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Title: AUSTRALIAN FEEDLOT CATTLE RESPONSE TO SHADE AND NO-SHADE

Author
item Eigenberg, Roger
item GAUGHAN, JOHN - UNIV QUEENSLAND
item BRYDEN, W - UNIV QUEENSLAND
item Nienaber, John

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Other
Publication Acceptance Date: 8/4/2004
Publication Date: 8/9/2004
Citation: Eigenberg, R.A., Gaughan, J.B., Bryden, W.L., Nienaber, J.A. 2004. Australian feedlot cattle response to shade and no-shade. American Society of Agri Engineers Special Meetings and Conferences Papers. Paper #044036

Interpretive Summary: Summer heat provides stressful conditions feeder cattle; in extreme instances these conditions can be lethal. One management option is to provide shade structures for feedlot animals. This study was conducted during the 2003 Summer season (January- February) at the University of Queensland-Gatton Australia, to determine physiological responses of cattle under shade or no-shade conditions. Six heifers were involved in the study; three pens had access to shade and three had no shade available. Animals were rotated through pen assignments. Heifers that had shade access had average respiration rates considerably lower than heifers without shade during daytime. As ambient temperature increased, respiration rates increased at a rate that was about three times higher for unshaded heifers than shaded heifers during daytime measures. A relationship was developed to estimate respiration rate that includes effects of temperature, humidity, and solar radiation for temperatures above 25 deg/C. Comparison of these data for Australian Black Angus heifers to similar studies with steers in the United States indicated that estimates of stress apply to a broad range of cattle and climates.

Technical Abstract: Summer heat provides stressful conditions for Bos taurus feeder cattle; in extreme instances these conditions can be lethal. One management option is to provide shade structures for feedlot animals. This study was conducted during the 2003 Summer season (January- February) at the University of Queensland-Gatton, Australia to determine physiological responses of cattle under shade or no-shade conditions. Six heifers were assigned individual pens. Three pens allowed access to shade structures (SA); the remainder had no shade access option (NS). Animals were rotated through pen assignments. The NS heifers in this study had average respiration rates 20 breaths per minute (bpm) higher than SA heifers during daytime. As ambient temperature increased, resultant respiration rate (RR) increased at a rate that was about three times higher for NS heifers than SA heifers during daytime measures. A threshold was observed to occur at an ambient temperature of about 25 deg/C based on treatment effects on RR. A linear regression equation was developed to estimate RR that includes effects of temperature, humidity, and solar radiation for temperatures above 25 deg/C. Comparison of these data for Australian Black Angus heifers to similar studies with steers in the United States indicated that estimates of stress apply to a broad range of cattle and climates.