Evaluating the impact of breed, pregnancy, and hair coat on body temperature and sweating rate of hair sheep ewes in the tropics.

The objective of this study was to evaluate the effect of pregnancy, breed, and hair coat on body temperature and sweating rate (SR) of hair sheep. St. Croix White (STX; = 9) and Dorper × STX (DRPX; = 9) ewes (3.6 yr of age) were evaluated over 4 d at 126 d of gestation (PREG) and over 4 d at 46 d postpartum (OPEN) in the shade and sun and in the morning (AM; 0900 to 1200 h) and afternoon (PM; 1300 to 1600 h) after a 20 min acclimation to each condition on each day. Data loggers recorded vaginal temperature (VT) at 10-min intervals for 96 h. Rectal temperature (RT) was measured using a digital veterinary thermometer, and respiration rate (RR) was measured as breaths per minute (bpm). Sweating rate was calculated from measured air properties passing over a shaved (300 cm) and unshaved area of the ewes' body using a portable calorimeter. Data were analyzed using GLM procedures of SAS (SAS Inst. Inc., Cary, NC) with breed, pregnancy status, sun exposure, and time of day as main effects. Mean temperature, relative humidity, temperature-humidity index, wind speed, and solar radiation on the days of data collection were 28.2°C, 82.8%, 80.3, 4.2 km/h, and 237.5 W/m, respectively. There was no difference ( > 0.10) in RT, RR, and SR between DRPX and STX ewes. The PREG ewes had lower RT ( < 0.007) and SR ( < 0.0001) and higher RR ( < 0.007) than OPEN ewes (38.5 ± 0.2 vs. 39.1 ± 0.2°C, 70.2 ± 3.1 vs. 88.3 ± 3.1 g⋅m⋅h, and 79.5 ± 2.2 vs. 72.1 ± 2.2 bpm, respectively). During the PM, RR, RT ( < 0.05), and SR ( < 0.006) were higher than in the AM. In the sun, RR ( < 0.001) and SR ( < 0.0001) were higher than in the shade, but there was no difference ( > 0.10) in RT. There was no difference in SR ( > 0.10) between the shaved and unshaved area of the ewe. The DRPX ewes had higher ( < 0.0001) VT than STX ewes. The PREG ewes had higher ( < 0.001) VT than OPEN ewes during the night time and lower VT than the OPEN ewes during the day time ( < 0.0001). The OPEN ewes had a greater ( < 0.009) daily range of VT than PREG ewes did (2.5 ± 0.4 vs. 1.1 ± 0.4°C, respectively), but there was no breed difference ( > 0.10). Hair coat did not have an influence on the SR of the ewes, and PREG ewes appeared to use increased respiration as opposed to sweating to help control RT. The narrower range of body temperature, measured as VT, of PREG compared to OPEN ewes may be a protective mechanism for the developing fetus.

Technical note: Device for measuring respiration rate of cattle under field conditions.

Respiration rate (RR) is 1 of the physiological responses used to gauge the level of heat stress in cattle. Respiration rate is usually measured by counting chest movement of the animal. This procedure has some disadvantages including that the person who is doing the counting must be trained to ensure accurate results, the animals must be preconditioned to the presence of the observer, and the presences of the observer may influence the behavior and activity of the animals or their position in the pen. In this study, a device that continuously records RR without restraining the animal was developed. The device is lightweight, cheap, easy to install, and more importantly, does not interfere with the activities of the animal. The device is mounted in a halter and is placed around the neck of the subject. The device measures air temperature near the nostrils of the animal and RR is calculated as the number of oscillations of the temperature. The RR measured by the device were compared against RR observed by counting the flank movement (for 60 s, repeated every 10 min) of 5 Nellore cattle, 1 animal per d, and the results show no statistical difference ( = 0.45) between the 2 methods. This demonstrates that this device can be used to continuously measure RR of cattle under field conditions.

Placement of temperature probe in bovine vagina for continuous measurement of core-body temperature.

There has been increasing interest to measure core-body temperature in cattle using internal probes. This study examined the placement of HOBO water temperature probe with an anchor, referred to as the "sensor pack" (Hillman et al. Appl Eng Agric ASAE 25(2):291-296, 2009) in the vagina of multiparous Holstein cows under grazing conditions. Two types of anchors were used: (a) long "fingers" (4.5-6 cm), and (b) short "fingers" (3.5 cm). The long-finger anchors stayed in one position while the short-finger anchors were not stable in one position (rotate) within the vagina canal and in some cases came out. Vaginal temperatures were recorded every minute and the data collected were then analyzed using exponential mixed model regression for non-linear data. The results showed that the core-body temperatures for the short-finger anchors were lower than the long-finger anchors. This implied that the placement of the temperature sensor within the vagina cavity may affect the data collected.