Browsing by Author "Hansen, Peter Johannes"
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Item Differences in thermoregulatory ability between slick-haired and wild-type lactating Holstein cows in response to acute heat stress(Elsevier Science, 2008-09) Alava, Erin N.; Jardim Cury Pontes, Elenir Rose; Korku, Justin M; Olson, Timothy Aanen; Hansen, Peter Johannes; Dikmen, Serdal; Yılmaz Dikmen, Bilgehan; Uludağ Üniversitesi/Veterinerlik Fakültesi/Hayvan Bilimleri Anabilim Dalı.; Uludağ Üniversitesi/Ziraat Fakültesi/Zootekni Bölümü/Hayvan Yetiştirme Anabilim Dalı.; 0000-0002-4397-5428; 0000-0002-5611-4993; G-3725-2017; A-5731-2018; 8280302600; 1360971500Animals inheriting the slick hair gene have a short, sleek, and sometimes glossy coat. The objective of the present study was to determine whether slick-haired Holstein cows regulate body temperature more effectively than wild-type Holstein cows when exposed to an acute increase in heat stress. Lactating slick cows (n = 10) and wild-type cows (n = 10) were placed for 10 h in an indoor environment with a solid roof, fans, and evaporative cooling or in an outdoor environment with shade cloth and no fans or evaporative cooling. Cows were exposed to both environments in a single reversal design. Vaginal temperature, respiration rate, surface temperature, and sweating rate were measured at 1200, 1500, 1800, and 2100 h (replicate 1) or 1200 and 1500 h (replicate 2), and blood samples were collected for plasma cortisol concentration. Cows in the outdoor environment had higher vaginal and surface temperatures, respiration rates, and sweating rates than cows in the indoor environment. In both environments, slick-haired cows had lower vaginal temperatures (indoor: 39.0 vs. 39.4 degrees C; outdoor 39.6 vs. 40.2 degrees C; SEM = 0.07) and respiration rate (indoor: 67 vs. 79 breaths/min; outdoor 97 vs. 107 breaths/min; SEM = 5.5) than wild-type cows and greater sweating rates in unclipped areas of skin (indoor: 57 vs. 43 g.h(-1)/m(2); outdoor 82 vs. 61 g.h(-1)/m(2); SEM = 8). Clipping the hair at the site of sweating measurement eliminated the difference between slick-haired and wild-type cows. Results indicate that slick-haired Holstein cows can regulate body temperature more effectively than wild-type cows during heat stress. One reason slick-haired animals are better able to regulate body temperature is increased sweating rate.Item Is the temperature-humidity index the best indicator of heat stress in lactating dairy cows in a subtropical environment?(Elsevier Science, 2009-01) Hansen, Peter Johannes; Dikmen, Serdal; Uludağ Üniversitesi/Veteriner Fakültesi/Hayvan Bilimleri Anabilim Dalı.; 0000-0002-5611-4993; A-5731-2018; 8280302600Several temperature-humidity indexes (THI) have been used to estimate the degree of thermal stress experienced by dairy cows. The present objectives were to develop equations using meteorological variables that predicted rectal temperature of lactating cows in a subtropical environment and compare the goodness of fit of these equations to those using 8 different THI. Rectal temperature was measured between 1500 and 1700 h in 1,280 lactating Holstein cows in north central Florida between August and December. Meteorological data recorded in the barn where cows were located included dry bulb temperature (Tdb), relative humidity (RH), dew point temperature, and wind speed. Wet bulb temperature was calculated. In the first series of analyses, regression analysis was used to model rectal temperature using the meteorological variables as well as THI. The r(2) using Tdb (0.41) was slightly less than for models using all but one THI (r(2) between 0.42 and 0.43). The r(2) for equations using Tdb could be improved by adding RH (r(2) = 0.43) or RH and RH2 (r(2) = 0.44) to the model. In the second analysis, regression analysis was performed using forward selection, backward elimination, and stepwise selection procedures with the meteorological variables. All models gave a similar goodness of fit (r(2) = 0.44). An analysis of variance with rectal temperature as a class variable was performed to determine the least squares means of meteorological measurements associated with hyperthermia. A Tdb of 29.7 degrees C was associated with rectal temperature of 39 degrees C, and a Tdb of 31.4 degrees C was associated with rectal temperature of 39.5 degrees C. In conclusion, Tdb is nearly as good a predictor of rectal temperatures of lactating Holsteins in a subtropical environment as THI. Estimates of values of meteorological variables associated with specific rectal temperatures should prove valuable in relating environmental conditions to the magnitude of hyperthermia experienced by heat-stressed cows.