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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition, Growth and Physiology » Research » Publications at this Location » Publication #316601
Title: Metabolizable energy intake effects on tympanic temperature and ADG of steers finished in southern Chile during summer

Author
item ARIAS, RODRIGO - University Of Chile
item ALVARADO-GILIS, CHRISTIAN - University Of Chile
item Brown-Brandl, Tami
item MADER, TERRY - Mader Consulting, Llc

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/24/2015
Publication Date: 7/12/2015
Citation: Arias, R.A., Alvarado-Gilis, C., Brown-Brandl, T.M., Mader, T.L. 2015. Metabolizable energy intake effects on tympanic temperature and ADG of steers finished in southern Chile during summer [abstract]. Journal of Animal Science. 93(Supplement s3):861.

Interpretive Summary:

Technical Abstract: A total of 24 red Angus steers (BW = 431.16 ± 10.44) were used to assess the effect of metabolizable energy intake (MEI) on ADG and tympanic temperature (TT) during the summer time in southern Chile. Steers were sorted by BW (lighter or heavier) and allocated in 4 pens (6 head/pen) equipped with a Calan Broadbent Feeding System (American Calan, USA), and then allocated into one of two treatments: T1 = 1.85x or T2 = 2.72x MEI for maintenance. Animals were fed once per day with the same diet (grass silage + oat + canola meal + minerals); therefore treatments were applied by controlling DMI. Steers received a device to collect TT on 02/06/2014, being these recovered 10 days later. Ambient temperature (AT), relative humidity (RH), wind speed, and solar radiation (SR) data were obtained from a weather station located at 5 km southeast and used to estimate two thermal indices (THI and the Comprehensive Climate Index). All data were analyzed under a complete randomize block design arrangement (a = 0.05). Ambient temperature averaged 17.2 °C for all the period, however it was 26.1 ºC on the hottest day. In addition, a drop of 24 ºC was recorded between night and day AT. The low temperatures at night allowed for the dissipation of heat accumulated during the day. The steers fed with T1 showed higher TT than those fed with T2 through all days (38.07 vs. 38.02 ± 0.001 ºC; P < 0.01). However, this difference does not represent a significant change from the biological point of view. There was no risk of heat stress during the study period, as none of the observed thermal comfort indices outperformed the thresholds established in the literature (THI = 68 and Comprehensive climate index (CCI) = 25). However, maximum values of thermal indices THI, THIadj and CCI were 75.5, 79.97, and 34.66, respectively. Animals showed signs of thermal discomfort, due to the increase in respiration rate, which was higher by 20 points during the afternoon (P < 0.0001). This could be associated with the largest solar radiation received during the afternoon. On the other hand, there were no differences in ADG (1.25 vs. 0.95 ± 0.15 kg / day for MEI 2.72 and 1.85 respectively; P = 0.1836). In addition, both values are in line with those projected by the NRC Beef model, with superior value predicted in the case of MEI 1.85. Based on the data herein collected we can conclude that for southern Chile, the summer weather conditions and MEI had no impact on productive and physiological responses of animals.