|PARISH, JANE - Mississippi State University|
|Carroll, Jeffery - Jeff Carroll|
|BEST, TIMOTHY - Mississippi State University|
|STEWART, CHEYENNE - Mississippi State University|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 11/21/2016
Publication Date: 12/23/2016
Citation: Parish, J.A., Carroll, J.A., Broadway, P.R., Best, T.F., Stewart, C.O., Sanchez, N.C. 2016. Hair shedding score may affect body temperature more than hair coat color during heat stress in weaned beef heifers.. Journal of Animal Science Supplement. 2017. J.Anim.Sci. 95(Supplement 1):34.
Technical Abstract: The objective of this study was to evaluate the effect of hair shedding score and hair coat color on the vaginal temperature (VT) of calves during heat stress. Weaned Bos taurus beef heifers (n = 32; BW = 282 ± 6.4 kg) were assigned to a hair coat color class (BLACK; RED; or LIGHT, where LIGHT = yellow or gray) and evaluated for hair shedding score. Hair coat was subjectively scored on a 1 to 5 scale (1=slick summer coat, 5 = no shedding). Vaginal temperature recording devices were inserted at study onset utilizing a blank CIDR device equipped with a temperature data logger programmed to record VT at 5-min intervals for the duration of the 19-d study during July and August 2016. Calves were randomly assigned to one of three 2.02-ha pastures in Prairie, MS with equivalent shade allotment and balanced by hair color and shedding score. Environmental temperature and humidity data loggers were placed in each pasture. Temperature data were evaluated using the PROC MIXED procedure of SAS specific for repeated measures with LSMEANS separation evaluated at a = 0.05 using the PDIFF option. Throughout the study, the mean environmental temperature was 27.75 °C, and mean relative humidity was 82.81%. The temperature-humidity index was in the upper range of the moderate to severe heat stress range during the day and bordered the moderate heat stress range during the evening suggesting that environmental conditions were unconducive to heat mitigation and dissipation. Overall, hair color affected VT (P<0.0001), and RED heifers had increased VT when compared to BLACK (P<0.0001) and LIGHT (P=0.03). Hair shedding score also influenced VT (P<0.0001). There was no difference between hair score 1 and 2 (P=0.39) but there was a difference between hair scores 1 and 3 (P<0.0001) and hair scores 2 and 3 (P<0.0001) for all hair colors. As expected, VT increased as hair shedding score increased (39.30 – 39.83°C). There was an interaction between color and hair shedding score (P =0.02). In animals having a hair score of 1, RED animals had elevated VT compared to BLACK (P=0.0003), and there was a tendency for increased VT in RED animals compared to LIGHT (P=0.07). In heifers with a hair score of 2, there was a tendency for increased VT in RED heifers compared to LIGHT (P=0.08) and an increase in VT in RED compared to BLACK (P=0.0012). There was no difference between LIGHT and RED heifers in hair score 3 (P=0.14); however, they had elevated VT in comparison to BLACK (P<0.0035). Overall, RED heifers maintained elevated VT throughout the study. Future research endeavors are warranted to further explore and elucidate the observed interactions of hair color and hair shedding score on body temperature in beef calves in the Southeastern United States.