) and Spanish goat wethers (SPA) were used to study conditions for evaluating resilience to high heat load index (HLI). Moderate quality grass hay was consumed ad libitum with concentrate (80% corn, 20% soybean meal) at 0.5% BW. There was a 2-wk period with a target HLI of 70 (period 1), followed by 1-wk periods with target HLI of 80, 90, 95, and 100 during daytime and 70, 76.5, 80.75, and 85 at night in periods 2, 3, 4, and 5, respectively. Actual values averaged 66, 80, 92, 97, and 101 during the day and 66, 75, 84, 86, and 89 at night in periods 1, 2, 3, 4, and 5, respectively. Respiration rate was affected by an interaction (P < 0.001) between animal type and period (18, 71, 83, 121, and 105 for BOE, 25, 104, 101, 139, and 126 for KAT, and 22, 105, 104, 129, and 109 breaths/min for SPA; SE = 4.2), as well as was rectal temperature (38.4, 39.2, 39.4, 39.9, and 39.5 for BOE, 38.9, 39.1, 39.2, 39.6, and 39.6 for KAT, and 38.6, 39.4, 39.6, 40.0, and 39.6º C, for SPA in periods 1, 2, 3, 4, and 5, respectively; SE = 0.065). Change with advancing period varied with time of measurement (P < 0.001) for respiration rate (20, 71, 32, 83, and 37 at 06:00 h, 24, 100, 131, 150, and 151 at 13:00 h, and 32, 110, 136, 155, and 151 breaths/min at 17:00 h; SE = 3.5) and rectal temperature (38.2, 38.9, 38.6, 39.0, and 38.7 at 06:00 h, 38.8, 39.4, 39.7, 40.1, and 39.8 at 13:00 h, and 38.9, 39.4, 40.0, 40.4, and 40.2º C at 17:00 h in period 1, 2, 3, 4, and 5, respectively; SE = 0.056). Respiration rate at 06:00 h differed more (interaction, P < 0.001) among days of period 5 than at 13:00 or 17:00 h (82, 101, 118, 93, 57, 58, and 37 at 06:00 h, 152, 161, 165, 158, 151, 142, and 151 at 13:00 h, and 158, 162, 171, 161, 153, 152, and 151 breaths/min at 17:00 h on day 1, 2, 3, 4, 5, 6, and 7, respectively; SE = 3.9). In conclusion, a HLI in the range of 95/80.75 and 100/85 seems appropriate to investigate differences in resilience to high HLI, periods longer than 1 wk appear necessary for adequate adaptation, and measurements minimally should be during nighttime and the latter half of the daytime period.